Plutonium power for the people

One of the biggest threats to the continued wealth and power held by the global fossil fuel industry is a “plutonium economy” fueled by abundant resources of uranium that can be converted into fissile plutonium in a breeder reactor. (Yes, I know that a thorium economy is just as big of a threat to the dominant position of fossil fuels, but the understanding of the potential impact of that technology is less widespread than the understanding of fast breeder reactors.)

Of course, the fossil fuel industry has always employed plenty of experts in the field of communications. They also have a huge following of friends in the media, in finance and in government who have profited immensely by the hydrocarbon economy and would love to see those profitable relationships continue. Hydrocarbon communications experts and their friends recognized many decades ago that there would not be too many tears shed if they accurately explained why they were threatened by the idea of carbon based fuels being replaced in the energy market by concentrated fissile fuels, so they developed a much more effective sales pitch.

By helping to reinforce scary images of nuclear war and tying the fears inspired by those images to the materials used in building bombs, the antiplutonium propaganda machine has convinced many decision makers and voters that innovative machinery that turns relatively worthless uranium into useful fuel are secretly designed by mad scientists intent on creating bomb material. As one result of the effective campaign against plutonium, President Carter outlawed nuclear fuel recycling and turned multibillion dollar investments at Barnwell, South Carolina and at Clinch River, Tennessee from potentially profitable production facilities into expensive, non-functional eyesores.

Today, the propaganda machine is still actively working to stoke fears of plutonium because the material is still a strong threat to the prosperity of the fossil fuel industry.

After all, plutonium, like uranium and thorium, contains 2 million times as much energy per unit mass as oil. It releases that energy in the form of heat that can be converted into useful power in machines that are essentially identical to the heat engines used to convert coal heat into useful energy. It can be used in machines that are almost identical to those used to convert natural gas or diesel fuel heat into useful power, but that method is not yet in common use. Not only is heat from plutonium abundant and concentrated (which vastly reduces the transportation infrastructure required to supply power plants) fission heat also comes without any emissions of CO2, CO, SOX, NOX, fly ash, mercury or any of the other atmospheric pollution produced by burning stuff dug out of the ground.

This evening, at the Convention Center in Chattanooga, Tennessee, there will be a public hearing about one way of using plutonium that is sure to be both informative and entertaining. The hearing is being held to obtain public comments on the Department of Energy’s Draft Surplus Plutonium Disposition Supplemental Environmental Impact Statement. The agency’s preferred alternative for disposing of 34 tons of plutonium made surplus by an arms agreement with Russia is to mix that fissile material with uranium to create a mixed oxide (MOX) fuel that is compatible with our current generation of light water reactors.

Aside: From a nuclear standpoint, plutonium is an almost exact replacement for uranium-235, which is the fissile part of low enriched nuclear fuel. By mixing Pu-239 from decomissioned nuclear weapons with either natural or depleted uranium in concentrations of about 5% Pu to 95% U, a MOX fuel rod will work just like an LEU fuel rod and last just as long in the reactor. The difference is that the process gets rid of unwanted material and does not require the effort or energy investment required to enrich natural uranium. End Aside.

People opposed to the use of plutonium would prefer for the valuable, energy-dense material to be encapsulated into glass logs and buried deep into the earth’s crust where even smarter future generations will have trouble getting to it. They want to ensure that it is never used for productive purposes that compete with other forms of energy. Word has it that some antiplutonium demonstrators are planning to dress up as zombies to protest the conversion of weapons material into fuel for electricity generating stations. The zombies will be the entertaining part of the evening.

Though I spent my first career as a part of the military industrial complex, I share concerns about nuclear weapons with some of the people who are going to be in costume. However, I prefer using a process that permanently eliminates the material while providing a useful product. Once fissioned, the plutonium can never fission again.

The informative part of the evening will be the comments provided by members of the American Nuclear Society who are going to attend the meeting and take the opportunity to express their facts and figures about the value of the material and the moral imperative of turning weapons into useful electrical power that can be used for an incredible array of useful applications. I hope that some of the ANS members also take advantage of the opportunity to express their pride and emotional connection with the technology that has so much potential for making life better for the vast majority of the world’s population that is not engaged in the business of selling fossil fuel.

PS My personal feeling about using MOX technology to purposely get rid of plutonium is akin to the way I would feel about using ethanol technology to get rid of seed corn. However, it is not terribly difficult for us to make more plutonium once we have overcome the irrational fear of the material that has been instilled by the sustained propaganda campaign supported by the energy establishment.

One more related note – the Russians have decided to use fast reactor technology instead of MOX to dispose of their agreed 34 tons of surplus weapons material. A recent article in Spiegel Online, which was marred by significant quantities of misinformation about the basics of fast reactors, gives me some concern about the BN-800. I like fast reactor technology, but I am worried because Russia is almost as dependent on hydrocarbon sales for its wealth and power as Saudi Arabia is.

The statements in Spiegel’s Russia To Produce Electricity with Former Nukes made by an anonymous worker on the construction project lead me to believe that there is at least some possibility that the energy decision makers in Russia are setting up conditions that will result in their new fast reactor having enough problems to discourage everyone else from trying the technology. Though just one man was the source of the interview information it seems apparent that there might be significant safety culture and quality control issues on the project.

About Rod Adams

95 Responses to “Plutonium power for the people”

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  1. Daniel says:

    So what is the point of using Pu for MOX in LWR ? We should do as France does and await the next generation of reactors.

    I just can’t get any sense out of the ‘arithmetic’ like Bill Clinton says.

    So you have a LWR that produces X amount of Plutonium. You blend the LWR fuel with 5% Pu and 95% U. It will still produce more Pu at the end of the cycle than the 5% you burnt, no ?

    Am I missing something or this is just to calm the ‘spirits’ ?

    • Brian Mays says:

      So what is the point of using Pu for MOX in LWR ? We should do as France does and await the next generation of reactors.

      Uh … what? France currently manufactures MOX fuel and burns it in their reactors.

      This is why the company that I work for, AREVA, was chosen to build the MOX fuel fabrication plant in Aiken. We built the MELOX plant; we run the MELOX plant. Google it.

      So you have a LWR that produces X amount of Plutonium. You blend the LWR fuel with 5% Pu and 95% U. It will still produce more Pu at the end of the cycle than the 5% you burnt, no ?

      Am I missing something or this is just to calm the spirits ?

      Yes. You’re missing the energy that can be had by burning plutonium that you’ve already produced, instead of enriching an energy-equivalent amount of uranium to do the job instead.

      Don’t forget that the goal is to produce usable energy. If you want to burn actinides, then build a fast reactor that is tailored for that purpose. But if all you want to do is generate electricity, then MOX fuel works just fine.

      In the case of weapons-grade plutonium, once it has been fabricated into MOX fuel — and especially after it has been burned in a reactor — the plutonium is no longer suitable for being used in a weapon. So the idea of turning swords into plowshares is very real.

      This project really is about the closest that one can get to having a free lunch, because the majority of the meal has already been paid for by defense budgets during the Cold War.

      • Jeff S says:

        I have a question about MOX fuel. You mentioned fast reactors vs thermal reactors with MOX fuel, which got me to thinking about some questions I have. If we burn all this MOX fuel, can the “waste” still potentially be used in an IFR-style fast reactor? I think I read a discussion once which mentioned that as MOX fuel fissions, it tends to accumulate isotopes which are “neutron poisons” – that is, they tend to absorb neutrons without fissioning, so that the fuel doesn’t burn as well.

        But, what I’m not clear about is: A) are those “neutron poisons” still a detriment when you are talking about fast-neutron fission reactions, or are they only “poisons” in a thermal spectrum? B) If any of them are also poisons in a fast spectrum, would the IFR’s electrorefining plant be able to remove those poisons, so that you could still fabricate the MOX waste into useable fuel in the fast breeder reactor? C) Can the MOX fuel be recycled somehow (and any “poisons” removed) for re-use in thermal reactors (that is, as someone mentioned, more PU should breed in-situ in the MOX fuel as it is fissioning in the reactor, yes?). To what extent can you breed more fuel in your MOX fuel, in thermal reactors and just keep re-using MOX in them?

        • Jagdish says:

          A) Neutron poisons are still a detriment in fast reactors but less harmful due to lower “cross-section” for absorption for neutrons at higher energy.
          B) IFR’s electro-refining can separate these fission products (or most of them) from transuranics including plutonium.
          C) MOX fuel used in thermal reactors has less fissile isotopes and more of other, problematic ones. In fast reactors you can keep on using U-Pu MOX or even convert to Th-Pu MOX.

    • Joffan says:

      Daniel: you’re missing something.

      In my simple understanding, in the standard uranium-only fuel rod, the fissile and fertile materials are 4-5% U-235 and remainder U-238 respectively. In a Mox rod, the U-235 is replaced by Pu-239.

      In both cases, the fissile material is largely consumed to below 1% of the final rod, and some of the fertile U-238 is transformed to Pu-239; also ending up at less than 1% of the final mix. So in the case of Mox, the total inventory of Pu-239 has indeed signficantly reduced. Perhaps you had an exaggerated idea of how much Pu-239 a power reactor produces – not all that much, is the answer.

  2. DV82XL says:

    Nuclear supporters must get out of the Bolshevik/Menshevik mindset we are constantly struggling with. Polls continue to show that nuclear energy has the support of a majority of the public (http://www.nei.org/resourcesandstats/documentlibrary/publications/perspectiveonpublicopinion/perspective-on-public-opinion-may-2012/) yet we sill behave as if we were a minority. Yes this majority is razor thin but nevertheless does represent a very large number of people. We need to stop fencing with the demagogues on the other side and reach out to our own constituency. They need to be organized and mobilized if we are to effect the political changes that need to be made to push forward new builds. As it stands we constantly engage with the opposition and leave our own natural supporters to twist in the wind. If I could accomplish one thing as a commenter on nuclear issues it would be to change this.

    The other problem is that those of us active in our support for nuclear are visionaries, we had to be to take this on, but unfortunately that manifests itself as a desire to reach too far, too soon. Things like fast reactors, thorium, molten salt and other advanced designs on the horizon blind us to the need to walk the path we have in front of us. Looking to the future, we cannot see what needs to be done in the present. We have proven, approved and marketable designs available right now, no they are not ideal but they are what we have right now that could be built and it is these that we need to push. The time will come when new Gen IV designs can be considered, but not now, and we are expending far too much effort on these birds in the bush and not enough on the ones we have in our hand.

    We must work to consolidate the support we have now and leverage it to see new power plants started. We have to ignore the noises from the other side of the fence and keep our imaginations in check and focus on what we can do in the here and now to get the ball rolling.

    • Joel Riddle says:

      Robert,

      Will Davis posted a nice primer on the Korean nuclear plans. They seem to be going about their progression in a proper manner.

      http://atomicpowerreview.blogspot.com/2012/09/south-koreas-nuclear-energy-program.html

    • John Tucker says:

      “Nuclear supporters must get out of the Bolshevik/Menshevik mindset we are constantly struggling with.”

      I dont understand that. Is it a negative connotation? Early Communist moments technically were probably closer to American concepts of fairness and individual liberty than some American cultural moments of that time.

      Of course without a basis in reason (logic and empathy), and no protections from corruption, authoritarianism was able to quickly take over.

      What the situation probably shared the anti nuclear movement is that it was a populist movement based in the perception of a real injustice (horrific conditions/nuclear war) that morphed into a unreasonable, and self advancing phenomena.

      In more current terms Liberalism technically in itself is pro science, pro nuclear and pro new technology that reasonably improve the quality of all life in line with newer concepts of conservatism(they are not opposites). New conservationism now mostly pushes financial responsibility within a traditional balance sheet approach.

      All markets and economics depend on mutual agreements; regulation, exchanges and community standards so I dont even think using vague economic terms gets anywhere except perhaps if you are trying to convince someone of something in a quick and more convenient way.

      • DV82XL says:

        Bolshevik/Menshevik mindset was references to Lenin asserting that his faction was more powerful than Martov’s at the Second Congress by naming it ‘the majority’ when in fact things were more evenly split. Opponents of nuclear energy do the same by asserting the bulk of the public rejects nuclear and we have a tendency to accept this as fact when it is not. It is this attitude I want to see go.

        • John Tucker says:

          lol good lord. ok I see – I cant say you were being vague there!

        • David Walters says:

          Uh…they actually did have a majority and this increased at every subsequent congress (at least in the major working class centers), most notably the 1912 Prague Conference when few Mensheviks showed up. [BTW...that RDLP 2nd Congress transcription is up on the Internet transcribed your truly].

          But where I disagree more relevantly to DV82XL is that regardless of us being the real “Bolsheviks” (Majority) on the question of nuclear energy, the debate is controlled almost totally by the antis. Support for nuclear energy however, while a “majority” is very, very passive. There is almost no *active* support for nuclear energy among that great silent majority and the activism is almost totally by the other side!

