The MSR and the Veil of Secrecy

Sometime, not long after my father went to work as a chemist in Oak Ridge, I asked him what he did at work.

"That is a secret," he told me. His secret employment lead to the development of reactors for submarines. Later the same work lead to the development of civilian power reactors. Then his secret work turned to Molten Sale Reactors and the potential to build atomic powered bombers.

How secret his work was can be judged, by a document I found among his papers. That document recorded on data set numbers left out of a report because they were considered too sensitive to include in the report he had written for the AEC. All he would tell his family about what he was doing where the letters "ANP".

Gradually the veil of secrecy under which my father work was lifted, and the product of his research was opened to other scientists without regard to security considerations. During the 1960's ORNL scientists, working on Molten Salt Reactor technology, were quite open about their research, and their work product was distributed to anyone who was interested.

When Kirk Sorensen founded Energy from Thorium, he included an open science forum, which allowed anyone who was interested in MSR technology to openly talk about it. This began to change a couple of years ago, when Kirk left NASA for employment with a private business. It is probable that the words proprietary concerns were mentioned to Kirk. Other words may have been mentioned as well. Then a year ago, the Chinese appeared at an ORNL conference on MSRs. They did not have much to say, but they were listening intently.

The significance of Chinese interests were revealed earlier this year, when the Chinese announced that they were planning to develop Thorium Fuel cycle MSRs. They used words like intellectual property rights, and the whole game changed. Yesterday I pointed to a quote by Kim Johnson that illustrates how much things have changed in a short period of time:

Sadly however, I can no longer post important details Freely. Serious Foreign competition could very well, in a few years' time, leave the US so far behind in our own Fluoride-Energy tech we'd never recover economically.

People are starting to hold back information.

People who in the past held jobs that had nothing to do with MSRs, now are finding MSR related employment. As they do, they start withholding information. I am not scolding them, just pointing out what is happening. I could talk about who is doing this, and speculate about what they are not saying, but it is probably best to leave those questions alone.

This is, of course, a sign of progress. A sign that what I have worked for during the last 4 years is starting to come to pass. The unintended consequence of a success that can be laid at the feet of free information, is that the very same information begins to dry up.

The Molten Salt Reactor Family: Two Fluid Reactors

The two fluid Molten Salt Reactor uses separate fluids for fuel and carrier salts. In the two fluid desige, two seperate salt fluids are present in the MSR core. The first is the fuel carrier, that is it contains one or more fissionable isotope. U-233, U-239 or Pu-239. A second fluid carries a fertile material, in MSRs always Th-232. There were from the start a numbr of advantages to the two fluid approach, as David LeBlanc points out,

Advantages

* Much more practical fission product processing without thorium in fuel salt
* Have choice of Vacuum Distillation or Simplified Liquid Bismuth Extraction
* Strongly negative temperature/void fuel salt reactivity constants
* Pa removal easily avoided by simply increasing volume of blanket salt Neutron leakage near zero

There were also a number of disadvantages,

Disadvantages

* Interlacing of fuel and blanket salt within core is the “Plumbing Problem”
* Blanket salt has positive temperature/void coefficients
* Need for extra heat transfer loop for the blanket salt (5-10% of heat load)

The carrier salt is referred to as the blanket salt. David LeBlanc pointed out that one advantage of a two fluid design is that protactinium need not be removed immediately from the blanket salt, while its presence effects both the nuclear process and the chemistry of the one fluid design.

Protactinium 233 is the 27 day half life intermediate between fertile Thorium and fissile U233. The problem is that it has a moderately high cross section for absorption, such that if it stays in the reactor loop, it may capture a neutron and not become U233. The average neutron flux the Pa sees is the main factor on how many neutrons will be lost. By increasing the volume of salt that carries the Thorium, one can lower these losses and skip this processing step. However, in a Single Fluid design if one increases the salt volume (by a lower power density core etc.) then this also increases the amount of fissile U233 needed at the same time.

In a 2 Fluid design with Thorium only in the blanket salt, one can increase its volume which does not increase how much U233 is needed. This is a financial burden in terms of carrier salt and Thorium but it is by no means excessive.

Skipping the Pa removal step is important for two main reasons. First, the process must be done very quickly, on the order of processing the whole volume of carrier salt in3 to 10 days. This is an enormous technical and economic challenge. Second is that this introduces a unique proliferation risk. When U233 is produced while in the reactor, significant quantities of U232 are also present. This is highly radioactive and leads to an extremely strong gamma ray being emitted. This would make working with the material extremely difficult if not impossible and also make detection of illicit material easily detectable. However, if the Pa is removed and allowed to decay outside the reactor it produces relatively clean U233.

Despite the disadvantages of the single fluid reactor in the late 1960's ORNL leaders felt that they were in competition with Liquid Metal Fast Breeder Reactors, championed by Argonne National Laboratory. The LMFBR had some significant disadvantages, but it did feature a high breeding ratio, much higher, in fact than the breeding ratio of thermal cycle thorium breeders. Thus the slight theoretical breeding advantage of the single fluid MSR was attractive to them. Then ORNL scientists discovered

Liquid Bismuth reductive extraction process.

And although difficult, indeed quite possibly extremely difficult, it offered a route to staying in the breeder game for a little while. The breeder competition was itself evidence of the incompetence of the American Nuclear establishment. The LMFBR was a failure, that ended up costing billions of dollars only to end up being too expensive to build even a prototype. It could not compete with the MSR as far as safety or reprocessing technology. Eventually scientists at Argonne National Laboratory were to scrap the old LMFBR concept, and develop a new sodium cooled fast breeder design, the Integral Fast Reactor, that came much closer to matching many MSR advanced features. By that time the MSR was nothing more than a large series of research reports, and a shutdown prototype awaiting decommissioning.

At any rate, the ORNL two fluid MSR design from the 1960's was a very advanced reactor design that still looks very futuristic. reactor design. The design featured a 1000 MW power station, powered by 4 modular 250 MW two fluid MSRs. The motive for the modular design was not the cost advantage of factory production although ORNL researchers were no doubt aware of that. Rather, there intention was

replacement of an entire reactor vessel assembly after the core graphite received its allowable exposure to neutrons. [After] . . . about eight years of full-power operation.

ORNL 3996 stated,

An important factor in low power costs is the ability of the power plant t o maintain a high plant-availability factor. Thus design features
that can improve this factor are desirable if these features do not themselves introduce compensating disadvantages.

A four Modular Molten Salt Breeder Reactor (MMSBR) facility will clearly more reliable than a one reactor facility. If one reactor is down, 750 MWs of electrical power would still be available, while in a single reactor one GW plant the down reactor would mean that no power would be available.

Like all two fluid MSRs, the OENL Modular Molten Salt Breeder Reactor two fluid reactor design divided its core into reactive and blanket regions. A blanket suggests that the core would have an inner region for fissionable materials and an outer region for fertile materials. This was not in fact the case in the ORNL modular design. The graphite in the core was divided up into tubes and core and blanket tubes were interlaced. This feature was not viable. Graphite shrinks and then swells under neutron bombardment. This caused ORNL MSR designers one huge headache, because the core plumbing would vary in size as the graphite evolved, this would effect regional power output within the core in unpredictable ways, and introduce an unacceptable level of uncertainty into reactor operations. ORNL-4528 noted,

The major concern was whether mechanical failure of graphite tubes in the reactor core would cause the effective lifetime of the core to be significantly less than the eight years imposed by the effects of irradiation on the graphite.

ORNL-4528 added,

The change in radial dimensions presented a more difficult problem. Densification of the graphite to produce a 2.5% reduction in distance across the flats of the hexagonal tubes would cause the fraction of the cross section of the core occupied by fuel cells to decrease by 5%, and the space occupied by the blanket salt would increase correspondingly. For the reactor with an average power density of 20 kw/liter, the volume fractions in the core would change from 0.802 to 0.762 for graphite, 0.134 t o 0.127 for fuel salt, and 0.064 to 0.111 for blanket salt. Changes of equal magnitude, but opposite in direction, would occur during the expansion phase. The rates of change of dimensions would vary with local power density, so at no time during the life of a core would the volume fractions corresponding to the maximum contraction or expansion exist throughout the core. At the end of life the graphite at the center of the core would have reached its maximum volume; graphite in the regions of average power density would be about at its minimum volume, and graphite in the outer fuel cells would be about halfway into the contraction stage.

ORNL 4528 explained,

Under irradiation the isotropic graphite being con-sidered at the time of these studies would decrease in volume by 7.5% during the contraction stage and then would increase in volume by as much as 7.5% over its initial volume by the end of its useful life. These changes in volume correspond to changes in linear dimensions of M.5% over the initial dimensions and create several design problems.

