Accelerator Driven System promoters are playing to irrational antinuclear fears

By Ed Pheil

I mentioned at the Thorium Energy Conference 2013 that accelerator driven systems (ADS) were likely to hurt the nuclear industry more than help it with the following discussion.

The ADS proponents are justifying their participation, including with thorium, on the basis of two concepts that cater to the anti-nuclear crowd.

A) ADS supporters imply that nuclear reactors can blow up like a bomb. They imply this by saying we should not allow reactors to go critical. They think ADS systems are needed because they allow the reactor to stay subcritical, and inject the extra needed neutrons to create power. In actuality, commercial nuclear reactors have NEVER had a problem with criticality problems coming any where near a risk to the public. Also, to minimize the power of the accelerator needed you need to keep the reactor very close to critical, so it still needs control rods. That means you can STILL have the same criticality accident risk with rods, plus a steam line rupture equivalent accident that could take you critical. If the keff is too high and you turn on the accelerator at too high a neutron generation rate, you could also take the reactor super-prompt critical; being able to shut down the accelerator as claimed by the ADS community would not help you.

B) ADS advocates also say that transuranics (TRU’s), also known as minor actinides (MA) in Europe, ARE a major problem, again catering to the anti-nuclear community. All of the MA’s in the world would not fill the room we were in at the conference center, barring criticality control and cooling systems. That is, only the MA’s after reprocessing by removing the air, cladding, useful fuel, and fission products (FPs). Spent fuel with all those things un-reprocessed would only cover 1 football field to a depth of 7 meters. So, there is no possible way that either spent fuel and, especially MA’s/TRUs, are a real waste problem because the volume of waste is SO VERY TINY.

The only real issue is that countries like the US and many others do NOT REPROCESS fuel because they fear proliferation. LWR fuel has too much 240Pu, so is NOT weapons grade, and can’t easily be used for weapons. Further, I said that MAs/TRUs may have a half-life of 10,000 years, but, with such a small volume, why does it matter — from a purely technical point of view. The toxic waste from coal, solar, wind, etc. could bury Geneva in toxic waste that has an INFINITE half-life; it lasts forever. And those wastes are not nearly as well controlled as nuclear waste.

At the very least we must weigh the risks of the different wastes on a fair basis and not treat nuclear waste as if it should be burned at the stake for being a witch (it was Halloween). They challenged me, saying that I did not care about getting rid of nuclear waste. I said that the normal environmental method is to reduce the production of waste. That can be done with liquid fueled reactors and fast breeders. It is not done by building more LWR’s and producing more waste so that the ADS reactors have enough Pu for fuel with the Th reactors. ADS advocates have it backwards on reducing waste; they say we need to produce more and then use the ADS to get rid of it.

Then I went over what I thought were the top three most important things to work on for future reactor designs to improve them

1) We must ensure that decay heat can be removed for an infinite grace period with NO power available. The ADS system does not address that explicitly. It makes it worse because it adds a huge high power accelerator that can overheat, cause huge capital losses, injuring the utility financially if repairs are required. The reactor that goes with the ADS system would have to address the decay heat removal, but that is no different from a reactor of the same type without the ADS, so there is no advantage.

2) We should reduce the potential of fission product dispersal from all reactor designs.
a. Water has high pressure steam blow down, steam-zircalloy exothermic reactions producing hydrogen that can explode, damaging the both the reactor vessel containment, and the large containment, i.e. the two other barriers to FP dispersal. I assume that FP’s have already been released to the coolant if the steam – zirc reaction is occurring, which is the first FP barrier of the three. These are all instigated by failing to successfully address criteria 1 above. Water-cooled reactor designers have to take these risks into account and provide mitigations like hydrogen recombiners and high pressure capable containment vessels or filtered vents.

b. Sodium cooled reactors have little or no pressure, but have air and water exothermic reactions that can break containment and/or disperse FP’s. Designers have to provide mitigations like large pool coolant systems and double tube heat exchangers.

c. Gas reactors have high pressure blowdown dispersive mechanisms, and the solid fuel could still overheat, depending on the design. Ensuring fuel integrity under accident conditions is a significant design challenge.

d. Pb and Pb/Bi have no pressure but tend to have steam cycles in the primary heat exchangers due to the need to limit temperatures to control corrosion. The corrosive nature of Pb coolants in the past has led to high corrosion in the heat exchangers, and occasional leaks of the higher pressure water into the Pb coolant. That can cause a steam explosion, which provides a dispersive mechanism of toxic and radioactive 210Po contamination, as well as any fission products that pass the fuel cladding due to corrosion in Pb/PbBi.

e. Liquid fueled (LF) Fluoride (F) or chloride (Cl) MSR reactors have low pressure, do not react aggressively/exothermically with air or water, would have an intermediate loop so the power loop would not be adjacent to the primary loop. Even if a volatile power cycle fluid like water is used, any steam explosion is not on primary coolant/FP’s, and air or nitrogen could be used in the high temperature power cycle. LF reactors can be designed to constantly remove gasses from the reactor, and require systems designed to protect them, so any reactor accident would have very little FP gasses to release.

The boiling point is 600C above the operating point and the reactor shuts down due to fuel expansion. Under certain accident conditions it dumps the coolant to a dump tank which must be designed to provide sufficient decay heat removal to prevent it from heating to the boiling point, but this is easier with a coolant that can take high temperature because heat transfer rate is proportional to the delta T, and the surface area required to remove goes down with increasing temperature.

