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 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 carry a significant cost penalty over conventional LWRs.
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.
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 progr
am, 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 nucl
ear 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 as
sociated 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.
Both Eugene Wigner and Enrico Fermi were brilliant scientists. Both made enormous contributions to the theoretical and practical development of atomic energy. Their educational background was different, and for this reason their thinking about long-range reactor design diverged. Fermi was a classic physicist. Fermi thought of reactors first in terms of physics experiments. The CP-1–the ancestor of almost all solid fuel reactors–was first of all a physics experiment. Physicists depend on other people to deliver to them the materials they need to conduct their experiments. Once the materials are present, they are assembled, and the physicist then runs his experiment. Byproducts from the experiment may be carted off or turned over to other people for reprocessing. The experiment is never designed with easy disposition of byproducts in mind.
Eugene Wigner was trained as a chemical engineer. The orientation of chemical engineers is quite different from that of theoretical physicists. First theoretical physicists usually think in terms of very large scale entities and events, or in terms of very small scale entities or events. Chemical engineers think of intermediate, human scale objects and events. The difference in scale and purpose of the events is makes a major difference in the professional outlook of chemical engineers. Chemical engineers expect to work for profit-making enterprises. For that reason the cost of inputs must be minimized, and the sale of outputs maximized. The chemical engineer thinks of waste as a potential new profit sources rather than something to be disposed of. It was, after all an engineer, Herbert Hoover, who introduced the United States to its first war on waste. The word “Hooverizing” signifies a parsimonious use of resources in order to cut down on waste. Wigner, who had worked as a a chemical engineer at his father’s Tannery, would undoubtedly understood the “Hooverizing” impulse.
Liquid metal fast breeders will never hope to compete on construction or electrical production cost with LFTRs , as Eugene Wigner and Alvin Weinberg understood. And Liquid Fluoride salts would never, never, never catch fire.
Many years ago, Alvin Weinberg pointed out the issue of LMFBR safety:
We have no real estimates of accident probabilities for liquid metal fast breeder reactors (LMFBR’s). The Rasmussen estimate (one in 20,000 per reactor year with an uncertainty of five either way) 6 would lead to a meltdown every 3 years. This is probably an unacceptable rate; an accident rate at least ten times lower, and possibly 100 times lower may be needed if the system is to be acceptable.
Weinberg pointed to another, very significant problem with the LMFBR, the issue of nuclear waste:
Each 5,000 MW LMFBR produces about 75 cubic feet of high-level solidified waste per year, contained in about 50 steel cans. According to present plans, these would occupy about 1.5 acres of burial space. Thus the entire syst
em of 7,000 reactors would require about 15 square miles of burial space per year. After 1,000 years, 15,000 square miles level wastes will have decayed sufficiently to allow fresh wastes to be will have been used up; by that time, the radioactivity in the high layered over the older wastes. Thus the 15,000 square miles devoted to high-level wastes might be usable for much longer than 1,000 years.
To summarize, although we cannot identify physical limits that make a world of 7,000 large LMFBR’s impossible, one would have to concede that the demands on the technology would be formidable. Two issues appear to me to predominate: first, the acceptable accident rate will probably have to be much lower than the Rasmussen report suggests. If one uncontained core meltdown per 100 years is acceptable (and we have no way of knowing what an acceptable rate really is), then the probability of such an accident will have to be reduced to about one in 1 million per reactor per year. This is the design goal for the LMFBR project in the United States. Second, a nuclear world such as we envisage will have long since had to make peace with plutonium. Ten tons of plutonium per day is mind-boggling. It is hard to conceive of the enterprise being conducted except in well-defined, permanent sites, and under the supervision of a special cadre -perhaps a kind of nuclear United Nations.
I for one do not morn the passing of the Integral Fast Reactor. Sodium cooled reactors are bad ideas as Weinberg subtly suggested. It would be most unfortunate if a single cent more is wasted on Fermi’s folly. Let’s nail the coffin of the sodium-cooled fast breeder shut once and for all.
A Primer on Nuclear Safety:
2.6 Defense in Depth
Molten Salt Reactors, Moir-Teller Defenses
The term Molten Salt Reactor is generic. All reactors that use liquid salts as both coolant and fuel carrier are Molten Salt Reactors. Reactors that use Liquid Fluoride salts, and operate on a thorium rather than a uranium fuel cycle are Liquid Fluoride Thorium Reactors. Most discussions about Molten Salt Reactor safety are primarily directed to LFTR safety, but many of the safety features of the the LFTR will also be present in other MSRs.
Many of the safety features of the LWR are not required for the MSR. For example the massive steel pressure vessel can be dispensed with since MSRs operate under atmospheric pressure. There is always a risk of steam explosion with the LWR but of course no risk with the MSR. If the pressure vessel is removed from our reactor design, we lose one of the physical barriers present in the LWR defense-in-depth system. A way should be found to compensate for that loss.
The rigid, hidebound, intellectually stunted, stubbornly prejudiced, and inflexible bureaucracy of the NRC simply sees the absence of pressure vessels as a safety issue. The NRC leadership is too narrow-minded to look at the the possibility that the MSR and the PBR require a different intellectual approach to reactor safety.
A second feature of MSRs, one that it does not share with the PBR is the potential to remove radioactive isotopes from the carrier salts. These would include fission products, transuranium isotopes, and tritium that is produced by neutron radiation of lithium in the carrier salt. This opens a route to an alternative containment system, one which removes, processes, separates and concentrates and then diverts to useful purposes. This approach, incidentally, eliminates the problem of nuclear waste, represents both a safety feature, and a potential means of producing valuable byproducts during the nuclear process.
Thus the ability to process fuel while the reactors is operating constitutes a type of defense that will not entirely preventing the release of radioactive materials during a worst case MSR accident, certainly would partially mitigate that release.