The MMSBR was intended to be a true breeder and depending on core design could breed at about a 1.05 or 1.06 ratio, with a fissile inventory as low as 220 kgs, or about a ton of U-233 per GW of rated electrical output. This was spectacular, but a larger core would mean longer graphite life and would nearly double the fissile inventory of the MMSBR. In order to capture every spare neutron, 150 times as much thorium was to be pumped through the MMSR core. The fissile inventory performance of the MMSBR is quite impressive when compared to that of recent French Fast Molten Salt Reactor designs that require as much as a six times larger fissile inventory. Sodium cooled fast breeders require a fissil inventory of as much as ten times as large.

Thus we have seen that the two fluid ORNL MMSBR although promising posed some significant materials and design problems. There was no advance in two fluid MSR design for nearly 40 years, until Canadian Physicist David LeBlanc proposed a radical change in two Fluid MSR core design. The old two fluid design had a diameter of 10 feet or more, while LeBlances new design had a diamiter of one meter.

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The LeBlanc tube core represents a potential breakthrough in reactor core design. It is extremely simple and manufacturing costs would be mainly material costs. The core itself could be built in a day. It can either be graphite moderated, coolant moderated or fast.

A recent paper by Reactor researchers from the Czech Republic, Jan Frybort and Radim Vocka argued that some problems of the ORNL MMSBR could be solved, while pointing out a new and previously unrecognized safety problem. The Paper, titled Neutronic Analysis of Two-Fluid Thorium Molten Salt Reactor (See Kirk Sorensen's discussion). Kirk summarizes,

In part 4A, they found that the temperature coefficient was strongly negative and that the breeding factor was good. In part 5, they looked at changing the design to improve it, and found that by making the fuel channels bigger than the original design, they improved nearly all parameters. This is an important result, since it’s not often that you change a parameter and find improvements in nearly all outputs from that parameter.

And then notes,

In part 7 of the paper, they mention the second key issue with a two-fluid reactor–the problem of the blanket void coefficient. Since the original ORNL design had the problem, and since they modeled only parametric variations on that original design, it’s no surprise that the problem still shows up. It must be fixed, probably through a new design approach to the two-fluid reactor. I have some ideas, most all of them based around physical situations where a loss of blanket fluid leads to a loss of moderation. I anticipate that this could be done by floating moderator elements (graphite) in the blanket salt, so that as the level of the blanket salt falls, the moderation decreases more than the absorption decreases from the loss of blanket. These ideas definitely need more modeling, but I think they are essentially sound.

Would the same effect apply to David LeBlanc's two shell design? Probably not. The Blanket void, positive coefficient of reactivity problem stems from the interlacing of blanket and fissionable salts in the MMSBR. David LeBlanc does not interlace blanket and core salts, thus a blanket void would not seem to increase core neutrons. A simple solution to the problem in the ORN design would be to keep core salt tubes in the center of the tube array, while blanket salt tubes form a ring around them on the outside. I suspect that Kirk has something like this in mind as his solution to the blanket salt void problem. At any rate, the two blanket solution appears to be alive and a very promising path toward a nuclear future.

The Molten Salt Reactor Family: Fuel

I intend to offer a series of posts designed to explain the sometimes bewildering complexity of Molten Salt Reactor Technology. This first post explains two nuclear fuel breeding cycles.

Rather than offering a single potential reactor design, the Molten Salt Reactor (MSR) idea offers a large number of design options, each of which would require a significant amount of research, before a prototype reactor could be built. The Molten Salt Reactor designer is faced with a bewildering number of elective choices, each offering a set of advantages and disadvantages. Each choice that the designer makes will dictate a number of design features some of which require further choices.

Lets start with nuclear fuel. My father first demonstrated that not only U-235 but also Pu-239 could be used as a reactor fuel in MSRs. During the ORNL Molten Salt Reactor experiment Oak Ridge scientists tested the use of the three fissionable materials that can be used as nuclear fuels, Plutonium-239 (Pu-239), Uranium-235 (U-235) and Uranium-233 (U-233). Once during the operation of the Molten Salt Reactor Experiment (MSRE) they used all three potential fuels in the reactor at the same time.

Of the three potential fuels, U-233 had some significant advantages. Neither U-235 nor Pu-239 produced enough neutrons per neutron hit, to support breeding more nuclear fuel at a slow (thermal) neutron speed range. U-233, produced by breeding thorium did produce enough neutrons to breed thorium at a slow temperature range. We will see that this offers a very large advantage. U-235 is not efficiently produced by breeding, while Pu-239 can only be produced in the breeding range with fast neutrons.

Breeding means that for every fuel atom used in the nuclear process, at least one new fuel atom is produced. Thus in a plutonium fast breeder, if a neutron strikes a plutonium atom, it is very likely to fission into two smaller atoms, almost always with three neutrons left over. Those neutrons will be moving fast and will contain a lot of energy. Fast neutrons are more likely to produce fission in plutonium atoms than slow neutrons. Neither U-235 nor Pu-239 produce enough neutrons to maintain breeding if they encounter a slow (also called thermal) neutron. Thus Plutonium can only be produced as a nuclear fuel in so called fast reactors. There are, as we shall see, some major disadvantages to fast reactors.

Fast reactors are often thought of as having liquid sodium as their coolant, although liquid lead, and a liquid lead-bismuth mixture have also been used as a coolant in fast reactors. In addition it is possible to build fast Molten Salt Reactors. The stability of Molten Salt Reactor operations in enhanced by Xenon-135 removal. Xenon-135 is a radioactive gas that is a byproduct of nuclear fission and has a very large neutron cross section. Because it is very likely to capture neutrons, Xenon-135 can adversely effect a chain reactor in a reactor. Thus it would be highly desirable to get Xenon-135 out of a reactor core quickly after it is produced. That is impossible in a solid core reactor, but it is not difficult to do in a Molten Salt Reactor. The presence of Xenon-135 adversely effects to the ability of reactors to breed nuclear fuel, so any MSR that is designed as a thorium breeder would have a system for moving Xenon-135 out of its core.

There are decided advantages for fuel reprocessing with MSRs. Compare the fuel reprocessing technique for a Molten Salt Reactor with the fuel reprocessing technique proposed for the Integral Fast Reactor (IFR) a LMFBR. In two fluid MSR, the blanket salt flows out of the blanket, and protactinium and U-233 are withdrawn from it by chemical processes. Once they are processed out of the carrier salt, the U-233 is re-fluoridated and returned to the core. The protactinium is set aside until it undergoes a nuclear transformation to U-233, and then that U-233 is returned to the core. In a IFR, the spent fuel is fished out of the reactor core, and once recovered, dumped into a molten salt bath, in which it dissolves. Then by use of electroplating, various material from the old fuel, for example plutonium, are separated out of the bath, and deposited on electrodes. Eventually the separated metal, is recovered, melted and mixed into an alloy, which is then cooled enough to serve as fuel elements, and then returned into the reactor. The MSR fuel reprocessing technology is much simpler than the fuel reprocessing technology designed for the IFR.

In addition fast reactors require 10 times as much nuclear fuel to produce a chain reaction as thermal breeder reactors. It does not really matter if the fast reactor is cooled by liquid metal of liquid salts, a fast breeder reactor just needs a who lot more fuel in order to operate than a thermal breeder reactor does. This makes fast reactors poor candidates to replace fossil fuels like coal with nuclear power, because many reactors will have to be built quickly, and fueling enough fast reactors quickly will be a big challenge.

There are two breeding cycles, the Uranium 238 breeding cucle, and the thorium 232 breeding cycle. Both cycles have some advantage. Plutonium-239 produces more neutrons per fission event than thorium, but fewer fission events per neutron in the thermal spectrum. In fact Pu-239 produces so many fewer fission events in the thermal spectrum than in the fast spectrum, that it is impossible to achieve a positive breeding ratio for the U-238/Pu-239 breeding cycle in a thermal reactor. On the other nand U-233 produces about as many neutrons per fission event in the thermal range as in the fast range, and about as many fission events. That means that the Th-232/U-233 breeding cycle is as effective in the thermal range asin the fast range, and because thorium breeding only requires about 10% of the nuclear fuel in the thermal range as U-238 breeding requires in the fast range, thorium breeding cycle reactors can be deployed far faster.

