Presenting at ThEC2011
The second Thorium Energy Conference (ThEC2011) was held at City College in New York from October 10 to 12, 2011, and was hosted by the International Thorium Energy Organization (IThEO).
I had the opportunity to speak on the afternoon of the first day. Fortunately, my presentation was preceded by a very good presentation by Dr. Jess Gehin of Oak Ridge National Laboratory on the subject of molten-salt reactor technology and the history of the different types of MSRs. Jess’s presentation covered a great deal of material that I had reluctantly deleted from my presentation in order to fit it within the allotted time, so it worked out very well.
My presentation basically had two halves. The first half (slides 1-28) focused on how Flibe Energy intends to continue Weinberg’s vision of a “world set free” by clean and abundant nuclear energy from thorium. I highlighted the language in the Department of Energy’s Nuclear Energy division (DOE-NE) that expects industry to lead in the design, development, and implementation of new nuclear energy according to market principles. I described our focus on a portable, modular power source suitable for powering military installations, initially in the United States and later abroad. I described the operation of the LFTR and its safety features. I spent a bit of time talking about the people involved with the company and introducing the Board of Advisors. I closed the first half by describing how an analysis of reactor coolants and fuel cycles leads you to the unique combination of thorium fuel and fluoride coolant that enables long-lived, safe operation of a nuclear power source.
Then I shifted gears for the second half of my presentation (slides 29-55). I anticipated the first question would be the one that I always get in presentations such as these: “why didn’t this happen?” So I attempted to answer that question before it was asked.
Nature gave us three natural nuclear fuels (Th-232, U-235, and U-238) but only one was naturally fissile. It was also the one that was in the shortest supply. Nuclear pioneers saw that we had better get on to one of the abundant fuels (Th-232 or U-238) quickly if we were to sustain the generation of nuclear power. So the question became–which one? The fissile derivative of U-238, plutonium-239, promised sufficient excess neutrons in fast fission to build up a large fissile inventory through breeding gain, so the bulk of nuclear efforts were directly towards the “fast-breeder reactor”, most often cooled by reactive liquid-sodium.
Others saw a compelling possibility in thorium and its fissile derivative, uranium-233. This combination alone had the potential to “breed” in the thermal spectrum, and to avoid the significant complications of the fast spectrum. But the breeding gain would be low, if present at all. There were significant uncertainties, but there would be significant advantages to avoiding the huge fuel inventory of the fast-breeder reactor (some 10 to 20 times greater than the fuel inventory of a thermal reactor for the same power rating).
Despite meltdowns at the EBR-1 reactor and the Fermi 1 reactor, the US Atomic Energy Commission (USAEC) continued to pour hundreds of millions of dollars into fast-breeder reactor development. On June 4, 1971 they gained even more strength when Pres. Richard Nixon made the development of the fast breeder reactor the core of US energy policy. Nixon also saw the fast breeder as a political “treat” that he could dangle in front of audiences and constituents, and he did so both privately and publicly.
Weinberg’s efforts to show the efficacy of a thermal breeder based on molten-salts and thorium was politically doomed. He was fired in late 1972 and the program was cancelled in 1973. Things got worse in 1973. The Arab oil embargo was a blow to the US and caused Nixon to commit even more strongly to the fast breeder.
In 1974, India detonated a nuclear explosive based on plutonium that they had produced in a heavy-water reactor and the issue of proliferation attained far greater prominence in national discussions. It did not curb Nixon’s enthusiasm for the fast breeder nor that of his successor, Gerald Ford. But in the 1976 election proliferation was an issue where Ford felt a disadvantage relative to his opponent Jimmy Carter. Therefore, on October 28, 1976, just five days before the presidential election, Ford announced a ban on the reprocessing of nuclear fuel in an attempt to curb proliferation.
This ban was essentially the death knell for the fast breeder in the United States. Without plutonium recovered from light-water reactors to fuel its large initial fissile inventory, and without the reprocessing of its uranium-plutonium fuel to recover fissile materials, the central concept of the fast breeder was non-viable. Carter went on to win the 1976 election and to continue Ford’s anti-reprocessing strategy (little surprise). He spoke repeatedly about the opportunity costs of the fast breeder and blamed it for slow progress in solar technology. He also said the plutonium fast breeder was unnecessary and that the United States should make greater use of its coal resources.