In order to understand the containment issue we have to understand what problems lead to the necessity of defenses-in-depth. In the case of light water reactors it is the vulnerability of the water-based coolant systems to disruption. We have seen from the ESBWR design that it is possible to build in powerful protections against coolant failure. For LWRs coolant failure is a hazard because it leads to core meltdown. Since the core of the MSR is already molten, from the viewpoint of the NRC the MSR violates profoundly important safety rules. We have seen that much of the LWR’s defense in depth system is devoted to to prevention of core melt down, a molten core would represent a partial failure of the reactor defense system for those who view the ESBWR type Light Water Reactor as the non plus ultra of nuclear safety.
Not only has the core of the MSR melted down by design, but it lacks the containment defense of a pressure vessel. There is no guarantee that the MSR will never leak. I for one am a pessimist about reactor leaks. Anything fluid is want to leak, and will leak sooner or later. Advocates of sodium-cooled fast breeders should always remember that. Even with continuous fuel processing the core fluid of a MSR is very hot and radioactive. Thus MSR defenses-in-depth must assume core excursions of molten reactor fuel and fission products.
Not only that, but a standard safety feature of the MSR is the ability to dump core fluids into tanks in the event of a failure of the cooling system after shutdown. These are far from the only controlled fuel core excursion with the MSR design. MSR fuel is forced out of the core as it heats, because liquid salt expands with greater heat. Core salt is channeled out of the core in order to transfer heat from the the reactor to the generating system or in order to provide shutdown or emergency core cooling. Core salts are also withdrawn from the core in order to process them. Each controlled core excursion represents a breach of containment, and therefore a a serious safety issue.
It must be obvious then that defense in depth for a MSR must operate in a quite different fashion than for a LWR or a PBR.
Reactor defenses are the most reliable if they depend on the automatic operation of laws of nature, rather than human intervention. Thus if a reactor defenses depend on an ironclad natural law than cannot be violated, there is no need for redundancy or further defenses. We do not tie iron bars down to keep them from floating away. Defense-in-depth is necessitated with undesirable events that are unlikely but not impossible. Defense-in-depth thus is about defense against the unlikely. The purpose of defense-in-depth is to make the unlikely even more unlikely, if not impossible. More defense-in-depths-in-depth are not needed if undesirable consequences cease to be matters of practical concern, or when they stop being theoretically impossible.
MSR Defense in Depth: The Moir-Teller View
The levels of MSR defenses in this view are:
- the negative coefficient of reactivity – increased temperature slows down and eventually stops the nuclear reaction
- the low fuel burn up margin and fast burnup rate – failure to add new fuel slows and then stops the chain reaction process
- the continuous removal of radioactive gases
- The addition primary core containment structure, piping, drain tanks and other fuel holding and processing structures
- the reactor system chamber
- An outer containment vessel
- An underground location requiring escaping radioactive materials to counteract the forces of gravity before any above surface excursion.
Other potential barriers exist. In two-fluid MSRs, the blanket containment structure constitutes another safety barrier. Core salts breaching core containment must mix with blanket salts and then breach the blanket.
All out of core controlled excursion structures can be protected by secondary barriers. Thus pipes supplied with sleeves designed to drain any escaping salts directly into a holding tank if the primary pipe ruptures. Holding tanks can be double walled. Fuel processing equipment can be encased in an air tight structure. Thus the primary barriers can in every case be doubled.
The fluoride salt mixture also constitutes a significant barrier. Some radioactive materials are chemically bonded to the salt. Other materials, including noble gases and metals are dissolved in the salt liquid but can escape during a salt excursion. Thus the processing of fuel should always involve the removal of radioactive gases as part of the first line of MSR defenses. High priority should also be given to the removal of noble metals, whose presence inside the reactor is likely to cause problems. Thus to the extent possible, radioactive materials likely to escape from the fuel mixture during an uncontrolled out of reactor excursion, out to be removed before the excursion occurs. Thus under the best circumstances if an out of primary and secondary containment breach occurs, fuel either drains into catch tanks, or it freezes. In either case the further excursions of radioisotopes is contained. Of course, there will be a messy clean up problem with frozen fuel.
Core containment breaches with conventional reactors carries with them concerns about the release of radioactive gases. In the case of the MSR, that concern, while not disappearing, diminishes. Offsetting the decrease of radioactive gas release on occasions of uncontrolle
d core excursion is the increased likelihood of core excursions.
The mass of tritium (from CANDU reactors) added to the lake each year by Ontario Hydro’s PNGS and DNGSreactors is about 8% of the inventory of tritium currently in (Lake Erie)
My conclusion then is that the Moir-Teller scheme of defense in depth for MSRs would create a reactor that would probabilisticly safe for practical purposes. Even in the face of core breach, an underground MSR would not present an even slight danger to public safety. It would appear that the Moir-Teller system actually contains redundancies which are not required from the viewpoint of public safety, and further research my actually lead to dispensing with them. The Moir-Teller system coupled with modern security systems, would present a very hard and indeed invisible target, that would defeat terrorist threats. Thus implementation of the Moir-Teller MSR safety system would be practically safe and would never become so unsafe as to become a danger to public well being.
There was enough interest in Daniels pile, that in 1946 design work intended to facilitate its development began in Oak Ridge at the Clinton Laboratory, later Oak Ridge National Laboratory. Oak Ridge was the primary inheritor of the Metallurgical Laboratory’s tradition of reactor innovation. That pebble Bed research was set aside when the researchers were reassigned to help develop the light water reactor for the Navy. By early 1950′s ORNL research had focused on an even more radically innovative reactor concept, the Molten Salt Reactor, thus the Daniels’ pile, as it was called in Oak Ridge, was shelved.