          David

          • DV82XL says:

            When Lenin started calling his faction ‘Bolshevik’ things were not that clear cut and if indeed he had a majority it was razor thin and only for one key vote. The point was that he created the illusion his was the stronger position by calling it such, just as the antis do to us now.

            MY point is we have to stop debating with the antis, and start reaching out to those passive supporters with a view to mobilizing them, because the debating strategy isn’t yielding results.

          • John Tucker says:

            Political arguments don’t have to be factual. The historical narrative can even be viewed from differing perspectives. My initial irritation was more at a perceived clouding the issue with some connection to communism by the “enemies of a nuclear revolution.” That was incorrect and still dont really see the benefit of arguing early soviet party historical political perspectives here. (although moving into that time in Russia also is arguably one of the most artistically innovative periods in history. Not to mention a period of rapid technological upgrade and innovation).

            After that is the political failure. The French Revolution and Haussmannization of Paris especially would better discuss mass motivations here.

            But in the end this is a unique situation that is unlike any other and adding equivalencies, even when done to further popular sympathy, also adds analogies and translations, and so another level of complexity to the entire horrifically complex issue.

            I think like so many other things now in public forums its probably better to move more towards demanding reason and hard verified science specifically as a sole foundation for validity. We will probably collectively never get anywhere if we do not. Both literally and figuratively.

            Being a artist by training its not how I want it to be. Its just how it is.

          • DV82XL says:

            “I think like so many other things now in public forums its probably better to move more towards demanding reason and hard verified science specifically as a sole foundation for validity. We will probably collectively never get anywhere if we do not”

            Ya I can see that’s the way politics is practiced in the real world – I wish.

            Politics is a messy business and it is my observation that the validity of any idea in that broad forum is rarely based on verifiable fact and good reasoning. In fact it has been those political movements that have tried the route of pure logic that have been failures while the demagogic ones thrive.

          • John Tucker says:

            Thats probably going to be changing radically in the next few years. Look at all the posts and interest lately. Even with (and probably because of) the negative stuff. Issues of climate change and acidification, issues and approaches to energy, economics and science and space exploration even caused me to show up here. Give it time to collect momentum.

            Thats the good thing about taking effort to get it right in argument. Even if you have to change your mind to do so. All kinds of energy can be applied to push things in other directions but once that push subverted, wavers or is gone everything will start moving towards truth again.

          • John Tucker says:

            I missed this referenced article – we are not alone in this line of thinking:

            New Nukes
            Why We Need Radical Innovation to Make New Nuclear Energy Cheap ( http://thebreakthrough.org/index.php/programs/energy-and-climate/new-nukes/ )

            “Arguably, the biggest impact of Fukushima on the nuclear debate, ironically, has been to force a growing number of pro-nuclear environmentalists out of the closet, including us. The reaction to the accident by anti-nuclear campaigners and many Western publics put a fine point on the gross misperception of risk that informs so much anti-nuclear fear. Nuclear remains the only proven technology capable of reliably generating zero-carbon energy at a scale that can have any impact on global warming. Climate change..”

    • Michael R. Himes says:

      In the US reactors are at the end of their designed life. In short, the only thing driving new builds is Gen IV. I do agree that is seems a waste to move on when we just have gotten the science and operation of the “OLD” reactors perfected. After all, fourty years of working with the “OLD” reactors has keep the lights on in many a US City.

      • Daniel says:

        @ Michael,

        US reactors are at their end of their financing or amortization period of the nitial construction costs.

        When maintained properly, these little suckers can last one hundred years.

    • Joris van Dorp says:

      DV82XL. I think we should build about 500 to 1.000 GWe of new nuclear power plants per year on average until the middle of the century. To do that, existing LWR thermal is inadequate. A fast reactor build out is needed right away.

      My reasons for supporting nuclear power:

      - reduce polution and global warming
      - reduce dependance on (imported) fossil fuels and biomass
      - reduce energy costs

      If we can solve those problems without fast reactors I’m all for it, but if I understand it correctly, we must have fast reactors to do this right?

      • DV82XL says:

        I have never contended that research on Gen IV should stop, only that we need to kick-start the next round of builds with what we have on hand. Once the ball is rolling and the public is behind the idea of a nuclear economy new type of designs can be introduced if they are found viable.

        My beef is with those that think that new designs should be pushed too soon claiming that they have reached the stage where they can be considered commercial products when clearly they are not. It is too much to ask those who would have to invest money and the regulators to back radical new ideas at this time even if public were on-side. As well antinuclear forces of all stripes would be quick to leverage uncertainties around any novel design to generate a new wave of FUD that could not be dismissed by simply pointing at the record as we can do now.

        • Joris van Dorp says:

          I see. Fair enough. It’s just that the anti-nuke argument “There is not enough uranium to make nuclear power of much use” seems to be popular. To counter that argument, it would be nice if commercial fast reactors could also be pointed to on the record.

          • DV82XL says:

            The very last thing we should do is dance to any tune played by antinukes on any subject, this one included. Pronuclear supporters have to get it through their heads that the best way of dealing with the antinuclear crowd is to ignore them and address the public directly. You don’t see and of the fossil fuels debating directly with their critics nor do they feel the need to answer them every time they squeak – we shouldn’t ether.

          • Rod Adams says:

            @Joris van Dorp

            Having successful fast reactors in operation would make it easier to disarm the opposition of several arguments, including the notion of limited fuel resources. The major argument that would be harder for the opposition to make is the rhetorical question “but what do you do with the waste?” I like to answer with “reduce, reuse and recycle” but that is a slightly harder argument to make without having operating reactors that prove the point.

            I remain convinced that the effective opposition to nuclear energy is well aware of the implications of allowing fast reactors to achieve demonstrated success. That is why they have worked so hard to ensure as many obstacles as possible are placed in the way of their development.

            http://atomicinsights.com/2012/02/pursuing-the-unlimited-energy-dream-some-history-of-the-integral-fast-reactor.html

  3. SteveK9 says:

    Read the der Spiegel article. That was a bit unsettling. On the other hand the Russians have operated the BN600 for over 30 years. They are planning to sell (there is already an agreement I believe) two BN800′s to China. So, I don’t think they ‘want’ to fail. Hopefully they aren’t rushing the work, the way the article indicated.

    A bit off-topic but there is a fair amount of reporting right now on the fact that the extent of Arctic sea ice has set a new record low this year. There is also quite a bit of discussion on the release of methane that can result, and its potency as a greenhouse gas. A small negative for the PR campaign of the ‘cleanliness’ of natural gas.

    • Rod Adams says:

      @SteveK9

      I realize that it seems counterintuitive to believe that the Russians want to fail at fast reactors because they have a few potential orders at stake.

      However, if you understand that their fossil fuel export market brings in revenues of almost one billion dollars per day ($322 billion for 2011) you might understand why it is in the country’s short term financial interest to discourage anything that might reduce the price of oil and gas by adding a substantial amount of new energy supplies to the market.

      I suspect that the people on the project want to do their jobs, but if they are being starved of resources it is difficult to do the job correctly.

  4. Joel Riddle says:

    I too read the Spiegel article and had a few quick beefs/critiques.

    1. Do Russian reactor welds not get QC and radiographic inspections to ensure they were of proper quality/craftsmanship?

    2. Saying that Plutonium is “completely useless for civilian purposes” is quite untrue. Plutonium bred during normal operation in conventional nuclear reactors provides something greater than 30% of the total fission energy. Also, MOX is already used in some commercial reactors around the world and has been for 20-30 years, if I’m not mistaken.

    3. Really, the “Plutonium dust = automatic fatality” thing again?

    4. The part “need to be strong enough to withstand the fission energy of 34 tons of weapons-grade plutonium” seems to be trying to give the impression that all 34 tons will be loaded into the reactor at one time, and won’t have been diluted at all. This is surely not correct.

    • Rod Adams says:

      @Joel Riddle

      Quality control measures after the fact may catch poorly executed welds, but those measures are not perfect and cannot substitute for doing the job properly the first time.

      It is also very expensive to rip out welds that fail QC. Even if the testing is perfect and all bad welds are detected, that would not negate my concern that starving the project of resources in the construction phase is designed to ensure that the project looks difficult enough (expensive enough) to discourage anyone else from trying to pursue fast reactor technology as a means of producing abundant energy that has the real potential of displacing oil and gas from the market.

    • Michael R. Himes says:

      Russian welding is a major issue for Russia right now. The LADA class sub was canceled due to poor (cold) welding joints. In general Russian industry is suffering from lack of a trained new work force and the exodus of skilled craftsmen to western Europe. In fact, the problem is so severe that Russia is opting to purchase war machines outside Russia.

      I am certain that the ambitious attempt by Vladimir Putin to revitalize Russian manufacturing, excluding aircraft production, will fail for the lack of skilled workers. This will take a decade to rebuild and by that time climate change will be driving what happens in the industrialized world.

      • Jagdish says:

        Reactor vessels of thermal reactors using water are a real heavy engineering and Russians are one of the big players, behind only Japan. The number of failures will increase with number of actual production.
        One way out is the Canadian, also followed by Indians, practice of having many lighter tubes in place of one big vessel.
        The other one is using of less volatile materials for heat transport of heat, used in fast reactors.
        Russians try everything.

  5. Bill Hannahan says:

    Fast neutron reactors operate on the same physics as the Hiroshima bomb. I have yet to find proof that fast reactors are absolutely incapable of producing a high energy criticality accident, a nuclear explosion, based on fundamental principles of physics. That is my standard, claims of low probability, unlikely, probably, not possible or its never happened before, are not sufficient.

    Even a medium energy criticality, a few hundred tons TNT equivalent, would produce an accident several orders of magnitude worse than Chernobyl. We have discussed this before; I do not have time to do it again.

    http://atomicinsights.com/2011/12/kirk-sorensen-why-didnt-molten-salt-thorium-reactors-succeed-the-first-time.html

    The Russian fast neutron reactor does not have a containment building nor do the bigger follow on designs. Such an accident would kill nuclear power for a generation and condemn billions of people to needless suffering and early death, not from radiation, from lack of affordable reliable clean energy. The benefits of fission can be had without taking this risk.

    I would make two exceptions. 1… Solid fuel fast reactors buried underground deep enough to contain the worst case energy yield. 2… Molten salt fast reactors. A well designed fast neutron MSR has minimal excess reactivity; they operate at or near the most reactive possible configuration. That combined with intimate contact of fuel atoms with coolant and fission products, eliminating any delay in negative temperature feedback, makes a large, fast, burst of energy impossible.

    Existing solid fuel fast neutron reactors should be immediately defueled until proven absolutely incapable of exploding, by fundamental principles of physics.

    Plutonium can be slowly burned entirely to fission products in a simple thermal MSR fueled by enriched uranium without reprocessing. Heavy atoms are kept in the salt until they fission. There may be a small neutron penalty requiring an increase in uranium mined per kWh, but probably still less than for a conventional PWR. Uranium cost per kWh will be cheap for a long time given continuing improvements in mining and sea water extraction.

    • John Englert says:

      Bill,

      You would still need to get a lot of neutron generations to get to 100 tons. Even in a fast reactor, geometry and time are on your side.

      John

    • Cal Abel says:

      Fast Reactors do not operate on the same physics as weapons. What you are saying is a load of crap.

      Weapons operate on prompt neutrons alone. Power reactors operate on prompt and delayed neutrons. The physics are very different.

      Thorium reactors fast/thermal have a similar fraction of delayed neutrons as fast uranium reactors. From a reactor operator perspective there would be very little difference for solid-solid fuels or liquid to liquid fuels.

      Stop spreading stuff that is not true. You rely on theories that cores can do physically impossible things, such as instantaneously and uniformly melting. Maybe back when you used slide rules that was a passable assumption and was understood for its conservative nature as being a non physical process. We now have computer codes designed and validated with experiment that model how cores melt and these codes show if you would be willing to read the reports that you have unwarranted concerns.

      Get a clue, put away the slide rule and start learning Fortran as a start, we may graduate to C++ or heaven forbid some more advanced object oriented code that came out within the last 20-years. BTW we no longer use card decks either and my phone has more computational power than what we designed most of our nuclear weapons with.

      • Brian Mays says:

        put away the slide rule and start learning Fortran as a start, we may graduate to C++ …

        Ugh!! Why the hell would you want to do that?!

        If you really want to screw something up, “graduate” to C++. Between a slide rule and C++, I’ll take the slide rule, thank you. (And yes, I do know how to use one, and yes, I am forced occasionally to have to deal with the quagmire of C++.)

        The next thing I know, you’ll be telling me that I should start doing serious calculations in Java, in which case I’d just have to slap you for being silly.

