Month

WASH-1097 remains a good source of information on the thorium fuel cycle. In fact, some major recent studies of the thorium fuel cycle rely heavily on WASH-1097.

Sometimes, however, sources on thorium may draw indirectly on WASH-1097, without mentioning it in their bibliography. Although a recent IAEA report on Thorium appears to have been prepared without overt reliance on WASH-1097.

Because it is widely referenced and continues to be an important source of information, I will rely on WASH-1097 for most of the information found is this account.

One of the first things physicists discovered about chain reactions was that slowing the neutrons involved in the process down, promoted the chain reaction. Kirk Sorensen discusses slow or thermal neutrons in one of his early posts.

Under low energy neutron conditions, Th232 can be efficiently converted to U233. The conversion process works like this. Th232 absorbs a neutron and emits a beta ray. A neutron switches to being a proton and the atom is transformed into protactinium-233. After a period average a little less than a month, Pa233 emits a second beta ray and is transformed into U233. U233 is fissionable, and is a very good reactor fuel. When a U233 atom encounters a low energy neutron, chances are 9 out of 10 that it will fission.

Since U233 produces an average of 2.4 neutrons every time it fissions, this means that each neutron that strikes U233 produces a average of 2.16 new neutrons. If you carefully control those neutrons, one neutron will continue the chain reaction. That leaves an average of 1.16 neutrons to generate new fuel.

Unfortunately the fuel generation process cannot work with 100% efficiency. The left-over U234 that was produced when U233 absorbed a neutron and did not fission will sometimes absorb another neutron and become U235. Xenon-135, an isotope that that is often produced when fissile nuclei like U233 split, is more likely to capture neutrons than U233 or Th232. This makes xenon-135 a fission poison. Because xenon in a reactor builds up during a chain reaction, it tends to slow a reactor down as the chain reaction continues. The presence of xenon creates a control problem inside a reactor. Xenon also steals neutrons needed for the generation of new fuel.

In conventional reactors that use solid fuel, xenon is trapped inside the fuel, but in fluid fuel xenon is easy to remove, because it is what is called a noble gas. A noble gas does not bond chemically with other substances, and can be bubbled out of fluids where it has been trapped. Getting xenon-135 out of a reactor core, makes generating new U233 from Th232 a whole lot easier.

It is possible to bring about 1.08 neutrons into the thorium change process for every U233 atom that splits. This means that reactors that use a thorium fuel cycle, are not going to produce a large excess of U233, but if carefully designed, they can produce enough U233 that burnt U233 can be easily replaced. Thus a well designed thorium-cycle reactor will generate its own fuel indefinitely using thermal neutrons.

- Charles Barton

Introduction: This Russian paper, translated by the IAEA nicely lays out some of the advantages of the thorium fuel cycle.

From: STATUS OF NUCLEAR DATA FOR THE THORIUM FUEL CYCLE
by B.D. Kuz’minov, and V.N. Manokhin Russian Federation State Science Centre, Institute of Physics and Power Engineering, Obninsk

Adoption of the thorium fuel cycle would offer the following advantages:
- Increased nuclear fuel resources thanks to the production of 233U from 232Th;
- Significant reduction in demand for the enriched isotope 235U;
- Very low (compared with the uranium-plutonium fuel cycle) production of long-lived radiotoxic wastes, including transuraniums, plutonium and transplutoniums;
- Possibility of accelerating the burnup of plutonium without the need for recycling, i.e. rapid reduction of existing plutonium stocks;
- Higher fuel burnup than in the uranium-plutonium cycle;
- Low excess reactivity of the core with thorium-based fuel, and more favourable temperature and void reactivity coefficients;
- High radiation and corrosion resistance of thorium-based fuel;
- Considerably higher melting point and the better thermal conductivity of thorium-based fuel;
- Good conditions for ensuring the non-proliferation of nuclear materials.

WASH-1097 remains an invaluable source of information on the thorium fuel cycle. It explains why the thorium fuel cycle creates such a small problem with transuranium isotope. First, however, it is important to understand why there is a problem in the uranium fuel cycle.