Daniels Idea was embed uranium in small graphite balls or pebbles. The pebbles would be placed inside a chamber, and cooled with helium. The graphite would serve as a moderator, an given the presence of enough uranium inside the balls of moderating graphite, a chain reaction would commence.
After the death of Daniels project in Oak Ridge, the pebble bed idea lay dormant for a few years. then in 1956 a German physicist Rudolf Schulten picked it up and began to develop it. The British were developing gas cooled, graphite moderated reactors the time, and gas cooled reactors offered some attractive advantages over the rapidly emerging American Light Water Reactor. Schulten believed that a pebble bed reactor could be built that would be inexpensive to build and operate, and would be far safer than the American Light Water Reactor. In addition the Pebble Bed Reactor would operate at a far higher temperature, and thus would have greater thermal efficiency than the Light Water Reactor.
The Pebble Bed Reactor looked like a good match to the thorium fuel cycle and there were real concerns in the 1950′s and 60′s about how long the supply of uranium would last. So the original concept was to make the PBR a thorium breeder. This intention was defeated by the proliferation resistant nature of the PBR’s pebbles.
The first German Pebble Bed Reactor, the AVR was conceived to be highly safe. The Pebbles themselves are a major source of PBR defense in depth. Each pebble contains thousands of tiny Uranium dioxide particles. The Uranium dioxide particles are surrounded by multiple layers of material including a carbon inner buffer, followed by an inner layer of pyrolytic carbon, a layer of ceramic silicon carbide, followed by a second outer layer of pyrolytic carbon. Thus each fuel particle contains a five layered defense in depth. In addition the particles were designed to withstand the stress, and high tempreture expected to be encountered in the PBR.
The German Pebble Bed Reactors had one remarkable feature that is repeated in reactor developed from the PBR concept. The pebbles were blown into the reaction chamber by helium gas, and suspended within the reaction chamber by the gas flow. Thus the pebbles had to be designed to withstand the mechanical stress of constantly bumping into each other in the reactor’s chamber, as well as the high temperature encountered in the reactor core. The fuel particles were believed to be capable of withstanding the sort possible accident possible with a PBR, hence even without the other PBR fuel safety measures, they offered a high level of inherent safety. The Triso particles were are in turn embedded in graphite pebbles.
The Germens built two pebble bed reactors. The AVR was a successful experimental prototype operated between 11966 and 1988. The THTR-300 was a developmental reactor intended to prepare the way for commercial deployment of PBRs. During its brief operating history between 1983 and 1989 the THTR-300 suffered from the sort of teethings problems common with new technologies. It was by no means a failure, but at the time of the project shutdown there were clearly developmental issues remaining to be addressed. The THTR was originally intended to operate as a thorium fuel cycle reactor, but reprocessing the nuclear fuel proved to be complex and expensive, and the thorium cycle was dropped for a conventional once through Enriched uranium approach. The THTR used no less than 670,000 6cm fuel pebbles. The German Pebble Bed reactor research program was shut down in 1988-89 as a political consequence the Chernobyl accident. At The time of the project shut down, design work was proceeding on the HTR-500, which was intended to be the first commercial PBR.
The PBR was regarded as highly safe. It could be shutdown with cno core cooling without core damage. During AVR testing the reactor was actually brought to shut down with the cooling system turned off. No core damage occurred. This was a remarkable performance. Shutting down a LWR without cooling will lead inevitably to core meltdown due to the heat generated by the radioactive decay of fission products.
- The use of Graphite in the core structure and fuel pebbles.
- The fife layered defense in depth of each fuel particle contained within the fuel pebble
- The SiC coating layer on fuel particles intended to insures the retention of fission products
- Low radiation levels in the environment of the reactor – opperators received only 20% of the radiation experienced by LWR operators
- The use of Helium as a coolant
- Passive removal of decay heat
- Maximum core heating remained below the level that would damage core and fuel structures
- The use of very strong prestressed concrete in the reactor vessel
- The capacity of the outer reactor structure to withstand the impact of an aircraft
The NRC notes:
Because the PBMR is continuously refueled, the excess reactivity can be kept low. Also, the design has a more negative fuel temperature coefficient than LWRs, as the Doppler feedback is greater for the less-thermal neutron spectrum associated with a graphite moderator.* These features reduce the risk of reactivity accidents for most scenarios (but increases the risk for accidents involving core overcooling).
A major component of the PBMR safety basis is a low power density (an order of magnitude below that of an LWR) and large thermal capacity (as a result of the large mass of graphite in the co
re), together with the high-temperature resistance of the fuel. The maximum power rating of each module (265 MWth) and the high surface-to-volume ratio of the core were chosen so that in the event of a loss of coolant from the primary system, adequate cooling would be provided without the need for forced convection. PBMR designers claim that in the event of a total loss of primary coolant and no operator intervention, the core heatup rate would be slow and the maximum fuel temperature would not exceed 1600 C. Thus the design does not include conventional emergency core cooling systems, which are required for LWRs to provide emergency water sources in the event of a loss-of-coolant accident.
The German PBR project was subsequently regarded as an outstanding success. Not only wree over all project goals meet till the time of shut down but the expectation existed that the technology could be developed into a revolutionary commercial reactor that could be built at a lower cost than conventional light water reactors, yet would operate with at a higher temperature which in turn would lead to greater thermal efficiency. The PBR design has a high level of inherently safe.
Following the shut down the potential of the PBRM was recognized by commercial interests in South Africa, and by the Chinese. Projects to develop PBR technology for electrical generation and process heat have been undertaken in both countries. Both programs expect to build PBRs in factories with serial production beginning by 2020. Between 2020 and 2030 hundreds of PBRs may be built in Chinese and South African factories.
So far I have pointed to the numerous safety advantages of the PBR. However the NRC has questioned the safety adequacy of current PBR designs.