F and Cl are very chemically active and want to bond with everything, so most other FP’s and MAs/TRUs will be tightly bound in liquid or solid form, so are less likely to volatilize out of the fuel/coolant. The core operating temperature of LF – MSRs is just above freezing, so when the fuel gets dumped into the passive cooling tank or similar passive cooling system kicks in, it can freeze locking in most other fission products, unlike in water or gas reactors.(although this may be an advantage in Pb, Na, Li reactors as well).

The LF-MSR, would need to maintain the 3 fission product barrier rule, but since it eliminated the fuel cladding to get the liquid fuel advantages, another barrier would need to be added, such as a second double reactor vessel. All of the reactor vessels are low pressure, as is the containment vessel since there are no pressurizing mechanisms. This keeps adding the extra barrier outside of the primary vessel from being expensive.

As for ADS, if a liquid fluoride molten salt reactor (LF-MSR) is used they have these same advantages. BUT, due to the accelerator the design needs a reactor vessel (RV) window to get the beam in. Any dry well, or target at the center of the core would receive very high proton and neutron (1 GeV) material damage at the center of the core, potentially causing failure of the internal RV containment. If the target is water-cooled that is a potential water ingress (criticality) concern and steam explosion concern at the center of the reactor. Plus if the super-conducting accelerator cavities heat up, they can explode, very quickly risking the containment.

3) Today’s reactor capital and operating costs must be reduced. Adding an accelerator to fix non-existing reactor problems (1 and 2 above) violates this need for the nuclear community. When I said that an ADS system might double the cost of the reactor system, I was corrected. That was too low an estimate. Increasing the capital cost of nuclear reactor systems is THE PRIMARY method used by anti-nuclear activists for fighting the expansion of nuclear power.

At less than 20% efficiency in the accelerator, the accelerator will eat much of the electricity reducing the overall efficiency and thus profit. The low reliability of accelerators (32 trips/day, with a goal of 1 trip per day, equivalent to solar power “trip/day”) will reduce plant capacity factor of reactors from the current very high state of 95% in the US, to something lower, further reducing profit where as the LF-MSR will increase system thermal efficiency to 40-50% and may be able to increase the capacity factor beyond 95%, thus increasing electricity and profit/reduced cost to consumers.

Other than the challenge that I did not care about nuclear waste, which was solidly answered, the ADS community did not respond. They did say that Europe has a law to require getting rid of MA’s. I said that that is NOT a real/technical problem, but a problem of perspective and a political problem. At the end of the summaries they decided NOT to open the floor to the general community for comment as originally planned, but directed one ADS community person to make final statements, thus preventing further discussion on the subject. So I suspect the ADS community either didn’t want to address my comments, and/or didn’t want to hear others support my comments.

In summary, the ADS community is catering to the anti-nuclear community by saying:

  1. critical reactors are unsafe (they are NOT),
  2. MA’s/TRUs are a problem (they are a political problem, but not a real problem when weighing risks properly)
  3. they dramatically increase the capital and operating cost of reactors

Feedback/Corrections/Additions/Opposition/Discussion is not only welcome, but encouraged!

I got a LOT more attention at the conference after that soliloquy.

About the author: Ed Pheil is an advisory nuclear engineer who has been working as a nuclear energy professional for thirty years. He is current focusing on the potential for liquid fuel molten salt reactors with a variety of actinide fuel cycles.

About Guest Author

54 Responses to “Accelerator Driven System promoters are playing to irrational antinuclear fears”

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  1. Daniel says:

    Well it looks like the load guarantee for Vogtle is in the bag.

    One has to congratulate management who have stood up yo the DOE.

    As to the DOE good foot dragging as usual.

  2. Brian says:

    Rod, just a nitpick, but I don’t think your statement here is technically accurate without some qualification:

    “If the keff is too high and you turn on the accelerator at too high a neutron generation rate, you could also take the reactor super-prompt critical;”

    Criticality is a pure a system property and completely independent of the source. A higher source rate linearly increases the neutron output rate. It does not change the ability of the system to multiply neutrons.

    Now, your high neutron generation rate could, in theory (doubtful in practice from the neutron levels involved), change the system enough through heating to drive the system critical. This depends on a positive temperature coefficient, which would be a bad design in this case.

    • Brian says:

      I guess I should say “Ed”, not “Rod”, as this is a guest post. Sorry, Rod!

    • Ed Pheil says:

      Actually, I couldn’t think of a good way to simply say that if the keff was too high and you turned on the beam then the multiplication could be so high with the high beam neutrons thrown in that the power could spike very sharply, and behave as if it HAD been prompt critical and the sudden power spike could cause a a very high power transient similar in behaviour to being prompt critical. Both would tend to turn around by doppler broadening. Density based temperature coefficients wouldn’t really apply in this time scale. Indeed I would never design a reactor with even a possibility of a positive temperature (preferably all components of the temperature coeff.) or even void coefficient, so that is NOT an issue.

      One of the concerns I do have with graphite moderated systems though is exactly that, guaranteeing a negative temperature coeff. at all times in life, all fission product/fissile fuel combinations, and particularly for all graphite swelling and shrinkage conditions. Apparently a negative temperature coefficient requires a very specific moderator/fuel ratio and the shrinkage/swelling during normal operation and possibly during a casualty might make that very difficult. I have not analyzed this, so I don’t know for sure, so it is only a concern, not something that would kill the graphite moderator.