        By the way, almost all of the nuclear engineers that I know and work with still fondly refer to their input files as “decks,” even though this term has long been an anachronism.

        • John Englert says:

          Who knows what language future nuclear engineers will program in, but it will be called FORTRAN.

          • Cal Abel says:

            John and Brian,

            You are both quite right about the codes being in FORTRAN for perpetuity. The front ends and script manipulations are done in many different codes.

            Brian, yes the anachronism of input decks still exist. I was referring here to the physical stacks of punch hole cards that had to be fed in order into a card reader to load the program into the RAM. These went away about a decade before I went to school. We still had 8086′s running around in the office… Slide rules went away about the time scientific calculators came out. We still use slide rules all the time in the Navy, called them wiz wheels. They are much faster and reasonably accurate for rapid solutions.

          • Brian Mays says:

            Well, we all have our own biases. Personally, I like to avoid C++ and the newer versions of FORTRAN (post 77) like the plague. They are, in my opinion, attempts to fix something that wasn’t broken in the first place, and they have been very clumsily designed and implemented. Every project that I have been involved in that uses either of these languages has been a huge pain in the back.

            Of course, these are my own opinions. You are welcome to yours.

      • Dr. John Miller says:

        @Cal

        You are incorrect. Do you think God made two kinds of physics, one that allows a prompt nuclear excursion in bombs and another that prevents it in reactors?

        You clearly know from the Navy that its reactors can go prompt critical. When I was in, we were limited in the rate of reactivity insertion to 5 decades a minute. 9 was prompt critical. That’s an explosion.

        Dr. John Miller
        @NuclearReporter

    • Cal Abel says:

      You are going to need those codes in order to have something of a weak hope of being able to adjust the transport equation to deal with the thermal hydraulic transport of the delayed neutron precursors. I’d love to see how you would adapt MCNP to be able to handle that. The steady state problem is hard enough. Going through and having to add a temporal fluctuations in the single most important neutron source will break most computers and make a collisional plasma code look like chump change.

      For the time being at least until you can start validating the theories that you will have to create in order to make the necessary computational approximations so one code run won’t take the better part of a decade, why don’t you drop the holier than thou MSR will rule the world, and try to understand what it will actually take to build and design.

      You hope it will all work just fine. Hope is not a plan. A plan is a plan. Right now you don’t even have the theory to even begin creating the plan.

      • George Carlin says:

        Cal, I agree with your comments. I, however, find it fascinating that they built an MSR and ran it for 4 years using slide rules. They may not have known exactly what was going on kinetically, but they did show that the MSR works and works quite well actually.

        • Cal Abel says:

          I think the success with the MSRE was due to the small size. Slide rules and analytic approximations to the diffusion equation do some very amazing things. It was more of an art than skill back then.

          The MSRE had a high neutron leakage wich makes the shape of the flux in the core more stable against fluctuations. When the reactor is scaled up leakage will go down and the flux will flatten out. This loss of a spatial shape will lead to flux instabilities. This may not necessarily be bad, but without understanding the kinetics it makes it difficult to justify. If you take the neutrons as a thermodynamic system the flux instabilities are like boiling of water. It is a phase transition. It is an entirely new phenomena that we don’t fully understand yet. Maybe a boiling flux core is an ok thing to have. I don’t know. Typically with solid fueled cores flux instability can lead to breaking the fuel. Molten fuel, not so much, but molten fuel flows in graphite channels so there will be in-core pressure oscillations that could affect those.

          Also there is a negative flow coefficient of reactivity, the slower the coolant the more neutrons in the core. Loss of flow causes a positive reactivity insertion. Taking a below the power range pump trip with no scram, it would be entirely possible to have a non trivial reactivity insertion.

          I think the MSR has a lot of promise, its just not ready yet and will take a significant amount of work to bring online. Much more than what most advocates are thinking of as a worse case scenario.

    • Brian Mays says:

      Fast neutron reactors operate on the same physics as the Hiroshima bomb.

      So what? So do thermal neutron reactors. That is, the key set of physics is that a heavy atom fissions, neutrons are released, and more atoms absorb those neutrons and fission. Lather, rinse, repeat.

      The key difference between a bomb and a reactor is where do the neutrons come from?

      In the case of a bomb, the neutrons that keep the reaction going are prompt neutrons — i.e., neutrons that are released directly by the fission event.

      In both thermal and fast reactors, the neutrons that are necessary to keep the chain reaction going are delayed neutrons. That is, the atom fissions and a few prompt neutrons are produced, but these neutrons are not sufficient to keep the reaction going. Also produced by the fission event are unstable fission products that then decay (over a time period ranging from a fraction of a second to few minutes) releasing the additional neutrons that make up the balance to keep the system critical.

      The mean time period for a prompt neutron to cause a new fission event varies greatly between thermal and fast reactors (the difference being the time required for the neutron to slow down before being absorbed). Fortunately, this difference is not significant when it comes to the ability to control a reactor. The time scale that is the most important — the time for the delayed neutrons to appear — is roughly the same for both types of reactors.

      And that’s how reactor physics works.

    • Rod Adams says:

      @Bill Hannahan

      Without delving into the graduate level nuclear physics described by Cal and Brian, I can still call your initial statement false based on what should be rudimentary knowledge of bomb making. The Hiroshima bomb was a gun type device that required an explosive charge to fire a sub critical mass at high velocity into another sub critical mass. That was the only way to add reactivity fast enough to cause the device to achieve prompt criticality – where neutron lifetime is short enough to cause an explosive fission reaction.

      There are no conventional explosives in fast reactors and no way to move the masses of fuel or the neutron absorbing rods around fast enough to achieve the same kind of effect. The speed of reactivity addition can be readily limited by a number of different design choices.

      The Integral Fast Reactor was put through a substantial amount of physical testing that proved its passive safety. There are physics explanations associated with metal fuels and the large pool of sodium.

      Here is a short post I wrote on the topic several years ago

      http://atomicinsights.com/2008/08/recalling-the-integral-fast-reactor-ifr-passive-safety-experiments.html

      That post includes a link to a detailed paper on the history and technology development of the Integral Fast Reactor.

      http://cat.inist.fr/?aModele=afficheN&cpsidt=2532990

    • Dr. John Miller says:

      If you read the “bible” of fast-breeder design, Fast Breeder Reactors, by Waltar and Reynolds, 1981 (revised in 2012 by Waltar and a different co-author), they say that an explosion is a conservative estimate, which I take to mean more severe than what could happen. Or maybe conservative means the worst that could happen. Anyway, they say that meltdowns are much more likely than explosions.

      But given the positive void coefficient of reactivity, any accident that begins with a rapid power rise could lead to faster and faster power rises before the fuel heated up enough to bring in the two main negative coefficients of reactivity. In other words, it could explode.

      I agree with you that all sodium-cooled fast breeders should be shut down and defueled.

      Dr. John Miller
      @NuclearReporter

      • Cal Abel says:

        John,
        You need to apply that information with understanding of the model that they used. They approximated the core slump using Bethe Tait approximation for a Core Disruptive Accident. It assumes that the core instantly melts and coalesces into the bottom of the reactor vessel without being disrupted by flow or heat addition as a super critical geometry is selected.

        While it is “conservative”, it is not physically possible. It neglects most importantly the latent heat of fusion (energy needed to melt the core) and the time needed to add that energy.

        To apply such real world constraints requires more computation than what is contained in a slide rule. Fortunately for us we have computers that can model such complexities.

        Here is a more relevant report on this topic.

        http://prod.sandia.gov/techlib/access-control.cgi/2011/114145.pdf
        Please read the report. After reading the report, if you have any questions please don’t hesitate to ask. I am more than willing to explain the context of the results.

        Now as I understand your situation you have a few choices. First the scientific approach, you take head of the information that I gave you and we join in a discourse about the merits of the assumptions and results for each approach. This requires that both of us be willing to be incorrect. As an honest investigator that is the only approach that I can take. Based on researching this topic for a number of years, I am confident that I stand on firmer intellectual and empirical ground.

        Your second choice is to ignore what I told you. Here you can persist safely in your current state of ignorance. However, you are not really ignorant any more because I challenged your ideas with a very simple and sound argument. Therefor you are choosing to ignore information that is relevant to understanding this topic. I can only describe such an action as scientism and represents a specific belief structure. It is not science, although it pretends to be.

        Science seeks to identify and incorporate all relevant information to build a conceptual understanding of the world around us. Science cannot choose to ignore information because it is convenient. Science has to demonstrate that that information does not impact our understanding of the topic. To claim science as a moral philosophy, willful ignorance is not permitted.

        Pick your lot. The choice is yours.

    • Engineer-Poet says:

      Hans Bethe analyzed the explosive potential of a fast reactor meltdown and came up with a worst-case figure of 160 kg TNT equivalent.  This is about 670 MJ, or about 200 msec of full-power output of a 3.3 GW(t) reactor.

      It would be a real mess inside the containment, but that’s where it would stay.

  6. Jeff S says:

    One trend I’ve noticed over the years, and seems to be more and more the case, when it comes to reporting about nuclear power is that the media seems to have an obsession with reporting people’s fears, instead of reporting facts (well, I suppose that someone’s fear is technically a fact of itself, but not a very *useful* fact).

    Take as an example, Public Radio’s “Burn: An Energy Journal” project. They did a one hour “special report” on nuclear power. While there were a few moments of almost good journalism, I was STRUCK by how the whole first 20 minutes or so of the show was just an emotional retelling of one of the plant worker’s impressions of what was going on around him – now, in theory that could be useful; except, in this case, it was just talking about things which were not important – like how the steam turbine started shrieking “like a demon from hell” during the earthquake – well, yeah, that’s going to happen when a 9.0 magnitude earthquake hits any large, high-kinetic-energy turbine – it had NOTHING to do with nuclear power. . . a gas or coal plant with a large turbine would have had the exact same shrieking in the same conditions.

    It seems like Journalism is really reaching new depths of mediocrity at this point in history.

    • John Englert says:

      Makes you wonder what the standards of excellence are in journalism schools.

      • Joris van Dorp says:

        Journalism today is about catching the attention of the *average* reader and catering to his/her needs in terms of gossip and sensation. That’s where the money is. So that’s what a journalist who likes to keep his/her job will do.

        Fukushima led to an 18 month media frenzy condemning the ‘danger’ of nuclear technology in my country (the netherlands). But when reasoned scientific reports about the accident started finally coming out pointing to an almost complete lack of any actual dangerous consequences from the Fukushima nuclear accident, there was *almost nothing* reported about this. To this day, whenever I say in discussion with people that Fukushima was more like a dud than anything else and should be seen as a demonstration of the *safety* of nuclear power rather than of its danger, those people react with honest incredulity. In their minds, Fukushima has *clearly shown* that nuclear energy is ‘extremely dangerous and causes massive, lasting damage’. And these are well-educated intelligent people, MSc’s and PhD’s working in engineering jobs. If already these kind of people have evidently not been able to penetrate the FUD produced by journalists after Fukushima, what to think about the general population?

        • David says:

          Joris,

          The problem is mainly a lack of accurate information. It is also a willingness on the part of some to tell a very big lie and repeat it constantly.

          On the other hand, I am seeing (and participating in) more and more replies to this kind of mis-information.

  7. Bill Hannahan says:

    @cal
    “Fast Reactors do not operate on the same physics as weapons. What you are saying is a load of crap. Weapons operate on prompt neutrons alone. Power reactors operate on prompt and delayed neutrons. The physics are very different.”

    True during normal operation, however, when a large rapid reactivity insertion puts it in the super prompt critical range, delayed neutrons are irrelevant; the energy burst is over before any delayed neutrons are released. The physics are the same.

    “Thorium reactors fast/thermal have a similar fraction of delayed neutrons as fast uranium reactors.”

    Why the misdirection Cal? We are talking about plutonium fast reactors vs. uranium thermal reactors. For every 10,000 neutrons in a uranium reactor, 9,935 will be prompt and 65 will be delayed. In a plutonium reactor 9,980 will be prompt and 20 will be delayed. In addition, the average time delay is less for plutonium delayed neutrons. This makes plutonium reactors more sensitive to reactivity changes.

    “Stop spreading stuff that is not true. You rely on theories that cores can do physically impossible things, such as instantaneously and uniformly melting.”

    Not true. In the models I have seen the maximum velocities considered typically involve an overheated core slumping into the bottom of the reactor vessel under the force of gravity working through a short distance, or an object falling a short distance, not much velocity. I have no doubt that a low velocity criticality will produce a low energy burst. If designers can prove that there is no sequence of events that can result in a high velocity reconfiguration of the core to a superprompt critical condition, the requirement is achieved. They have not done that, and I do not think they can, because they cannot prove they thought of and modeled every possibility.