PBMR advocates are so confident in the safety of the reactor (some even call it “meltdown-proof”) that they have proposed a drastic weakening of a number of safety requirements that apply to the current generation of U.S. nuclear plants. These proposals include (1) use of a filtered, vented confinement building instead of a robust containment capable of preventing a large release of radioactive materials in the event of severe core damage; (2) a reduction of the size of the emergency planning zone (EPZ) from 16 kilometers to 400 meters; (3) a reduction in the number of staff, including operators and security personnel; and (4) a reduction in the number of systems whose components must meet the most stringent quality assurance standards.
However, there is insufficient technical justification for these measures. The presence of a pressure-resistant, leak-tight containment and the maintenance of comprehensive emergency planning are both prudent “defense-in-depth” measures that could mitigate the impact of a severe accident with core damage. Defense-in-depth is the requirement that nuclear reactors should have multiple, independent barriers in place to prevent injuries to the public and damage to the environment. The presence of multiple barriers is a hedge against uncertainty and an acknowledgement that the understanding of the performance of any one barrier is incomplete.
PBMR promoters claim that a robust containment is unnecessary because the design-basis depressurization accident cannot cause damage to the PBMR fuel severe enough to result in a large radiological release. They argue further that such a containment would actually be detrimental to safety because it would inhibit heat transfer and interfere with the passive mechanism needed to cool the core in the event of a loss-of-coolant accident. However, a containment is needed not only to inhibit the relatively minor releases that would occur during the design-basis accident, but also to mitigate the consequences of a more severe accident. Containments can also help to protect the reactor core from a sabotage attack utilizing truck bombs or hand-held rocket launchers — an ominous possibility that should not be discounted.
The NRC concerns seem speculative in that it involves the postulation of potential core damage that has not been demonstrated to be possible by simulation. The mention of truck bombs and hand held rocket launchers takes us clearly into the realm of fantasy because the use of such weapons against a PBR can be defeated by relatively low tech security measures already used to harden high risk targets. What sort of major accident did the the NRC have in mind?
Among the largest sources of uncertainty for the PBMR are the potential for and consequences of a graphite fire. The large mass of graphite in the PBMR core must be kept isolated from ingress of air or water. Graphite can oxidize at temperatures above 400 C, and the reaction becomes self-sustaining at 550 C (the maximum operating temperature of the fuel pebbles is 1250 C). Graphite also reacts when exposed to water vapor. These reactions could lead to generation of carbon monoxide and hydrogen, both highly combustible gases.
If a pipe break were to occur, leading to a depressurization of the primary system, it has been shown that flow stratification through the break can cause air inflow and the potential for graphite ignition. While the PBMR designers claim that the geometry of the primary circuit will inhibit air inflow and hence limit oxidation, this has not yet been conclusively shown.
The consequences of an extensive graphite fire could be severe, undermining the argument that a conventional containment is not needed. Radiological releases from the Chernobyl accident were prolonged as a result of the burning of graphite, which continued long after other fires were extinguished. Even though the temperature of a graphite fire might not be high enough to severely damage the fuel microspheres, the burning graphite itself would be radioactive as a result of neutron activation of impurities and contamination with “tramp” uranium released from defective microspheres. An even worse consequence would be combustion of carbon monoxide, which could damage and disperse the core while at the same time destroying the reactor building, which is not being designed to withstand high pressure. In contrast, the large-volume concrete containments utilized at most pressurized-water reactors can withstand explosive pressures of about 9 atmospheres.
Here we must raise a question since the risk of graphite fire seems greatly exaggerated. General Atomics, which has some experience with the operation of Graphite core and fuel reactors, states,
NUCLEAR-GRADE GRAPHITES ARE NONCOMBUSTIBLE BY CONVENTIONAL STANDARDS”
The General Atomics statement adds:
because graphite is so resistant to oxidation, it has been identified as a fire extinguishing material for highly reactive metals, including zirconium.
The oxidation resistance and heat capacity of graphite serves to mitigate, not exacerbate, the radiological consequences of a hypothetical severe accident that allowed air into the reactor vessel. Similar conclusions were reached after detailed assessments of the Windscale and Chernobyl events; graphite played little or no role in the progression or consequences of the accidents. The “red glow” observed during the Chernobyl accident was the expected color of luminescence for graphite at 700°C and not a large-scale graphite fire, as some have incorrectly assumed.
The NRC has a more realistic concern, howbeeit, one would not lead to a major PBR accident:
First, the fundamental fuel behavior must be sufficiently well understood that a complete set of technical specifications for the fuel can be derived. It appears that this is not yet the case. There are numerous instances in which TRISO microspheres manufactured to identical specifications and irradiated und
er identical conditions exhibited drastically different fission product release behavior that could not be attributed to observed physical defects like cracking of the SiC layer. This indicates that there are technical factors affecting TRISO performance that have not yet been identified.
Second, when a complete set of technical specifications is finally at hand, the PBMR fuel manufacturing process will have to be reliable enough to ensure that the specifications are met. Because PBMR fuel is credited to a greater degree than LWR fuel for maintaining safety under accident conditions, and is less tolerant than LWR fuel to defects, PBMR fuel will have to be subjected to more stringent quality control. However, even if the requirements were no more stringent for PBMR fuel than for LWR fuel, inspecting the enormous microsphere flow with a high enough sampling rate to ensure an adequately low defect level would be a considerable challenge. The number of TRISO microspheres manufactured annually to support ten PBMR modules (1150 MWe total) would be on the order of ten billion, three orders of magnitude greater than the number of uranium fuel pellets needed to supply an LWR of the same capacity.
