Lessons from Dai-ichi

Last Saturday, I began to form the opinion that one or more of the Dai-ichi reactor cores had experienced a partial melt down. I was by no means sure of this view because it assumed that the explosion had been a hydrogen explosion. My study of reports concerning the Three Mile Island accident had led me to speculate, that if the explosion had been a hydrogen explosion, the most likely source of the hydrogen was a chemical reaction between coolant water, and overheated core materials. I assumed that some core water might have boiled off, uncovered, uncovering the upper part of the core, which then overheated to the extent that it would begin to melt.

When Japanese technicians injected water into the reactor, it came in contact with the partially melted core, and a chemical reaction between Zirconium in the reactor fuel cladding and the oxygen in water molecules, had released hydrogen in the core. The Japanese technicians had vented the hydrogen from the core, and it vented along with hot steam, and then exploded when it recombined with oxygen in the air. This assumption indicated that the Dai-ichi crisis was at least as bad as Three Mile Island, if not worse. The Japanese, given my speculation, would have sacrificed parts of the reactor building, in order to protect the steel containment vessel from rupture caused by excessive gas pressure.

The reality of at least a partial core meltdown in Dai-ichi 1, 2, and 3 could explained by the release of radioactive gases from fuel pellets. When the core was subsequently vented, the release of the radioactive fission product gasses would explain why many spikes of radiation during the Dai-ichi event have occurred. The radioactive gasses, likely to be encountered during a core meltdown are not very dangerous in practice. They are noble gases, very radioactive but chemically inactive. They are dispersed by natural process in air, and very quickly become so diluted, that they pose no danger to human beings. Since noble gases do not form chemical bonds, they do not linger in the human body, thus do not pose health risks. When scientist looked at the human health consequences of the Three Mile Island accident, the realized that the radiation level of air down wind from Three Mile Island was simply not high enough to cause cancer and other radiation related illnesses.

In addition to radioactive gases, some easily vaporized radioisotopes were released by the Three Mile Island accident. Of these Iodine-131 is the most dangerous. Unlike the noble gases, Iodine-131 does form chemical bonds, is solid rather than gaseous at ordinary temperatures, and likely to enter the human body from the food chain. Iodine-131 forms volatile chemical compounds, that vaporize at high temperatures. Iodine-131 does stick around, but only for a short while. It has a half life of a little more than 8 days. Thus if people can be kept out of contact with Iodine-131 for a couple of months it ceases to be dangerous. In addition potassium iodine tablets offer some protection against iodine-131 forming chemical bonds with body tissues.

Three other potentially dangerous radioisotope are in danger of escaping a reactor core during a reactor accident. They are:

Sr-90
Cs-137
Cs-134

We ar talking about some very nasty stuff here, the stuff that keeps people out of the Chernobyl exclusion zones for nearly 25 years. Fortunately not much of these undesirables escaped during the Three Mile Island accident, so the good citizens of Pennsylvania were able to return to their homes. The difference between TMI and Chernobyl was that inChernobyl the core exploded, destroying all containment, and then caught on fire, and quickly began discharging copious amounts of volatile fission products

What the Japanese tecnicians appear to be doing at Dai-ichi is struggling to prevent the sort of fire that would release large amounts of volatile fission products. There has bee some release. How do we know this? Because when an NBC news man came back from Dai-ichi, he had radioactive material on his shoes. Not a lot, but too much to be tracking around.

The same story suggests that maybe not a lot of volatile fission products have escaped yet, just enough to be picked up on the shoes, by newspeople walking on soil that has been lightly dusted with radio-iodine and other nasties., but not at a level yet to be really dangerous.

It is now fairly clear that that some level of meltdown has happened, but that we are not yet at the China Syndrome by any means, but yesterday Nuclear Regulatory Commission Chairman Gregory Jaczko said,

We believe that secondary containment has been destroyed and there is no water in the spent fuel pool and we believe that radiation levels are extremely high which could possibly impact the ability to take corrective measures.

Is not clear that all of the water in the spent fuel pool is gone, but Jaczko's fears may not be entirely unjustified.

The New York Times has quoted a spokesman for Japan’s Nuclear and Industrial Safety Agency, Yoshitaka Nagayama, as saying,

Because we have been unable to go the scene, we cannot confirm whether there is water left or not in the spent fuel pool at Reactor No. 4.

If the Japanese don't know, how can Jaczko? The answer might be computer accident simulation. I don't know if such a simulation exists, but if Jaczko was not being irresponsible, he needed to be able to point to some back up to his assessment.

There are still dangers here, the crisis is my no means over, but the decay of fission products is already begin to slow down, and with it both the radiation and the heat that that decay produces. While it is too soon to imagine that the crisis is over, the fact that the first week of the crisis has passed is a signal that the hope that a disaster will be prevented is fully justified. We cannot be sure that the worst is over, but the odds are beginning to move in that direction.