  3. John Laurie says:

    The fourth problem not addressed by the ADS community at ThEC13 is the reliability of power accelerators.

    Electrical power generation is ALL about reliability.

    Roger Barlow set the record straight.
    (from 05:40)

    “They’re close in power, but they’re not close in reliability. At one point there was talk of 3 trips per year, which was over cautious, and the DOE white paper has revised this upwards (Hamid’s numbers are more than this), but they are still far, far more demanding than anything that’s been achieved. Carlo Rubbia said on Monday that this was a solved problem, because there had been a machine called LEP which was a reliable machine. And this is bullshit. I’m sorry he’s not here. It is DANGEROUS bullshit. LEP was a magnificent machine and a credit to CERN, but while Carlo was in the director general’s office, at this end of the ring, I was at the other end of the ring on the OPEL experiment, miles from anywhere, 100 metres under the ground. And I spent many, many, many hours in the experiment control room NOT taking data, because – read the logs – beam lost, operators say no beam before 08:00, high voltage trips, vacuum problems… Of course I spent many happy hours taking data, and I think on average I probably spent more time taking data than not taking data, so it was a reliable machine from the particle physics point of view in that it was up more than half the time. Which is great, magnificent, and I am privileged to have worked on it, but it cannot be used as a prototype for a reliable machine.”

    • Ed Pheil says:

      I totally agree with your assesment. My article mostly tried to address ADS claims that they were solving problems. But, this reliability thing is a really huge killer for ADS. Some of the best accelerators are around 32 trips per day, and as you stated they believe that they can get up to 1-3 trips per day. I challenged them also that no utility in their right mind would ever consider buying a reactor that trips once per day. They need to get both the reliability AND the maintenance periodicity of the accelerator up well beyond the refueling periodicity or at least well beyond the current unintended scram rate of current reactors before utilities would seriously consider them. Routine trips, is a reduction in capacity factor, which is a reduction in income, which is required to be higher for an ADS system because of the higher capital cost. Also, trips tend to translate into fatigue cycles for both the reactor, whether thermal or mechanical. That also translates into increased design or maintenance cost or reduced lifetime.

      Thank you very much for the comment.

    • Ed Pheil says:

      My understanding is that the accelerators require about a 100x increase in overall power output, and 10^5 increase in accelerator reliability. The latter seems insurmountable in a reasonable period of time.

  4. Andrew Jaremko says:

    Ed did an interview with Gordon McDowell on this very topic: Ed Pheil on Molten Salt Reactors & Accelerator Driven Systems . It’s worth watching, as are all of Gordon’s videos from the ThEC13 conference which you can find on his channel. They’re much better than the official conference videos.

    I’m not sure which presentation included it, but I recall a slide that showed the accelerator reliability. Currently it was of the order of 10 trips per day, each of which would shut the reactor down. The goal was to get to 0.1 or 0.01 per day – figures that are better than wind and solar intermittency, but fall far short of the world’s current reactor fleet’s capacity factor. A trip every 10 days? Every month? Every 100 days? At completely unpredictable times? Solar at least is half predictable – we know when the sun is down.

    I haven’t seen a justification of accelerator driven reactors that convinces me that they are a useful idea. Ed, you are right on target. John Laurie, thanks for transcribing the segment of Roger Barlow’s talk.

  5. Pete51 says:

    ADS reactors are an answer to a problem that doesn’t exist.

  6. gallopingcamel says:

    The author should save his breath for cooling his porridge.

    This rant and similar ones objecting to coal, natural gas and whatever as a means for generating electricity are an absurd waste of time.

    If you believe your favorite technology is so wonderful stop criticizing the competition and bring your design to the market place. Let consumers decide which technology serves them best. A pox on experts who want to use politics and the power of government to prevent new technologies emerging.

    That said I used to be an advocate for ADR’s starting with Charlie Bowman’s GEMSTAR that was tested at TUNL (Triange Universities Nuclear Laboratory) and later at LANL, thirteeen years ago. Later the project moved to Virginia Tech.

    I have got over my infatuation with ADRs. Even with the price of neutrons falling rapidly I can’t see them competing with LFTRs when it comes to construction costs or LCoE.

    • Ed Pheil says:

      I also have talked to the GEM*STAR team. It depends on how fast you want to take to destroy weapons 239Pu. The GEM*STAR can supposedly consume the 239Pu faster than in a conventional LF-FMSR. That may be very true, and the liquid fuel ultimately averages out the burnup by mixing the fuel after every circuit. This faster burnup is probably true. But, as you say having both a costly reactor AND a costly accelerator does not make for an overall cost effective system. My thought was that it does not matter how long it takes to burn through weapons 239Pu because we will always need fuel, and no one is using them, so they are safely storing the 239Pu in a perfectly acceptable manner now, until we build LF-MSR’s to use it as start up fuel for LFTR designs or simply as fuel for LF reactors. So, here again I don’t see accelerators in a reactor being a cost effective benefit.

      • Engineer-Poet says:

        Another angle on this:

        ADS is being sold as a sub-critical scheme to eliminate transuranics, which would otherwise wind up as waste.  But we can burn them now in critical reactors, until there’s too little left to sustain a chain reaction.  By that time we ought to have fusion running, and the supply of 14.7 MeV neutrons from D-T fusion is more than good and abundant enough to destroy the remainder.