Finally, even if the above two criteria are satisfied, there must be assurance that the behavior of the fuel will not be significantly worse than expected if conditions in the core deviate from predictions — that is, the fuel should “fail gracefully.” It is on this count that the current TRISO fuel technology is clearly a loser. While past experiments have shown that the SiC layer of TRISO fuel limits the release of highly hazardous radionuclides like Cs-137 to below 0.01% of inventory up to 1600 C, the retention capability is rapidly lost as the temperature continues to increase. At 1800 C, releases of 10% of the Cs-137 inventory have been observed, which is on the order of the release expected during a LWR core-melt accident. Without a leak-tight containment present, the release into the environment would be comparable to the release from the fuel.
Thus in order to justify the absence of a leak-tight containment, Exelon needs to demonstrate that the PBMR maximum fuel temperature will not exceed 1600 C during the design-basis depressurization accident, and that more severe accidents that could cause higher fuel temperatures are so improbable that they do not need to be considered. However, given the uncertainties discussed in the previous section — like a discrepancy between calculated and measured maximum temperatures of at least 130 C — there are serious grounds for skepticism.
There is a strong element of the “not invented here” syndrome in the NRC statement, and the reminder that since the repair of the American nuclear safety establishment was never made good after the havoc that Milton Shaw visited on it.
There are still problems with PBR safety. Rainer Moormann, a German researcher who studied the decontamination of the decommissioned AVR, found an unexpectedly high level or radioisotope contamination in the decommissioned AVR. He attributed the contamination to fuel breakdown at high temperature. While Moormann’s findings ought to be taken seriously, radioactive contaminants in a decommissioned experimental reactor built during the 1960′s ought not by themselves seen as evidence of a fatal flaw in the reactor design. The AVR used something like 20 separate pebble designs during its over 20 year history. Moormann believes that the problem stemmed from the over heating of fuel pebbles within the reactor. This is most likely a fixable problem, but fixing it requires resources.
Alvin Weinberg who certainly understood the advantage of nuclear safety, viewed the successful design of large scale technological objects like reactors and the product of big science. Nothing can substitute for the large scale deployment of technological resources in seeking technological objectives. Unfortunately the sort of large scale nuclear establishment which the United States possessed in the 1950′s and 60′s. I would expect the Chinese to deploy the major resources needed to insure Pebble Bed Reactor safety. The Chines need the PBR simply because they need a low cost nuclear technology to replace hundreds of coal burning steam plants. If the politicians do not disrupt it, a safety culture should emerge within the Chinese nuclear community which will provide china and the world with a highly safe PBR. For society, nuclear defense in depth includes a strong nuclear research community that has the curiosity and the resources to investigate nuclear safety concerns ands identify safe materials, designs, and safe production and operation standards without political interference.
A Primer on Nuclear Safety:
2.4 Defense in Depth
A Brief Note on ESBWR Safety
How Safe is the ESBWR? Given a probabilistic approach to nuclear safety, we first note that the ESBWR designers at General Electric have estimated that a likelihood of core meltdown every 29 million years. But a core meltdown is far from a release of a large amount of radiation from the reactor into the environment. Thus we must look at the likelihood of a failure of not only the pressure vessel, but of the core catcher, a system designed to trap and contain molten material from the core and to prevent its movement outside the reactor containment system. The core catcher is a passive safety system that uses the force of gravity to move molten core materials into a series of dead- end underground passages. Finally, our large amount of radioactive material must escape the massive outer containment dome of the reactor. Let us assume that each of these containment structures works as intended. We know, for example, that the pressure vessel will contain a core meltdown, because the core of the Three Mile Island reactor was contained by its pressure vessel. Thus it is very unlikely that the pressure vessel of a ESBWR would fail if its core did melt down. Let us consider that the likelihood of that the average time to pressure vessel breach by a molten core is average time to core meltdown multiplied by a factor of 10. That would give us a figure of 290,000,000 years to pressure vessel breach.
Now the failure of the core catcher is far more unlikely than the breach of the pressure vessel because the core catcher relies on natural forces to capture and hold the molten core. Let us assume for the sake of argument that the likelihood of a core catcher failure is the average time to pressure vessel failure multiplied by a factor of 10. That would give us a period of time of about 2,900,000,000 years before core catcher failure.
Once the core catcher fails there are still the massive outer containment walls of the reactor to prevent a large scale release of radioactive materials. Again we will assume that this structure will increase the likelihood of containment by a factor of 10. This would give us a catastrophic release of radioisotopes into the environment once every 29 billion years. That figure happens to be over twice the age of the Universe, and several times the expected lifespan of the earth.
Given a probabilistic world, many natural catastrophic events are far more likely than containment failure including the eruption of the Yellowstone super-volcano and event which could kill millions of people, and which is likely to occur sometime within the next 160,000 years.
Of course if more ESBWRs are built, our probability of catastrophic containment failure will increase. With a set of 1000 ESBWRs, we end up a gain with the figure of once every 29,000,000 million years between containment failures. To put this figure into some perspective collisions between the Earth and asteroids of at least 5 km in diameter occur once every 10 million years. The impact of such an asteroid with the earth would cause enormous damage to human society. Such events are three times as likely to occur as the catastrophic failure of containment in a ESBWR in a thousand-reactor system. The worst possible consequences of reactor core containment failure would be very small compared to the consequences of a once every 10 million year asteroid impact event.
It is my contention then that the dangers posed to the population of the world by a massive 1000-reactor system of ESBWRs is insignificant when compared with far more likely natural disasters. However, as safe as the ESBWR is, it is not the ultimately safe reactor. I will turn next to an exploration of how to make reactors even safer than the ESBWR is.