Nuclear power will survive the events in Dai-ichi. This accident will be studied for some time to come for lessons about nuclear safety. The first lesson, and this is obvious, is to assume that the worst earthquake or tsunami ever recorded for an area is possible again, and build accordingly. The Dai-ichi reactor complex was not designed to withstand a 10 meter plus tsunami, while it probably should have been built to withstand at least a 10 meter tsunami. Earlem College Geologist Wesley Nutter found evidence in 2009 that 10 meter (or even higher) waves had repeatedly pounded the coast of northern Japan over the last 3000 years. The geological record suggests that the tsunami of 2011 was a once in every 500 year event. For most people, once in every 500 years is never. Americans have built the cities of Memphis and St. Louis in a zone in which evidence suggests episodes of multiple great earthquakes - up to magnitude 8 - occure every five hundred years or so. Should people live, let alone build reactors in such a dangerous area? Should people live, let alone build reactors in Japan, California, or anywhere eles along the 24,000 mile Pacific ring of fire?

The second lesson has to do with reactor design. Some new reactors, most particularly the the Westinghouse AP-1000, and the GE ESBWR feature gravity powered emgency water tanks above the reactor core. In the future, reactors designs may be subject to the Dai-ichi test. Could the reactor design survive the Dai-ichi event without core melt down. In the case of the AP-1000 the answer is possibly yes, while in the case of the ESBWR he answer is very likely yes. The ESBWR design sets the new bar for reactor safety, and that bar his high.

A third lesson is that the Dai-ichi demonstrated an impressive seismic performance. They survive an earthquake of a far greater magnitude than they were designed too. No doubt this seismic performance will be the subject of further research.

A fourth lesson is that reactor safety design, should include a method of mitigating any China syndrome incident, in the event of a emergency coolant failure. Devices such as steam explosion proof core catchers will be researched,and perhaps modifications to existing reactor designs considered.

A fifth set of lessons, as of yet largely undefined, will come about as the result of studying what actually happened inside the cores of Dai-ichi reactors.

Finally, I would argue, that the day of the Light Water Reactor is drawing to a close. Several Generation IV reactor technologies would have survived the Dai-ichi incident without a serious incident. These include Pebble Bed Modular Reactors, and Molten Salt Reactors. In the case of Molten Salt Reactor Technology, the safety technology appears to be consistent with lowering nuclear costs. The PBMR can be shudown without core melting, while if a MSR begins to overheat, a plug will automatically melt and the reactor core will drain into a series of tanks that uses a well understood simple and natural technology, the chimny effect, to keep the fuel cool.

I have, in Nuclear Green, repeatedly pointed to the issue of nuclear safety, and the need to develop radical high safety nuclear technology. It is not that reactors are unsafe, but rather that safer reactors are possible without increasing nuclear costs, and we ought to build the safest reactors possible, within our financial limits. Not only are safer reactors possible, but they will be superior to Light Water Reactors in many other respects, including the long term sustainability of their fuel sources, and their scalability. If the Dai-ichi crisis fails to teach us the importance of moving forward on the implementation of a more advanced and safer nuclear technology, it would be a tragedy.

The Green Reactor: LFTR Green Engineering

This repost was one of a series in which I examined the Liquid Fluoride Thorium Reactor from a "green" perspective. My basic view if the words "not nuclear" are removed from a list of green engineering standards for electrical generation, the LFTR conforms to objectives expectations for "green" technology.

The "green" status of nuclear power has been challenged because nuclear power allegedly does not conform to "Green" principles. Whether or not the supposed green principles are in fact environmentally sound is of course open to question. The current post, however will not travel down that route, rather I intend to demonstrate that one form of nuclear reactor, the Liquid Fluoride Thorium Reactor conforms to "green" standards.

The 12 Principles of Green Engineering are said to be:

Principle 1: Designers need to strive to ensure that all material and energy inputs and outputs are as inherently nonhazardous as possible.
Principle 2: It is better to prevent waste than to treat or clean up waste after it is formed.
Principle 3: Separation and purification operations should be designed to minimize energy consumption and materials use.
Principle 4: Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
Principle 5: Products, processes, and systems should be “output pulled” rather than “input pushed” through the use of energy and materials.
Principle 6: Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.
Principle 7: Targeted durability, not immortality, should be a design goal.
Principle 8: Design for unnecessary capacity or capability (e.g., “one size fits all”) solutions should be considered a design flaw.
Principle 9: Material diversity in multicomponent products should be minimized to promote disassembly and value retention.
Principle 10: Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
Principle 11: Products, processes, and systems should be designed for performance in a commercial “afterlife”.
Principle 12: Material and energy inputs should be renewable rather than depleting.

1: Designers need to strive to ensure that all material and energy inputs and outputs are as inherently nonhazardous as possible.
Materials inputs into the structure of the LFTR, its fuel and carrier salts are not highly hazardous. The reactor can be built from a variety of materials, and variety fluoride salts can be used as carrier salts. Most of the hazards of LFTR are internal to its operation, and can be controlled through the application of principles containment barriers to the design of LFTRs and their housing facilities. Containment barriers will protech the biological environment, by preventing accidentally released hazzardous materials from reaching it. The LFTR makes little to no intrusion on the landscape. There need be no tall towers associated with the siting of LFTRs as there is with windmills,. Indeed LFTRs can be sited underground or underwater and thus have absolutely no undesirable aesthetic aspects. Unlike "green" windmills, LFTRs can be built to be wild life safe. Unlike huge solar or wind arrays, LFTRs use little space, and thus are far less likely to have unintended negative consequences for local ecology.

2: It is better to prevent waste than to treat or clean up waste after it is formed.
The material outputs from the fission process in the LFTR can be inputs into industrial processes, or can be used in medicine, agriculture, food preservation, and sanitation. Heat not lost to the second law of thermodynamics can be put to a variety of uses. All long lived hazardous materials can be recycled as fuel in LFTRs until they are completely dissipated.

