1. Wait, I stand corrected. I followed the link to Exelon’s page and see that you are correct. I actually did not know that First Energy owns TMI-2 despite the fact that I work at Beaver Valley. *embarrassed*

  1. Rod – thanks for the videos – I got sucked in to watching. The videos make me appreciate just what a complicated, high precision machine a solid fuel reactor core is. And how that complicates things when anything goes wrong.

    I commented on another blog post somewhere in cyberspace that the enriched uranium solid fuel cycle seemed to me to be just about the worst possible reactor design. All through the video I was imagining what would happen with a molten salt core – pull the plug, the salt drains out. Even when it’s cooled enough to solidify, just heat it up and pump it out. No wonder chemical engineers like fluids and fluid processing!

    1. Andrew – I have a different opinion. I think that the video shows how resilient the basic design is. Sure, if you lose cooling, you can destroy the core, but the vessel remains intact.

      You and your fellow molten salt advocates do a bit of handwaving when it comes to the actual machinery and containers that will allow you to just heat up the solidified salt and to protect all of the systems from its corrosive nature. The material challenges are not all solved, despite all dreams to the contrary.

      LWRs are not perfect, but they work reliably and at a competitive cost right now. No uncertain development needed. That is not to say that I want LFTR advocates to stop thinking, developing and working towards solutions, it is just that I wish you would recognize that you are not “there” just yet.

      1. Rod – “The material challenges are not all solved, despite all dreams to the contrary”.

        Finding material with the required high-temperature strength and chemical compatibility with the fluoride salts is part of the quest to build real Liquid Fluoride Thorium Reactors. To get the required combination of high temperature and corrosion resistance required for LFTRs operating at ~800 degrees C, cladding or coatings of materials can accomplish things that single alloy solutions cannot.
        By cladding an ASME Type III structural alloy (Alloy 617 or Alloy 800H) with a corrosion resistant layer (perhaps Hastelloy-N modified with 1.5% Niobium) you can provide the high temperature strength and corrosion resistance that advanced high performance LFTRs will require.
        Some while back, when Dr. Chu made his “corrosion” statement to the Senate in response to Senator Jean Shaheen’s question, Charles Barton wrote a fine Blog article on LFTR materials issues as a response entitled “Secretary Chu’s answer and the facts”
        Many LFTR advocates thereafter wrote Dr. Chu letters to try to update the good doctor’s personal knowledge base on recent advances on LFTR materials issues (including yours truly) and we have polite DOE post card responses drafted by kind secretaries at the department to prove it.
        (I personally feel that all of the LFTR corrosion and materials issues now have responsible answers permitting safe construction of low temperature [704 degrees C exit salt temperature] single fluid LFTR prototypes). The advances in cladded materials will permit safe construction of more advanced higher temperature and higher efficiency LFTRs. A significant new ORNL report on “CLADDING ALLOYS FOR FLUORIDE SALT COMPATIBILITY” by Govindarajan Muralidharan has just been released. –

        1. Robert – Pretend for a moment that I am from Missouri. Show me a real life example of a system operating at the temperatures and pressures proposed with some sort of documented testing of the long term effects of erosion, neutron embrittlement, and cycling operations. Show me the machinery required to apply the cladding you are talking about along with the documentation of the process steps required to ensure that it is adherent and will last as long as it needs to last. Show me that you have a good plan for supplying the materials, training the companies that need to use the materials and training the operators to keep all system parameters within designed limits. Show me that you have lined up a supply chain that can supply the liquid fluoride in the required quantities at the required purity. Show me that you have something more than blog entries behind this effort.

          I’ve been through this myself, admittedly with fewer people and less enthusiasm than the LFTR community. I abandoned my quest for an improvement to light water reactors even though I could answer nearly all of the above types of questions because there was one “dead rat” – I could not show anyone that there was a fuel supply chain for the high temperature TRISO coated fuel that was a fundamental component in the closed cycle gas turbines that I wanted to produce. Material issues were solved, coolant activation issues were manageable, there was ready proof of an adequate supply chain from the combustion gas turbine market, and there was operating history from systems using all of the components in the form required.

          There is significant progress in the fuel cycle development, but the timeline showed that it would not be ready until sometime in the early part of the next decade.

          I know that folks supporting LFTR keep pointing to an announcement by China that they are going to pursue development of the technology, but do they even have a demonstration sized reactor operating yet? At least with the high temperature pebble beds that they are also developing (along with a whole bunch of LWRs under construction) there is an operating demonstration unit that has been running for close to a decade and there are two fully designed units under construction with a planned commissioning date before 2014. There is a pilot scale fuel manufacturing facility that has been fully qualified and is making fuel to exacting standards and there is a larger scale facility that will be ready to support the two units that are under construction.