In addition Liquid fuel reactors have advantages over solid fuel reactors. Once a sollid fuel is inserted into a reactor it almost always stayes there for a year or more, while fission products build up in the fuel. We have already seen that Xenon-135 becomes a reactor control problem, although Xenon-135 eventually reaches an equalibrium because of its short half-life. The presence of Xenon-135 in a nuclear core, can interfear with a reactor's capacity to bread, especially in the thermal breeding range. Thus Thorium fuel cycle breeder reactor are better candidates for rapid deployment than U-238 fuel cycle breeders, and liquid fuel thorium breeding reactors have advantages as solid fuel thorium breeder. Liquid fueled thorium breeders, as we have already noted, have advantages over solid fuel U-238 breeders. Thus the Thorium fuel cycle Molten Salt Reactor (often called the LFTR) would seem to offer several advantages over U-238 fuel cycle liquid metal fast reactor.

In the next post of this series I intend to explain the difference between single fluid and twoi fluid Molten Salt Reactors.

The Molten-Salt Reactor Demonstration Reactor

Ed Bettis, who was one of the inventors of the Molten Salt Reactor concept, and was a pioneering champion, went on to become lead an ORNL design group during the 1960's and 1970's. Bettis designed both one and two fluid reactors, including a pioneering ORNL two fluid 250 kWe Modular MSR. Bettis also realized that a practical MSR, based on MSRE tested technology and in ORNL-TM-3832 (DESIGN STUDIES OF A MOLTEN-SALT REACTOR DEMONSTRATION PLANT) offered a practical design for such a reactor. The purpose of the Demonstration Reactor project was to

represents a molten-salt reactor plant which is feasible to build, will produce a significant amount of electrical power, and will be a major step toward a useful family of breeder reactors.

The abstract of ORNL-TM-3832 reads

The MSDR, a 350-MW(e) Molten-Salt Reactor Demonstration Reactor, is based on technology much of which was demonstrated by the MSRE. The cylindrical vessel (26 ft diam by 26 ft high) houses a matrix of graphite slabs forming salt passages having 8 volume fraction in the core of 10%. . . In the secondary exchanger, heat is transferred to a stream of Hitec salt (in at 800 F, out a t 1000F). The Hitec oxidizes tritium to tritiated water which is removed and disposed of. The Hitec generates steam at 9OO F, 2400 psi in a boiler, super- heater, and reheater. Electricity is produced a t an overall efficiency of 36.6%. Soluble fission products are removed by discarding the carrier salt every 8 years after recovery of the, uranium by fluorination. Volatile fission products are removed by sparging the fuel salt with helium bubbles in the reactor primary system. The fuel cycle cost was estimated t o 0.7 mill/kWhr for inventory, 0.3 mill/kWhr for replacement, and 0.1 mill/kWhr for processing, giving a total of 1.1 mills/kWhr.

Although ORNL's primary reactor development focus during the early 1970's was on the development of a Molten Salt Breeder Reactor, Bettis suggested:

An alternative approach to the development of a commercial MSBR has also evoked interest. This approach emphasizes more rapid attain- ment of commercial size but more gradual attainment of high performance. The step beyond the MSRE is construction of a 300-MW(e) Molten-Salt Demonstration Reactor(MSDR). The purpose of the MSDR would be to demonstrate the molten-salt reactor concept on a semi-commercial scale while requiring little development of basic technology beyond that demonstrated in the MSRE.

We see from the abstract that many improvements would be possible with the 1972 design. Compared to the MSBR, Bettis and his associates proposed,

First, the MSDR has only such chemical processing as was demonstrated in the
MSRE and has no provision for removing fission product poisons on a short time cycle. Thisresults in a much less complicated chemical processing plant, although it means that the reactor has a breeding ratio less than one and i s therefore a converter. The second major simplification i s that the power density was made low enough for the graphite core to last the 30-year design lifetime of the plant, thus simplifying the reactor vessel and eliminating the equipment for replacing the core.

At the time ORNL MSBR plans called for the periodic removal and replacement of the MSBR Graphite core, as a solution to the problem of core swelling caused by neutron bombardment. This involved design complexities, and so Bettis proposed an alternate scheme to deal with graphite swelling, a scheme that involved core enlargement.

The ORNL-TM-3832 design although interesting is flawed. The MSDR designers, in an effort to solve core a graphite problem increased the amount of core graphite, this in turn increased the size of the core. But a large core increases reactor construction costs. From a cost viewpoint, it is probably better to replace a small core every few years, than to build a very large core, that will last for 30 years.

While ORNL-TM-3832 represents a serious attempt to simplify MSR design, it hardly represents the last word in MSR simplification. While we may appreciate the ingenuity of Bettis' 1972 design, a revolutionary innovation in core design by Dr. David LeBlanc has greatly simplified MSR core concepts. If the MSDR was altered by substituting Dr. LeBlanc's two tube core for the original core design the entire reactor design would require great alteration. The LeBlanc tube core would almost certainly lower MSR costs, compared to all ORNL core designs of the 1960's and 1970's.

Other problematic features of the Demonstration Reactor involved the use of LiF-BeF2 salts. Since the purpose is not producing nuclear fuel in the breeding range, other salts might carry significant advantages including lower costs, and the elimination of the tritium problem. By switching to another salt combination the tritium problem associated with LiF-BeF2 salts. The MSDR included a third heat transfer loop as part of its tritium control system, and that loop decreased thermal efficiency, increased reactor complexity and costs. If the goal of MSR design is breeding, LiF-BeF2 are the preferred carrier salts, but when breeding ceases to be the objective, then the possibility of using other salts comes into play.

The MSDR was designed to generate power through the medium of superheated steam turbines. Gas turbines, and particularly CO2 turbines would be preferable, if available, but they are not an option yet. As it is the use of superheated steam would make the MSDR more efficient than Light Water Reactors.

Thus it would appear that development of the original MSDR design is not warranted, but that development of the design concept could be. Compared to a MSBR (a LFTR), an advanced MSDR would be a design slam dunk, because of the reliance on tested technology and because of the simplicity of the design. Not only would the MSDR cost less to manufacture than LFTRs, it would probably cost significantly less than LWRs and IFR SMRs such as the ARC-100.

In our current energy situation, a MSDR type reactor would be highly desirable. Not only would it serve as a route to a LFTR type molten salt thorium breeders, but it would offer a potential low cost alternative to the Light Water Reactor, that would be both safe, and would reduce the nuclear waste problem.

A candidate silver bullet

In his David J. Rose Lecture John Holdren voiced an oft repeated urban myth, that is there are no silver bullets in energy. Does the statement "there are no silver bullets," representative of good science, the sort of thing a Science Advisor should be telling the President, or is it a myth?

Some 11 years ago, Cato Institute scholar, Jerry Taylor, wrote a paper on Clinton Administration Energy Policy titled, Energy Efficiency No Silver Bullet for Global Warming. Taylor argued that the Clinton Administration Climate Change Technology Initiative was

little more than a sham. The CCTI is but a repackaging of failed programs that have littered the federal budget for 20 or more years. The program offers misleading and incomplete cost/benefit analyses, is obsessed with remedying market failures that do not in fact exist, projects emission reductions that are wildly implausible, asserts a correlation between energy efficiency and energy consumption that is demonstrably false, proposes counterproductive labeling and product standards, and misleads the public about the ability of such a program—even if it performs as advertised—to measurably affect global temperatures.

The CCTI is built on economic ignorance and political symbolism. Regardless of one’s position on the threat of global climate change, the CCTI is nothing but an empty and expensive political gesture.

That makes thing clear.

Taylor Commented,

More than half of the CCTI comprises ongoing R&D programs for energy efficien- cy and renewable energy. The Clinton administration is rather cavalier about pre- dicting the future of those speculative programs. Typical is the claim that “by 2010, DOE will help develop and commercialize fuel efficiency and alternative-fuel technologies that reduce oil consumption by nearly 1 million barrels per day and reduce greenhouse gas emissions by 25 million metric tons.”9 The EIA, however, cautions rightly that predicting which technologies will be successful is highly speculative. A direct link cannot be established between levels of funding for research and development and specific improvements in the characteristics and availability of energy technologies. In addition, successful development of new technologies may not lead to immediate penetration in the marketplace. Low prices for fossil energy and conventional technologies; unfamiliarity with the benefits, use, and maintenance of new products; and uncertainties concerning the reliability and further development of new technologies are all factors that may slow technology penetration.1 0

The government’s track record of successful energy-related R&D projects hardly gives one confidence that the R&D component of the CCTI will prove as successful as the administration claims.