Principle 3: Separation and purification operations should be designed to minimize energy consumption and materials use.
Proposed fission product separation and extraction technologies are energy efficient and they would be operated either continuously or periodically as part of the reactor system. Extraction and purification systems are understood to be a vital and required part of LFTR design.

Principle 4: Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
The LFTR is outstanding performance in its minimization of mass, energy, space and time efficiency:
* The structure of the LFTR requires less material per kW of electrical output than conventional reactors.
* The LFTR requites fewer materials inputs per KW of rated electrical output than solar or wind generating system.
* The fuel and coolant inputs into the LFTR are tiny compared to conventional nuclear power plants. The LFTR can be air cooled, eliminating water use.
* The EROEI of the LFTR is potentially superior to the EROEI of not only Light Water Reactors, but also wind generators, and all forms of solar electrical generators. The EROEI superiority is at least two orders of magnitude.
* The LFTR is smaller than Light Water Reactors and its gas turbines are also smaller the steam turbines of LWRs. Since the LFTR produces a small percentage of the radioactive byproduct produced by the LWR, far less space needs to be devoted to the storageof radioactive fission products.
* Not only is the energy density of LFTR is superior to conventional LWRs, but is superior by several order of magnitude to either solar generation or wind generation systems.
* The LFTR produces as much energy per unit of time as the LWR, and it produces far more electricity per unit of time than solar or wind generation systems with comparable output ratings.

Principle 5: Products, processes, and systems should be “output pulled” rather than “input pushed” through the use of energy and materials.
The LFTR potentially has a materials, and energy output to input ratio to any other electrical generation system. Virtually 100% of the fuel input into the generation process is potential useful output. The EROEI of the LFTR is far superior to any "renewable" generating system.

Principle 6: Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.
The energy input into recycling, reuse, or beneficial disposition of reactor materials and fission products is a far smaller fraction of total electrical output than is the case with either conventional LWRs or "renewable" electrical generation sources. Heat not lost to the second law of thermodynamics can be recaptured for space heating, water heating, low tempreture industrial process, and desalinization.

Principle 7: Targeted durability, not immortality, should be a design goal.
Nearly 100% of the fuel input into the LFTR is recyclable. The extraction and separation of many recyclable materials is part of the basic LFTR technology. Carrier salts can be reused. Materials used in te construction of the reactor are recyclable.

Principle 8: Design for unnecessary capacity or capability (e.g., “one size fits all”) solutions should be considered a design flaw.
The LFRT has outstanding potential for modular design. Factory production of small 100 MW to 300 MW LFTRs, and the clustering of several small LFTRs allow for the production of large amounts of electricity without the enormous capital investment required for both large conventional reactors and large renewable power generating projects.

Principle 9: Material diversity in multicomponent products should be minimized to promote disassembly and value retention.
A high degree of materials standardization is possible with the LFTR. the LFTR can easily be designed to facilitate decommissioning, and the recycling of parts.

Principle 10: Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
The LFTR is unique among reactors in that its system is designed to facilitate the integration and interconnectivity of energy and materials flows. In this regard it shows superior qualities to both renewable electrical generators and conventional reactors. It possess the ability to respond instantaniously to electrical load demand, and can serve as back up generating capacity.

Principle 11: Products, processes, and systems should be designed for performance in a commercial “afterlife”.
In this regard the LFTR is far superior to the LWR and superior to renewable power generation systems. Not only does the LFRT produce far fewer materials outputs than the LWR, but its materials outputs can either be safely recycled as useful and even valuable materials, or have value in medicine, industry, food processing, agriculture, and sanitation because of their radioactive properties. Waste heat from electrical generation with LFTRs can be reused for space or water heating, or in desalinization.

Principle 12: Material and energy inputs should be renewable rather than depleting.
All materials use in electrical production are either present in the earths crust in such large amounts that they cannot be depleted given the efficiency of the LFTR or are indefinitely recyclable. The amount of recoverable thorium in the earths crust greatly exceeds the amount that would be to produce all human energy till the time that solar evolution destroys the potential of earth to sustain human life. Thus the capacity of LFTRs to produce massive amounts of energy is indefinitely sustainable in cosmic terms, and has equivalent sustainability to other renewable electrical generating systems.

It is clear that not only is does the LFTR meet the requirements for green engineering, but far surpasses many of the "green engineering" characteristics of other renewable electrical sources. It possesses superior EROEI to all other renewable electrical generating systems. The LFTR makes more efficient use of all of its inputs compaired to both LWRs and other "renewable" electrical generating systems, and the use of its outputs is only limited by the laws of nature.

Is There a Point to the Sodium Cooled Fast Reactor?

For two generations Argonne National Laboratory has obsessively pursued the development of the liquid sodium breeder reactor. Although Argonne claims they have solved all safety issues related to the liquid sodium breeder, in fact significant safety issues probably remain, and indeed lists of remaining research tasks related to the liquid sodium breeder reactors indicate a lack of assurance about safety claims being made about the LMFBR. In addition to safety concerns, there are cost questions. Sodium cooled reactor are viewed as having a significant cost penalty over conventional LWRs.