        As has been said before, ADS is a solution in search of a problem.

        • Ed Pheil says:

          Atually, in a liquid fueled reactor you can just leave the TRUs in the reactor until they are consumed. This is best done, I believe in a fast liquid fueled reactors. So, there is no specific need to ever need a D-T fusion reactor. Besides, if you wanted to do that then you would build a hybrid fission-fusion reactor, which is also a faster way to burn the TRUs, BUT you don’t really need to burn them fast, as long as you burn them. Don’t forget that all of the TRU’s that people are so worried about are NOT and increase in the number of radioactive atoms. Both Uranium and Thorium are radioactive to start with, so anything transuranic is just a transformation from one radioactive thing to another. Any fission doubles the number of radioactive atoms initially, but fission products mostly decay to less radioactive atoms than the original in about 500 years, so fission is a net decrease in radioactive material. The point of consuming the TRUs should be to consume all fissile or potentially fissile fuel, not worry about getting rid of something that already existed, just in another form.

  7. starvinglion says:

    Ironically, Ed Pheil did more damage to nuclear fission’s credibility with his response than NOBEL PRIZE WINNER Carlo Rubbia did with his embarrassingly naive paper nuclear ractor design.

    Pheil: ” We should reduce the potential of fission product dispersal from all reactor designs.”

    Thats the polite way of saying the reactor is a nuclear bomb. When I said this in another article comment, Rod said I didn’t know what I was talking about. Note that Pheil did not say “we should *eliminate* the potential”. I don’t think its even possible in principle to eliminate the possibility of an explosion that ejects fission products. The issue here is not the few # of deaths because its not a nuclear explosion, its about deformed babies from radiation. This is a huge issue and Pheils lame attempt to position the molten salt chemical goop reactor as a solution is not really legitimate because he has no solid operational data to back up his claims.

    Oh well, don’t feel bad, Carlo Rubbia. Another nobel prize winner, Robert Laughlin made a fool of himself when he wrote that the national ignition facility would change the course of humanity with its fusion pipedream experiments which of course never happened.

    • Rod Adams says:


      Fission product dispersal is not a euphemism for “bomb”. We like to keep fission products inside several layers so that they do not enter public spaces. There are situations that can result in breaching those layers that allow some of the fission products to escape — as happened at Windscale, TMI, Chernobyl and Fukushima — but we like to reduce the probability of those events and to reduce their impact when they happen. Human beings and other living creatures are not harmed by low levels of radiation; they are harmed when radiation levels are high enough to overcome our natural defenses to them.

      The level at which damage occurs varies among species; for humans, 100 years worth of research has shown that levels under about 100 mSv cannot be shown to cause even long term health effects and it takes something like 500 mSv to 1 Sv to cause immediate negative health effects.

      What makes you think that low levels of radiation have any effect on the rate of birth defects? There is no credible science that supports that claim.

      By the way, there is no need to shout when you insert an irrelevant appeal to authority. A Nobel Prize in one field has nothing to do with expertise in another, any more than winning a National Football League MVP makes one an expert swimmer.

      Rubbia’s Nobel Prize was awarded in 1984 for particle physics, specifically the discovery of particles W and Z.

      That discovery has absolutely nothing to do with producing economical electricity using nuclear fission as the heat source.

      • Ed Pheil says:

        What Rod said is absolutely correct. I was NOT implying that the reactor could blow up by using the word “dispersion.” It cannot blow up like a nuclear bomb, nor can any of the the reactors. All of the explosions in reactors were chemical or steam explosions. What I was trying to do was to eliminate any chemical energy reactions or steam or pressure related blowdowns, AFTER a reactor was shutdown, but the core still melted or was otherwise damage due to overheating the solid fuel, and these chemical mechanisms would cause the released fission products to be distributed outside the reactor or containment. Eliminating these mechanisms would be to make the public feel more comfortable with reactors. Even without those improvements though, nuclear reactors are the safest for of electricity production to date because the nuclear industry IS so careful to prevent casualties. Neither TMI nor Fukushima Daiichi had anyone or expects anyone to die due to the reactor accident, but in both cases people were killed due to fear induced panic during evacuations.

  8. gallopingcamel says:

    Here is another Nobel laureate commenting on another pipedream:

    Too bad he dragged my alma mater into this farce.

    • Ed Pheil says:

      Be careful ridiculing what you don’t understand. Many scientists have repeated low energy nuclear reactions. There may or may not be fusion involved, but there is definitely nuclear interactions occuring. Ridiculing the few scientists that did it once but did not fully understand the conditions required to make it repeatable is not proper and actually hurts the development of the science, because the ridicule is pure politics, even among scientists. Give them latitude to continue studying, until they figure it out. Inventions are 10% inspiration and 90% persperation. Do not ruin scientific study even if it is wrong. People learn a lot when they make mistakes, more so than when they get it right the first time.

      • Engineer-Poet says:

        If the effects really are that subtle, it seems much less likely that they can be turned into major sources of energy.