One of the few serious third-party evaluations of federal R&D programs—conducted for the Brookings Institution by economists Linda Cohen of the University of California at Irvine and Roger Noll of Stanford University—found that energy R&D has been an abject failure and a pork barrel for politi- cal gain. “The overriding lesson from the case studies is that the goal of economic efficiency—to cure market failures in privately sponsored commercial innovation—is so severely constrained by political forces that an effective, coherent national commercial R&D program has never been put in place.”1 1

Taylor in fact believes that the best energy policy is no energy policy, But it is a far cry from failed Clinton Administration policy on efficiency to a blanket statement that there is no silver bullet that can prevent global warming. This week the silver bullet problem again emerged in the Financial Times, which posted a story, Masdar: ‘No silver bullet’ for problems facing cleantech city.

Masdar City was meant to be the world’s first carbon neutral city. Based in Abu Dhabi, its creators envisioned a glittering city in the desert, entirely self-powered, and after the initial building stage, having no net effect on the world’s carbon emissions.

Maslar City CEO, Sultan al-Jaber, and the city’s director, Alan Frost both told the Financial Times,

Do you think that a silver bullet solution exists to help Masdar city achieve its goals today? Obviously it does not. If it did we would have seen Masdar city developed in a number of places around the world.

How do Sultan and Frost know that no "silver bullet" exist?

The Utah Statesman's Face book page carries an account of a speech delivered earlier this month by New York Times Correspondent, Matthew Wald. Wald repeated the

no silver bullet

formula, but then went on to offer some observations that were helpful in understanding what sort of silver bullets were being specified.

Wald said there are many renewable energy sources available that could be put to good use and the only thing holding them back is the market and simple economic principles like supply and demand.

Calling the energy crisis the nation and world are facing a “steep hill,” Wald said the people have to make the decision with their dollars to make a switch to alternative energy sources.

“This is a steep hill and it’s got to be climbed by market economics,” Wald said. “The government is just not big enough or powerful enough to subsidize massive amounts of electricity.”

Cost effectiveness plays a major role in the current energy crisis, Wald said, citing the use of gasoline and other carbon-emitting fuel sources as being more affordable and consistently available than renewable energy sources.

So the silver bullet has to go over in the market/ None of the currant post-carbon energy options are likely to do so, and as much as consumers love the idea of renewable energy, they are unlikely to buy renewable energy given its costs and limitations.

The question should be then, what other options do we have available, if renewables and conventional nuclear costs too much, and the other options emit CO2? if we have another option that can potentially work in the market, that option would be a possible "Silver Bullet."

What would that option have to look like? Well first it should be cost competitive with coal and natural gas. In fact it would be highly desirable for our silver bullet to cost less than the current cost of fossil fuel generated electricity from new generation units. "Not going to happen," you say. Maybe, but according to Wald's analysis, a switch to post-carbon generation sources is not going to happen until better deals are offered to consumers. The first product into the market that offers CO2 free energy coupled with reliability, scalability and low cost will be the "silver bullet."

Critics of the nuclear option offer the following complaints:

* Its too dangerous

* It leaves the problem of nuclear waste

* It creates a danger of nuclear proliferation and thus nuclear war.

* It is too expensive

* Nuclear power plants take too long to build

* We cannot build enough nuclear power plants fast enough

On Monday I heard a distinguished Japanese Scientist say that the nuclear critics are wrong. I heard him say that it is possible to build nuclear power plants that are

* Safe

* Solves the nuclear wast problem

* Is very unlikely to lead to nuclear proliferation or nuclear war

* Cost at least 30% less than conventional Nuclear Power Plants

* Can be rapidly built in factories

* Can be mass produced in factories

In short the scientist, Professor Kazio Furukawa of Japan, said that a candidate energy silver bullet does exist. It is a thorium fuel cycle Molten Salt Reactor. Dr Furukawa calls his silver bullet the Fuji Molten Salt Reactor. Now the interesting thing was that I was not in a bar when I heard Dr. Furukawa talk about his silver bullet, I was in a conference room at Oak Ridge National Laboratory. There were a couple of retired ORNL researchers in the same conference room, Uri Gat, and Dick Engel, and they both backed up what Dr. Furukawa had to say. Furthermore, I had heard a Canadian physicist, Dr. David LeBlanc make the claim that Molten Salt nuclear technology was the silver bullet, also at ORNL in May. No one, least of all Dr. LeBlanc was drinking when he made the claim, and no one at ORNL said to either Dr. Furukawa or Dr. LeBlanc, "Your crazy, there is no silver bullet."

These ideas are not new, and the conclusions of Dr. Furukawa and Dr. LeBlanc have been endorsed by other well informed observers who were acquainted with the facts. When Tammy L. Stoops wrote her thesis for her BS and MS in Nuclear Engineering at MIT, She consulted with Furukawa, Gat and Engel before writing her thesis. Her Thesis advisor, Professor Michael W. Golay wrote

The results of this investigation show that this molten salt breeder reactor concept is passively safe. The reactor power may be increased without bound, provided that an increase is made in reactor fuel salt volume, thereby reducing the decay power density. The ability of this concept to meet the desired characteristics for a global warming response is very powerful.

The only reason Golay did not proclaim this is the silver bullet was

The questions of economic performance are not considered in the work reported here.

In her thesis, Stoops argued

For the future of our planet, an alternate means of energy production must be developed to mitigate the effects of global warming. A nuclear system suitable for this use must be capable of large-scale power production, fuel breeding, hydrogen production, online fission product removal, and nuclear proliferation resistance.

She concluded,

With these (suggested) system augmentations, the degree of passive safety of the molten salt reactor system is enhanced. Capable of large-scale breeding, hydrogen production, active fission product removal, and resistance to nuclear proliferation, this safe reactor system meets all of the characteristics required in a global warming mitigation effort. Thus, the molten salt breeder reactor represents a viable and sustainable energy option to ensure the long-term protection of the global environment.

Clearly then if the thorium breeding molten salt reactor can be made economically viable, we have a silver bullet candidate. We will of course not be able to say that this is the silver bullet until we have the candidate in the market and actually delivering energy. Dr. Furukawa and others have vouched for the potentially superior economic performance of Molten Salt breeding reactors. This argument point to parsimonious use of materials, and diminished labor requirement per kW of electrical generation capacity. Given the fact that compelling reasons for rejecting this assessment have not yet emerged, we should at the very least consider the thorium breeding Molten Salt Reactor to be a candidate silver bullet. As a candidate silver bullet, it will face a number of significant tests before it can be said to have emerged in full blown silver bullet status. But given that we have a candidate silver bullet, the assertion that "there are no silver bullets" is wrong. We have a possible silver bullet, but we will need to know much more, before we can say with certainty that there either is or is not an energy silver bullet.

Dr. Furukawa and Mr.Fukushima Reveal Future Fuji Reactor Plans at ORNL

Monday Afternoon, I drove to ORNL to hear a presentation by Dr. Kazuo Furukawa and Keishiro Fukushima of the "International Thorium Energy & Molten-Salt Technology Inc." (IThEMS). Dr. Furukawa is a distinguished Japanese nuclear scientist who for over a generation has worked to keep international interest in Molten Salt Reactors alive. IThEMS is a vehicle for launching Dr. Furukawa's Fuji reactor technology. Dr. Furukawa and Mr. Fukushima are looking for investors and development partners. They want to build their first prototype, the 10 MW Mini-Fuji in the United States with an American partner doing the prototype construction. The Mini-Fuji is a practical project because uses technology developed at ORNL for the Molten Salt Reactor Experiment (1965-1969). Thus the little research would be involved in prototype development. IThEMS business plans call for the Mini-Fuji prototype to be operational by 2015 and for a larger 200 MW Fuji reactor to follow by 2020. IThEMS plans to market both reactors.

Mr. Fukushima stated that IThEMS is negotiating with Korean Shipbuilders over the potential sale of Mini-Fujis for ship propulsion systems. According to Mr.Fukushima the Korean shipbuilders are in competition with the Chinese, and view mini-Fuji power as potentially offering a competitive advantage. It should be noted that in the long range energy picture decarbonization would require that fossil fuel powered engine technology be replaced by energy from non-carbon emitting source. The options appear to be nuclear power, or synthetic liquid fuel. IThEMS claims that it can build the Fuji for 30% less than conventional water cooled reactors. Thus ship propulsion would appear to represent a market opportunity for the Mini-Fuji. Industrial process heat would be another. The Mini-Fuji would also serve as the energy source for a stand alone nuclear battery system, although that field looks crowded at the moment. The Mini-Fuji would have some advantages over its competitors including superior safety and low cost.