An 1998 Essay by Lawrence M. Lidsky and Marvin M. Miller of the Massachusetts Institute of Technology titled "Nuclear Power and Energy Security: A Revised Strategy for Japan", laid out significant questions about the usefulness the LMFBR.

While this essay raises serious questions about the LMFBR and indeed the LWR, it by no means is hostile to the LFTR. In their Introduction the authors of this essay stated.

'Nuclear power, in its present incarnation, has not lived up to its great promise. . . . There is good reason to suspect that other implementations of nuclear power technology might allow nuclear power to play a greater role in energy supply and energy security".

For example they note:

Although the LWR had been placed in a privileged position by the political situation, it had significant shortcomings, many of which were apparent from the beginning. It had low thermodynamic efficiency with little potential for improvement. Fuel burnup was limited. It was considerably less forgiving of mechanical or operational error than such competitive designs as the molten salt reactor and the gas-cooled reactor. The LWR’s necessary complexity (required to provide defense-in depth) implied “economies of scale” such that it could be economically competitive, if at all, only in very large sizes. These disadvantages were obvious enough to show that the LWR would be a poor choice to play the central role in nuclear generation strategies. Its shortcomings were tolerable only because the LWR was originally intended for a stop gap role, tobe substantially phased out by the breeder by 1990.

Oh wow! I hope Kirk Sorensen reads this.

The essay adds:

Thorium fuel cycles have also been promoted on the basis of lower long-term waste toxicity and greater proliferation resistance, . . . The initial rationale for introduction of the thorium cycle was the perception that it was more abundant than uranium, and that it could be used to breed U-233, an isotope with superior properties for use in thermal reactors. However, Its terrestrial abundance is not germane to Japan’s energy security concerns because Japan has no indigenous source of thorium and it is hard to imagine a scenario in which uranium is cut off but thorium is available. Conceivably, the use of U-233 in an advanced reactor could reduce the possibility of a common mode failure of a reactor fleet consisting of LEU-fueled LWRs and HTGRs. The Molten Salt Reactor would be a strong candidate for consideration for this role, with a solid research base and an international support group, . . .

Because the Lidsky-Miller essay offers an extensive account of the history of and the rationale for the LMFBR, it is worth quoting at length from its opening sections.

1. Introduction
The paradigmatic LWR/FBR nuclear power system was conceived in the United States over 50 years ago, and soon achieved “Official Technology” status, with resulting strong government support, preferential access to capital, and the capture of path dependent advantages. 5 The LWR/FBR approach rapidly became dominant, aided by its Official Technology status and by aggressive state-subsidized marketing. The LWR very quickly began to make significant contributions to power production in the U.S. and other industrialized countries and the FBR became the singular focus of development efforts.

However, after very rapid expansion in the 1970–90 time period, nuclear power’s rapid growth has slowed significantly; in some countries, installed nuclear capacity has actually started to shrink. Overall, the nuclear share of global electricity production, 17% in 1996, has begun to decline, and the current economic crisis in Asia does not bode well for growth in a region where rapid growth had been anticipated 6 .The other components of the LWR/FBR paradigm, the breeder and plutonium recycle, have not fared even as well. The U.S. and Germany have abandoned their breeder programs. The French government has recently announced that the 1200MWe Superphenix breeder reactor will be dismantled, while the Japanese demonstration breeder, Monju, remains shut down more than two years after a loss-of-sodium accident. The situation is almost as bleak for recycle of plutonium as Mixed-Oxide (MOX) fuel in LWRs; existing contracts are being honored but MOX fuel is not popular with reactor operators or the public. Nuclear power, in its present incarnation, has not lived up to its great promise. The fundamental question is whether such failure is inherent and unavoidable or if, perhaps, other technological embodiments of nuclear power systems can satisfy society’s economic and political requirements. There is good reason to suspect that other implementations of nuclear power technology might allow nuclear power to play a greater role in energy supply and energy security. The current LWR/LMFBR scheme is, after all, just one of many fundamentally different ways to exploit nuclear energy. It was chosen in response to the political and military conditions existing circa 1950, on the basis of contemporary assumptions regarding uranium and fossil fuel availability, the anticipated growth rate of nuclear power, and the predicted costs associated with both the FBR and the associated reprocessing technology. At the time, it was believed that uranium was in critically short supply and that fossil fuel prices would soon rise sharply, that nuclear power would become the dominant energy source, and that the costs of the FBR and its fuel cycle would actually be less than that of the LWR. All of these assumptions have proven to be false. Now, a better understanding of the actual situation along with improvements in technological capability make it possible to develop a clearer idea of nuclear power’s proper role in energy supply, and to develop technological embodiments that optimize the desired characteristics.

I ought to note at this point that the motive of Eugene Wigner and Alvin Weinberg in developing the fluid core thorium cycle reactor was to make sustainable nuclear power competitive on cost with coal. Fluid core reactors were never envisioned as providing weaponizable materials. This perhaps explains why the thorium fuel cycle MSR concept received such limited backing. It was not envisioned as being of value for weapons production.