    For example, a large leak drains most of the sodium from the reactor, the core overheats and a large part of it falls into the bottom of the reactor producing a low energy explosion. The blast from that crushes the remaining part of the core against the vessel wall at near supersonic velocity, resulting in a huge fast reactivity insertion. What happens next?

    Terrorists load a jumbo jet with a large cylinder of tungsten and fly it into the reactor building at 600 mph. they get lucky and crush the reactor vessel or spent fuel pool at high velocity squeezing the sodium out of the core in a fraction of a second, resulting in a huge rapid reactivity insertion. What happens next?

    “We now have computer codes designed and validated with experiment that model how cores melt and these codes show if you would be willing to read the reports that you have unwarranted concerns.”

    I read your reports last time and pointed out the weakness in them. I marvel at your confidence that the computer codes have modeled the absolute worst case scenario. I do not share your confidence.

    “Maybe back when you used slide rules that was a passable assumption and was understood for its conservative nature as being a non physical process. Get a clue, put away the slide rule and start learning Fortran … BTW we no longer use card decks either and my phone has more computational power than what we designed most of our nuclear weapons with.”

    Keep it up Cal Insults are the last refuge of a looser who lacks a solid answer.

    When I was a grad student I asked my professors why a full meltdown accident was not a design basis accident. They answered that the probability of a full meltdown was so small we did not have to consider it. And here we are locked in the pre Model T era of nuclear power, having melted several reactors.

    If a meltdown was a design basis accident from the beginning, the Fukushima reactors would have had a core catcher, battery backed hydrogen igniters and accident rated containment vent filters. They would have melted down with a negligible release of fission products. A lot more reactors would be under construction now.

    And now you assure me that a high energy criticality in a sodium cooled plutonium fast neutron reactor is too improbable to worry about. I’m not buying it.

    • Cal Abel says:

      Bill,
      The only source of the size of reactivity insertion you are talking about is through a Core Disruptive Accident, CDA. In order to achieve that the density of the fuel has to come together. To do this the fuel needs to melt. This requires an addition of latent heat to conduct the phase transition from solid to liquid. My confidence is in the physics behind how cores operate and how they fail.

      Each core has a finite about of heat thus the evolution of a core melt is done over a period of time. As John Englert said, “Even in a fast reactor, geometry and time are on your side.” Phase transitions do not happen instantaneously and because of this, melted material is removed from the core inserting negative reactivity. The codes that I referenced in our previous communications take this into account. They model the process based on intentional fuel melting done in EBR-II and have validated the physical approximations.

      The existence or even thought of a CDA can only occur if you make one simplifying assumption. That the core instantaneously melts allowing it to rapidly slump giving you the reactivity insertion you need. This is physically impossible.

      As for the comparisons between fast and thermal reactors. The fraction of delayed neutrons matters based on the driver fuel and the spectrum here is a summary so you can understand the kinetic effects.
      U-233 fast/epithermal 0.0030
      U-235 fast/thermal 0.0065
      Pu-239 fast/thermal 0.0020
      U-238 fast 0.0170

      Solid fueled fast reactors have betas that are on the order of 0.0030 due to U-238 and Pu-239 fissions (direct fission of U-238 is on par with that of Pu-239 at fast energies). This is on par with solid fueled thorium reactors. Molten fueled reactors fast uranium and thermal thorium have betas that are lower because the longer lived DNP decay outside of the core. They are on the order of 0.0027 or so.

      From a kinetic perspective solid fueled breeder reactors thermal thorium or fast uranium will behave identically. They will have the same limitations and concerns. Similarly molten fueled breeders will behave identically wether fast uranium or thermal thorium. Again these reactors will have the similar advantages and limitations.

      You were the one who brought up MSR. I am pointing out the limitations in your pet design as you are sure and have done to point out in anything else LWR or LMFBR. Denigrating one particular design or groups of designs, of which you have a demonstrated propensity shows a fundamental lack of understanding of how a power reactor works as the reason why you demonize one is equally transferable to the other designs when comparing apples to apples.

      As for the argument of liquid vs solid fuel, there you have to understand the assumptions used in deriving the transport equation and then remove those assumptions and take those into account physically. Here the quadrature of the DNP distribution is very complex and impossible to do with existing codes, as they all assume a fixed distribution of DNP. CASL is the first major attempt to integrate T-H and neutronics, however it is for solid fueled thermal reactors and has a large set of empirical data to validate the code.

      The one thing that allows us to control the reactors are the DNP if they are not properly handled in spatial representations then the control of the reactor is in doubt. Additionally, use of the point kinetic model is invalidated by choosing molten fuels. The time dependent solution to the transport equation is very difficult to begin with, removing the assumptions of the PKE will make life very difficult.

      Good luck getting a license in any country without understanding the kinetics of the reactor, much less finding some poor sap to purchase a reactor that they cannot reasonably predict kinetic behavior.

    • Cal Abel says:

      “For example, a large leak drains most of the sodium from the reactor, the core overheats and a large part of it falls into the bottom of the reactor producing a low energy explosion. The blast from that crushes the remaining part of the core against the vessel wall at near supersonic velocity, resulting in a huge fast reactivity insertion. What happens next?

      Terrorists load a jumbo jet with a large cylinder of tungsten and fly it into the reactor building at 600 mph. they get lucky and crush the reactor vessel or spent fuel pool at high velocity squeezing the sodium out of the core in a fraction of a second, resulting in a huge rapid reactivity insertion. What happens next?”

      I suppose the sodium will drain out of the pool that is in the ground because a fault line opens up directly underneath providing an escape path for the sodium…

      Have you ever tried to land an airplane at 60 kts imagine flying down the runway at 600 kts. Now, imagine flying through a small hole about as big around as the airliner’s cabin while pointing the ground at an 80° angle.

      I will worry about those things when I start worrying about the asteroid that is going to hit the planet. You are clueless.

  8. Bill Hannahan says:

    @Brian Mays

    “In both thermal and fast reactors, the neutrons that are necessary to keep the chain reaction going are delayed neutrons. That is, the atom fissions and a few prompt neutrons are produced,”

    As I mentioned to cal, for every 10,000 neutrons in a uranium reactor, 9,935 will be prompt and 65 will be delayed. In a plutonium reactor 9,980 will be prompt and 20 will be delayed.

    “The mean time period for a prompt neutron to cause a new fission event varies greatly between thermal and fast reactors (the difference being the time required for the neutron to slow down before being absorbed).”

    Right, neutrons live about a thousand times longer in thermal reactors.

    “Fortunately, this difference is not significant when it comes to the ability to control a reactor.”

    True during normal operation, but with a huge reactivity insertion the delayed neutrons are insignificant. The long slowing down time makes a big difference in the rate of power increase, the difference between Chernobyl and Hiroshima.

    • Brian Mays says:

      Bill – This stuff has been studied to death, staring with the Bethe-Tait approach and continuing on to more sophisticated analysis that includes effects such as Doppler and better representation of the fuel.

      Your hyperbole about “Hiroshima” is simply unwarranted.

      (And by the way, if your beef is with plutonium reactors, shouldn’t you be comparing it to Nagasaki instead of Hiroshima? Geez … you can’t even get your bombs straight!)

      What I find ironically amusing, however, is that you take the time to lecture Cal about the value of a “core catcher” at Fukushima, when it was a core catcher that caused the meltdown at the Fermi-1 fast reactor. I guess they hadn’t “thought of and modeled every possibility.”

      Sorry, Bill, but I’m not buying your BS. Please take it somewhere else.

      • Daniel says:

        Brian,

        What happened at Nagasaki and Hiroshima after the bombs landed ?

        How long were people kept away ? When did they start reconstructing ?

        When I look at pics of modern Hiroshima and Nagasaki, looks like people were allowed back a long time ago.

        Why was no one afraid of radiations then? Obviously, there are no mutants in those 2 cities !!

        • gmax137 says:

          Daniel, the fission product inventory in a power reactor is vastly greater than that produced in a bomb explosion. The hiroshima weapon yield (about 15,000 ton TNT) is equivalent to around 18,000 MW-hr. A 1000 MWe power plant core generates that in about 6 hours. Considering the plant might run for 12-18 months between refuelings the fission products available for release are then about 1500 times greater than those in the bomb.

          • Brian Mays says:

            A bomb, by its very nature, is designed for maximum dispersal. A nuclear power plant is designed to contain as much as possible in the event of an accident. This is why one worries primarily about the volatile fission products, which are a small fraction of the core’s inventory. The noble gases are not much of a health concern. Almost all of the other stuff either stays where it is or plates out before leaving the containment.

          • John Chatelle says:

            @gmax137;
            A bomb lifts and irradiates a huge amount of ground material instantly, lifts it to thousands of feet, and spreads it around to cloud tops and all lower layers of the atmosphere. That’s most of the fallout, which is the danger after the infrared and gamma flash, and the shockwave. It’s the stuff that gets lifted in the stem of the mushroom, not the fission product that is the culprit of the latter radiation/fallout.

        • Daniel says:

          @ Gmax & Brian,

          This is not quite the answer I am looking for. You can see here pics from Hiroshima and Nagasaki:

          http://collecitonpix.blogspot.ca/2009/04/night-in-hiroshima-and-nagasaki.html

          Beautiful cities and quite a contrast compared to Chernobyl.

          My question is as follows:

          Why did people stay in Hiroshima and Nagasaki and started rebuilding ? Is it because in the aftermath of a nuclear bomb there are only alpha and beta emitters around ? (ie no gamma emissions?)

          Was it because of lack of fear and people just ignored radiations that were obviously harmless and forged ahead ?

          The Hiroshima and Nagasaki situations contain valuable information for the pro nuclear cause once I look at the vitality of those towns. So does a bomb create a less toxic environment once everything has been torn down ? No gamma emissions …

          Ciao

          • Brian Mays says:

            Daniel – Kiev is still a thriving metropolis. The location of the Chernoybl nuclear plant really was the sticks. The only nearby town existed simply to house workers for the plant. It’s not surprising that the area was allowed to remain abandoned. There was no great incentive to reclaim it.

            On the other hand, Hiroshima and Nagasaki were just two of many cities devastated during World War II. So they were rebuilt just like the other cities, which were severely damaged by (non-atomic) bombing campaigns. Have you ever been to Dresden and seen the old buildings that the people had to reconstruct after the war?

          • Daniel says:

            @ Brian,

            Then Japan has all the empirical evidence to resist evacuations of the surrounding areas near Fukushima, to pursue civil nuclear applications and move on with their lives.

            This is what gets to me. Nagasaki and Hiroshima have not been evacuated but Fukushima must.

            There are just too many people not getting this that it makes me wonder why journalists, scholars, the UN and citizens lack the basic and elementary skepticism in face of all this nonsense.

          • John Englert says:

            Daniel,
            Littleboy and Fatman were both detonated high enough so the fireball didn’t contact the surface. Therefor the was very little local fallout; with most of the bomb debris being carried away by upper winds. The dose to people was from prompt gamma and neutron radiation. Persistent radioactivity on the ground was from neutron activation. One might still be able to measure some Eu-152 in the concrete at ground zero.

  9. Bill Hannahan says:

    @Rod
    “I can still call your initial statement false based on what should be rudimentary knowledge of bomb making. The Hiroshima bomb was a gun type device that required an explosive charge to fire a sub critical mass at high velocity into another sub critical mass. That was the only way to add reactivity fast enough to cause the device to achieve prompt criticality – where neutron lifetime is short enough to cause an explosive fission reaction.”

    Rod, you can call my statement wrong, but you would be wrong in doing so. Numerous fast burst reactors have been built and operated fairly reliability in the superprompt critical region without the use of explosives. In another discussion I described how the first Sandia Fast Burst Reactor sometimes sat for many seconds in the superprompt condition, resulting in the addition of a neutron source.

    The Hiroshima bomb would probably have worked using springs or compressed air, but the probability of a full yield explosion would be slightly less. For a power reactor it must be zero.

    “There are no conventional explosives in fast reactors and no way to move the masses of fuel or the neutron absorbing rods around fast enough to achieve the same kind of effect.”

    That is what needs to be proven; you’re saying it does not prove it is true.

    “The Integral Fast Reactor was put through a substantial amount of physical testing that proved its passive safety. There are physics explanations associated with metal fuels and the large pool of sodium.”

    Yes, the IFR can survive some failures like the loss of pumping power with all plumbing intact. That does not prove is will fail gracefully for every set of circumstances.