At no time was there any indication that the decision to kill the molten-salt reactor was ever revisited at a presidential level. In fact, there is little indication that anyone at the executive level even knew what a molten-salt reactor was, or what the potential for thorium could be.
The breeder reactor program was cancelled after the expenditure of billions of dollars, and the Three Mile Island-2 accident in March 1978 ended political interest in exploring advanced nuclear reactor technology.
I summarized my answer to the question “why didn’t this happen” with these observations:
The USAEC saw plutonium as a “sure bet” in a breeder reactor, but thorium was more uncertain (but proven in the end at Shippingport). They invested early and heavily in the liquid-metal fast-breeder reactor (LMFBR) despite failures and meltdowns. Industry got involved with $200M in investment In June 1971, Nixon announced that the fast breeder was US policy, and he saw it as a strategy for energy independence. Weinberg was fired and the MSRP was cancelled. Ford cancelled fuel processing and Carter extended the policy. Without fuel reprocessing and plutonium extraction, the plutonium fast-breeder was non-viable. No one in DC revisited the decision to cancel the MSR program. The team disbanded and dispersed; the knowledge was lost; and MSR technology was wrongly considered a failure for many years.
For those who are interested, here is a copy of the slides I presented at ThEC2011. Many of the videos and audio files related to the Nixon administration nuclear policies are embedded as links in the presentation:
My presentation given yesterday at ThEC2011 in New York. (PPT, 3.7MB)
Hi Kirk —
Nice presentation; even after all this experience you're still improving and refining with each new go.
I'd like to ask a quick question, which is particularly relevant in the aftermath of Fukushima. Slide 15 of this presentation describes passive safety, including the freeze plug contingency in the case of total power failure. What I'm wondering about, is the description of the core material draining into a "passively cooled configuration". I've seen this discussed a couple times in the Forum, but have never really gotten what I would say is a satisfactory answer: what is the passive cooling mechanism, and how can you be sure it will work even in the case of a large earthquake/flood?
The old MSRE drawing shows the drain tank, which is fine for catching the core material into a non-critical configuration. But, a tank in an underground cave can't possibly dissipate the 50-100 MWatt residual decay heat that would have to be rejected from the core material of a large commercial station (say 3 GW thermal in operation). So this drawing doesn't necessarily show what the real LFTR passive cooling system would look like; but what does it look like?
The old MSRE drawing shows some kind of piping "to heat reject stack"; is this some kind of passive, convectively pumped coolant loop? Can you really push 100 MW through that kind of circuit? What does its radiator look like? Can you be sure it will operate in the wake of an earthquake?
It seems more reliable if the drained configuration can convect straight to the open air, conduct straight to the ground, or radiate to the open sky; are any of those possible? I'm very curious to see what Flibe has in mind, as a robust scheme for residual heat rejection seems to me a very important part of the overall argument for LFTR passive safety.
Paul –
Kirk can respond about what FLIBE has in mind. I can provide some information based on the ORNL MSBR design and our recent work on salt-cooled reactors.
There is a good discussion of the drain tank cooling system in ORNL-4541 (single fluid) and ORNL-4528 (two-fluid designs). They each had a different drain tank cooling system design, with the design in ORNL-4541 the most developed. Basically in this design there was a natural circulation loop to move the heat from the drain tank to a water-cooled heat exchanger. They looked at FLIBE and NAK as an intermediate heat transfer medium. For the salt-cooled reactors that we are looking at we use a similar system, but with heat exchangers in the reactor vessel (no drain tanks) and heat reaction to the air. The system is design to remove 1% of full power. In this case, the reactor was a small modular design operating at 125 MWt, so the decay heat removal system was designed for 12.5 MWt. It can be scaled to larger systems. The heat exchangers are low-pressure-drop shell and tube type designs. This would be a safety-related system that is designed to survive earthquakes with sufficient redundancy.
Other concepts can be used as well, such as heat pipes and such. There have been discussions on the forum on using the containment building as a radiator.
Jess — Thanks for your detailed reply. Before re-replying, one quick question: you mention a small modular design operating at 125 MWt, and a cooling system designed to remove 1% of full power = 12.5 MWt. Isn't there a decimal point slipped in one of these? or am I missing something?
All – be sure you go over to thoriumremix and check out the new videos with Kirk. IMO they are awesome! Gordon McDowell and his crew have done a superb job and have paid special attention to the sound quality. Be sure to order the extended cut DVD with the 143 minute version of the 120 minute LFTR in 5 minutes web video!