The most important aspect of safety in Light Water Reactors is the cooling system. The coioling system also serves te purpose of moderating the nuclear reaction in Light water reactors. As we have noted, a loss of coolant in Light Water Reactors will stop the chain reaction, but will lead to core overheating because of the continued core heating caused by the radioactive decay of fission products. For that reason it is vital to maintain the presence of cooling water in the reactor core. There is one major variation in the LWR cooling system. Pressurized Water Reactors use secondary coolant systems. The secondary coolant system, in the PWR is responsible for stem generation. Water at high temperature and under heavy pressure leaves the reactor core and flows through pips to a steam generator. In the steam generator the water from the reactor passes through a heat exchange where is passes heat to the secondary coolant water. The primary coolant water then pumped back into the reactor, where it begins the cycle again. The secondary coolant water, once it has entered the heat exchange begins to rapidly boil. The steam is then routed to steam turbines where power is produced. Upon exiting the turbine the steam is cooled and condensed, and returned to the secondary coolant system.
The Boiling Water Reactor only has a primary coolant system. Water, under somewhat lower pressure in a BWR turns to steam in a BWR. the steam then flows to the turbines, the spent steam is cooled and condensed, and the cooled water is returned to the reactor where the cycle begins again. The coolant system of the BWR is simpler, and simplicity often enhances safety. Hence the BWR is potentially very safe, but at a price of somewhat lower efficiency.
Coolant systems usually rely on pumps to move water around, and like any other mechanical objct pumps do break down. They have to be periodically serviced, and in addition have been known to fai lin the course of reactor operations. There is a work around for pump servicing and pump failure, and that is back up coolant systems, that can be either automatically brought into operation in the event of pump failure, or when the pump of the primary coolant system is being serviced. One of the major contributing factors to the Three Mile Island Accident was the failure of the secondary coolant system, due to the tripping of a water pump. The backup pumps had been accidentally locked off line, so the essentially the primary coolant system lost its ability to dump heat from the reactor core. The reactor shut down, and other systems to maintain core safety automatically came into play. At that point the accident would have been over, had not an operator not shut down the emergency coolant system.
Thus the Three Mile Island accident illustrates the successful function of the defense in depth philosophy. Because even though secondary coolant system failed, and its backup was off line, and the the emergency coolant system was turned off, and the reactor core suffered partial meltdown, defense against a major release of radioactive material held. The cost of the coolant system failures was however, major damage to the reactor core.
Since the Three Mile Island accident illustrated the vulnerability of LWRs to coolant system failure, much attention has been paid both by reactor manufacturers and the Nuclear Regulatory commission of the United States to the improvement of the safety and reliability of Light Water Reactor coolant systems. One major approach for improvement has been the replacement of pumps with thermal syphons. Thermal syphoning is not exactly high tecnology. The principle was sucessfully used to circulate engine coolant in the Model T Ford! A thermal syphon takes advantage of the natural tendency of heated liquid to rise in a liquid column, while cooled fluid falls. In a closed system where the liquid is both heated – for example in the engine of a Model T Ford – and cooled – in the radiator of the Model T Ford – the coolant may achieve natural circulation without mechanical pumps. Remarkably, the same thermal syphon principle which works with antique cars, also works for the latest models of very large reactors. One notable example of this is the Evolutionary Simplified Boiling Water Reactor (ESBWR), which has is the Latest Word in Generation III + reactor safety. Because the ESBWR dispenses with cool water pumps, it also eliminates the very possibility of pump related accidents. A second feature which the ESBWR has in common with other Generation III+ reactors is the use of gravity feed emergency water systems. These systems place large tanks of emergency cooling water above the reactor core. In the event of a loss of coolant accident, water from the emergency coolant tank will automatically flood the reactor core. The ESBWR emergency coolant system does not rely on pumps. Rather gravity feeds the energency coolant water into the reactor core.
The sophisticated features of the ESBWR greatly enhances its safety compared to other Light Water Reactors. The ESBWR is calculated to be in danger of core melt down once every 29 million years. One would expect that with the extreme unlikelihood of core meltdown with the ESBWR, and the success of core containment by the reactor pressure vessel in the Three Mile Island that no provision for the containment of a molten reactor core would be made in the case of pressure vessel failure. Such is the safety of the ESBWR design that provision is made for the almost infinitely slight probability of that a molten core would escape its pressure vessel. In that case a core drainage and capture system has been been included in the ESBWR reactor design.
In a probabilistic world it is impossible to completely dismiss the possibility that a ESBWR Will ultimately fail in a catastrophic accident that will cost human lives, but the sun will also fail costing the life of everyone left on earth, and in a somewhat similar time frame. Thus the advanced safety features of the ESBWR coolant system, coupled with standard reactor defenses in depth against radiation releases, and a very advanced molten core capturing system, render concerns about ESBWR safety irrational.
Enrico Fermi was the first nuclear scientist to find a solution for controlling chain reactions in a nuclear reactor. Fermi said that his Chicago Pile was “a crude pile of black bricks and wooden timbers.” Of course natural uranium fuel was added. There was, Fermi realized, something else needed in order to make his reactor safe. That was a means of soaking up the neutrons created by the chain reaction in order to control it. The way Fermi chose to control the Chicago Pile was to insert a number of cadmium-coated control rods into the reactor. Inserting the rods would slow the chain reaction and eventually stop it. In fact history reports that the chain reaction in Fermi’s first pile was initiated by lifting control rods that were initially embedded in the pile.
Fermi and his associates were none too confident in the mechanical reliability of the control rods. Thus a back up system was devised for an emergency shut down of the reactor in case the control rods failed to operated properly during a shut down. A history of the Chicago Pile experiment states:
Since this demonstration was new and different from anything ever done before, complete reliance was not placed on mechanically operated control rods. Therefore, a “liquid-control squad,” composed of Harold Lichtenberger, W. Nyer, and A. C. Graves, stood on a platform above the pile. They were prepared to flood the pile with cadmium-salt solution in case of mechanical failure of the control rods.