When U238 absorbs a neutron a transformation process is triggered. After a couple of sub-nuclear events (beta radiation), the two neutrons in the atom become protons. This process turns the uranium-239 atom into plutonium-239. Pu239 is fissile. But Pu239 has some characteristics that make it something less than a desirable fuel, in ordinary reactors. Fission is most likely to occur with low energy neutrons. Pu239 has a healthy appetite for these low energy neutrons, but only fissions about 2 times out of 3 when it absorbs these neutrons. The net effect is that Pu239 doesn’t “pull its weight” in the reactor when it is fissioned by low-energy neutrons–it doesn’t produce enough neutrons per absorption to make up for the neutrons lost in absorption.

In the ideal uranium fuel cycle, a Pu239 nucleus absorbs a neutron, splits and emits two neutrons. One of them is absorbed by another fissile atom (U235 or Pu239) atom which splits. The other is absorbed by a U238 atom which is transformed into U239. As you get more and more of the absorption products of Pu239 building up in the nuclear fuel (Pu240, Pu241, etc), the neutronics become more and more unfavorable.

The heart of the problem is the fact that low energy neutrons split Pu239 atoms only about 2/3rds of the time according to WASH-1097. In the other 1/3rd of the time, Pu239 becomes Pu240. If Pu240 absorbs a neutron it becomes Pu241 and if Pu241 absorbs a neutron, 75% of the time it fissions. Thus by the WASH-1097 account, 25% of the time when Pu 241 absorbs a neutron it becomes Pu242. Thus after absorbing 4 neutrons, nearly 9% the atoms that started out as U238 are still plutonium. This is what is called a poor neutron economy. The neutron economy of fast breeders is better, because a neutron absorption in Pu239 is more likely to cause a fission with more energetic neutrons. Hence the desirability of fast breeder reactors in a transuranium reactor economy.

As we have seen conventional fast breeders use sodium as a coolant, and sodium is really nasty, dangerous stuff. In addition, as Kirk Sorensen points out, using liquid sodium as a coolant, limits the thermal efficiency of a reactor. Thus not only are LMFB reactors inherently dangerous, they
are also not as efficient as power producers as fluoride reactors.

But here we must ask, why are we producing plutonium in breeder reactors? If we are producing it to go into conventional reactors, we are not producing very good nuclear fuel.

- Charles Barton

Once when I was in junior school the school I attended offered a science demonstration in assembly. The whole idea was absurd, because many of our parents were scientists, and the demonstrator was a science teacher, who was far less versed in real science than my father. The demonstrator showed us a few tricks with chemistry, but the highlight of the show came when he chucked a small piece of carefully stored sodium metal into a container filled with water. The sodium bounced on the surface of the water as it burned strongly, illustrating that water – or for that matter air – does not mix well with sodium. Had the demonstrator chucked a larger piece of sodium into the water a violent explosion would have occurred.

The demonstration left a vivid impression on my mind, and similar demonstrations probably effected the views of early reactor scientists like Eugene Wigner and Alvin Weinberg. In 1966 Alvin Weinberg gave a lecture on nuclear technology to the Autumn meeting of the National Academy of Science.

Weinberg noted, “in spite of the great emphasis on fast breeders that the world now displays,
there are some difficulties that must be overcome before fast breeders become commercially successful.”

Weinberg did not comment on the safety of sodium cooled reactors on that occasion, but in a lecture delivered at Argonne National Laboratory ten years later, Weinberg observed:
“We have no real estimates of accident probabilities for liquid metal fast breeder reactors (LMFBR’s). The Rasmussen estimate (one in 20,000 per reactor year with an uncertainty of five either way) would lead to a meltdown every 3 years. This is probably an unacceptable rate; an accident rate at least ten times lower, and possibly 100 times lower may be needed if the system is to be acceptable.”

Later in the same lecture Weinberg added, “the acceptable accident rate will probably have to be much lower than the Rasmussen report suggests. If one uncontained core meltdown per 100 years is acceptable (and we have no way of knowing what an acceptable rate really is), then the probability of such an accident will have to be reduced to about one in 1 million per reactor per year.”