      • Rod Adams says:

        @Ed Pheil

        From my study of technical history, ridicule happens, but truly useful discoveries are readily repeated by the curious who do not bother to ridicule. I’ve recently done quite a bit of reading about the amazing speed with which knowledge about fission and chain reactions spread after Meitner, Hahn, Straussman, and Frisch recognized what was really happening when you bombard uranium with neutrons. There will be a post on ANS Nuclear Cafe later today to share a little of what I found published in the popular press within 18 months of that discovery.

        • Ed Pheil says:

          Actually the ridicule of of Fleishman and Ponds on cold fusion accelerated the study of low energy nuclear reactions, just quietly. Actually, it is my understanding that Meitner, Hahn, Strassmand and Frisch were not the first to discover/understand that fission was taking place. It was actually discovered 4 years earler the same year that the guy finished his report about the isotopes he produced by bombarding every element with neutrons and he discovered transuranics that way. But, a woman something like Eva N? was reviewing his notes and realized that he was only looking for production near the mass of the original isotope and figured out that there were other elements produced from the uranium bombardment far below the mass of the original isotope, and deduced that there had been fission. She was ignored as a woman though. I will look up her name tonight.

  9. Brian Mays says:

    Any time someone gets into one of these “pissing contests” over whose reactor has the best design, it helps the anti-nuclear cause. First, it focuses on what’s “wrong” with other designs. (You can’t say that my design is so much better than another design when it comes to some concern or feature, without implying that the other design is “bad” in some way.) Often lost in this trash talking is whether the supposed “defect” matters in the least. Someone like me, who is familiar with the technology and understands how engineering tradeoffs work, can absorb all of this in its proper context (and possibly offer up a rebuttal), but the takeaway message for the layman is that reactor X is “flawed” because of Y, even through he or she might not have any understanding of Y at all.

    Furthermore, the boosterism that is inherent in these discussions also causes damage, because it raises expectations by making fantastic promises that will be a very long time in coming, if they ever come at all. This is particularly important when dealing with a population like the American public, who — because of several generations of bombardment by commercial advertizing promising instant gratification — has developed a deep-rooted “gotta-have-it-now” mentality.

    The LFTR folks are the worst when it comes to this. They have been very successful at getting their message out — I come across blog articles and comments on the internet about how we should be building LFTR’s all the time. Sadly, almost none of the people making these imporations seem to understand that we can’t start building them tomorrow.

    My advice is to save these types of sales pitches for research grant proposals and closed-door meetings with venture capitalists.

    As for ADS technology, one of the things that I have noticed over the years is that the idea is usually promoted by physicists (particularly high-energy physicists), not engineers. So I’ve always considered this design to be the result of the Law of the Instrument: if all you have is a hammer, then everything looks like a nail. These physicists know a lot more about accelerators than they know about reactor physics.

    Finally, I agree with a couple of the other comments here. First, the ADS is a “solution” to a non-problem. Next, these devices, if ever built, would be a reliability nightmare. Then again, understanding how engineering tradeoffs work, I can see how that could be a useful feature to the developer of the technology, in the form of service and maintenance contracts that the sucker … er … customer will need purchase to keep the system running.

    • Engineer-Poet says:

      One of the points of LFTR is to have an answer when the questing soul asks about the anti-nuke talking point, “What about the waste?”  Being able to burn the current crop of spent fuel in anything, LFTR or otherwise, eliminates the main reason for demanding an immediate shutdown “until the problem is solved”.

      • gallopingcamel says:

        Good point. To call spent fuel rods from Gen I or II reactors “Nuclear Waste” is Orwellian Doublespeak.

      • Brian Mays says:

        It’s not as if the LFTR is the only thing that can burn “nuclear waste.” In fact, if you were really serious about burning the stuff, you’d get rid of the graphite … but then it wouldn’t be a LFTR.

        • Engineer-Poet says:

          I believe I’ve read bits about graphite-free thermal MSRs, using just the FLiBe salt as the moderator.  Of course, that still leaves you with a thermal spectrum.

          The real thing about LFTR is the low fissionable inventory and relatively high breeding ratio.  That offers the prospect of rapidly expanding the fleet to replace coal (fast-spectrum reactors can’t come close).  However, explaining THAT to the public takes a lot more education, and in a sound-bite world few are willing to put in the time to learn.

          • Ed Pheil says:

            I think you can get rid of the grapite and make a fairly fast reactor. The EU EVOL (Eva Merle-Lecotte, project recently decided to forgo the graphite and the BeF in their concept and went to a fast reactor design. The reason for this decision was because they did calculational studies on the positive component of the temperature coefficient frequently associated with graphite expansion. Getting a negative overall temperature coefficient occured in very limited conditions. So, yes it is possible, but you have to prove that you stay there for all graphite growth and shrinkage conditions and casualty conditions. So, they decided to forgo the graphite and get rid of the replacement need and Xe absorption concerns at the same time. Getting rid of the Be helped make the reactor faster as well. Of course you can still breed 233U from 232Th in the blanket in a fast core. A fast core also allows you to use 238U denaturing if desired and still consume the TRUs.

          • Engineer-Poet says:

            The problem with a fast reactor being that your fissile inventory goes way up and your doubling time goes way up with it.

    • charles barton says:

      According to Karl Popper, criticism is the hallmark of science. Advocates of ant nuclear technology ought to be prepared to defend their favored technology aginst criticisms. If they cannot do so, they must seek alternative grounds, or give up their failed belief. Debates over alternative nuclear technologies are not “pissing contests,” they are part of the quest for important truths. The future of energy matters, and our flaw so far has been to little debate, not to much.