In many respects the Fermi’s CP-1 was the evolutionary ancestor of the Light Water Reactor, and the control scheme for Light Water Reactors is basically the same as for the CP-1 although a few twists have been added. The control rods now use Hafnium rather than cadmium for neutron absorption. And rather than flooding the core with a Cadmium salt solution, boron in the form of boric acid is injected directly into the cooling water. Because the dilution of the boric acid in the cooling water can be easily altered, the use of boron is by no means limited to reactor shutdown. By altering the boric acid content of cooling water reactor operators can actually control the chain reaction, thus providing a simple but effective throttle for a chain reaction.
It is possible to completely shut down a LWR by increasing the boron content of the coolant water, or by a high concentration of boric acid in the emergency coolant water. However reactor shut downs and start ups are normally controlled by the control rods. Control rods can also be used to control chain reactions in parts of the reactor, and the play a major role in counteracting Xenon poisoning.
Xenon-135 is a noble gas that is produced in the fission process. It is highly radioactive, but in addition it has a very powerful neutron absorbing property. Because of this property, even a relatively small amount of Xenon-135 produced during a chain reaction has the capacity to slow down and even stop the chain reaction. Hence reactor controls must posses a means of balancing reactor power output as the amount of Xenon-135 in the reactor increases due to Xenon-135 production by nuclear fission.
Controlling reactor power in the face of Xenon poisoning is not simple. Xenon builds up with the fission process, and decreases as it undergoes nuclear decay. There can be a lag between the positioning of a control rod and its effect on the power level and heat generation of a reactor. Running a light water reactor at low power increases difficulties related to Xenon poisoning. Xenon may not be evenly spread through the core. Thus hot and cool spots may develop in the core since coolant flow is based on average power output, coolant flow to reactor hot spots may not be sufficient, and as fuel pellets begin to overheat, and their cladding begin to overheat, their integrity may begin to break down.
Control rods played a far more critical role in the Chernobyl accident than would be possible in a light water reactor accident. In the Chernobyl RBMK reactors the control rods were divided into three segments. The upper and lower segments were made of graphite, a nuclear moderator, while the middle segment was made of a of a material that served as a neutron poison. As the control rod is lifted coolant water fills the bottom of the control rod channel. Under normal operations the control rod is lifted to the position in which its lower graphite segment fills the channel inside the reactor core. But because a highly dangerous test was being conducted on the Chernobyl reactor, the lower graphite segments of control rods were also partially withdrawn from the reactor. Thus more water entered the reactor core through the control rods channels. As I have already observed coolant water served as a brake on the chain reaction within the Chernobyl reactor. As we observed poor management of the Chernobyl reactor during a test lead to the boiling of the coolant water inside the reactor and the voids created by the steam bubbles began to removed the break placed on the chain reaction by the presence of coolant water in the core. As the overly withdrawn control rods began to descend into the core of the Chernobyl reactor they first displaced water that had served as a brake on the chain reaction, and replace it with graphite, a moderator that greatly increased the chain reaction.
The insertion of the graphite tips of the control rods into the core of the Chernobyl RBMK was sort of like attempting to hit the brakes of car that is running out of control, and hitting the accelerator instead. The power level of the Chernobyl reactor went off the charts, and as reactor heat increased dramatically the remaining coolant water in the reactor core flashed to steam. There was a large steam explosion, which as we have seen destroyed the top of the reactor and the surrounding radiation shield.
A similar accident could not occur in a light water reactor because (a) water in the control rod channels increases rather than slows the nuclear reaction, (b) the water in the control rod channels is immediately displaced by a neutron poisoning material in the control rod, and (c) voids created by heat related bubbles in the reactor coolant work in concert with the control rods rather than against them.
Control rod insertion during an accident can be accomplished by gravity rather than mechanical means. Control rods can be attached to the lifting mechanism by electro-magnets. The termination of power output during an accident would automatically produce control rod insertion and shut down. The shutdown can also be triggered by operator control.
There are redundancies in the control rod system and of course reactor operators always have the options of shutting the reactor down by adding more boric acid to the coolant water. The loss of reactor coolant does cause a termination of the chain reaction, because the water serves as a moderator for the chain reaction in Light Water Reactors. At the same time the loss of coolant water is highly undesirable, because coolant water is required to remove the residual heat from fission product decay from the reactor core.
The control system of Light Water Reactors thus provides for operational redundancies and safety backups. Emergency shutdowns can be accomplished by passive safety features that use the law of nature to insure that a chain reaction stops as soon as
the reactor ceases to produce electrical power. Different control systems insure that operators have more than one emergency shutdown system available. Finally automatically operating passive shut down systems, insure that the reactor will automatically shut down before serious safety problems emerge, thus interrupting chains of events that could lead to serious reactor accidents.
The Defense in Depth philosophy is applied to the release of radioactive materials from inside the core of light water reactors. Helen Caldicott, the ceaseless critic of nuclear power notes
Nuclear power creates massive quantities of radioactive isotopes, which are classified as nuclear waste. Among these materials are strontium 90, . . cesium 137 . . . plutonium, . . . plutonium has a radioactive life of half a million years. It enters the body through the lung, where it is known to cause cancer. It mimics iron in the body. Hence it migrates to the bone, where it can induce bone cancer or leukemia, or to the liver, causing liver cancer; and it crosses the placenta into the embryo, where, like the drug thalidomide, it can cause gross birth deformities. Finally, it has a predilection for the testicles, thus inducing genetic mutations in humans and other animals that are passed from generation to generation for the rest of time. Meanwhile, the plutonium itself lives on to enter testicle after testicle, lung after lung, liver after liver for the rest of time as well. Children are 10 to 20 times more susceptible to the carcinogenic effects of radiation than are adults.