I offered to have lunch with Dr. Furukawa and Mr.Fukushima today, but they were headed south and would be, I surmise, talking with a potential business partner.

Investing in or partnering up with IThEMS would certainly have its risks. The upside for the investor would be to make a ground floor investment for a potentially huge Molten Salt Reactor market. The down side is that IThEMS is basically a start up with no money and no resources. All it really has is an idea and Dr. Furukawa's name.

The Mini-Fuji represents a potential opportunity for the American prototype development partner. First Dr. Furukawa's name does mean something and it offers an entry to a number of research laboratories in Japan, Russia, and Central and Western Europe. Participating in the Mini-Fuji prototype development would be a great opportunity for anyone who wanted to get into the Molten Salt Reactor business. Even if the Mini-Fuji failed as a business opportunity, the prototype development experience could prove invaluable for anyone who was interested in further MSR development.

Sources of nuclear cost saving from small and advanced reactors

There are eight primary sources of nuclear costs:

The cost of the land upon which the nuclear power plant (NPP) is built.
Costs related to designing the NPP
Cost related to the materials from which the NPP is built.
Labor costs related to manufacture and construction.
The cost of obtaining regulatory approval
Investment related costs (interest, etc.)
Transportation and Access related costs
The cost of the electrical transmission system that connects the NPP to the grid

Any attempt to lower nuclear costs must find a way to lower the cost of one or more of these.

Land related costs can be lowered if the investor already owns the land. In the case of NPPs, land costs can be lowered if the NPP is built on a preexisting NPP site. Other, for example transportation related investments may not be required, and access to water is very likely to be available. NPPs can also be located on the site of obsolete coal fired power plants slated to be shut down for technological or environmental reasons. The same advantages of the NPP location would apply to the coal powered site, and additional facilities – for example the turbine hall, parking lots, administrative buildings, workshops, transformer farms, etc. - can potentially be recycled. The layout and size o an existing coal fired power plant may not be appropriate for adaptation for a large nuclear plant, but a cluster of small reactor approach would allow for far greater flexibility in facility layout, and would be far more easy to accommodate.

Small reactors, especially advanced technology small reactors, offer advancements is siting flexibility. For example, clusters of small reactors can be located in former salt mines.

Serial production lowers design costs. Design costs are largely fixed. Design costs can be divided among all of the units produced. If one reactor of a particular design is produced, then the recovery of the cost of that design would be through sale of that unit. If hundreds of units are produced, the recovery of the design cost can be divided between all of the units.

Finally, design simplification can lower nuclear coss. The Generation IV Molten Salt Reactor design offers revolutionary design simplification. In the Molten Salt Reactor the fuel is dissolved in the coolant. Thus much of the core structure is eliminated. Because the Molten Salt Reactor features a negative coefficient of reactivity, the reactor is highly stable without operator control input. Control rods can be partially or completely eliminated. These simple features lower manufacturing costs. And lesson manufacturing time.

The material input into a NPP per watt of output typically decreases as total reactor output rises. Traditionally this has lead to the economies of scales argument, which maintains that the larger the reactor output, the lower the per watt cost. There are, however, problems with this assessment. While it is true that larger size usually means lower material costs per unit of electrical output, there are exceptions to this rule, especially with respect to advanced nuclear technology.
For example:

The greater thermal efficiency of a reactor of similar core size might lower output cost per unit of heat, compared to that of a similar sized, but efficient design.

Reactor safety issues may effect materials input. Light Water Reactor cores and heat exchanges operate under very high pressure. They require significant amounts of material to prevent steam explosions. LWR outer containment structures are typically massive, and thus require large

A more compact reactor core may lower material requirements. Thus if two reactors have the same output, the one with the smaller core is likely to require fewer materials.

Underground reactor siting could potentially lower reactor structural costs, by offering protection against terrorist attacks from aircraft and at surface levels with lower materials inputs.

Small generation componants can lower material requirements. Thus supercitical carbon dioxide turbines are much smaller than steam turbines used in convential reactors. Small turbines require fewer materials, and can be housed in smaller turbine halls, which in turn require less material and labor input to build.

Thus a small advanced technology reactor with a compact core and high thermal efficiency, that operates at a one atmosphere pressure level, and can be sited underground might require fewer materials inputs per unit of electrical output than a much larger conventional reactor.

In addition manufacturing costs can be lowered by simplifying reactor design. Passive safety features can in some instances lower nuclear costs. For example thermosyphoning of reactor coolant, may save the cost of manufacturing and installing coolant punps. Gravity feed emergancy coolant systems save on manufacturing costs in several ways, They do not require backup generators or pumps, thus many of the expenses of older emergancy coolant sysyems can be saved.

Labor costs can be lowered by shifting work from the field to a factory. The more labor which can be performed in a factory, the lower the over all costs. Modular production is consistent with factory manufacture. Factory manufacture lowers labor costs in several ways. First serial production leads to the division of labor, which in turn typically increases labor productivity. The division of labor decreases the skill set required from individual workers. Decreased labor skill sets decrease labor wage expectations. Factory work settings, as opposed to field work settings also decrease wage expectations.

Thus serial production of small reactors in factories would tend to lower labor costs of nuclear manufacture.

The current nuclear regulatory environment favor serial manufacture. Once an example of a particular nuclear design is approved by the NRC is approved, the approval of all subsequent reactors using the design is automatic. Environmental aspects of subsequent application, however, receive the same attention, since they varie from facility to facility.

In addition to NRC license requirements, other licenses may be required. For example, the use of cooling water from rivers and lakes is not automatic, and usually requires regulatory approval. One of the advantages of recycling coal fired power plant sites, is that water access permits may already exist, and potentially can be transferred.

But what if obtaining a water use permit is not possible? With small reactor designs air rather water cooling is practical, with relatively modest efficiency penalties. With efficient advanced reactors, the efficiency benefits may far outweigh the efficiency losses related to air cooling.

Interest accrues as nuclear power plant construction, and accrued interest may amount to a significant percentage of NPP capital costs, especially if the construction project st reaches to half a decade or more. Small factory built reactors are expected to have shortened construction times, compared to large conventional reactors. Simplified advanced reactor designs are also expected to shorten NPP construction time. These shortening construction time can decrease the interest component of capital costs significantly.

Interest charges may reflect the market's assessment of project risks. The greater a projects assumed risk, the higher the interest premium the market will assess. By decreasing a project's size, and lowering projected manufacturing/construction time, nuclear project builders can offer the market lower perceived risks. Lower perceived risks, will lead to interest discounts compared to higher risk large nuclear projects.

Small, factory manufactured reactors offer advantages in transportation costs. Conventional reactors include a number of very large and heavy components, that present transportation challenges. Components such as pressure vessels and steam generators may require special and highly unusual transportation arrangements if they are transported overland. Special huge road transportation vehicles, some capable of moving no more than three miles an hour may disrupt highway uses in large areas over several weeks as they transported conventional reactor steam generators and pressure vessels to reactor sites. In contrast, small reactor cores may be moved by trucks or by rail as ordinary freight.

In areas where water shortages represent acute problems, small reactor access to reliable water supplies is unnecessary. Air cooling will enable small reactors to operate with out a reliable water supply.

Small reactor clusters located at recycled coal fire power plant locations potentially have greatly simplified grid connections. Not only can they be located near to the cities they are intended to serve, but grid hookup is facilitated by existing transformer farms, and grid connections. Because they can be located close to served cities new transmission lines will not cover long distances, thus lowering grid expansion costs. Large reactors may require new transmission lines that are hundreds of miles long, in order to move surplus electricity to market.

In addition to the above savings, and potential savings mentioned above there are other potential savings that may be available with small reactors. For example, with advanced nuclear technology, for example molten salt reactors, combined Rankine (steam) and Brayton (gas) cycles are possible. A bottoming desalinization cycle could be offered to to the system, thus offering formidable efficiency from small reactor packages. A high temperature reactor can provide top cycle heat for industrial processes, as well as producing middle cycle electricity generation, and bottom cycle heat for electrical generation. By adding a second generating cycle, small reactors can lower their electrical generation costs. Desalinization would add a further revenue stream from the reactors operation through the sale of portable water.

Thus it can be concluded that shifts to small nuclear power plants will potentially offer significant savings over current conventional nuclear costs. Shifts from conventional nuclear technology, to some advanced nuclear technologies, also offer significant potential savings. Some advanced technology savings are available to both large and small nuclear power plants, but the flexibility of small NPPs may mean that at least in certain situations small advanced nuclear power plants may offer very significant potential savings in comparison to large conventional NPPs.