2. History - Runup to Current Status

Status Nuclear reactors were developed in secrecy during the first decade of the nuclear era (1945–1955) at the National Laboratories of several countries, under the control of the military. The first reactors, fueled with natural uranium, were used to produce plutonium for weapons use. Shortly there after, the U.S. decided to use an enriched uranium fueled, light water cooled reactor, a LWR, for submarine propulsion. In the prevailing Cold War atmosphere, the development of nuclear powered submarines had very high priority. The pressurized LWR was chosen over several competitors for the submarine reactor because it employed “familiar” technology (liquid water and steam) and because it was capable of very high power density. When, in 1953, the race for dominance in the area of civilian nuclear power was set in motion bythe Atoms for Peace program, and the U.S. needed a rapid response to counter the British (commercial) and Soviet (propaganda) threats, the LWR was the obvious choice. Research into the use of reactors for civilian power production, although widespread, was still exploratory and unfocussed, and no other U.S. reactor design was ready for deployment as quickly. The LWR had a number of features in its favor. It had benefited from continuing research and development in the Navy’s ship propulsion program and there were manufacturers familiar with the required technology. It used enriched uranium, which was, for a time, a U. S. monopoly, and therefore gave American manufacturers an important competitive advantage with respect to potential competitors (France, England, and the Soviet Union). The U.S. hegemony in this area was further strengthened by a series of bilateral “Agreements for Cooperation” in which the U.S.provided loan funds which could be used only for the purchase of equipment, materials (including enriched uranium), and technical services from U. S. nuclear vendors. 7 This reinforced the“Official Technology” status of the LWR throughout most of the Western Block countries.

Although the LWR had been placed in a privileged position by the political situation, it had significant shortcomings, many of which were apparent from the beginning. It had low thermodynamic efficiency with little potential for improvement. Fuel burnup was limited. It wasconsiderably less forgiving of mechanical or operational error than such competitive designs as the molten salt reactor and the gas-cooled reactor. The LWR’s necessary complexity (required toprovide defense-in depth) implied “economies of scale” such that it could be economically competitive, if at all, only in very large sizes. These disadvantages were obvious enough to show that the LWR would be a poor choice to play the central role in nuclear generation strategies. Its shortcomings were tolerable only because the LWR was originally intended for a stop gap role, tobe substantially phased out by the breeder by 1990. Development of the breeder was the overarching goal of the scientists involved in both the military and civilian development of nuclear power. There was a pervasive belief that uranium wasa very limited resource, so limited that weapons production would be seriously impacted and significant civilian use would be impossible. Nuclear power proponents saw themselves in a race with fossil power generation schemes, and so needed a way to expand the number of nuclear power plants rapidly enough to gain market share and then to keep up with the anticipated very rapid rise in electricity demand. But not just any breeder would do. Because of the anticipated rapid growth of nuclear capacity, it would not be sufficient to breed at a rate capable of merely replenishing the fissile material burned. A “fuel factory” was needed which would produce enough excess plutonium not only to sustain itself but to simultaneously produce enough additional plutonium to serve as seed stock for a rapidly growing fleet of similar reactors. The measure of the ability to function as a fuel factory, not just as a self-sustaining reactor, is the "doubling time", and only the LMFBR had, at least in theory, the ability to achieve a short enough doubling time. The LMFBR performs best with an initial charge of plutonium to start the breeding process, which could be provided by extracting plutonium from spent LWR fuel, using methods and facilities similar to those developed for the weapons program. Thus, the LWR/LMFBR combination was thought to provide the most rapid path to a self-sustaining nuclear cycle. Even when it finally became obvious that uranium availability would not constrain the growth of nuclear power, the U.S. Atomic Energy Commission (AEC), and later the U.S. Department ofEnergy (DOE), remained firmly committed to the original plan, using both strategic and economic arguments to argue against any alternative to the LWR-LMFBR vision of the future. In 1969, Milton Shaw, director of the USAEC’s Division of Reactor Development and Technology, in a foreword to a study of alternative breeder reactors, wrote.

"The widespread acceptance of the light water reactor is an established fact. The large industrial commitments and improvements in technology should result in further improvements in performance. These factors will make difficult the introduction in the United States of any new system even though a potential economic gain is indicated. Because of the urgent need to introduce breeder reactors at the earliest date, the USAEC has committed itself to an extensive program involving LMFBR’s. For this reason, development funds for competing concepts are limited. The possible role of such reactors in the U. S. nuclear power economy is, therefore, not yet clear."

The degree of unwavering government support for its vision of the nuclear future is exemplified by the AEC’s 1973 (!) estimate that, by the year 2000, the U.S. would get half its electric power from 400 breeders and 600 LWRs. Only 41 reactors were ordered after 1973 and every one was subsequently canceled, as were nearly 70% of those ordered after 1970. In 1998 there are 103 licensed plants, all LWRs, and the number is expected to decrease substantially in the next decade. The U.S. utility industry was also advocating early introduction of the LWR. In 1970, a General Electric Company vice president, recalling the reasons for the decision to offer the “turnkey” loss-leader plants that started the nuclear stampede in the United States, said "If we couldn’t get orders out of the utility industry, with every tick of the clock, it became progressively more likely that some competing technology would be developed that would supersede the economic viability of our own. Our people understood that this was a game of massive stakes, and that if we didn’t force the utility industry to put those stations on line, we’d end up with nothing."