The basic problem with sodium cooled reactors like the Liquid Metal Fast Breeder Reactor is the safety problem inherent in the use of sodium as a coolant. Sodium reacts chemically with both air and water, and will burn strongly with either. Hence sodium leaks become a significant issue with sodium cooled reactors. The history of sodium cooled reactors give scant comfort to those who argue that they are safe.

Perhaps the best known Internet video related to reactor safety is the video of Japanese reactor workers responding to a sodium leak at the Monju Sodium cooled breeder reactor. The Monju reactor has been shutdown since the 1995 accident although reportedly the Japanese plan to reopen it this year. The Japanese were fortunate that the leak occurred in a secondary sodium coolant system, and that no radiation was leaked, however the danger of working with sodium are best illustrated by a 1996 attempt by Japanese researchers to recreate the conditions that lead to the Monju accident. Researchers concluded that the liquid sodium released during the accident, could have melted steel doors, and come into contact with a cement floor. A reaction between the liquid sodium and water in the cement would have caused a violent explosion. What would have happen next is not reported but the leaked sodium was not the only sodium that could have potentially been involved in the accident. Not only does primary coolant sodium burn easily in contact with air, it is also highly radioactive.

Weinberg, who had common sense, and who worried about nuclear safety, thought that the safety risk from using sodium as a reactor coolant was too great.

Like all reactors with solid fuels, sodium cooled reactors requite extensive piping in order to move the molten sodium fluid from the reactor to the heat exchange and back. Secondary sodium systems carry the heat to a steam generating systems, or to a gas turbine generating system. The movement of sodium through a system of pipes, coupled with the existence of two heat exchange systems, create an inherent safety danger for sodium cooled reactors.

The amount of sodium involved, and its radioactivity, potentially makes for a catastrophic accident.
In addition other fluid coolants, for example fluoride salts are superior to liquid sodium in many ways:

* Fluoride salts do not burn in contact with water or air.
* Fluoride salts boil at a much higher temperature than sodium, thus a fluoride salts cooled reactor can operate at a much higher temperature, hence with greater thermal efficiency.
* Nuclear fuel can be dissolved in Fluoride salts eliminating the need to fabricate nuclear fuel.
* Chemical operations involving fluoride compounds are well known in the nuclear industry and are relatively simple.
* Some fluoride salts have lower neutron cross sections than sodium, thus facilitating the transformation of fertile isotopes like Th232 into fissionable U233.
* Fluoride salts reactors have many features that make them inherently safe.

- Charles Barton

Comment: anonymous said…
Aside from your usual dose of ad-hominem fallacies, do you have specific information about van Leeuwen’s alleged errors?

My Response: I would not classify my argument as ad-hominem. I did not argue that Storm van Leeuwen was wrong because of the facts I laud out, rather I argued that his background did not qualify him to be an authority on nuclear power. The fallacy is the assumption that Storm van Leeuwen is an authority without carefully examining criticisms of SvL’s work.

If you are interested in Storm van Leeuwen’s errors I can provide you with some discussions. David Bradish discusses some “Storm-Smith” math errors here.

Roberto Dones compared “Storm-Smith” findings on CO2 emissions associated with nuclear power to several studies published in peer reviewed journals. Dones notes, “SvLS guesstimate relatively high to very high energy requirements and hence corresponding CO2 emissions for the electricity of nuclear origin, the highest to be found in the literature circulating in Internet,2 especially when low grade uranium ores are considered. The main explanation for SvLS’ high figures lies in their extreme assumptions (often rough guesses, as the authors admit themselves) and partially flawed methodology.”

Dones, whose paper is published under the letterhead of the Paul Scherrer Institute, like other critics argues that “Storm-Smith” cherry pick data: “the authors do not critically address their own evaluation in view of findings from those studies. Instead, they extract worst data from just one presentation (Orita 1995: Preliminary Assessment on Nuclear Fuel cycle and Energy Consumption), which is a highly incomplete survey, was never reviewed, nor it reports the used sources. ISA (2006, #35) discard figures reported in Orita (1995) on mining as “outliers”. . . SvLS qualify the data presented at that meeting as oversimplified and incomplete as if this were representing the whole of studies on the nuclear chain. Incidentally, several studies whose intermediate results were presented at the IAEA had and have been published in reports and journal papers and are acknowledged as reference LCA studies.”