Thus small factory produced advance reactors may offer a revolutionary approach to lowering nuclear costs. Economies of scale, often viewed as the only decisive factor in nuclear costs does not control many nuclear cost sources, and is unlikely to be a decisive approach to controlling nuclear costs. Numerous cost containment stratagies, some involving the factory construction of small reactors, but most compatible with small reactors can be drawn on to lower nuclear costs.

Why the LFTR is Still Needed

A new MiT report, The Future of the Nuclear Fuel Cycle, argues that

Uranium supplies will not limit the expansion of nuclear power in the US or around the world for the foreseeable futurer . . .

This should quiet the anti-nuclear power camp on that particular issue, but it won/t. Critics of nuclear power have a tin ear when it comes to evidence. Any evidence that discredits their position simply does not exist, in their minds, and thus they will discount the MiT Report, and continue to tell us that we are running out of uranium.

If we are not running out of uranium is their any justification for the LFTR, a reactor that operates on an alternative - Thorium - fuel cycle? The answer is that there are several good reasons for adopting LFTR technology, even though there may be a large supply of accessible uranium.

One major reason for choosing the LFTR is that it invites far lower fuel cycle related capital investments. If the future reactor fleet is to be entirely uranium fueled, very large capital investments will have to go into uranium mines, processing facilities, enrichment facilities, and spent fuel management. in addition all of these facilities have significant operation costs attached.

Now consider fuel related the capital costs associated with a fluoride salt thorium reactor deployment compared to that of a massive deployment of uranium fueled molten salt reactors. First thorium is a bye product of rare earth mining, and with increasing rare earth use in the economy, more and more thorium will be coming out of the ground anyway. Thus, unlike uranium which is often mined in costly uranium only mines, thorium basically comes out of the earth at no added cost, from mines that would exist whether or not we wanted to recover thorium.

Secondly, while the milling expenses for thorium and uranium would probably be similar, 200 times more uranium would have to be milled, because uranium reactors operate on a once through fuel cycle reactors, which consumes less than 0.5% of the milled uranium, while nearly 100% of the milled thorium will be consumed in closed fuel cycle LFTR.

Secondly, the uranium must be enriched, and this involves another costly, energy intense process. With thorium the enrichment process can be skipped. Following enrichment uranium oxide must be prepared fabricated into reactor fuel pellets. in contrast thorium would be prepared for reactor use by fluoridation, a simple, inexpensive and well understood chemical process. At that point the thorium would be inserted into a reactor blanket where it would be bombarded with neutrons. After thorium absorbs a neutron it is transformed into protactinium 233, which will be separated from the blanket salts by fluoride chemical processes, that will be performed by processing equipment that is directly attached to the reactor. Then the p
rotactinium is stored for a few months, while it undergoes nuclear transformation to fissionable U-233. Once that occurs, the U-233 is automatically inserted into the reactor core by another reactor mechanism. All of these processes are low cost.

The advantage of the Thorium Fuel cycle LFTR is that it requires a fuel infrastructure that is 200 times smaller than a fleet of once through uranium cycle reactors would require. The added cost of the uranium infrastructure is not the primary problem. Rather it is the enormous task of building the infrastructure. The LFTR will require a large infra structure as well, but the infrastructure that will be required to keep LFTRs fueled will be tiny compared to that of a once through uranium fueled reactor fleet.

If we draw the comparison between LFTRs and LWRs, even more U-235 has to be prepared per GWh of power delivered. LWRs waste about 17% of the U-235 that goes into the core, as well as an even larger percentage of the plutonium created in the core. These inefficiencies mean that more U-235 has to be produced relative to the fuel requirements of LFTRs.

LFTRs produce little or no nuclear waste, and indeed can be significant consumers of actinides, which are the most troubling components of LWR nuclear waste. LFTR waste products reach benign levels of radioactivity after 300 years, but many useful and valuable fission products become safe after a few years, and can be mined from the fission product stream for use in industry. Long half life fission products have uses in medicine, and industry. Thus the fission products from LFTRs can be viewed as material resources rather than nuclear waste.

Although Fast Breeder Reactors share many of the advantages of the LFTR, they are likely to be considerably more expensive to build and deploy in large numbers. In addition, FBRs require 10 times the fissile inventory of LFTRs or even more, thus limiting the size of the initial deployment of FBRs. FBR advocates argue that the higher breeding ratio of the FBR will make up for the disadvantage. But it will take time to breed up to the size of an initial LFTR deployment. Supplementing the FBR start up stock with freshly separated U-235 would require the same sort of uranium mining, processing and seperating facilities that would be required by a uranium fueled reactor deployment. Using the nuclear fuel inventory in existing LWR waste stockpiles, more than enough LFTRs could be started to provide 100% of American electricity. If the LFTRs simply replaced the fuel they consumed through nuclear breeding, no further reactors would only be required except to meet added electrical demand.

The LFTR offers both lower cost and significant deployment advantages over the FBR.

Thus the LFTR offers economic and deployment advantages over any of its competitors including Light Water Reactors, Uranium fueled Molten Salt Reactors, and fast breeder reactors. It would be far cheaper to invest in LFTR development and deployment than to build the new uranium mines, mills, isotope separation and fuel fabrications facilities that would be needed to support a uranium fueled reactor deployment. Clearly then even given adequate uranium supplies, the LFTR continues to offer significant advantages for a large scale nuclear deployment.

Molten Salt Reactor Safety Related Advantages

The molten salt reactor was not exactly intended although Ed Bettis and his associates were concerned with the safety of the original sodium cooled Aircraft reactor design. They just understood that the original reactor had a positive coefficient of reactivity, and that coupled with the sodium cooling was extremely bad news. Their calculations had shown that a fluoride salt cooled reactor would feature a negative coefficient of reactivity. Their choice of fluoride salts was not a fortuitous accident. They worked for the Oak Ridge K-25 plant, which was the largest industrial facility in the world that used chemical processes based on fluoride chemistry, and thus knew that their project would have in house access to chemists who understood fluoride chemistry.

But after the ANP shifted to ORNL in 1950' the scientists involved began to understand that Molten Salt Reactors offered exceptional nuclear safety characteristics. First, reactors are made less safe by dangerous things that you put into their core. Things like water and sodium Water is dangerous because under heat and pressure it turns to steam and can explode. Steam explosions are well known problems with the use of water as a heat to work transfer medium. The literature of the early age of steam features dozens of accounts of boiler explosions. Boiler explosions are not just a curiosity from the past, witness the 2003 boiler explosion aboard the cruse ship Norway while in port in Miami. Light and heavy water cooled reactors are basically boilers heated by nuclear reactors. In order to operate efficiently core coolant water is superheated and kept liquid by high pressure. The presence of critically heated water in the core of water cooled reactors is a fundamental safety issue, that requires special design features to manage. Those features cost money to design and implement.

In contrast Molten Salt Reactors, even while operating at high temperatures, do not produce more than a single atmosphere's pressure, and thus will not produce anything like a steam explosion. Thus MSRs are at a significant advantage as far as nuclear safety costs.

The MSR was designed to cope with a number of safety problems associated with a liquid sodium cooled reactor. While liquid sodium cooled reactors including sodium cooled fast breeders do not operate under high pressures, the chemical nature of sodium, as well as some particularities of sodium flow inside reactor cores, create some safety issues. Sodium is extremely chemically active and will burn in contact with air and water. Thus special care must be taken with sodium cooled reactors to maintain separation between between coolant sodium and air, as well as structural materials which contain water such as concrete. This necessitates special design features which may increase the cost of sodium cooled reactors.

In contrast molten salts used in MSR cores do not burn. In addition the tend to freeze as some as their temperature is dropped by air contact. Thus MSR salt leaks can be expected to self seal. Since the reactor core salt is under only a one atmosphere pressure the frozen salt leak seal can be expected to hold. During the Oak Ridge Molten Salt Reactor Experiment researchers experienced reactor salt leaks on laboratory floors. These were cleaned up without difficulty.

In addition, research on fluid flow inside sodium cooled fast reactors has indicated the existence of flow problems called voids. A void can potentially cause a loss of operator control of a sodium cooled reactor, and lead to reactor run aways with potentially catastrophic consequences. Avoiding the void problem may lead to penalties such as limiting reactor performance and breeding capacity.

A simple Uranium cycle Denatured Molten Salt Reactor (DMSR) would not include such a potential for reactor reactor run away. Single fluid MSRs are extremely stable, and will shut down automatically if they overheat, due to fluid fuel expansion. For this reason there is no reason for control rods, or reactor monitoring by operators. ORNL researchers preparing for the 1960's Molten Salt Reactor Experiment determined that MSR operators would have nothing to do, and so would be board. They chose to design the MSRE without a control room, and ran the reactor without an operator present.