The strategy of a rapid buildup of LWR power generating capability, followed by an equally rapid conversion to reliance on LMFBR’s had a compelling technological logic. It had an equally attractive economic logic for the industrial participants who were eager to begin profiting from their enormous investments in nuclear technology. Unfortunately, for both the U.S. and those who followed the U.S. lead, both logical analyses were wrong because the underlying axioms and assumptions were untrue. The price now being paid for these errors is enormous in terms of both financial loss and lost opportunity. The financial loss is almost incalculable; it has been called the greatest managerial disaster in business history. 15 Moreover, even in countries where it has eventually failed, the LWR, by virtue of its Official Technology status, stifled the development and introduction of safer, cheaper nuclear power plants that might have taken advantage of modern technology and been better suited to contemporary constraints and the specific needs of various countries.

It is most gratifying to find that ideas which I have been advancing in Nuclear Green were understood and accepted by Lidsky and Miller ten years ago.

3.Current Status of the LWR/FBR Nuclear Power Paradigm

The cost and complexity of the systems needed to deal with the danger of severe accident makes the LWR a poor choice for large central station power plants. Ironically, it is the LWR’s high power density, the very reason it was chosen for submarine use, that is its Achilles heel. Even a 10-second interruption in the supply of cooling water at the surface of a fuel rod can lead to local overheating and irrevocable, cascading damage to the reactor core. As a result, the LWR must rely on defense-in-depth, a system of diverse and redundant backup devices, to guard against such an event. This is a widely used technique, but defense-in depth can not, by itself, guarantee absolute safety; it can only reduce the probability of a serious accident. All nuclear power plants,because of their cost and potential for off-site hazards, have a very low “acceptable” probability of failure. The larger the plant, the lower the acceptable probability of failure. Because the consequence of failure is so large in gigawatt-scale plants, LWR’s have been forced to employ engineered safety systems that promise unprecedentedly, and perhaps unattainably, low probability of failure.

The first LWRs employed defense-in-depth systems which were calculated to achieve failure probabilities of 10 -4 /year or less, i.e., an expected mean time before a major accident (such as core meltdown) of at least 10,000 years, for a single, given reactor. This is a commonly accepted level of risk for high capital cost industrial facilities from the standpoint of investment protection. However, it is clearly inadequate from the perspective of public safety for the case of nuclear reactors. 16 As a result, all reactors were required to have a confinement dome to protect the public, in addition to the engineered safety features which were of high-level industrial grade. Itwas clearly prudent to have such an extra level of protection for a new technology with possible unexpected failure modes, and largely ill understood consequences. The resulting risk of a given reactor undergoing a major accident with public health consequences was believed to be less than10 -6 /yr, with the confinement dome playing a major role in reducing the consequences of the accident. This arrangement made perfect sense for the first generation of 200-400 MWe LWR’s, but set a subtle trap for the next and successive generations of much larger reactors.

The complexity of defense-in depth safety systems leads to size-independent costs that are better borne if the costs are supported by the revenues of a larger power plant. This factor, in combination with the scale economy of steam generators and turbines, and the more difficult than anticipated competition with low cost fossil fuel, led to a very rapid scale up of LWR size. But above about 500-600 MWe, engineers could no longer guarantee the integrity of the confinement system 17 . It was not realized until it was too late to modify development plans that the inability to build a confinement vessel that could withstand a major accident in such a large reactor violated the initial safety concept. Because the confinement vessel could not be counted upon, defense-in-depth would have to be solely responsible for public safety. This meant that failure probability levels of 10 -6 /year, that is, a mean time before major accident of one million years, had to be achieved for the reactor itself, without reliance on any additional safety credit for the dome. This unprecedented level of safety for a defense-in-depth system, when applied to so complex a system as a nuclear reactor, meant that the safety system itself had to be enormously complex, which made it maintenance-intensive, and, as it happened, actually more problem prone than the device it was meant to protect. As a result, LWR power plants are expensive, complex, difficult to operate, and incapable of simultaneously competing with fossil fuels and achieving the desired level of safety . All of these problems are attributable, at least in part, to the reliance on defense-in-depth. However, despite all the attention given to the safety system, the public remains unconvinced of the safety for which so high a price is paid. This skepticism is well justified because insufficient data is available to calculate the true probability of a major accident and it is literally impossible to demonstrate, by definitive test, that the requisite level of safety has been achieved.

The sodium-cooled LMFBR was the device that was intended to replace the LWR when mined uranium supplies became prohibitively expensive. The LMFBR was chosen over other breeder reactor designs because it was, in theory, capable of very short fuel doubling times, shorter than that of any competing reactor design. The doubling time is the time required to produce an excess of fuel equal to the amount originally required to fuel the reactor itself. In other words, in one doubling time there would be enough fuel available to start up another reactor. In the absence of mined uranium, only a short doubling time would, it was believed, allow nuclear power to grow fast enough to compete with alternative sources of power. Unfortunately, the theoretical advantages of the LMFBR could not be achieved in practice. A successful commercial breeder reactor must have three attributes; it must breed, it must be economical, and it must be safe. Although any one or two of these attributes can be achieved in isolation by proper design, the laws of physics apparently make it impossible to achieve all three simultaneously, no matter how clever the design. The fundamental problem originates in the very properties of sodium that make the short doubling time possible. The physical characteristics of sodium and plutonium are such that a loss of sodium coolant in the center of the core of a breeding reactor (caused, for example, by overheating) would tend to increase the power of the reactor, thus driving more sodium from the core, further increasing the power in a continuous feedback loop. The resulting rapid, literally uncontrollable, rise in reactor power is clearly unacceptable from a safety standpoint. This effect, the so-called “positive void coefficient” can be mitigated by, for example, changing the shape of the core so that more neutrons leak out of the core, but this immediately compromises the reactor’s breeding potential. Safety and breeding are thus mutually antagonistic. This situation can be alleviated to some extent by making radical design changes, but these changes lead to greatly increased costs, and make the reactor prohibitively expensive. Even if the LMFBR could meet its original, highly optimistic, operating goals and the LWR/FBR power cycle were put into operation, it is unclear that the goal of energy security would be achieved. As discussed in the following sections, the measures that would have to be put in place to protect all parts of the fuel cycle against terrorism would have very high social costs. Equally important is the increased risk of accidental or maliciously-induced technological failure. Compared to light water reactors operating on the once-through fuel cycle, the breeder fuel cycle is much more complex and error-prone. This implies a higher probability that the entire nuclear system or a significant fraction thereof might need to be shutdown because of a generic problem, e.g., with sodium containment, in the reactors or an accident in one of the reprocessing or fuel fabrication plants that serve the system.