          Manufacturing nuclear systems is hard work that requires a lot of patience because it take a long time to test and document every step along the way. I wish that were not the case, but one of the reasons that we all love nuclear fission energy is that the fuel lasts a very long time. When you want to prove that you know how it will perform for its full cycle, there are not very many available shortcuts – the FFTF does not exist, and there is not much space available in the ATR. Those facts are not show stoppers, but they can sure delay the curtain call.

      2. Rod – thanks for your reply. I absolutely understand that molten salt reactors aren’t commercially proven designs yet. Yes,there are a lot of materials challenges that I, personally, am not able to solve, but what that means is that we should be building research facilities. When Kirk Sorensen met with a group at Protospace in Calgary before his TEDxYYC talk, he pointed out that a lot of that engineering could be done without having a reactor; all you need is hot salt.

        At least my handwaving is about the engineering. Many renewables advocates have to do handwaving about thermodynamics, physics, and chemistry. Some aren’t so sure about arithmetic, either…

        At least one of the research molten salt reactors at Oak Ridge National Laboratory was drained and restarted once a week for more than a year, IIRC. I got that info from Kirk’s Energy From Thorium site.

        We need to be building what we know how to build, developing better things, and keeping this world in shape for all living things.

        You might have a personal interest in the paper COL Paul E. Roege – Can Nuclear Energy Fill Critical Gaps In The Military Energy Portfolio? given at the recent Thorium Energy Alliance conference. The link is to a PDF of the presentation slides – videos from the conference are promised.

  2. I’ve seen this in a few places (this is from Idaho Samizdat)

    University of Tokyo’s Naoto Sekimura told a committee of the National Academy of Sciences it took all of 11 hours for the melting fuel to punch holes in the bottom of the reactor pressure vessel. Now it is leaking radioactive water. (March 18, 2011 NHK TV interview)

    Is this possible? Likely?

    1. There is a big difference between leaking water and the radionuclides that dissolve in water and letting the rest of the core materials escape from the pressure vessel.

      Though the bottom head of a PWR is a single piece of thick steel that is unlikely to ever be penetrated. the bottom head of a BWR like those at Fukushima is a bit more complicated. There is a possibility that some of the welded transition pieces for the control rod drive mechanisms are leaking. The vast majority of the hazardous material remains safely inside the pressure vessel.

      1. I had also read a few comments like that which seems a lot more likely. I don’t know if something was lost in the translation but you would hope that responsible experts would be a little more careful about how they describe something.

  3. Rod – I am confused by reports that the Reactor Pressure Vessel on the Daiichi Fukushima Unit 1 is reported to be leaking.
    Do you (or perhaps anyone else reading your Blog) have knowledge of what thickness and type of steel is used for the RPV on the GE BWR Mark 1 Containment Reactors?
    My best (but incomplete) information is that the Reactor Pressure Vessel for the GE BWR Mark 1 Containment incorporates a reactor pressure vessel manufactured out of 6 inch thick steel, with extremely temperature, vibration, and corrosion resistant Inconel 600 plate on both the inside and outside.
    In the TMI accident, the hot corium produced by the partial melting of the core slumped to the bottom of the Reactor Pressure Vessel and penetrated a maximum of approximately 5/8th of an inch into the inner lining of the RPV.
    I do not see how is it possible that the corium sitting at the bottom of the RPVs covered by water in Units 1-3 at Daiichi Fukushima has burned all the way through the bottom of the 6” thick Reactor Pressure Vessel as reported by University of Tokyo’s Naoto Sekimura?
    What are “welded transition pieces” for the control rod drive mechanisms and why put them in a spot where they could compromise the containment of the RPV?

    1. Robert – The control rod drive mechanisms for boiling water reactors are at the bottom, not the top of the RPV. In BWRs, rods are driven up into the core instead of dropped down into the core. During normal operation, the top of the reactor pressure vessel in a BWR is full of steam, not water. Here is a quote from a slide presentation that introduces the BWR basics for a nuclear engineering class at Oregon State University:

      “BWR control rods are always placed at the bottom of the reactor rather than at the top as in the case of the PWR. The reason is that much of the upper portion of the BWR core is normally occupied by steam voids, and movement of the rods in this region does not have as large an effect on the nuclear reaction as rod motions in the lower, water filed part of the core.”

      Every one of the control rods requires a penetration that must include some kind of welded transition. I know that there are BWR experts who comment here that can provide more technical details. There is also some kind of sealing system involved since the rods have to be able to move in and out. Those welds and seals are potential failure points when exposed to molten corium, though they will probably not fail catastrophically. The description that I have heard most is “cracking”, which can allow water to leak, but not much else.

      The pressure vessel is not the “containment” boundary; it is the reactor coolant pressure boundary.