    Consider this EBR I experiment.

    the system was placed on a period of 60
    seconds at a power of 50 watts. About 3 seconds later the
    power was 1 megawatt, the period had decreased to 0.9
    seconds, and core temperatures were rising significantly.
    The signal to scram the system was given, but by error
    the slow moving motor driven control rods were actuated
    instead of the fast acting scram—dropping part of the
    natural uranium blanket under gravity… This change in
    reactivity caused a momentary drop in power, but was
    inadequate to overcome the natural processes (very
    slight bowing inward of the fuel elements) adding
    reactivity to the system. After a delay of not more than 2
    seconds, the fast scram was actuated, both manually and
    by instruments, and the experiment completed….
    Later examination disclosed that nearly
    one-half the core had melted and vaporized NaK had
    forced some of the molten alloy into the reflector.
    Theoretical analysis showed that the excursion was
    stopped by the falling reflector, after the power reached
    a maximum of 9 to 10 megawatt.

    Rod, we can have clean cheap safe kWh’s for hundreds of years without messing with solid fuel fast neutron reactors. At best their kWh’s will cost more than those from the simplest thermal uranium reactor, conventional or MSR. At worst they will end the nuclear power age for a generation.

  10. Michael R. Himes says:

    The perception that Russians depend on slide rules is crap! Building an article based on western perceptions of what Russian Engineering is about is poor editorial policy. The real issue is a labor force that can no longer produce quality machines. In fact Russian Engineering may far exceed our own in quality. This fact is only made more clear by both Russians and Americans contracting engineering with India because the volume of work exceeds their capacity. Further, the Russian nuclear industry has more vitality than our own NRC dominated and politically driven energy management. That is not to say Vladimir Putin has a closed eye to how much the oil and gas industry provides to Russian income.

  11. David Walters says:

    A Few Questions/Points:

    1. My understanding is that MOX burned in a LWR leaves a LOT of mess; that its waste is a lot “worse” than from a standard non-MOX LWR. What truth is there in this?

    2. The BN-800, as I understand it, is NOT a IFR. It’s a FR without the I. They are also building a set in China.

    3. Russia is not so much a “fossil fuel provider” (It is that) but an exporter of natural gas. But this is limited for them and they want to also export as much a possible. To do this they need a viable alternative to nat gas and they openly state it’s nuclear. Their VVER reactors appear viable and few overseas complain as the Russians *expand* this market, a market that is for sure more a possibility of a growth industry than natural gas is. Thus, it’s my one area of disagreement in terms of motives the Russian have for perhaps doing a bad job on the BN-800. Also, they are building a BN-1000 and BN-1200 and lots more of these.

    David

  12. Bill Hannahan says:

    @Cal
    “The only source of the size of reactivity insertion you are talking about is through a Core Disruptive Accident, CDA. In order to achieve that the density of the fuel has to come together. To do this the fuel needs to melt… The existence or even thought of a CDA can only occur if you make one simplifying assumption. That the core instantaneously melts allowing it to rapidly slump giving you the reactivity insertion you need.”

    This is a very dangerous and false assumption. Crushing the core rapidly, increases the average density of plutonium adding reactivity far faster than a meltdown accident.

    “U-238 fast 0.0170”

    Good point. That helps during normal operation, but delayed neutrons play no role in the superprompt region.

    “From a kinetic perspective solid fueled breeder reactors thermal thorium or fast uranium will behave identically”

    Another false and very dangerous assumption in the superprompt region where neutron lifetime makes such a big difference.

    “Similarly molten fueled breeders will behave identically wether fast uranium or thermal thorium”

    Again false in the superprompt region, but not so dangerous, because fissile and coolant atoms are mixed on the atomic level, it is impossible to rapidly eject the coolant atoms and increase the density of fissile atoms.

    “Denigrating one particular design or groups of designs, of which you have a demonstrated propensity shows a fundamental lack of understanding of how a power reactor works as the reason why you demonize one is equally transferable to the other designs when comparing apples to apples.”

    The implication that all reactor types, fast and thermal, behave similarly in the superprompt region is stunning. If you were a terrorist and had unlimited access to a simple thermal neutron uranium MSR, how would you get it into the superprompt critical region? There would not be enough fuel on site to do that, and even if there was, the reactor vessel would not be large enough to hold it all, and even if it was, you could not load it fast enough to get a significant yield.

    To prove fast neutron solid fuel reactors are safe, model an accident that envelopes all possible accidents. Start with a core early in startup, very low power, K slightly above 1.0 now crush the core into a pancake in 0.1 seconds, squeezing out all the sodium. If the resulting energy burst is reliably contained I’m satisfied. Feel free to do this with a water moderated reactor or MSR.

  13. Bill Hannahan says:

    @Brian
    “And by the way, if your beef is with plutonium reactors, shouldn’t you be comparing it to Nagasaki instead of Hiroshima? Geez … you can’t even get your bombs straight!”

    Brian, my beef is with solid fuel fast neutron reactors. I compared a uranium fueled thermal system with a uranium fueled fast system.

    “What I find ironically amusing, however, is that you take the time to lecture Cal about the value of a “core catcher” at Fukushima, when it was a core catcher that caused the meltdown at the Fermi-1 fast reactor”

    Do you have a reference for that? A core catcher goes under the reactor vessel and is not normally in contact with coolant.

    The story I received from a knowledgeable expert is that someone decided to be helpful and installed a flow baffle that did not appear on the drawings. It fluttered, broke off and blocked a coolant channel.

    • Brian Mays says:

      A core catcher goes under the reactor vessel and is not normally in contact with coolant.

      Yes. That’s the way it works in a design like the EPR. Fermi-1, however, had a core catcher inside the reactor vessel.

      The story I received from a knowledgeable expert is that someone decided to be helpful and installed a flow baffle that did not appear on the drawings. It fluttered, broke off and blocked a coolant channel.

      The “flow baffle” that you refer to was the zirconium core catcher inside the vessel. It wasn’t there to direct flow. If I recall correctly (and I could be wrong on this), its purpose was to divide and separate any corium resulting from a meltdown so that it would not pool together in one big mass and present a criticality problem.

      As you describe, part of the core catcher broke off and caused a blockage leading to core melt accident. In other words, it caused the accident that it was designed to mitigate.

  14. Bill Hannahan says:

    @Cal
    “Have you ever tried to land an airplane at 60 kts imagine flying down the runway at 600 kts.”

    It is not very hard if you know the trick. When you are on a collision course with another plane or stationary object, it does not move on the windscreen, it just gets bigger. Countless times I have flown through tiny translucent wisps of cloud not more than 20 feet in diameter. I can go through the center, left edge, right edge etc., you call it.

    One 9/11 pilot hit the ground floor of the Pentagon in nearly level flight without rolling it up on the ground before impact, unfortunately.

    “Now, imagine flying through a small hole about as big around as the airliner’s cabin while pointing the ground at an 80° angle.
    I will worry about those things when I start worrying about the asteroid that is going to hit the planet.”

    The trick works at 80 deg, but the actual angle and direction would depend on the detailed design of the plant.

    “You are clueless”

    Yet another mature and impressive argument.

    • Cal Abel says:

      Bill,
      No offense to your flying ability. The problem is relative speed. The ability and the exactness that is needed for that control is much more like what the Blue Angles do. I’ve flown most of my life. I do not even consider myself anywhere near the capability or ability of those pilots. Or even a Naval aviator for that matter. They land at 3-4 kts above stall speed on a pitching deck at 130-160 kts. Most pilots never get that precise ability. It is possible, just not likely.

      As for the pentagon. Great example. Thank you for bringing that up. The top of a reactor vessel is very thick on the order of feet as it provides the entire structural support to suspend the vessel, on to of that is a containment. The airliner when it hit the Pentagon, left a hole through the outer ring and punctured the next ring. This is a sturdier building than the WTC’s and a hardened reactor containment is that much stronger. I seem to recall the NRC also has an aircraft impact rule.

      What do you give as the possibility of a terrorist or lets say some hostile country dropping a 2,000# guided munition. I think that would have a much more probable occurance than what you describe. Why don’t we design our reactors to withstand direct hostile attack with modern conventional munitions. Or should we make our reactors to withstand a nuclear device. It makes little sense for a terrorist to attack a reactor (actual harm done is miniscule) It makes a great deal of sense for a hostile country to attack our energy infrastructure with either ballistic or conventional munitions.

      By your logic nothing is safe enough. You are thinking like a scientist not an engineer. There is some cutoff, some level where one has to say, “If we ever get to this point the reactor is the last thing we need to be worried about.” Right now that is ~10^-6/yr. If you want to go lower than that take up the work of Arnie Gunderson.

      Another who uses similar logic wrote a book about the Covair being unsafe at any speed. Except your title would be “The IFR unsafe at any power.” Have at it. Please. A regulatory or policy guideline you can use that is widely accepted is called the precautionary principle. Your logic is consistent with that principle. If you are interested do some work on this, these should give you a good place to start and your background in nuclear engineering would serve to give a good bit of hype and you would make a reasonable amount of sales, especially if you lumped every kind of reactor that exists in there, as they seem to fail to meet your impossible standard. You would have no problem finding a publisher. Also don’t forget to use the idea of collective dose to give really big and scary numbers to the estimated death toll. You could even have Jazcko provide a review on the cover, especially if you justified the 50-mile evacuation zone, hell you could even get Barbra Boxer to write an endorsement at that point. Go off and chase your dreams, you’ll be famous.

    • Cal Abel says:

      BTW,

      The precautionary principle is an argument that relies on the idea the complete knowledge can be obtained. This is akin to the use of ergodic theory in statistics which also happens to lead to a great deal of theoretical inconsistencies and such aberrations as the Copenhagen Interpretation and probability as a physical property. You may abide by all those approaches. Fair enough. The problem where they fail is that they presume complet knowledge of the system, whatever that system is. Hayek called that the Fatal Conceit.

      What we are arguing here comes down to the simple presupposition of what is knowledge and what is knowable. This is a much larger argument than us, and is being waged at a societal level. Your assumption works to a point, but then fails. It fails to acknowledge the other side of the coin and that is the gain that is realized. Here there is a simple way of enforcing the standard. That the implementer of the technology bears the full responsibility for the consequences of its existence, good or bad. You presume that you know what is the risk threshold for that individual. We do far more harm to our society burning coal each year than blowing up a nuclear reactor once every decade ever will.

      Nothing in life is perfect, especially not our knowledge, which is why the comparrison of the alternatives is needed. MSR great idea, much work needs to be done. The alternative to a fast reactor is a coal plant or a natural gas plant. Coal is a problem when burned directly, natural gas is a problem in that wells leak and leak badly at a very real level causing harm to the society.

      I have very little appreciation and tolerance for those who presume that complete knowledge is knowable. My “mature remarks” are a sign of that contempt of your ideas and logic. It is why I think you are a fool.

  15. Bill Hannahan says:

    @Cal
    “The airliner when it hit the Pentagon, left a hole through the outer ring and punctured the next ring.”

    It penetrated 3 rings and did not contain a massive tungsten penetrator.

    “By your logic nothing is safe enough”

    Now you are just making stuff up.

    “Right now that is ~10^-6/yr”

    Your faith in PRA might have been appropriate in the 60’s. How many PRA’s assumed operators would fail to diagnose a small loss of coolant condition until after the core was severely damaged and a shift change brought in some new people who recognized the situation, before TMI?

    How many PRA’s assumed operators would bypass safety system after safety system and run a reactor way outside its envelope until it explodes, before Chernobyl.

    How many PRA’s assumed reactors would be allowed to continue operating after identifying tsunami protection at half the historic record, before Japan.

    “Except your title would be “The IFR unsafe at any power.””

    My position is that it is not proven safe. Some computer modeling indicates that it can survive some events, that does not prove safety. Recall what I found when I reviewed the document you provided as proof the IFR is safe, NUREG-1368.

    “Regarding accommodation of HCDAs, there is not sufficient data to confidently predict the size of an HCDA in a metal fuel ALMR.”… “The major contributors to core melt all lead to energetic core disassembly accidents and Release Category R4A.”…
    “For the R4A no-evacuation case, prompt fatalities were shown to increase from 7 to
    124, and latent fatalities increased from 1,520 to 3,320.

    “The PRISM design has been described as passively safe. On this basis, the designers contend that core melt and sodium boiling do not have to be considered in the design””

    That sounds very similar to “We don’t have to worry about core melt accidents because the PRA proves it will probably never happen.

    “A regulatory or policy guideline you can use that is widely accepted is called the precautionary principle. Your logic is consistent with that principle. If you are interested do some work on this, these should give you a good place to start”

    Heal thyself Cal. If you understood the precautionary principle you would understand that such a person would oppose all new reactor designs. I support the simplified BWR and PWR with passive safety features, the design Rod is working on, and MSR’s, thermal and fast.

    I oppose the IFR until it is proven safe, and I told you how to do that in a previous comment. Why do proponents spend so much time and money modeling a slow meltdown into the bottom of the reactor vessel if it can be shown to contain a high velocity, high reactivity rate criticality that can envelope any real world accident?

    “The alternative to a fast reactor is a coal plant or a natural gas plant.”