More complex MSRs such as 2 fluid LFTRs would have more complex control issues, but it seems possible through careful design that they can be made as safe as the DMSR.

Reactor safety problems are created by things that are put in reactor cores, as well as things that are created in reactor cores. Solid core reactors are stuck with dangerous fission products, and other materials like plutonium which are created in the reactor core. In the event of a catastrophic accident such materials are seen as a significant menace. Radioactive gases are of continuous concern. Most of the escaped fission products following the Three Mile Island accident were radio active gasses, and voluble fission products. It is possible to bubble radioactive gases out of the carrier salt of a molten salt reactor at low expenses, and the recovery of voluble fission products would not be too expensive. In addition the recovery of other fission products, called nobel metals would not be technically difficult or expensive. Thus many of the most dangerous fission products can be removed from a Molten Salt Reactor core as the reactor operates. By removing radioactive fission products either periodically or as they are produced, the worst case MSR can be rendered significantly less dangerous,

In addition actinides such as plutonium-239 can be simply left in the reactor core until they burn up. In might be desirable to periodically clean the salts of DMSRs or LFTRs, but dangerous materials called actinides can be automatically returned to the reactor core with out ever being accessible to people. This would prevent the diversion of nuclear materials by terrorists, or state based would be nuclear proliferators. The DMSR was designed to be proliferation resistant, and it has many features that would lead a would be nuclear proliferator to chose other routs to produce nuclear weapons.

Molten Salt Reactors, such as the DMSR offer very teal safety advantages over Light and Heavy water reactors as well as sodium cooled fast reactors. These MSR safety features can significantly lower reactor safety related costs, while increasing public confidence in the safety of nuclear generated electricity.

Phoenix Rising

I attended David LeBlanc's lecture at ORNL yesterday (May 18, 2010).

Jess Gehin, our host, took the opportunity to do a set of show-and-tell presentations about molten-salt-related programs at ORNL. It is safe to say, from what I saw yesterday, that the phoenix is rising at ORNL.

David's talk was exciting. David has been in contact with retired ORNL MSR researcher Dick Engel. Dick participated in the ORNL 1980 fling at getting backing for Molten Salt Reactor development, the DMSR. (For documentation of the DMSR concept, see here, here, here and here.) David notes in his Mechanical Engineering article,

The “D” stands for “denatured”—the uranium in the reactor contains too much U-238 to be useful in weapons. The concept also dispenses with processing the salt to remove fission products; the same salt is used throughout the 30-year life of the reactor with small amounts of low enriched uranium added each year to keep the fissile material constant. The amount of uranium fuel needed—about 35 metric tons per GWe year—is only one-sixth of what is used by a pressurized water reactor. . . .

The amount of fissile material needed to start new reactors is also very important, especially in terms of a rapid fleet expansion. The 1 GWe DMSR was designed for 3.5 metric tons of U-235 (in easy-to-obtain low-enriched uranium) which can be lowered if uranium costs go up. A new PWR, by contrast, needs about 5 metric tons, whereas a sodium-cooled fast breeder such as the PRISM design requires as much as 18 tons of either U-235 or spent fuel plutonium. Any liquid fluoride reactor can be started on plutonium as well, but this turns out to be an expensive option, since removing plutonium from spent fuel costs around $100,000 per kilogram.

Reviewing the DMSR from a 2010 perspective, LeBlanc finds many advantages.

The DMSR features a larger, lower power density graphite core than other MSR breeder concepts. So while the graphite would last a full 30 years, the DMSR would still be only a fraction of the size of gas-cooled graphite reactors and would not require a pressure vessel. In fact, the simple thin-walled DMSR containment vessel would be wider but much shorter than those of PWRs and BWRs. The construction of the reactor containment building offers savings as it does not need the huge volume and ability to deal with steam pressure buildup needed for LWRs or CANDU reactors.

The overall thermal efficiency of the plant would be quite high. With a salt outlet of 700 °C and using the latest ultra-supercritical steam cycles or gas Brayton cycles, efficiencies close to 50 percent would be possible.

While up-to-date cost estimates for a molten salt reactor are not available, it is quite simple to see the potential overall advantages. The DMSR needs no capital and O&M costs for fuel processing, and the superior nature of the salts as coolants results in far smaller heat exchangers and pumps. Building and fabrication costs should be lower than conventional nuclear plants, since the design doesn’t put the same sort of stresses on the system.

Among the advantages LeBlanc points out, the potential to lower nuclear costs is the most conspicuous.

It is not unreasonable, then, to assume that capital costs could be 25 to 50 percent less for a simple DMSR converter design than for modern light water reactors. Compared to fast breeders such as the integral fast reactor, which rarely try to claim low capital costs, the DMSR should be even better.

In his ORNL talk, LeBlanc noted the possibility of simply eliminating a Thorium blanket for the DMSR entirely, and running the DMSR as a pure uranium-fuel cycle reactor. While the Uranium fuel cycle DMSR would offer less sustainable technology than the LFTR, it would be a very strong competitor for the current generation of Light Water Reactors. It would offer a very high level of safety, proliferation resistance and nuclear waste control, at a lower cost that current light-water reactor technology. Actinides, the big problem in nuclear waste, could be separated from reactors salts, either periodically or when the reactor is decommissioned. The recovered actinides can be returned to the core of a DMSR where they will be burned as nuclear fuel. Other fission products will essentially disappear after 300 years, if reactor managers chose to treat them as waste, but this is unlikely. Fission products present in "spent nuclear fuel" represent a potential source of valuable materials and noble gases, and the DMSR concept opens the door for the recovery of these minerals.

LeBlanc concluded his Mechanical Engineering essay by declaring,

Molten salt or liquid fluoride reactors will also take a large effort, but every indication points to a power reactor that will excel in cost, safety, long-term waste reduction, resource utilization, and proliferation resistance. As we move deeper into a century that portends financial instability, political uncertainty, environmental catastrophe, and resource depletion, this technology is too valuable to once again place back on the shelf.

Nuclear Green concurs with this view. The DMSR represents a technology that is doable in the year 2010. The technology required to build it exists now, thus developers would not be saddled with huge R&D costs, and and the technological uncertainties that would confront LFTR development. The DMSR would represent a transition, between the traditional solid fuel reactors, and the sustainable LFTR technology. The Phoenix is beginning to rise from its ashes.

Review of ORNL’s MSR Technology and Status

In a pioneering study of the practical application of controlled fusion to energy production, my father, C.J. Barton, Sr. pointed out the potential use of a Molten Salt formula which he helped to develop for the Molten Salt Reactor Experiment. My father's suggestion has received a rather considerable follow up, and most of the research on the use of Molten Salt nuclear technology during the last generation has focused on fusion related applications. Other applications of MSR technology were subsequently developed. Accelerator driven transmutation technology is a proposed technology uses accelerator driven particles to "smash undesirable heavy metal atoms found in nuclear waste. A 1994 Los Alamos uses report stated that ADTT was intended as an alternative method of disposing of nuclear waste: These processes are driven by an accelerator. with a high-energy proton beam (800- 1000 MeV) that smashes a target atom into many atomic fragments producing a large num- ber of neutrons (around 20–30 per atom smashed). The neutrons can penetrate into the nuclei of neighboring atoms and be captured. rhis capture changes the nuclear identity of the atom capturing the neutron; thus the term transmutation. So the neutrons are the invis- ible alchemists that do the work of transmuting various elements.

ORNL prepared its' "Review of ORNL's MSR Technology and Status, as a brief introduction to both the MSR concept and its application to ADTT technology. This review gives us an insight into ORN:'s own view of MSR technology behind closed doors.

The reader might be puzzled by the mention of reactivity fluctuation as a MSR liability. Gat and Dodds explain.

There are safety concerns associated with FFR: "Possible fluctuations of reactivity caused by density or concentration changes in the fuel, e.g., bubbling." For MSRs this concern is primarily the coalescence of dissolved gas into large bubbles and their collapse, or in some concepts, such as the MSBR, the expansion of bubbles. To assure that this does not occur, continuous removal of gaseous (fission products) must be employed, usually through sparging.

I would expect that many if not most MSR advocates are familiar with the concept, and most of us simply assume that the technology for the continuous removal of radioactive gasses will be built into LFTRs and other Molten Salt Reactors.