Dones points to methodological errors:
“SvLS (2005) often convert costs into energetic terms using generic factors, not reported in the text, lacking critical consideration of cost components, and lacking use of technical match to compare with real energy expenditures.”

“SvLS (2005) add thermal to electric energy directly to give “total energy”, which is certainly not recommended practice.”

“SvLS do not provide explicitly conversion factor(s) PJe or PJth to CO2 mass.”

Dones also notes, “SvLS (2005) comparison of CO2 emission from nuclear with natural gas is not consistent..” and “SvLS (2005) use references that are likely to be outdated.”

Dones also states, “SvLS (2005) is not accounting for mine industry practices.” Dones, as well as other critics reports, SvLS (2005) pay no consideration of co-production of minerals as common practice for economically viable mining and milling (processing) of the ore especially in case of low grades. If co-production or by-production occurs, the energy expenditures shall be allocated to the different products according to the specific needs, accurately analyzing (to the extent possible) the complete process flow.”

Dones then points to “Storm-Smith’s” notorious Olympic Dam mine error:

“[A]s reported in (ISA 2006), in the Olympic Dam mine, where uranium is extracted as
a byproduct of copper, “most energy requirements would have been attributable to the recovered copper” under consideration of energy allocation to different products by process flow analysis. ISA (2006) reports the results of Olympic Dam’s own calculations based on such energy allocation, obtaining 0.012 GJ of energy to uranium “for every tonne of ore that we process in its entirety (from mining through to final product)”. This would correspond to 0.012/0.7/0.85/0.82 = 0.024 GJ/kgU for U-grade of 0.07% (proved ore reserves), or 0.041 GJ/kgU for 0.04% U-grade (total resources).9 Application of the formula in (SvLS 2005, Chapter 2, #5) would give for 0.07% grade the energy intensity of 4.4 GJ/kgU and 10.6 GJ/kgU, respectively for soft and hard ores, while with 0.04% the energy intensity would be 8.2 GJ/kgU and 19.5 GJ/kgU, respectively for soft and hard ores: i.e., SvLS formula would calculate two to three orders of magnitude higher values than this specific case.”

Dones argues, “SvLS (2005) systematically overestimates energy expenditures, thus the associated GHG.”

Rather than continue a summation of Dones devastating critique of “Storm-Smith”, I suggest that you read the whole thing.

Martin Sevior‘s well known critique of Storm-Smith together with the debated between Sevior and “Storm-Smith” are to be found here with links. Savior’s arguments are presented along with an extensive discussion, are presented on The Oil Drum here, and here.

Critics of nuclear power continuously miss represent “Storm-Smith’s” authority. For example, David Thorpe, in the Guardian’s “Comments are Free” blog, claimed “extensively peer-reviewed empirical analysis of the energy intensity and carbon emissions at each stage of the nuclear cycle has produced much higher figures. In fact, nuclear power produces roughly one quarter to one third as much carbon dioxide as the delivery of the same quantity of electricity from natural gas, ie 88-134g CO2/kWh.” In fact Thorpe did not supply a link to any peer reviewed study. Indeed Thorpe provided a link to the Storm-Smith web page. None of the “Storm-Smith” studies were ever published in reputable, peer reviewed journals, so Thore is clearly either ignorant or dishonest.

Other common misrepresentations of Storm van Leeuwen’s authority are the titles Professor and Doctor which are used with his name. To point out that SvL does not qualify for either title is surely not an ad-hominem fallacies. It is simply a counter to common misrepresentation of SvL’s credentials. The fallacy then is the overblowing and misrepresentation of SvL authority, by people who for ideological purposes, use SvL’s alleged authority to hid the flawed nature of his work.

David Fleming argues in his booklet, “The Lean Guide to Nuclear Energy: A Life-Cycle in Trouble,” that the era of nuclear energy is over.