    How many IFRs in operation now? How many under construction? A small modular factory mass produced reactor would be a better option.

    “My “mature remarks” are a sign of that contempt of your ideas and logic. It is why I think you are a fool”

    Cal, you reveal more about yourself than about me, and it is not attractive. Good luck with that.

    I am on travel for a few day, you all have fun!

  16. Joris van Dorp says:

    @Bill Hannahan,

    Would you agree that a PACER power plant would be an option that can be proven safe? I’m mean, if the working principle of a nuclear reactor is that you *want* to have nuclear explosions happening, then I guess that means at least you don’t have to worry about *unwanted* nuclear explosions, right? (unless you put in a bomb with a yield that is accidentally too high, but how likely is that going to be)

    For my information: do the experts here believe that PACER is a real option, or is it not worthwhile to consider it before other options?

    • Robert Steinhaus says:

      @Joris -
      There is no energy system that is completely safe, but as a very tiny voice for a technology that today receives little or no practical consideration by virtually anyone, I would like to suggest that there are some good reasons for believing that a PACER power plant would be as safe or safer than any nuclear power plant currently operating.
      What are the reasons for my belief?

      1) PACER is tested fusion technology that has a longer track record than any form of commercial fission nuclear power generation. D-D fusion was demonstrated in the Ivy Mike nuclear test in 1952 (four+ years before the Shippingport Atomic Power Station went online). Since the successful Ivy Mike nuclear test, LANL and LLNL Field Test Divisions have been able to demonstrate practical thermonuclear fusion on demand in over 900 shots at the Nevada Test Site and on the Pacific Test Range. The critical and high tech component of a PACER fusion power plant is the small ultra-clean peaceful nuclear explosive, the rest of the PACER power plant is pretty low or basic tech (a large steel lined cavity with a molten salt breeding blanket and a conventional steam turbine-generator). Fission ignited D-D and D-T fusion works, first time – every time – at the command of the President and has for many decades.
      2) A PACER NPP is buried 100 meters underground. This makes PACER a tougher target than any existing NPP to terrorists or even to actual war time nuclear strikes.
      3) A PNE (peaceful nuclear explosive) is a an example of controlled release of fission initiated fusion energy. At the end of the US Field Test program, the proficiency demonstrated in producing exactly the yield desired from a device under test became so routine that people higher up in government decided that it was no longer important to continue to test the devices in the US arsenal and negotiated a comprehensive test ban treaty. Some fuels are just best exploited by using the fuel to make small controlled explosions. I suggest that D-D and D-T fusion (and gasoline) are such fuels.

      One of the most important benefits of PACER fusion energy is the fact that its fuel is almost inexhaustible, cheap and accessible to everyone. In addition to this, only a tiny amount of fuel is required: operating a PACER fusion power station of 1000 MW for a year requires 250 kg of deuterium-tritium mixture.
      Deuterium is the non-radioactive isotope of hydrogen. Around 0.015% of all the hydrogen on earth is deuterium; a liter of water contains 33 milligrams. This makes deuterium available in copious amounts: the quantity of deuterium in the world’s oceans is estimated at 4.6 x 1013 tonnes. Deuterium can be recovered via electrolysis of water (heavy water is more difficult to electrolyze and remains behind during the electrolysis of water), via the distillation of liquid hydrogen, or using various chemical adsorption techniques.
      The complete conversion of deuterium releases an energy content of 250 x 10^15 joules per metric ton of deuterium. The deuterium present in seawater will therefore yield around 5 x 10^11 TW-year of energy. In the year 2011 the entire world consumed around 16 TW-year of energy, which means that the energy content of the deuterium in seawater would be enough for 31 billion years of energy supply, longer than the sun will burn. In view of the enormous amount of deuterium available, it is important that we learn to use the D-D (and D-T) fusion reaction in the long term.

      Why keep up the fiction that fusion is something that we will not be able to do for at least another 50 years. In fact, PACER style fusion has been demonstrated successfully over 50 years ago, and it remains the practical style of fusion, using fission to ignite the D-D or D-T fusion plasma, that remains the style of fusion that can actually be built and produce real energy today (more power out than the power it takes to run the fusion experiment).

      • Rod Adams says:

        @Robert Steinhaus

        I still don’t get how your technology results in sustained power production. Pointing to successful bursts indicates that you can control a single event, but that is about equivalent to proving that you can carefully control a single burst in a volume of vaporized gasoline. The question I have is how do you make the rest of the required system work? What is the analog of the fuel injectors, the crankshaft, the alternators, the gasoline station, the supply lines to the gas station, the refined fuel, etc.

        It is kind of ridiculous to point to the amount of deuterium in the oceans to calculate the quantity of energy you can produce. One might just as logically point to the carbon contained in the Earth’s atmosphere as a measure of the amount of energy we could provide through combustion.

        • John Englert says:

          Rod,

          If you could make the explosions very small, then direct conversion to electricity could be done via a magnetohydrodynamic system. This has been investigated for space nuclear power with a burst mode, ultrahigh temperature UF4 vapor core reactor .

          • Rod Adams says:

            @John Englert

            Sorry. I think you have mistaken me for a dreamer. Systems that have “been investigated for space” have a long way to go before they are solving real problems here on earth.

        • Robert Steinhaus says:

          @Rod –
          Here Is a quick synopsis of how a Thorium ignited PACER fusion power plant works.

          The PACER cavity, which is 27 meters in diameter and 127 meters length and of cylindrical shape vertically oriented and buried at 100 meters depth in the ground, is first pumped down to a soft vacuum, this reduces that pressure peak experienced inside the cavity while firing the PNE (peaceful nuclear explosive).
          The PNE is lowered on a cable/steel sheathed optical fiber until the device is in a position about 60 meters from the top of the cavity.
          High velocity pumps flood a spray of hot molten salt from nozzles in the roof of the PACER Cavity. This hot salt falls from the roof of the cavity and then collects in a pool at the bottom of the cavity.
          While the molten salt is falling through the PACER cavity from the roof, a large but still commercial fast pulse laser housed on the surface above the PACER cavity fires an intense, short, femtosecond pulse of laser light. This intense burst of laser light compresses and ignites a micro fission pellet of U-233 surrounded by a cryogenic bath of deuterium-tritium forming the fission primary. Laser compression and initiation of the advanced fission primary causes approximately 50% of the atoms of the fissile fuel in the primary to fission. This fission produces high energy gammas and X-rays that pump the fusion secondary while confining the fusion primary using a form of inertial confinement – thereby reliably creating the conditions for D-D or D-T plasma ignition. In excess of 97% of the energy released by the PNE then comes from nuclear fusion (with 99% or greater believed possible for a PACER optimized device). The controlled small PNE explosion produces intense heat which is transferred to the flowing molten salt falling through the partially evacuated PACER cavity. This heat collects in a molten salt pool at the bottom of the cavity. The hot salt stores the heat which is transferred through a heat exchanger and additional engineered heat matching heat reducing apparatus to ultimately be transferred to a conventional steam turbine generator that produces electricity. The stored heat in the molten salt pool permits that PACER power plant to continuously produce power until the next PACER shot occurs (the pacing of PACER shots is a function of device size and the power generation level desired – a small 3kt PNE device must be ignited every half hour to produce a continuous power level of 1GWe from the PACER power plant. LANL implementations of PACER tended to be larger with PACER PNE devices up to 50 kilotons in size. These larger devices might have to be fired only every 8 hours or so to maintain the same 1GWe output from a PACER NPP.

          I would like to suggest that the best way to get a complete and comprehensive idea of how PACER Fusion works is to read Dr. Ralph Moir’s paper “PACER Revisited”
          http://www.osti.gov/bridge/purl.cover.jsp?purl=/6718615-nhbbsq/

          Ralph was the senior nuclear designer at the Lawrence Livermore National Laboratory during the three decades it was my privilege to work at that great Lab. Ralph originated LLNL’s concept of PACER fusion (there was also a large body of additional PACER fusion work performed at LANL independent of LLNL’s efforts)
          I was a member of LLNL Engineering assigned to Field Test Division who was tasked with conducting nuclear tests of both experimental devices and qualified weapons in the arsenal to ensure safety and reliability.
          Dr. Ralph Moir was the designer and very able technology leader of LLNL PACER fusion efforts – I was a tester and technology fixer.

          • Rod Adams says:

            @Robert Steinhaus

            That description does not sound at all like a low capital cost way to provide reliable power. How far did LLNL get in concept development?

            Just to make sure I am clear on the dimensions – are you telling me that the top of the 127 meter tall cylinder is buried 100 meters underground, making the total excavation 227 meters deep and 27 meters in diameter? Is all of the rest of the equipment on the surface or did you plan on putting all of the salt piping and pumps, along with the steam power plant and the control room underground? Did you plan to use a Plowshares type device to get that done?

          • Brian Mays says:

            Did you plan to use a Plowshares type device to get that done?

            Well, if all you have is a hammer …

          • Robert Steinhaus says:

            @Rod – The question of the economics of PACER fusion is a bit challenging to answer. The actual size of PACER optimized PNEs is tiny compared to conventional nuclear devices. The amount of nuclear fuel, both U-233 fissile and Deuterium fusion fuel is very small. Only about 20 grams of Deuterium is required to produce 99% of the energy generated by the D-D fusion PACER device. A D-T fusion based PNE, which might be the first style available, would require about 11 grams of Deuterium and 16 grams of Tritium for a 3 kiloton PNE. Modern designs should allow shrinking the size of the fission primary dramatically, to require only what would normally be considered “subcritical” amounts of fissile through incorporation of an advanced high efficiency fission primary requiring laser initiation. Remote Robotic manufacture of the PACER devices combined with “just in time” addition of the fission and fusion fuel right before the device is used in the PACER power plant greatly reduces the risk of a PACER PNE being stolen and used for some illicit purpose. No PACER device would ever be shipped in a condition where the nuclear fuels were loaded. If a terrorist stole a PACER PNE that had been produced at a robotic factory, all he would get for his effort is a couple of small castings and some sheet metal that he could hold in his hand, nothing that would be explosive or interesting.

            Back in the early 1970s, AEC offered a 50 kiloton device to US industry as part of the Plowshare program for $50,000 dollars per device. Much smaller, robotically assembled PACER devices consisting of a couple of small castings and sheet metal that yield only 3 kt that you literally can hold in the palm of your hand should bring the price down dramatically, hopefully to something on the order of $2000 per device or less. A large commercial fast pulse laser may need to sit on the surface to direct an intense powerful 60 femtosecond pulse of light into the PNE to ignite it, but this laser is not destroyed in the successive PACER explosions and is used over and over again on successive PACER shots.

            Aside from the PACER PNE device itself, the rest of PACER is pretty low tech. The PACER cavity must sustain a pressure wave of about 30 MegaPascals of pressure and a 0.2 meter (8 inch) thick wall of SS316 stainless steel should be able to take the pressure and heat and provide a lifetime in excess of 200,000 PACER shots. A PACER cavity, such as LLNL’s Dr. Ralph Moir designed was 27 meters in radius and 127 meters in length. The total volume of stainless steel required to fabricate this artificial cavity is 4283.36 m^3 of SS316 steel. The density of SS316 steel is about 8000 kilograms per m^3, so the total mass of stainless steel required to make the PACER cavity is 34291 metric tonnes. Steel vendors in China are willing to supply stainless SS316 for as little as $750 per tonne but $1000 per ton may be a better cost estimate from US suppliers.

            The cost in SS316 stainless steel to build a PACER cavity 27 meters radius x 127 meters long x 0.2 meters thick is about $34.3 million dollars.

            The world needs at least another 10 TWe of power [1] by 2050. This corresponds to starting 10,000 new 1GWe LFTRs. To start this number of LFTRs requires a very large supply of fissile U-233 to form the initial LFTR startup charges (about 8000 metric tonnes of U-233). This fissile could be quickly provided by a relatively small number of Thorium PACER fusion reactors. A small number of Thorium PACERs could contribute to LFTR’s rapid success by manufacturing new LFTR startup fissile core charges faster than any other competing fuel manufacturing technology.
            [1] – http://bit.ly/aglriT

            Thorium PACER is in my view complementary nuclear technology to Thorium LFTR. PACER permits rapid production of rare U-233 to produce the startup charges for new LFTR reactors. A calculation by Dr. Walter Seifritz of PACER U-233 breeding potential when operating using D-D fusion indicates that a 1 GWe PACER could be expected to produce about 20.3 metric tons (20,300 kilograms) of U-233 per year in a PACER fission suppressed Thorium breeding blanket. This is enough U-233 to start about twenty-five conventional 1 GWe Thorium LFTRs per year or about fifty 1GWe LFTRs that use quick change-out replaceable high flux density reactor cores.
            As a contrast, the 1 GWe ORNL MSBR (ORNL-3996) was expected to breed about 37 kilograms of U-233 per year (the U-233 fuel doubling time for the MSBR was about 11 years).