Other MSR/LFTR internal liabilities would be familiar to anyone who follows the discussions on Energy from Thorium. What is most remarkable then is the extent to which the ORNL attitude in the 1990s saw MSR/LFTR development as a matter of ordinary rather than heroic science. By heroic science I mean science that involves big gambles. Ordinary science is work, and quite probably a lot of work, but for those who do the work there is a fairly assured payoff. This would be the case, if we follow the conclusions of the following assessment. One final note, I have spared my readers some of the more technical discussions, especially those which primarily are related to ADTT. Anyone who is interested in that aspect of this report can follow up by following the link that follows:

Review of ORNL’s MSR Technology and Status

L. M. Toth, U. Gat, G. D. Del Cul, S. Dai, and D. F. Williams

Oak Ridge National Laboratory, Oak Ridge, TN 37831

Abstract. The current status of molten salt reactor development is discussed with reference to the experience obtained from the Oak Ridge Molten Salt Reactor Experiment. The assessment of the future for this reactor system is reviewed with both consideration of advantages and disadvantages. Application of this concept to ADTT needs appears to be feasible by drawing on the experience gained with the MSRE. Key chemical considerations remain as: solubility, redox behavior, and chemical activity and their importance to ADTT planning is briefly explained. Priorities in the future development of molten salts for these applications are listed with the foremost being the acceptance of the 2LiF-BeF2solvent system.

The molten salt reactor experiment, MSRE, was operated from 1965-1969 and was shut down by draining the homogeneous fuel from the reactor circuit into two drain tanks located at a lower level in the MSRE facility. The purpose of this review is to identify the ORNL position with respect to MSR’s; review the pertinent MSR chemistry and the significant understanding gained since the MSRE operation era; and, finally, to relate these two elements to present accelerator driven transmutation technology, ADTT,interests.

If one surveys the current attitude at ORNL with regard to MSR’s, he would observe that there is no official position. In parallel with the current national and DOE attitudes toward advanced nuclear programs, it is difficult to discern a definite position or proactive attitude toward the MSR status and technology. Rather, there is, at best, a “wait and see” attitude in spite of the fine history of development associated with this reactor concept and this attitude is consistent with the current DOE attitude toward all advanced reactor concepts. When viewed from outside, however, it is possible to become dismayed even though interaction with individuals or groups is still taking place.

The most recent expression of a ORNL interest in MSR’s came in 1992 with documents written by F. J. Homan (then, director of reactor technology programs, ORNL) and U.Gat. While this expressed position is dated[l],it served to demonstrate the attitude toward MSR’s that still prevails with some individuals. At that time, Homan and Gat identified the MSR advantages as:

(1) Simplicity: External cooling allows optimization of the core design to maximize efficiency. Molten salts have low vapor pressures at high temperatures, reducing the need for thick walled pipes and vessels.

(2) Ease of fuel handling: Fluid fuel can be moved with pumps and pipes eliminating the need for complex fuel handling machinery.

(3) Simple fuel cycle: No head end preparation for reprocessing, or complex waste management. The fuel is in fluid form, amenable to chemical manipulation. Molten salts can be purified using the very simple fluoride volatility process.

(4) Simplified waste disposal: The waste which comes out of the reprocessing step contains little or no uranium or actinide elements. This simplifies waste management and results in better resource utilization than other reactor fuel cycles.

(5) Versatility: A single, basic design can be operated as modules, or in varying sizes; temperature control assures efficiency. One design can operate on any fuel. The MSR can burn actinides, burn plutonium from dismantled weapons, or breed.

(6) Ease of shutdown and maintenance: Fuel can be drained for maintenance, reducing occupational exposure.

(7) Economy: MSRs have been shown in various studies to have an excellent economic potential.

From today’s stand point we might qualify waste disposal and economy realizing that these issues are now seldom simple or economical. Relative to other reactor systems, however, these points could be valid.

On the negative side of the issue, Homan and Gat identified disadvantages and unresolved issues as:

(1) Possible reactivity fluctuations due to density variation or bubble formation.

(2) Necessity for a large external (to the core) fuel inventory,

(3) High radiation levels in primary system due to presence of fuel throughout.

(4) Reliability of components which contain and circulate the molten fuel.

(5) A not fully integrated (combined) chemistry.

(6) Lack of utility and industrial support.

(7) Lack of licensing experience.

In addition to these listed issues, we might also add graphite swelling and undeveloped plutonium chemistry.

As a result of this analysis, Homan and Gat identifiedthe following position reflecting the ORNL attitude of the time:

(1) The MSR has promise.

(2) The economic climate is not right to recommend the rebirth of MSR’s.

(3) A small program should be established to retain MSR experience lest retirement and/or death cause it to be lost.

(4) M S R s might even be more attractive than LMFBR’s in today’s climate.

Since the 1969 shutdown of the MSRE, several evaluations of MSR technology have occurred[2, 3, 4]. While many evaluations have been and will continue to be made, the primary requirements for the molten salt in a homogeneous fluid-fueled reactor still remain as expressed earlier.[5]

The salt should have:

(1) Low neutron cross section for the solvent components.

(2) Thermal stability of the salt components.

(3)Low vapor pressure.

(4) Adequate solubility of fuel and fission product components.

(5) Adequate heat transfer and hydrodynamic properties.

(6) Chemical compatibility with container and moderator materials.

(7) Radiation stability

(8) Low fuel and processing costs.

It is readily seen from Table 2 or Ref. 5 that several of the fluoride salts satisfy the two or more salts are combined to produce still lower melting mixtures. The most developed fluoride solvents consist of LiF and BeF(2), in 2:l mole ratio and melting at 452°C as shown in the phase diagram of Fig. 1 of Ref. 5. The 2LiF-BeF(2) solvent has acceptable viscosity, low vapor pressure and good thermal stability for use as the solvent system in a molten salt reactor.

In considering the application of these molten salts to a MSR situation, three important and interrelated chemical concepts must be controlled. These are solubility,redox chemistry, and chemical activity.

Solubility as applied to molten salts involves more than what we ordinarily understand for queous systems. In the case of the pure fluoride materials, solubility is determined by phasediagramsofthemixtures. These temperature versus composition determinations give the temperature at which components might fall from solution (as determined by the liquidus line on the plot) and the identity of the salt phase which precipitates out. Because this information was of such vital importance to the control of the molten salt solution, much attention was given to the determination of phase diagrams in the early stages of the ORNL/MSRprogram. While much has been learned already about this phase diagram behavior, comparable information relating to PuF, is sorely lacking. . . .

(What follows is a technical discussion of the application of Molten Salt Reactor technology to accelerator driven transmutation technology. I will skip this discussion because it adds little to our understanding of the MSR development task and move on to the conclusion.)

CONCLUSIONS

Molten salt reactors are a proven concept and merit future development for ADTT applications. The molten fluoride chemistry for the 2LiF-BeF2system is well established and can be applied with great confidence. However, other less understood solvent systems must be considered with caution lest subtle solvent effects such as those presented here cause severe problems with process operations. The chemistry of plutonium, as PuF,, needs further study and testing, especially in corrosion loop studies for redox control. Processing of the fuel salt needs further development with continuous on-line processing as the ultimate objective. Nevertheless, the future for systems utilizing this high-temperature fluid can be very promising based on the fine record established over the past several decades.

REFERENCES

Homan,F. J. and Gat, U., “Status Position on the Molten Salt Reactor,” June 1992m (unpublished).

MacPherson, The Molten Salt Reactor Adventure, Nuclear Science and Engineering, 90,(1985).

Rosenthal, M. W.,Haubenreich, P. N., McCoy, H.E., and McNeese, L. E. , “Recent Progress in Molten Salt Reactor Development”, Atomic Energy Review, IX,3,601,(1971).

McNeese, L. E., et al, “Program Plan for Development of Molten Salt Breeder Reactors,” ORNL-5018, December 1974.

W. R. Grimes, “Chemical Research and Development for Molten Salt Breeder Reactors”, ORNL/TM- 1853, (1967).

L. M. Toth, G. D. Del Cul, S. Dai, D. H. Metcalf, “Molten Fluoride Fuel Salt Chemistry”, First International Conference on ADTT and Applications, Las Vegas, Nevada, USA, July 25-29, 1994.

Gilpatrick, L. O., and Toth, L. M., “The Hydrogen Reduction of UF, in Molten Fluoride Solutions,” J. Inorg. and Nuclear Chemistry, 39 (10), 1817, (1977).

Baes,C.F.,“Molten Salt Reactor Semiannual Progress Report”, ORNL-4548,Feb.28, 1970, p. 152.