Fleming argues that “The world’s endowment of uranium ore is now so depleted that the
nuclear industry will never, from its own resources, be able to generate the energy it needs to clear up its own backlog of waste.” I have previously demonstrated in Nuclear Green that it is not the case that we have exhausted the world’s uranium resources, and indeed given current technology, it is possible to extract abundant amounts of uranium for a period of time that would extend many tens of thousands of years into the future. Thorium is three to four times abundant as uranium, and through nuclear alchemy, thorium can be converted into U233. I have discussed David Fleming’s numerous errors in his discussion of thorium. Fleming, however, committed numerous other errors in his pamphlet.

A review of Fleming’s booklet reveals that he relies on one source for his information, that is the work of Jan Willem Storm van Leeuwen and the late Dr. Philip Smith. Fleming acknowledges that before he wrote his booklet, he had a consultation with Storm van Leeuwen that lasted many months, and he mentions Storm van Leeuwen 86 times in his 50 page booklet.

Fleming argues that: “Back-end” energy – the energy needed to clear up all the wastes produced at each stage of the front-end processes, including the disposal of old reactors – is of two kinds: (1) the energy needed to dispose of the new waste – that is, the waste produced in the future, and (2) the energy needed to dispose of the whole backlog which has accumulated since the nuclear industry started-up in the 1950s. Back-end energy is the combined total of both of these.

Thus according to Fleming if the industry really had 60 years’ supply of uranium left for its use, it would only have some fifteen years left before the decisive moment; from that turning-point, its entire net output of energy would have to be used for the essential task of getting rid of its
stockpile of wastes, plus the wastes produced in the future.

How does he know this is true? Fleming gives us a footnote:
“Oxford Research Group (2006a); and Storm van Leeuwen (2006B), and (2006E).
SVL, Parts C2, C4. ” In case you are wondering Storm van Leeuwen is listed as the source of the Oxford Research Group’s findings by Fleming himself. The title “the Oxford Research Group,” itself is something of a misnomer, since none of the listed authors appears to have any connection with Oxford.

Thus Fleming placed a great deal of reliance on Storm van Leeuwen authority. It is clearly questionable if Storm van Leeuwen, can be uncritically relied on in matters involving such broad judgements. He is not a nuclear scientist or a resource economist, indeed it is not clear if Storm Van Leeuwen has ever published a paper in a peer reviewed journal. He is listed as a Senior Scientist, Ceedata Consultancy, Chaam, Netherlands. A search for Storm Van Leeuwen uncovered the following information:

“Jan Willem Storm van Leeuwen, M.Sc., was born in Indonesia in 1941. He attended gymnasium (high school) in Utrecht. After graduation he served in the armed forces for two years. He then studied chemistry and physics at the University of Utrecht, B.S. He took his degree of M.Sc. at the Technical University Eindhoven in chemical technology (catalysis) in 1971. During the US exhibition ‘Atoms at Work’ in Utrecht in 1966, he was reactor assistant, with great interest in nuclear sciences.”

“After completing his study, he chose a mixed occupation as a part-time teacher of chemistry and physics at a high school (A-level) and as a free-lance investigator. He has more than 30 years of experience in technology assessment. The main fields of his expertise are chemistry and energy systems (solar, fossil and nuclear), with related ecological aspects. The profile of his consulting work is making complex systems transparent and to make relevant data accessible to policy makers. During the years 1981-1982 he was a senior consultant of the Centre for Energy Conservation (CE), Delft, as member of a team working on the development of an innovative social-economic scenario and to assess all aspects of large-scale implementation of nuclear power. His technology-assessment studies of nuclear power started at the CE in 1978 and continued until 1987. During the last few years, these studies have become topical again, since the nuclear industry began claiming a practically zero emission of CO2. ”

Another biography adds:

“Storm prepared, in collaboration with other experts, two reports on nuclear energy on in-vitation of the Dutch government, published in 1982 and 1987 respectively. During that pe-riod Storm was a senior consultant at the Centre for Energy Conservation and Sustainable Technology (CE) at Delft, and member of a team working on the development of an innovative social-economic scenario. In collaboration with Prof. Philip Smith he assessed all aspects of large scale implementation of nuclear power, including the forgotten ones. The CE scenario had a significant effect on the Dutch energy policy during the 1980s and 1990s. During the 1990s the discussion on nuclear power faded into the background. In 2000 the Greens of the European Parliament asked Storm, then independent consultant, to update his report from 1987, and to prepare a background document for the UN Climate Conference COP6 (The Hague, 13-24 November 2000).From 2000 on, again with Philip Smith, Storm van Leeuwen continued the broad and in-depth reassessment of nuclear power. The results were published on the web, to facilitate interaction with the target group: scientists, policy makers and interested individuals. From then on the authors keep in close contact with many scientists all over the world.Storm van Leeuwen is one of the international group of expert reviewers of the Fourth Assessment Report (AR4) of the IPCC.“

Storm van Leeuwen is the secretary of the Dutch Association of the Club of Rome.

Storm Van Leeuwen does appear to come from a distinguished Dutch family. His biography suggests that most of the first four years of his life were probably spent in a Japanese internment camp in Indonesia. Such early experiences can have a negative impact on the life of a very young child from whom much is expected. Storm Van Leeuwen’s was educated as a chemical engineer who does not appear to have worked as a chemical engineer, and who appears to have struggled to find his place in society. His place appears to be associated with the the Malthusian wing of the European Green movement. The “Storm-Smith” study appears to have been paid for by the anti-nuclear, European Green Lobby.

Thus Fleming rests his argument that bac
k end energy requirements of nuclear power represent such a singular energy demand, that it would consume all of the output of reactors, on the rather slender authority of “Storm-Smith” and in particular on the even more slender authority of Storm Van Leeuwen.

“the Sure Way, (though most about,) to make Gold, is to know the Causes of the Severall Natures before rehearsed, and the Axiomes concerning the same. For if a man can make a Metall, that hath all these Properties, Let men dispute, whether it be Gold, or no?” – Frances Bacon

I recently stumbled across an internet discussion of the idea of transforming thorium 232 into uranium 233 in a reactor. The term breeding was used, and this lead to confusion. Someone mentioned plutonium. There is a natural linguistic association between the term “breeder reactor” and the word “plutonium”.

The word “breeder” is “breeder reactor” is used metaphorically. What happens inside reactors is arguably nothing at all like the biological process of reproducing. Nothing new is produced in the nuclear transformation process, but something is changed. So not only are the words “breeding” and “breeder” problematic from the standpoint of associations, they represent a weak metaphor.

A breeder is someone who selects animals for desirable characteristics to reproduce in offspring, and who controls the reproductive process. But what happens inside reactors is that certain physical processes occur, that lead to the transformation of isotopes of one element into isotopes of another element. Is there an appropriate name for the transformation process? The word alchemy comes to mind. The goal of alchemy was the transformation of elements as understood by the alchemist. Such a transformation takes place inside a reactor. Thus the term nuclear alchemy would seem appropriate for the nuclear processes that transforms one element into another. In fact it is quite possible to turn lead to gold inside a reactor.

The reactor enables us to achieve the goal of the ancient science of alchemy, that is the conversion of atoms of an otherwise useless material, into atoms of a material that is of value.

Thus the term converter reactor would seem the best to use for a reactor which transforms Thorium into nuclear fuel. Nuclear alchemy is the name of the process, and is the name of any process by which elements are transformed as a consequence of controlled nuclear fission.

(Posted by Charles Barton, cross posted on Nuclear Green)
Introduction: I wrote Dr, Ralph Moir last week, seeking an email interview. Dr. Moir was an extremely distinguished scientist at Lawrence-Livermore Laboratory, and a personal associate of Dr. Edward Teller. Dr. Moir was extremely gracious in answering all of my questions. I have split the three pasts of the interview into three separate posts. The first questions address Dr. Moir’s work with fission/fusion hybrid reactors.