            A 1GWe D-D fusion Thorium PACER reactor with a fission suppressed Thorium breeding blanket should produce 548x times or (54800%) the U-233 produced by a 1GWe ORNL MSBR in a year.

            If you want to start a large number of LFTRs in a hurry and operate them in the Thorium Fuel Cycle where they produce the minimum amount of nuclear waste, it is beneficial to have one or more Thorium PACER fusion reactors operating alongside to make U-233 startup fuel charges for the new LFTR reactors.

            The waste produced from D-T nuclear fusion is only non-radioactive helium (although the very high fluence of fusion neutrons can neutron activates the SS316L metal walls of the PACER cavity). LLNL’s PACER cavity was designed for a lifetime in excess of 200,000 PACER shots which is over 30 years of commercial operation. The highest cost portion of a PACER power plant is the conventional Rankin cycle steam turbine-generator which has a cost of $300 million dollars or less. The total cost of a 1GWe PACER plant is estimated at about $450 million including the PACER cavity and fast pulse laser. Compared to the costs of other forms of nuclear, the upfront capital costs of PACER fusion power plants are low. To compete on operational costs with conventional LWRs, the cost of PACER PNEs would have to be about $2000 each (or less). LLNL and LANL designers believed that they could provide PNEs that would satisfy all the requirements needed for practical PACER power plants. Buried 100 meters underground, it is suggested that rather than digging up a PACER power plant to decommission it, you instead cement over the surface entries to the plant and abandon it. This produces a lower PACER decommissioning cost than most forms of nuclear power generation.

  17. Michael R. Himes says:

    I can’t help but notice the commentary trend toward rehashing old times in nuclear engineering. Granted it comes from years of experience and training and that is good but it narrows the scope of the discussion to theory that is 30 years old. The issue is when one retires a void is left in the work force. No one is being trained for an industry that is hobbled by government control and a biased banking industry. After all, what is the incentive to do so when planning a 35-40 year career path? I believe there are a few options available for a graduate engineer in nuclear science. One of the options is joining an R & D team to produce modular and new technology reactors. The other is to train a new generation of technical staff to operate existing nuclear plants and to decommission plants long past their designed life. One other is to learn to produce energy via new technology now being considered by our national laboratories like ORNL, Sandia Labs and Livermore Lab. If one considers nuclear power dangerous then correct the problem and build better with new talent and new technology…it is just that simple!

  18. Robert Steinhaus says:

    Michael R. Himes briefly explored what options are available for a graduate engineer in nuclear science. I would like to add one additional choice to the list he provided.

    A graduate engineer in nuclear science has the option to take the skills in nuclear engineering or physics that he has acquired and put them at the service of those who oppose progress in the field of his training (nuclear technology). This approach has worked well as a career path for Dr. Edwin Lyman of the Union of Concerned Scientists, who went directly from academia to active opposition to nuclear technology without spending any time in the industry he regularly fights to limit. Another example in this same vein is Dr. Gregory Jaczko, who upon graduating with a PhD in Physics, went directly into the service of Representative Edward Markey as a staff member, and employed his skills acquired through formal training in Physics to craft regulation that hinders and impedes the wider expansion of commercial nuclear energy.
    As a young man I tended to admire engineers because I thought that they usually try to build things that are of value to society. It is saddening that a significant fraction of the engineers and physicists graduating today use their technical skills immediately to invent blocks and hindrances, generally in the way of crafting of new laws and regulations, that are designed to slow technical progress and advancement in their chosen field of nuclear technology.

    • Rod Adams says:

      @Robert

      Your two examples of Lyman and Jaczko – and several others I can think of – were physics majors whose studies had little or nothing to do with the production of useful energy by nuclear fission. Because the American media and general public tends to think of “scientists and engineers” as being essentially the same category, those two gentlemen were able to convince people that they had valid credentials for being critics of nuclear energy production. Even within the technical community there is little understanding that some physics majors do not study anything that is practical – instead they spend their time thinking of ways to describe & model the low energy behavior of baryons and mesons or other such theoretical minutia.

  19. John Tucker says:

    Im am thankful for the detailed discussion and appreciate the links. “Nuclear Power” was never one technology and letting the anti nukes set the tone by discussing it incorrectly in that framework has been a huge mistake.

    Japan kinda sortof announced plans to abandon nuclear technology in electricity production today. Again little reason/science and pure politics. ( http://www.nytimes.com/2012/09/15/world/asia/japan-will-try-to-halt-nuclear-power-by-the-end-of-the-2030s.html?pagewanted=2&hp )

    On the topic of Russians sabotaging fast reactor progress – I dont know about that considering the amount of spent fuel they have and the supply problems they recently experienced with their gas empire. Also wouldn’t the IAEA step in and publicize the matter if they were behaving foolishly?

    • Rod Adams says:

      @John Tucker

      It is difficult to do large projects correctly. Even when everyone is trying hard to do the right things with good leaders making good choices there are going to be challenges along the way. If the top leadership is not really interested in a standout success story that can be followed with a massive buildout of repeated projects, there are many ways to slow things down that would not attract any attention as being unusual.

      For example – have you heard anything recently about the floating nuclear power reactors that Russia has been talking about building for at least 15 years.

      http://atomicinsights.com/1996/07/news-july-96.html

      Here is a more recent article from 2011 indicting that the Russians are still making progress and plan to start operating the first of 8 floating nuclear power stations in 2012.

      http://www.aljazeera.com/video/asia-pacific/2011/06/201161475512754605.html

      • John Tucker says:

        I kinda remember the stories about a “reactoron a barge” in the press. Certainly it seems they put a lot more thought into it than that. If they can get the concept working properly I dont think there will be a problem finding good uses to put it to. I wish we would have worked on that.

  20. Gunnar Littmarck says:

    Good post Rod Adams:
    I guess that when the Indian step two goes critical next year and has as one purpose to produce new Pu239 from a blanket of U238 for use as fuel in coming reactors, the debate will changes in our countries.
    Sellafield think they have a problem with 100tons of plutonium and India will breed U238 just to get Plutonium…
    Another good thing with the Indian way, is that it also can produce U233 from Th232,
    I’m a fan of MSR so I want plenty U233.

    My best //gunnar

  21. Robert Steinhaus says:

    @Rod – (From earlier Fusion thread)
    You are correct on the dimensions of the LLNL molten salt version of PACER. The PACER cavity is formed from SS316L stainless steel and is 27 meters in diameter and 127 meters long and is about 0.2 meters (or 8 inches) thick. This device is about the size of a US football field with end zones turned vertical buried 100 meters in the ground (the top of the PACER cavity is 100 meters below the ground surface).

    The question of the economics of PACER fusion is a bit challenging to answer. The actual size of PACER optimized PNEs is tiny compared to conventional nuclear devices. The amount of nuclear fuel, both U-233 fissile and Deuterium fusion fuel is very small. Only about 20 grams of Deuterium is required to produce 99% of the energy generated by the D-D fusion PACER device. A D-T fusion based PNE, which might be the first style available, would require about 11 grams of Deuterium and 16 grams of Tritium for a 3 kiloton PNE.

    Modern designs should allow shrinking the size of the fission primary dramatically, to require only what would normally be considered “subcritical” amounts of fissile through incorporation of an advanced high efficiency fission primary with laser initiation. Remote Robotic manufacture of the PACER devices combined with “just in time” addition of the fission and fusion fuel right before the device is used in the PACER power plant greatly reduces the risk of a PACER PNE being stolen and used for some illicit purpose. No PACER device would ever be shipped in a condition where the nuclear fuels were loaded. If a terrorist stole a PACER PNE that had been produced at a robotic factory, all he would get for his effort is a couple of small castings and some sheet metal that he could hold in his hand, nothing that would be explosive or interesting.

    Back in the early 1970s, AEC offered a 50 kiloton device to US industry as part of the Plowshare program for $50,000 dollars per device. Much smaller, robotically assembled PACER devices consisting of a couple of small castings and sheet metal that yield only 3 kt that you literally can hold in your arms should bring the price down dramatically, hopefully to something on the order of $2000 per device or less. A large commercial fast pulse laser may need to sit on the surface to direct an intense powerful 60 femtosecond pulse of light into the PNE to ignite it, but this laser is not destroyed in the successive PACER explosions and is used over and over again on successive PACER shots.

    Aside from the PACER PNE device itself, the rest of PACER is pretty low tech. The PACER cavity must sustain a pressure wave of about 30 MegaPascals of pressure and a 0.2 meter (8 inch) thick wall of SS316 stainless steel should be able to take the pressure and heat and provide a lifetime in excess of 200,000 PACER shots. A PACER cavity, such as LLNL’s Dr. Ralph Moir designed was 27 meters in radius and 127 meters in length. The total volume of stainless steel required to fabricate this artificial cavity is 4283.36 m^3 of SS316 steel. The density of SS316 steel is about 8000 kilograms per m^3, so the total mass of stainless steel required to make the PACER cavity is 34291 metric tonnes. Steel vendors in China are willing to supply stainless SS316 for as little as $750 per tonne but $1000 per ton may be a better cost estimate from US suppliers.

    The cost in SS316 stainless steel to build a PACER cavity 27 meters radius x 127 meters long x 0.2 meters thick is about $34.3 million dollars.

    Fissile Requirements required to start production of energy at this 1 GWe level for PACER, LFTR, LWR, IFR and the cost to provide the fissile startup material-
    IFR – 18000 kilograms (costs $1.8 billion)
    LWR – 5000 kilograms (cost $600 million)
    LFTR – 800 kilograms (costs $24 million)
    PACER – 2.5 kilograms (cost $75 thousand)

    The cost of fissile can be a significant part of the cost of starting up a nuclear reactor. The Russians are the current low cost suppliers of fissile materials at about $30,000 per kilogram HEU. The cost of providing the startup fuel for a 1 Gwe IFR may be understated, as an IFR would probably use Pu-239 as its fuel rather than mined and enriched U-235. It is hard to establish a price on Pu-239 which does not trade commercially.

    The highest cost portion of a PACER power plant is the conventional Rankin cycle steam turbine-generator which has a cost of $300 million dollars or less.

    The total cost of a 1GWe PACER plant is estimated at about $550 million including the PACER cavity, the PACER chemical recycling plant ($34 million) that separates bred U-233 from a fission suppressed Thorium blanket, and a commercial fast pulse laser.

    Compared to the costs of other forms of nuclear, the upfront capital costs of PACER fusion power plants are low. To compete on operational costs with conventional LWRs, the cost of PACER PNEs would have to be about $2000 each (or less). LLNL and LANL designers believed that they could provide PNEs that would satisfy all the requirements needed for practical PACER power plants. Buried 100 meters underground, it is suggested that rather than digging up a PACER power plant to decommission it, you instead cement over the surface entries to the plant and abandon it. This produces a lower PACER decommissioning cost than most forms of nuclear power generation.

    The world needs at least another 10 TWe of power [1] by 2050. This corresponds to starting 10,000 new 1GWe LFTRs. To start this number of LFTRs requires a very large supply of fissile U-233 to form the initial LFTR startup charges (about 8000 metric tonnes of U-233). This fissile could be more quickly provided by use of a relatively small number of Thorium PACER fusion reactors. A small number of Thorium PACERs could contribute to LFTR’s rapid success by manufacturing new LFTR startup fissile core charges faster than any other competing fuel manufacturing technology.

    Thorium PACER is in my view complementary nuclear technology to Thorium LFTR. PACER permits rapid production of rare U-233 to produce the startup charges for new LFTR reactors. A calculation by Dr. Walter Seifritz of PACER U-233 breeding potential when operating using D-D fusion indicates that a 1 GWe PACER could be expected to produce about 20.3 metric tons (20,300 kilograms) of U-233 per year in a PACER fission suppressed Thorium breeding blanket. This is enough U-233 to start about twenty-five conventional 1 GWe Thorium LFTRs per year or about fifty 1GWe LFTRs that use quick change-out replaceable high flux density reactor cores.
    As a contrast, the 1 GWe ORNL MSBR (ORNL-3996) was expected to breed about 37 kilograms of U-233 per year (the U-233 fuel doubling time for the MSBR was about 11 years).

    A 1GWe D-D fusion Thorium PACER reactor with a fission suppressed Thorium breeding blanket should produce 548x times or (54800%) the U-233 produced by a 1GWe ORNL MSBR in a year.

    If you want to start a large number of LFTRs in a hurry and operate them in the Thorium Fuel Cycle where they produce the minimum amount of nuclear waste, it is beneficial to have one or more Thorium PACER fusion reactors operating alongside to make U-233 startup fuel charges for the new LFTR reactors.