      1. It’s my understanding that the steam separator and dryers inside the RPV above the core are also reasons for having BWR control rods inserted from the bottom. I hadn’t heard of the control issues before.

  4. Rod – I would just like to thank you for your thoughtful multi-question response to my earlier post on the current status of LFTR materials development. I am afraid that I would not be able to respond to even a few of your specific questions/challenges without exhausting your patience and the tolerance of the fine people that regularly read your blog. I conceed that Thorium LFTRs are at an earlier stage of commercial development relative to LWR technology. Many important additional steps in qualification of the materials to be used in LFTR will be necessary.

  5. Rod, you mentioned that the lack of TRISO fuel supply chain for your Adams Atomic Engines practically rendered it dead in the water, but aren’t alternatives available? For instance, Hyperion was supposed to use uranium hydride in their modular reactors, just like Triga reactors, but in order to speed up development and delivery times, they ended up settling for a liquid-metal-cooled uranium nitride fueled reactor core for the time being.

    From what we’ve been reading about LFTR technology, these reactors are able to attain extremely high temperatures, and the heat can be effectively captured by helium gas turbines for power generation.

    Is there any possibility that a closed-cycle nitrogen gas turbine such as those for your AAE can be used for a high-temperature thorium-fueled molten salt reactor?

  6. @Jae Senn – do you have any numbers associated with your qualitative description of “extremely high temperatures”? Without numbers, I cannot answer the question.

    All of my research pointed to the TRISO particle based fuel as the only one that offered any real potential for a directly heated, simple cycle gas turbine. Without being able to apply direct heat without the need for reheat or recuperation heat exchangers, the Adams Engine(TM) would have had no real advantage over other nuclear fission alternatives. My goal was a dramatic reduction in initial capital cost enabled by extreme cycle simplification.

    That is one reason why I chose to apply my nuclear training to improving light water reactors by taking a job working on small light water reactors.

  7. I know what a bullet looks like, but I don’t want one shot in my direction. Seeing a nuclear core doesn’t change the devastating effect radioactive contamination will do to one’s body.

    It’s easy for someone to say living close to the nuclear accident is safe, especially when you don’t live there. Nobody with knowledge of radiation effects on children would suggest this area is safe. It’s not safe. It may not kill 100% of the middle aged adult population if they stay around. But, it’s most definitely not something any reasonably well informed physician would allow near his children.

    It’s not safe, it’s not clean and continuing to say so doesn’t make it so.

    1. Jason N – Your ignorance does not make it any more dangerous ether. Many of us here know what we are writing about because we are professionals or have sufficient education and background to evaluate the situation.

      Comments like your’s brings to mind Ed Brayton’s quotation from Isaac Asimov:

      “There is a cult of ignorance in the United States, and there always has been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that ‘my ignorance is just as good as your knowledge.”

  8. Mr Adams, Thank you for posting these video’s. It exposes what must face TEPCO over the coming years.

  9. Well the past is the past now. Who else is looking forward to watching the live HD color video of the reactor cores when they eventually open them up?

  10. Rod, useful and interesting material, but I think you’re missing one key factor.

    De-fuelling TMI was indeed possible, and relatively soon after the accident – certainly less than most of the commentary at the time would have had was the case. But, there’s a key difference between TMI and Fukushima.

    At TMI, the containment and refuelling equipment was intact. That meant the vessel and core could be submerged, as in a normal refuelling operation, and the pressure vessel lid removed while maintaining cooling. Plus, the water provides essential shielding.

    At Fukushima, it appears that in at least two cases there is substantial leakage from the containments, and probably in all three damaged reactors. That means that either that damage has to be repaired (not easy, given radiological challenges), or that there’s no easy option to submerge the vessel. Add to that the damage to the reactor buildings, meaning there’d be no pressure-tight boundary above the exposed core during any operation to extract the damaged fuel.

    It’s all likely to be further complicated by a need to extract the various steam-drying equipment from above the damaged core – itself likely to be very highly contaminated, and damaged.

    It’s hard to see how those facts wouldn’t make this a much harder situation to remediate than TMI – even allowing for improvements in robotics and remote handling.

  11. The Yomiuri Shimbun daily paper reports that the Japanese govn’t is going to inform the AIEA in the coming days that the molten nuclear fuel in reactors 1, 2 and 3 may have pierced their pressure vessels and pooled at the bottom of the containment vessels. I guess we only have to be patient to finally know.

  12. As an aisde, Rod, one area in which we have to admit our profession is uniquely skilled….

    How does anyone manage to make the process of recovering melted nuclear fuel from the bottom of a b*******d reactor sound quite as mundane – no, dull – as those videos make it seem?

    I know we’re arch rationalists, and the last people to get overheated in a crisis – but even wonder if we overdo it, sometimes?

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