On Mar 13, 2008, at 9:49 AM, Charles Barton wrote:

Dear Dr. Moir, There are numerous questions I would like to ask you. This would be of course contingent on your willingness to spend the time required to respond to my questions. I take the view that scientists are people who work on important questions, and their views should be known to a broader public. I have posted a number of my father’s public papers along with an account of his career at ORNL on my blog, Nuclear Green. I have also given a considerable focus to the writings and career of Alvin Weinberg. Since you are a senior scientist, your knowledge and experience should be of considerable public interest. If you so choose, I would very much appreciate if you answer some or all of these questions.

During much of your own working career, you worked on the fusion/fission hybrid concept. I have a number of questions in connection with that:

1. Do you still think that concept is viable?
Yes.

2. What would see as its strengths and weaknesses?
Fusion holds the promise–yet to be fulfilled–of providing a supply of neutrons that can be used to produce fissile fuel for fission reactors. Even if fusion cost twice that of fission per unit of thermal power produced, its fuel would be competitive with mined uranium at $200/kg. Fusion will be even more competitive as its costs come down. This produced fuel can be used in fission reactors to completely burn up the fertile fuel supply, that is depleted uranium or thorium. Its weakness is fusion is not here and past slow progress suggests future progress might be slow. Furthermore, we are not assured that fusion’s costs will be less than twice that of fission.

That fusion can produce or breed fissile fuel is an advantage and simultaneously any facilities must be guarded against their misuse towards making fissile material for unauthorized explosives.

3. What technical advantages, if any would you see for a fusion/fission hybrid over a conventional molten salt reactor?

A conventional molten salt reactor can produce almost all of its own fuel but needs initial fuel for start up and needs some makeup fuel and also some fuel to be used to burnout certain wastes. So the fusion/fission hybrid can be this fuel supplier. In this way the combination of a hybrid fuel supplier and molten-salt burners can supply the planet’s power for many hundreds or even thousands of years at an increased nuclear power level enough to make a big impact in decreasing carbon usage. Such a combination might have one hybrid fusion fission reactor for every fifteen fission reactors.

If a hybrid reactor produces both fuel and power by fissioning this fuel in-situ, I am afraid the system will be uneconomical relative to the combination of a fuel producer and separate burner fission reactors and relative to other fission reactors.

4. In what timeframe might we expect to see an technically and economically viable product?

So far fusion concepts that are approaching the feasibility stage suffer from being very expensive. Tokamak magnetic fusion and laser fusion facilities are very expensive making “productizing” uneconomical based on our present state-of-the-art. The next tokamak called ITER might be built and tested in 15 years and with advances the projected costs in a follow-on might be low enough that a product or viable product can come out after another 15 years or 30 years from now.

The laser fusion facilities are also too expensive but with advances in the next five years a follow-on set of facilities might be an economical product in another 15 years or 20 years from now. A key to progress in fusion is getting better performance in smaller lower cost facilities.

(Posted by Charles Barton, cross posted on Nuclear Green)
1. Can you tell us why you shifted your interest from fission/fusion hybrids to more conventional Molten Salt Reactors?

My job at Lawrence Livermore National Laboratory involved studying and designing fusion/fission hybrid reactors. I led the effort of many terrific researchers including those at other labs: ORNL, ANL, INL, PPPL and industries: Westinghouse, GE, GA, Bechtel. During this time I became increasingly more familiar with all the fission reactor concepts. My favorite technology for fuel production was the use of molten salt pumped through the blanket surrounding the fusion reactor.

My favorite fission reactor was the molten-salt reactor whose program was terminated in the 1970s. While others were forgetting about the molten-salt reactor I became more interested but this was not a part of my job. After retiring from full time work in 2000 I increased my effort on the molten-salt reactor.

2. Why do you think that the Molten-Salt Reactor is important?

It holds the promise of being more economical than our present reactors while using less fuel. I published a paper on this topic that the ORNL people did not feel they could publish. It can come in small sizes without as much of a penalty as is usually the case and can be in large sizes. It can burn thorium thereby getting away from so much buildup of plutonium and higher actinides.

3. What is your relationship to the Fuji Molten-Salt Reactor project?

I became familiar with this effort and its leader Professor Furukawa in about 1980 and appreciate his carrying on the ORNL work after they stopped. He has been a friend and colleague ever since.