      • Brian Mays says:

        Debates over alternative nuclear technologies are not “pissing contests,” they are part of the quest for important truths. The future of energy matters, and our flaw so far has been to little debate, not to much.

        Nonsense! As a someone who works in the nuclear industry, I have participated in these types of “debates” throughout my career. These types of discussions are best done through either forums of experts (e.g., the Gen IV International Forum), peer-reviewed publications in the relevant literature, engineering trade-off studies, or even informal, friendly chit-chat among knowledgeable professionals over beers or cocktails.

        Some people, however, (and the molten salt people are the worst when it comes to this, particularly the amateurs, who seem to constitute the majority of the group) think that the proper way to go about this “debate” is to publish one-sided, overly simplistic sales pitches on the Internet — to an audience that is ill-equipped to understand what is being sold to them — that trash every competing technology, while offering nothing but glowing recommendations for their preferred option, pitches that are worthy of Madison Avenue. That, my friend, is a pissing contest.

        Amazingly, these people manage to undermine the fundamental technology that their product is based on, while simultaneously promoting the snake oil that will end up being the final nail in the coffin, when it is eventually realized that the stuff doesn’t live up to all of its over-hyped promises.

        For what it’s worth, I have a whole laundry list of criticisms that I could bring against these molten-salt designs; however, I have the good sense not to publish them all on the Internet. Meanwhile, the molten-salt folks are running around like a jealous child who has found a new toy. It’s time to grow up. You are not helping.

        • Rod Adams says:

          @Brian Mays

          I agree that one sided sales pitches and overly simplistic denigration of competitors is not helpful, but I disagree with the implication that the discussion should be limited to “experts” and peer-reviewed journals.

          Admittedly, I have a long history of engaging in internet discussions about atomic energy design options, dating back almost a quarter of a century. My credentials as an expert are rather minimal, and I’ve never been employed by any institution that would pay the outrageous page fees imposed by peer reviewed journals.

          • Brian Mays says:

            Rod – I didn’t use the word limited; instead, I said best, and by best I meant most likely to result in changes in R&D priorities. I hate to burst any bubbles here, but one million random tweets about how much better design X is than everything else is unlikely to change research funding for advanced technologies anytime soon.

            My first point was that these discussions, debates, or whatever you want to call them already are going on, and claims of “too little debate” are unfounded and simply wrong.

            By all means, discuss what you want, but my other point — which has been my overriding theme — was that ill-framed messages end up causing more harm than good. The same person who becomes enthusiastic about a particular futuristic design for a nuclear reactor can easily end up protesting his local nuclear power plant, because it isn’t the “safe” (whatever that means) design that he prefers.

            Personally, I’d prefer to avoid that, even though I originally entered this industry to work on advanced, so-called “safer” designs.

          • Rod Adams says:

            @Brian Mays

            Sorry. You did not use “limited” and have certainly proven, through your participation, that you agree that the internet is a reasonable supplementary venue for nuclear plant design discussions. I agree with your point about tweets.

            However, I can point to at least one substantial result of internet discussions on research priorities. Do you think there would be much interest in SMRs in the US WITHOUT the interest first expressed on the internet?

        • charles barton says:

          Brian, I firmly believe in the advantages of open science. Opening our discussions to the public, has been a huge advantage for Molten Salt Reactor advocates, and not being afraid to call a spade a spade has benefited us. We have made huge advances in thew last 6 years. I was the 33rd person to join the very public Energy from Thorium Discussion Form. Today we have a voice, The Weinberg Foundation, inside the British House of Lords. 6 years alon the MSR and the LFTR werevirtually unknown world wide. A grassroots movement has changed this, and changed it world wide. IFR advocates have also used open science to advance public interest in their ideas, and controversies between MSR/LFTR advocates and IFR advocates has benefited both.

          Brian perhaps your problem is that you are stuck in old ways of thinking about how to get your ideas across. .

        • charles barton says:

          Brian you stated: “Some people, however, (and the molten salt people are the worst when it comes to this, particularly the amateurs, who seem to constitute the majority of the group) think that the proper way to go about this “debate” is to publish one-sided, overly simplistic sales pitches on the Internet — to an audience that is ill-equipped to understand what is being sold to them — that trash every competing technology, while offering nothing but glowing recommendations for their preferred option, pitches that are worthy of Madison Avenue.:

          This statement is most unfair. First MSR backers have debated endlessly, among them selves, with advocates of other nuclear technology, and with anti-nuclear spokespeople/ We have made a serious effort to create an extensive archive of rresearch related documents and acquaint ourselves with them. Our discussions, amounting to over 40,000 seperate comments are research based.

          We believe that the Nixon administration made a serious mistake in shutting down MSR research, in order to fund research on the expensive and unsuccessful LMFBR. An equil investment would have funded ORNL’s LFTR project, the MSBR.

          As for us using Madison Ave. techniques, we did not get our voice in the House of Lords by Madison Ave. style advertising.

  10. gallopingcamel says:

    Brian Mays is on the money.

    While I like LFTRs for the long term there are several other solutions that have many of the same merits while being much closer to large scale roll outs. The B&W small modular reactor and GE’s PRISM come to mind but there are plenty of others.