I will skip over much of the next section of the essay, although rest assured, gentle reader, it has interesting things to say, and may be consulted through the link which I supply at the beginning of this post. However, I could not skip over the following passage.

4.3.Technological Failure A breeder-based nuclear supply system is inherently more complex and error prone than one based on LWRs operating on a once-through fuel cycle. Not only does the breeder system have complex components which have no counterpart in an LWR system, e.g., reprocessing plants, but even when a counterpart exists, e.g., the reactors themselves, fuel fabrication plants, and a transportation network, they are more complex in a breeder-based system. Aside from the reactor, much of this added complexity is due to the radiological hazards, criticality risks, and security threats associated with the presence in the breeder fuel cycle of large quantities of unirradiated plutonium, i.e. plutonium without fission products. Actual failure of, or just loss of public confidence in, any component of the breeder fuel cycle could shut down a significant part of, or even the whole system, thus negating its potential energy security advantage. In the following, we comment briefly on the technological vulnerabilities of breeder reactors and the associated reprocessing and fuel fabrication plants. Proponents of the LMFBR have made many claims regarding the robust engineering base of sodium reactor technology, but experience around the world has demonstrated that sodium-cooled systems often suffer serious disruptions even in the event of relatively minor failures. 24 The potential for sodium-air and sodium-water reactions accounts for some of this sensitivity, and the problem is exacerbated by the opacity of sodium, which makes fault detection substantially more difficult for such systems than for those in which visual inspection is possible. These technological problems, in addition to the design difficulties associated with the tension between breeding and safety, strongly suggest that any large-scale LMFBR would be more problem-prone than the current generation of LWRs. Large plants for reprocessing LWR spent fuel in France and England have achieved high capacity factors in recent years. However, the radioactive effluents emitted by such plants during normal operation, and the accumulating stocks of separated plutonium as well as high-level and transuranic wastes are a source of growing concern among the public, the media, environmental groups, and bureaucracies in many countries. Moreover, because of the much higher fissile content and burnup of breeder compared with LWR spent fuel, reliable operation of breeder reprocessing plants will be more difficult and costly. That is, breeder plant equipment must be smaller to ensure criticality safety, the contact time between the extraction phases must be shorter to avoid radiative decomposition of process materials, and the need for higher fission product decontamination increases the volume of liquid waste streams. Similar remarks apply to plutonium fuel fabrication; as with reprocessing, fabrication of LMFBR fuel is more demanding than making MOX fuel for LWRs.

In sum, while the potential risks of both nuclear proliferation and terrorism as well as technological failure associated with a breeder-based nuclear supply system are difficult to quantify, they appear to be substantially greater than those associated with the current LWR-based system. Thus, in light of the strong adverse societal response to relatively minor mishaps with the present system, the chances and consequences of failure of any portion of a breeder-based system are too large to warrant reliance on it for a significant fraction of Japan’s electricity requirements. But is it possible to achieve energy security via nuclear power without the breeder?We believe that the answer is yes, and that the essential element is uranium stockpiling.

Finally we have the following statement from the conclusion:

This will provide a more realistic perspective on the need for nuclear power including the preferred technological embodiments and international institutional frameworks for dealing with safety and proliferation concerns. The role of nuclear power, decisions as to the optimal makeup of the power reactor fleet, and the degree of reliance upon seawater-derived uranium can be postponed until the technical, economic, and political issues are better resolved. However, it is of paramount importance to ensure that current actions do not unreasonably prejudice support for a nuclear component of energy supply. Strong support for plutonium recycle, with its associated technical risks and societal costs, in the face of increasing evidence that alternative strategies are superior, is clearly counterproductive.

Well there you have it. A very accurate though brief analysis of the history of nuclear power, and the flaws of the current thinking as well as the problems of the LMFBR concept, coupled with a firm statement that things can be cone much better.

The LFTR Emulates Natural Systems

The Rocky Mountain Institute advocates using the closed loop sort of materials and energy handling system found in nature:

Using nature as mentor, model, and measure often yields superior design solutions that profitably eliminate waste, loss, and harm.