Paul –
I wasn't too clear in my previous response. The 1% is used to size the decay heat removal system. Of course the standard cooling system removes the full 125 MWt. Actually, it has three heat exchangers, but only two are required to move the 125 MWt.
— Jess
Jess —
Thanks for the reply, though I'm still a mite confused (though that doesn't strictly matter; see below). If the SMR you mention needs to reject 1% of full power as decay heat, then that would be 1.25MWt of decay heat, right? so where did the 12.5MWt figure come from? Also, isn't the usual ratio between decay heat and full power more like 7%? or do you get down to as low as 1% from some kind of continuous reprocessing?
Anyway, what I'm really wondering about, engineering-wise, is the statement that the decay-heat removal system for a 100MWt SMR "can be scaled to larger systems." Suppose you've designed a system that can reliably reject 10MWt decay heat from a SMR. Now how does it scale when you need to reject 100MWt decay heat from a big gigawatt plant? I love the idea of using the building as a radiator; but if you're going to radiate 10x as much power at the same limiting temperature then you need 10x the surface area to do so; this is not a simple "scale up" to larger systems.
At a simple level, the same goes for any kind of piping system; if the temperature profiles are the same, the big plant needs 10x the coolant flow and 10x the pipe heat-exchange surface area, as well as a 10x bigger radiator down the line. All this is to say, the fact that you have a good solution for 1MWt or even 10MWt decay heat removal does not, in itself, convince me that a similar solution exists at the 100MWt level.
Of course, if by "scale up" you just mean building many copies of the SMR, then that's fine for heat rejection — as long as they're far enough apart that their rejection paths don't overlap much. But then you're really saying that LFTR only provides full passive safety at the SMR level, not at the gigawatt plant level, which is certainly not the message that Kirk was strongly implying in the talk.
Yes, 1.25 MWt (not 12.5 MWt).
The system in SmATHR and other systems do not use radiators, they use heat exchangers with natural circulation convective cooling So the scale up is achieved by increasing heat exchanger capacity and the number of heat exchangers. We have 1GWe designs that use the same principle for decay heat removal as the small system. I suggest that you read the following reports:
http://info.ornl.gov/sites/publications/files/Pub… http://nuclear.inl.gov/deliverables/docs/status_r…
Starting on page 81 of this second report you can find details about the different decay removal systems considered, including DRACS, which is what we are using in our design.
Hi Jess — Great! thanks very much, this is just the sort of thing I'd been looking for. I don't have a good intuition for natural-convection-driven systems so I'll be glad for some education. I'll take a careful look before commenting again.
Independent of that, though, I'm still interested in what Flibe has in mind.
Hello everyone!
I wonder what system Flibe Energy are considering as the first?
I like David LeBlanc's pipes whit in a pipe.
But I wonder if you can not let the fuel salt circulated in the reactor and the energy is carried out with helium or salts through pipes? Then we will not have any opposition from those worried about the spontaneous neutron radiation outside the reactor, also makes the system more compact and fuel salt can circulate by convection.
The next question is whether a system with both graphite and graphite-free areas provide a reactor with both fast and thermal neutron spectrum?
My last question: For the military should, perhaps, small reactors without thorium cycle, being the best?
Perhaps large LFTR can produce U233 to all small and simple reactor?
Best regards Gunnar Littmarck
The presentation outlines a tragic story that will one day be worthy of feature film. Does anybody know somebody in holywood?
OT
The UK NNL has been asked to give a report to the House of Lords, and I looked on their site to find what I could about it and found this:
NNL Managing Director, Paul Howarth, recently gave a lecture at the North West Branch of the Nuclear Institute. http://www.nltv.co.uk/index.php?option=com_hwdvid…
About half way through this lengthy speech he presents a slide on Generation IV projects which lists Molten Salt Reactors. In his narration he skipped that completely. At the very end he talks about the report to the House of Lords and says that NNL's recommendation is that Britain should have a nuclear R&D program. The major portion of his speech was devoted to various fast neutron reactors and how they would be beneficial to reducing waste.
Jess and Paul,
Can't you guys meet in the cafeteria next to the pond, eating some Buddy's BBQ?
Joel, Jess — I'll be at the cafeteria at noon Wednesday and wouldn't miss the chance for Buddy's BBQ; but after that I'll be off-site for quite a while and will have to continue by remote communication.
Great presentation. My 2 cents, use fewer slides, devote less time to why didn't this happen.
Ed