    • Ed Pheil says:

      Gallopingcamel and Brian, I agree with you on most of your terms. My goal originally was to try to get the ADS folks just to explain what the specific benefits they were providing were, and how the economics and reliability would be resolved. The problem being, that when they couldn’t do that, it looked like I was bashing them, which was not the actual intent. I tried to enguage them in discussions on the topic. But, as you said their reasons were to solve political perception problems. Political problems are real problems, but most of us are technical and engineers and can’t understand why you would spend extra money to solve a political problem, but it does happen all the time. Yucca mountain being a prime example.

      I also agree that SMR’s and GE PRISM are much nearer term and should be built out now, in preference to large LWR’s where possible, but large LWR’s need to be built now to help replace fossile fuel plants quickly to try to curb climate change and ocean acidification. I also think there are great strides that can be made in energy efficiency and reduction in demand that can help along those lines. In NY City, one company is taking the waste heat from one block of apartment complexes to heat an entire other block of apartment complexes. This is a phenominal improvement in energy efficiency and reduced water usage. This kind of effort needs to be expanded as quickly or more so than nuclear power replacing fossile and gasoline/diesel.

      • Rod Adams says:

        @Ed Pheil

        I’ve come to the conclusion that many people who promote energy efficiency are doing so out of a recognition that it helps to discourage new capital investment in energy production, even if that capital investment would result in far cleaner power, using far more abundant fuel sources that have a far lower marginal costs. In fact, I strongly suspect that most energy efficiency and conservation advocates – like Amory Lovins’s RMI the Natural Resources Defense Council – specifically favor low capital cost equipment that burns expensive and highly profitable hydrocarbon fuel instead of uranium, plutonium or thorium.

        As you stated, you are technical and an engineer, so perhaps you have not studied human behavior, politics, and business gamesmanship very much.

        Since the supply of energy from fission is functionally unlimited (by the time we got close to using it up even I would agree that fusion would be harnessed) and so much cleaner than hydrocarbon fuel sources that conserving it is about as useful as conserving bytes when writing computer code.

        I’m old enough to remember the days when programmers were taught to be conservative with every byte and remember some of the incredibly difficult to maintain code that resulted from that conservation. I like living in an era where bits and bytes are so cheap that no one worries about conserving them. I think it would be wonderful if we let energy demand grow in a similar manner because there would be incentive for capital investment to meet that demand with clean, low marginal cost fuel sources.

        • Ed Pheil says:

          I agree that most attempts at conservation are puny and tend to results in reduced investment in clean energy. This one technique is far superior to most though and uses a new technology to the US. This same technology provides a water, and possibly molten salt, pump that requires only a delta T in two input fluids to work, and has no need for electricity and has no moving parts. This is the Fisonic company located in NY City. The pump can be used to fix the problem of no pump in situations like Fukushim Daiichi easily pumping massive amounts of water as long as you have a hot water source. If there is no heat source then it can’t pump, but it does not need much delta T to pump. I just went down to see several of these systems in action last week. We set the system to 0 psig steam in and 2 psig cold water in in a test system, flow rate was 3 gpm water out with 0 psig back pressure. I was able to increase back pressure to 165 psig with NO decrease in flow rate out of the pump. 35% reduction in steam required, 50% reduction in city water and 50% reduction in sewer cost to heat the 27 story apartment buildings. that is not a small increase in efficiency.

      • gallopingcamel says:

        Thanks for your reasonable reponse. Clearly you are not one of those dogmatists who use government power to impose their views to the detriment of everyone else. Please accept my apologies for jumping to conclusions.

        While I am in favor of limiting CO2 emissions I disagree with your assertion:
        “….large LWR’s need to be built now to help replace fossile fuel plants quickly to try to curb climate change and ocean acidification.”

        Climate change and ocean acidification are not problems that can be solved by reducing mankind’s CO2 emissions. If the CO2 concentration were to increase ten fold (~4,000 ppm) the climate would remain highly beneficial to mammals as it was in the Eocene, ~50 million years ago. When the CO2 concentration reaches 4,000 ppm, the ocean will still be ALKALINE so don’t worry about all those mollusk shells dissolving. As a fish farmer I can assure you that there are benefits resulting from a lower pH. When the pH falls, the toxicity of ammonia (fish pee) is reduced dramatically.

    • charles barton says:

      Brian, You make the very point that brought me to advocate Uranium fueled, or denatured uranium fueled MSRs. The technology has already been tested in a proof of concept prototype by ORNL in the 1960′s. UMSRs and DMSR, would not take long to produce, are highly scalable in factory produced modular form. Iy would cost less than water cooled reactors. Considering these and the numerous other advantages of Liquid Salt Reactors, there is scarcely any wonder that Generation III advocates want MSR advocates to keep quiet. Qyite obviously we are not going to play your game. The LWR represents the technology of the past. Hidiong this fact will not bring sales to the LWR.

  11. david says:

    Hi all this article makes it sound like gas cooled, sodium cooled, and lead cooled fast reactors have issues that can make them go wrong but aren’t all designs way safer than light water reactors? Especially in an accident to where we don’t we need to worry about it? Also, specifically concerning sodium cooled fast reactors, I thought they were one of the safest designs? My “evidence” would be the EBR2, and the designs for the Integral Fast Reactor. Now I know that Japan had some issues with it’s sodium reactor but don’t EBR2-based designs have an almost impossible chance to have fire problems? Also, aren’t lead reactors very safe (though I’m not sure what they are like compared to sodium reactors) and it’s impassible for the lead reactors to melt down in an accident as well? Thanks
    (I wrote this quickly so please forgive for the grammatical errors)

    • gallopingcamel says:

      When it comes to safety all those reactors cooled with liquid metals are far safer than BWRs. While that may be true, LFTRs should be safer still.