Natural systems operate in closed loops. There's no waste—every output is either returned harmlessly to the ecosystem as a nutrient, like compost, or becomes an input for another process. In contrast, the standard industrial model of our age is a linear sequence of "take, make, and waste" — extract resources, use them, and throw them away — a process that erodes our stock of natural capital by depleting resources and replacing them with wastes.

Reducing the wasteful throughput of materials — indeed, eliminating the very idea of waste — can be accomplished by redesigning industrial systems on biological lines that change the nature of industrial processes and materials, enabling the constant reuse of materials in continuous closed cycles, and often the elimination of toxicity.

The LFTR had its origin in the desires of the great scientists, Eugene Wigner and Alvin Weinberg to eliminate the wastefulness of early reactors. They saw that in order to eliminate waste from nuclear systems, materials had to flow from one process to another. Most reactors use a structured core with solid fuel that is moved mechanically in and out of the reactor. Nuclear fuel is desiogned only to serve as fuel in a nuclear reactor. It is difficult to repricess. Eugene Wigner was trained as a chemical engineer, and thought in terms of efficient use of materials. And of the efficient transport of chemicals dissolved in, suspended in or bonded to liquids that flowed from process to process, within a chemical plant. Alvin Weinberg was trained in biology as well as in physics. He understood the role of fluid flow in live systems, and how fluids carried materials form one biological process to another. Weinberg also understood the transport of materials between organisms in environmental systems.

Wigner and Weinberg believed that reactors could, in effect, be turned int o closed loop systems in which little would really go to waste. It is impossible, according to the second law of thermodynamics, to design a system in which nothing hoes to waste. But it my be possible to design more efficient systems. Wigner and Weinberg determined that Thorium was a more efficient basis for nuclear fuel than uranium. The efficiency of the thorium fuel cycle rests on something called "neutron economy", that is the efficient use of neutrons produced in a nuclear process.

Neutron are the keys to both chain reactions, and the creation of nuclear fuel inside reactors. The nuclear fuel for thorium cycle reactors is Uranium-233, and U-233 has the best neuton efficiency of any fissionable material. The efficiency of the LFTR rests on its emulation of living organisms. Like living organisms it has a system to produce and distribute energy, a system to rid itself to of unwanted heat and materials, and systems to recapture energy, and the eliminated materials. Recapture of energy can be used for heat in industrial processes including hydrogen production, also for water desalinization, or for space heating, and of course to produce electricity, Recaptured materials can be used in industry, medicine, in food preservation, and in sanitation. Nothing need go to waste.

The LFTR also operates with thermal efficiency. It is capable of operating at a much higher heat than conventional reactors. High temperatures create potential for greater thermal efficiency. In addition, the use of closed cycle gas turbines create the potential for greater generating efficiency. The use of bottom cycle heat for space heating or desalinization, holds promise to further increase thermal efficiency,

The LFTR is efficient in terms of materials use. Some of the essential material used in the LFRT including Thorium are essentially wasted now in existing industrial processes. Other materials like graphite, can be manufactured, and thus are virtually renewable resources. Resources like nickel are rarer than craphite, but their use is LFTR is fully justified because no other energy use for Nickel would bring as high a rate of energy return.

A further efficiency of the LFTR is its capacity efficiency . The LFTR is capable of producing electricity 24 hours a day for extended periods of time. Unlike Light Water Reactors which must be shut down periodically for refueling, new fuel can be added to the LFTR while the reactor is operating. Thus the LFTR can operate continuously at 100% of capacity but need not do so.

The LFTR is demand efficient. Renewable energy systems, like Solar and wind generation produce electricity without any relationship to demand. Windmills generate electricity when moderate winds are blowing, but not in high winds, or on calm days. PV solar output varies with light conditions, while the electrical out put of Concentrated Solar generators is effected by clouds and dust storms. All Solar generation systems produce more electricity over a longer periods of time during the summer than during the winter. Generated output from renewables like solar and wind, cannot be regulated by consumer demand. When renewables produce more electricity than the market demands, excess electricity has to be dumped. This is a significant inefficiency. On other occasions renewable generated electricity is sold on the spot market for at loss. Owner of renewables demand financial subsidies to cover costs during the frequent periods when the selling price of renewable generated electricity is sold at a loss.

In contrast the LFTR can always generate the amount of electricity consumers demand. The temperature of reactor salts rises as load drops, and as salt temperature rises, reactor salt expands, and thus is expelled from the reactor core. The loss of salt and fuel from the core slows and eventually stops the fission process, but the reactor salts continue to draw heat from the radioactive decay of fission products. Thus the salt will remain hot until consumer demnd leads to electrical generation, and the electrical generation process, draws heat from reactor salts, lowering salt temperature, shrinking salt volume, drawing nuclear fuel back into the core, and starting the chain reaction again. This system allows for power to be immediately available from stopped reactors without neutron or fuel loss. Demand efficiency is the ability to respond quickly and automatically to ups and downs in grid electrical demand. Renewables just can't do that, and convintional reactors cost to much to operate at any rate other than 100% of capacity.

Finally the LFTR is time efficient. Unlike renewables the LFTR can produce power at any time. Unlike conventional Light Water Reactors the LFTR does not need to stop producing power during refueling. Because of then LFTRs high level of inherent and passive safety, it is far less likely to experience emergency shutdown than LWRs. This means that 100% of the LFTR capacity will be online virtually 100% of the time. Renewables and conventional nuclear do not match this temporal efficiency.