    The waste produced from D-T nuclear fusion is only non-radioactive helium (although the very high fluence of fusion neutrons can neutron activate the SS316L metal walls of the PACER cavity and this can take decades to decay back to the level of the natural background). LLNL’s PACER cavity was designed for a lifetime in excess of 200,000 PACER shots which is over 30 years of commercial operation.

    [1] – http://bit.ly/aglriT

  22. Robert Steinhaus says:

    @Rod –
    You are correct on the dimensions of the LLNL molten salt version of PACER. The PACER cavity is formed from SS316L stainless steel and is 27 meters in diameter and 127 meters long and is about 0.2 meters (or 8 inches) thick. This device is about the size of a US football field with end zones turned vertical buried 100 meters in the ground (the top of the PACER cavity is 100 meters below the ground surface).

    Aside from the PACER PNE device itself, the rest of PACER is pretty low tech. The PACER cavity must sustain a pressure wave of about 30 MegaPascals of pressure and a 0.2 meter (8 inch) thick wall of SS316 stainless steel should be able to take the pressure and heat and provide a lifetime in excess of 200,000 PACER shots. The total volume of stainless steel required to fabricate this artificial cavity is 4283.36 m^3 of SS316 steel. The density of SS316 steel is about 8000 kilograms per m^3, so the total mass of stainless steel required to make the PACER cavity is 34291 metric tonnes. Steel vendors in China are willing to supply stainless SS316 for as little as $750 per tonne, but $1000 per ton may be a better cost estimate from US suppliers.

    The cost in SS316 stainless steel to build a PACER cavity 27 meters radius x 127 meters long x 0.2 meters thick is about $34.3 million dollars.

    Fissile Requirements required to start production of energy at this 1 GWe level for PACER, LFTR, LWR, IFR and the cost to provide the fissile startup material-
    IFR – 18000 kilograms (costs $1.8 billion)
    LWR – 5000 kilograms (cost $600 million)
    LFTR – 800 kilograms (costs $24 million)
    PACER – 2.5 kilograms (cost $75 thousand)

    The cost of fissile can be a significant part of the cost of starting up a nuclear reactor. The Russians are the current low cost suppliers of fissile materials at about $30,000 per kilogram HEU. The cost of providing the startup fuel for a 1 Gwe IFR may be understated, as an IFR would probably use Pu-239 as its fuel rather than mined and enriched U-235. It is hard to establish a price on Pu-239 which does not trade commercially.

    The highest cost portion of a PACER power plant is the conventional Rankin cycle steam turbine-generator which has a cost of $300 million dollars or less.

    The total cost of a 1GWe PACER plant is estimated at about $550 million including the PACER cavity, the PACER chemical recycling and fuel manufacturing plant ($34 million) that separates bred U-233 fissile from a fission suppressed Thorium blanket, and a commercial fast pulse laser.

    Compared to the costs of other forms of nuclear, the upfront capital costs of PACER fusion power plants are low. To compete on operational costs with conventional LWRs, the cost of PACER PNEs would have to be about $2000 each (or less). LLNL and LANL designers believed that they could provide PNEs that would satisfy all the requirements needed for practical PACER power plants. Buried 100 meters underground, it is suggested that rather than digging up a PACER power plant to decommission it, you instead cement over the surface entries to the plant and abandon it. This produces a lower PACER decommissioning cost than most forms of nuclear power generation.

    • Rod Adams says:

      @Robert

      Do you realize how small a portion of the cost of a nuclear power plant is in the material? The amount of cost in the material of the reactor pressure vessel is far smaller than that.

      Much larger contributors to cost are financing, labor, welding, NDE, quality assurance paperwork, regulations, construction, inspections, site preparation, excavation, transportation, etc.

      Your cost estimating skills must have been developed in a national laboratory.

      • Robert Steinhaus says:

        Thorium Ignited PACER Fusion – Practical fusion to fully power the planet longer than the earth has existed or our sun will burn

        My cost estimating skills were developed at a National Laboratory (and a great one).
        I will freely admit that my estimation of cost is sketchy, but it is a first pass, I have tried to identify the major costs and cost drivers of a PACER power plant and to put those elements clearly before you. Cement and steel tend to dominate the cost of construction of new nuclear plants. While large in physical size, a PACER cavity is only moderate in its use of steel, and downright conserving in its use of reinforced concrete, relative to other forms of nuclear generating the same 1 GWe power output. Things like regulatory costs, quality assurance paperwork, inspections, etc. are difficult to evaluate for a first of a kind technology and would have to be added for a better and more comprehensive cost estimate.

        I would like to emphasize that virtually all elements of PACER fusion have already been proven to work by LLNL and LANL Field Test Divisions. There are no areas of significant technical risk left to disincline decision makers and energy planners from actively considering building nuclear technology producing huge qualities of energy from nuclear fusion. America should revaluate Thorium PACER and Thorium LFTR and use these technologies to help lift the American economy and solve climate problems while reducing the likelihood of future wars over resources that will otherwise have to be fought to secure access to diminishing sources of fossil fuels. There is no justification for the widespread, but quite incorrect belief that fusion is always and will always be only 50 years away, and as a result fusion is of no practical interest or concern. America should not fail to secure the benefit that could be had by using its two currently unused but abundantly available nuclear fuels, Thorium and Deuterium. Thorium Molten Salt Reactors and practical PACER fusion power plants should not be kept on the technical sidelines and effectively suppressed by widely held but incorrect beliefs that these technologies are somehow not ready, or not economical, or not safe, as they are none of those things.

        PACER fusion is the cheapest form of nuclear power generation when the full lifecycle from construction of the power plant to its final decommissioning is considered. PACER fusion is also a practical form of energy generation that does not depend on technical breakthroughs to make practical, but could practically produce Gigawatts of power from fusion in a successful prototype with very high certainty in less than 3 years.

        Over 80 tunnel shots were conducted at NTS that entailed drilling large carefully shaped caverns up to 1/4 mile in length and large enough to drive several large tanks and military vehicles into and those shots were performed at a total project cost of on average about $10 million dollars each (1974 dollars). In Amchitka Alaska LANL and LLNL field test division dug shot holes of over 1 mile in depth
        (6,104 ft or 1,800 meters, considerably deeper than PACER’s 227 meters) and successfully performed the Cannikin nuclear test in 1971 with a yield of 5 megatons (21 Peta-Joules) underneath a frozen Aleutian Island. Cannikin was a very deep shot in a very hostile and remote location and cost Field Test Division closer to $200 million to perform.

        Why not use a practical form of nuclear fusion that is ignited reliably by nuclear fission that produces less waste (non-radioactive helium) to improve the conditions of people around the world and sustainably produce all the power the planet needs at a 30 Terawatt level from Deuterium for 31 billion years (practical power longer than the earth has existed or our sun will burn).

        • Rod Adams says:

          @Robert Steinhaus

          Cement and steel tend to dominate the cost of construction of new nuclear plants.

          That may be true in text books. It is an incorrect statement in real life.

          I’ve been a member of a large and growing team of people assigned the task of preparing an application for a license to build a new light water reactor power plant for just over 2 years. Without releasing any competitive information, I can tell you that our team includes several hundred professionals. We have been holding numerous meetings with the Nuclear Regulatory Commission (NRC) in the pre-application phase. The very first one was “free”; all others are billed to my employer at the current rate of $279 per hour per regulator. As is the case when you work with attorney’s, that clock runs every time there is an interaction and all the time that is spent between meetings reviewing the detailed documents that are turned in during the meeting.

          We might be ready to submit the application we have been working on since before my arrival sometime within the next 6 months. After that application is submitted, there is a minimum of 42 months worth of review by the NRC. They will be reviewing a carefully prepared document that I expect might be as long as 20,000 pages – the INSTRUCTIONS for preparing that document are about 4,600 pages long.

          However, the DCA (design certification application) is just a summary document; the statements of fact that are included in that document require detailed supporting technical information that includes computer codes, calculations, and drawings. Every document has to have a traceable pedigree prescribed by detailed procedures and independently verified by individuals or groups not involved in the initial design work. All of the work is subject to regulatory review at the bargain price of $279 (which will escalate with inflation & cost of operating NRC). Getting to the point of a design certification rule will probably cost in excess of $100 million in NRC fees alone.

          Also during the review process, our team will have to expand significantly in order to allow completion of the detailed design work. A certified design is not detailed enough for actual manufacturing or construction.

          We have not spent ANY money on cement and steel.

          • Robert Steinhaus says:

            @Rod – I would just like to say I am grateful to have the insights provided by your comment regarding realistic evaluation of the cost of nuclear. Clearly, those that have fought the battle and have labored to push a real reactor through NRC regulatory review know the difficulty of that task.

            A (few) final words -
            The very first US thermonuclear test (Ivy Mike) conducted in 1952 was in fact an example of controlled D-D fusion. Ivy Mike produced far more energy out than was required to initiate the ignition of the fusion plasma. Diffuse energy ignited fusion experiments that use tokomaks and laser fusion to ignite fusion plasma do not produce any energy gain and all produce a Q factor of less than one (less energy out than it requires to run the fusion experiment). In 1952, the Ivy Mike test demonstrated that LLL Field Test Division could produce practical D-D fusion on demand at huge levels of power generation (10.4–12 Megatons) with a Q> 100,000 (you got 100,000 times the energy out of the Ivy Mike test device as the energy it took in chemical explosives to initiate the fission primary that drove the thermonuclear D-D fusion secondary.

            Today, we can make practical energy generation systems that produce huge practical amounts of energy on a controlled continuously basis from D-D fusion. This energy system is called PACER.
            http://www.yottawatts.net

            Note (warning based on a historical event): When a physicist of the excellence of Edward Teller sends you a telegram stating only “It’s a boy”, it might not mean what you think.

            At least that was the experience of the small team of weapons developers at Los Alamos X-Division when they received word in the form of an unclassified telegram from Teller that the Ivy Mike test had worked.

  23. Bill Hannahan says:

    @Cal
    “When the (MSR) reactor is scaled up leakage will go down and the flux will flatten out. This loss of a spatial shape will lead to flux instabilities.”

    Sometimes true for large solid fuel reactors due to the delayed generation of xenon which is a neutron poison. How does this happen when the xenon fission product precursors are continuously mixed in the cooling loop and the xenon gas comes out of the molten salt as it is created. Explain the actual physics, no computer jargon.

    “If you take the neutrons as a thermodynamic system the flux instabilities are like boiling of water. It is a phase transition. It is an entirely new phenomena that we don’t fully understand yet.”

    I have never seen anyone else make this claim for a MSR. Are you proposing salt boiling during normal operation? Explain the actual physics or provide a reference, no computer jargon.

    Obviously a team designing a large MSR (or IFR) will have to demonstrate safety, first with computer models and then with a full scale prototype. I expect this to be much easier for the MSR due to the low excess reactivity and impossibility of very fast, very large, reactivity additions.

    Cal, still waiting for your response to this question of January 6, 2012 at 2:59 PM.

    I will ask for the third and last time. Define instability. What is the exact mechanism of the instability? Assume that mathematics and computers have not been invented, just explain what actually happens based on fundamental principles of nature.

    “My critique of your claims to build a large LFTR is on the basis of the flux instability due to low leakage.”

    Consider the following thought experiment. Imagine the MSRE running at a steady 5 MW. Now increase the diameter of the reactor to infinity and reduce the concentration of the fissile atoms to maintain k=1. Now increase the height of the reactor to 50 feet and reduce the concentration of the fissile atoms to maintain k=1. We have no radial leakage and negligible leakage from the ends.

    Imagine we are riding on an incremental volume of fuel salt approaching the core. We see a rapid increase in neutron flux and in fission rate. As we enter the core, flux, fission rate and temperature are increasing. As the fuel heats up its reactivity is decreasing. Soon the power peaks, but the fuel continues to heat up at a decreasing rate. In this long core, the fission rate and neutron flux drop very low at the discharge end, so very low leakage.

    Now imagine we perturb the core by injecting neutrons into a region of the core near the entrance. We double the flux in a zone about 10 feet in diameter for 30 seconds. The fuel passing through that region heats up much faster than before. The graphite also heats up, but slowly.

    When the extra neutrons are cut off, fuel in that region and downstream is warmer than it was in equilibrium, suppressing the fission rate a bit until the excess heat is carried away, and the equilibrium profile is restored.
    Most importantly, fuel flowing into that zone has no memory of the neutron pulse. It may see slightly warmer graphite for a while, and that will suppress fission slightly until equilibrium graphite temperature is restored.

    Perform the same experiment in a solid fuel reactor and the fuel will have memory of the neutron pulse, in the form of additional xenon precursor fission products in that region of the core. The xenon will show up and suppress the flux in that region, perhaps starting an unstable oscillation.

    So Cal, how do you get power oscillations in a molten core if the core has no spatial memory of the power history of the core?