      • Engineer-Poet says:

        And that leads me around an interesting chain of inference.

        1.  We know that Japan was part of the original IFR project.  (When it was cancelled, refunding Japan’s contribution cost more than running the remaining experiments.)  The IFR was a likely next generation for Japanese power reactors.  If it was at all like S-PRISM, it would have been air-cooled in a loss-of-site-power scenario.

        2.  John Kerry was instrumental in killing the IFR.  This set fast-spectrum reactor technology back by roughly 20 years, at least outside Russia.

        3.  TEPCO resisted any attempt to recognize the tsunami defenses of the Fukushima Dai’ichi site as inadequate.  While some of this may have been pure pig-headed denial, part of it may also have been due to a lack of alternatives:  if they shut down the ancient BWRs because of the design flaws, what would replace their generating capacity?  The IFR, once on track to be the replacement, had been done in a decade and a half before.

        So in a sense, John Kerry bears responsibility for the Fukushima meltdowns.

        • charles barton says:

          I an actually not opposed to the IFR, once its limitations are acknowledged. The Indians are working on development of a similar reactor, and their program is very ambitious. The quiockes path to a viable IFR would be to join the Indian effort. The Indian reactor breeds thorium and produces both U-233 and plutonium. This approach would turn the IFR into a winner. Of course fast MSR designs exist, and there are certainly advantages to the FMSR as opposed to the IFR.

  12. Jim L. says:

    Isn’t the ADS designs really a jobs program for accelerator people? To me, the ADS design is like using a horse to pull a functional automobile – its not needed and actually is a hindrance.

    • Joel Riddle says:

      Jim L.,

      To me, the ADS design is like using a horse to pull a functional automobile – its not needed and actually is a hindrance.

      That sounds like an excellent analogy to me.

    • Ed Pheil says:

      Actually there are good functional uses for accelerators that we mustn’t overlook.

      1) They can be used to neutron, proton, or electron irradiate materials for fission and fusion reactors, particularly since many of our materials irradiation reactors have either been shut down or are getting very old and soon will be shutdown.

      2) They can be used as neutron gamma spectroscopy to identify elements and isotopes in various materials samples, including environmental samples.

      3) They can be used for medical isotope production for the same reason as in 1) above.

      I am sure there are other uses I have not thought of as well.

      Indeed irradiation testing could use both higher power and higher reliability accelerators, so they are not just a jobs bill. And to be honest many areas are having their research budgets slashed these days, and they are just trying to find some way of keeping the accelerators alive, exactly as we are doing in the nuclear industry. My understanding is that Fermi Lab research has gone down so much that they can no longer maintain their previous accelerating staff and they have gone off to other jobs. Once that experience is lost, it is very expensive to recover. Fermi lab was hit hard when the Super collider was cancelled by the US for example, and the LHC was built at CERN instead.

      • Jim L. says:

        I agree with the accelerator uses that you have listed, and for other research uses too. I just do not think that having hundreds of accelerators for hundreds of fission power plants is realistic let alone necessary.

      • gallopingcamel says:

        ADRs have many potential applications but the large scale generation of electric poower is not one of them simply because there are several Gen IV reactor designs that have the potential to produce power at a much lower cost.

  13. Ed Pheil says:

    The intent of the article was more to focus on what are real technical bases for decision making and political ones. While political problems are real, they should not be used as an excuse to dramatically increase the complexity and cost of reactors, which would defnitely price them out of the competitive electricity market. Increasing the cost of the reactor unnecessarily ultimately favors fossil fuel usage and increases in climate change, ocean acidification, assuming that solar and wind are just an expensive form of gas fossil fuel usage.

  14. Ed Pheil says:

    Two useful quotes in the Liquid Fueled Molten Salt Reactor area.

    “Everybody knows that something can’t be done and then somebody turns up and he doesn’t know it can’t be done and he does it.” – Albert Einstein

    Someone was made a ridiculous challenge of desiging a reactor for an airplane, but those same extreme challenges drove innovation and creativity.

    “I can explain it to you, but I can’t understand it for you.” – Ed Koch

    We discuss and debate among whomever wishes to discuss the topic. This is critical to the education of the public that don’t even know such reactors are conceivable possible. Debate among knowledgeable people is needed to refine what needs to be worked on and which concepts are best, or even what “best” really means. The same discussion and questions educate others. The Challenges of other knowledgeable designers, physicists, and yes ADS folk require us to strengthen our knowledge, which improves the design. Knowing why and how ADS systems could benefit reactor designs is why this topic was started. Being knowledgeable about all design concepts helps decide which are better and/or take the best aspects from all designs to make the “best” ultimate reactor. I have not given up on ADS benefits, I just need someone to be willing to honestly, scientifically, and professionally discuss and debate the benefits and challenges rather than clamming up and being offended when questions are asked. Questions and debate are the scientific method, and scientific review by someone of the same position as an article is not as strengthening to the determination of the best reactor.

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