4. What project is that project making?

The next step in molten salt reactor development should be the construction and operation of a small <10 MWe reactor based largely on the MSRE that operated at ORNL at about 7 MWth but without electricity production. The FUJI project has not gotten funding and is making no progress other than a paper here and there on some particular aspect.

5. Do you believe that a crash development of the Molten-Salt Reactor concept is warranted?

Yes, that is in fact the conclusion of the paper Teller and I wrote. Surprisingly the cost of a crash program is not so great, less than $1B but its progress could be rapid owing to the feasibility proven by the work at ORNL so long ago on MSRE.

6. What is your opinion of the use of carbon-carbon composites in Molten-Salt Reactors?

I am impressed by the ideas for use of carbon-carbon composites for high temperature heat exchangers and maybe piping and vessels. If metals are not used in the primary system then the temperature could jump from the 700°C of MSRE to 1000°C by use of carbon-carbon composites. This development could be rapid by building on the work taking place in industry today.

7. What is any techniques would you suggest to counteract the effects of neutron radiation of graphite and carbon-carbon composites?

I am not very knowledgeable on graphite technology and can only assume small incremental improvements in its radiation damage abilities can be expected. However, I am intrigued by the dedicated effort of a number of individuals who are studying ways of eliminating the use of graphite as a moderator in the molten-salt reactor. Perhaps carbon-carbon composites might be used as replaceable shields to protect walls from the direct neutron damage or be used to separate two fluids, an old concept at ORNL that was dropped over three decades ago but composites might resurrect it.

(Posted by Charles Barton, cross posted on Nuclear Green)
Questions on Edward Teller

1. Edward Teller remained a controversial figure at the time of his death. Since you worked with Teller, what do you think the public should know, in order to better understand him?

He was brilliant, multi-dimensional and focused. He promoted action via the political process that gave him fame and infamy but most importantly gave results. His writing and that written about him tells the story. It is most inspiring and I recommend its reading to anyone interested.

2. My own understanding of Teller was that he was a complex person. Can you give us some insights?

Yes he was complex but getting to know him told you he was in depth on many axes. He focused on one topic at a time. Sequentially he could switch to another topic but preferred to stay on the topic at hand and work it hard. He treated science as having fun. It was a joy to him to discuss ideas.

3. Teller appears to have had a long time interest in the molten-salt reactor. How important did Teller think the development of the Molten-Salt Reactor was?

Teller had a long term interest in seeing fission reactors built for mankind’s benefit. His interest was to encourage that end rather than work directly in pursuit of reactor development. He strongly favored thorium and thermal reactors and undergrounding them. He periodically over the past 25 years of his life would call on me to review the characteristics of various reactor types. I always treated all of them but ended by saying I preferred the molten-salt reactor. He finally agreed with me and we wrote the paper together. In other words he was not a strong advocate of the molten-salt reactor over a lot of years. He thought the program must have been terminated for good reasons. After examining the reasons for terminating the program he came up with the phrase, “it was an excusable mistake.” He believed building a small molten-salt reactor to get the development going and get deployment going was most urgent because our energy options are running out (especially natural gas).

4. Did Teller have any time frame in which he anticipated to molten-salt reactor development?

At a spending level of $100M per year for R&D and $100M per year for construction, such a program could have a ~10 MWe unit operating in a decade and be well on the way towards a large scale power plan.

5. Teller was interested in setting up reactors underground. Why did he prefer underground placement, rather than using conventional containment structures?

He used the word “obvious” safety. Bomb tests conducted underground contained the radioactive products very well. It was this fact and the fact that waste are to be stored underground both suggest building the reactors themselves underground. I repeatedly brought up the point that under grounding increases the cost and if the cost increase is too much, perhaps over 20% the reactor will most likely not be built. He accepted the idea that 10m underground was a good compromise between the safety benefits of undergrounding while keeping the cost add on small enough to not preclude the deployment.

My web site gives links to downloading my paper with Teller on the thorium-fueled underground power plant based on molten-salt technology. Also there are papers on the cost of electricity compared to other reactors and recommendations for a restart of molten-salt reactor development.