That it is possible for such radioactive materials to escape in massive amounts from some reactors is certain given the Chernobyl accident. Even though massive amounts of radioactive materials that escaped during the Chernobyl incident did not lead to the sort of human disaster Dr. Caldicott imagined large scale releases of bioactive radioactive materials from reactors is highly undesirable.
Nuclear safety researchers were by no means satisfied with their accomplishments. In 1967 my father, C.J. Barton, Sr. wrote
In order to promote confidence in such large reduction factors, continued research into the efficiency of removal for all the various forms of the released fission products will be required.
During the 1960′s researchers at ORNL, Battelle Northwest, and Phillips-Idaho conducted sophisticated containment and reactor accident research with facilities that were designed to simulate nuclear accidents. Again the findings of this research were fundamental to reactor safety design. As I have pointed out elsewhere in this blog, the continuation of nuclear safety research at AEC facilities became during the late 1960′sane early 1970′s became a major matter of political controversy.
Even though the politically inspired attack on nuclear safety research was never completely rectified by the American political establishment, enough progress had been made to allow for great improvements in Light Water Reactor safety.
Physical Barriers increase Light Water Reactor safety
Defense in Depth against the release of radioisotopes required a series of physical barriers that inhibited the movement of radioisotopes from the nuclear fuel pellets into the environment. In order to illustrate the defense in depth of civilian light water reactors, a brief comparison to the Soviet RBMK reactor is in order. The failure of the safety features of one of the RBMK at Chernobyl lead to the release of large amounts of radioisotopes from the reactor core. The RBMK reactor like Western Light Water Reactors featured ceramic uranium fuel elements made of uranium dioxide baked at high heat. In Western reactors the fuel pellets are clad with Zirconium, a sturdy metal that resists the reactors heat and radiation.
The Uranium Oxide fuel is itself the first barrier in the defense in depth, and it is a one of the strongest barriers in the whole defense. Fission products are basically locked in to the rock like fuel pellet. As George Parker and my father were to observe that the release of fission products from Light Water Reactor fuel was caused by a variety of mechanisms that were all triggered by overheating. Thus the first barrier could be breached by reactor over heating.
The Zirconium cladding adds protection against fission product escape. Zirconium has a high melting temperature, although not as high as uranium oxide. Like uranium oxide, zirconium and zirconium alloys are dependent on reactor cooling to prevent to maintain integrity as a barrier to fission product escape. A further consequence of the failure of Zirconium cladding would be that it would subject uranium oxide fuel to mechanisms that promote fission product loss.
A Zirconium tube in which the fuel pellets rest in the reactor core constitute a third barrier to fission product release, however in practice if reactor core heat is sufficiently high to cause the failure of Zirconium cladding, it will also cause the failure of zirconium tubes. The outer structure of the reactor provides a further barrier to fission product release. In LWRs the pressure vessel is a major barrier to solid fission product release, although radioactive gases can work their way around the barrier in major reactor accidents. The RBMK does not have a pressure vessel, which is perhaps the most significant reason for the massive release of radioisotopes in the Chernobyl accident. The Chernobyl RBMK appears to have included an outer structure designed to maintain the RBMK core in a helium environment in order to prevent graphite burning. This containment structure failed during the Chernobyl incident, and the resulting graphite fire contributed greatly to the fission product release during the Chernobyl incident.
The next barrier to fission product release is the reactor outer radiation shield. Although this shield is seldom mentioned in discussions of defenses in depth, it does provide a barrier to the release of solid and molten fission particles whose movement is limited by the forces of gravity. Thus in the event of a core melt down which penetrated the pressure vessel, the radiation shield would offer considerable containment of the molten fission particles. Because of its massive nature, the radiation barrier would also mitigate a steam explosion powerful enough to rupture the wall of the pressure vessel. The sideways and downward pressure of the steam explosion would be baffled by the massive radiation shield while gravity would contribute to containing the movement of non-gaseous fission products within the outer containment structure. The Chernobyl reactor was surrounded by a radiation containment structure which failed because the of a powerful steam explosion. The cause of the blast was a combination of design flaws that caused a dramatic rise power levels in the reactor when an operator attempted to shut the reactor down.
The destruction of the radiation shield of the Chernobyl reactor removed the last level of containment for that reactor, while another level of containment, re
presented by the outer containment dome, would have still survived a Chernobyl like explosion. The failure of the Chernobyl radiation shield and the subsequent graphite fire lead the the massive release of radioisotopes from the burning Chernobyl reactor. Thus the critical features that lead to the radioisotope release from the Chernobyl radiation release were not present and two outer barriers to the release of solid radioactive materials, the massive 8″ thick steel pressure vessel, and the even more massive outer dome of the reactor were not features of the Chernobyl reactor design. Other unique features of the RBMK reactor design including the use of a graphite moderator, and numerous design flaws that created safety problems contributed to the accident.
Anti-nuclear critics of nuclear safety often point to the Chernobyl accident as evidence of the fundamental safety flaws of all reactors, without noting the significant differences in safety features between RBMK reactors and LWRs. In fact during the Three Mile Island accident the outer safety barriers, the pressure vessel, the radiation shield, and the containment dome all remained intact. There were no verified cases of radiation related health problems as a result of the Three Mile Island accident, and subsequent research failed to identify any increase in the number of cancer cases that could be associated with the accident. Thus the defense in depth deployed at the Three Mile Island Reactor was successful.
A Note on Radioactive Gases
The radioactive material released as a consequence of the Three Mile Accident were primarily noble gases. The noble gases and other radioactive gases are fission byproducts that are present in the uranium oxide fuel pellets. Normally they would remained trapped in the uranium oxide pellets, but if the reactor core heats enough to melt down, the zirconium cladding will rupture or melt, and the melting of the uranium oxide pellets will release the noble gases. The gases escape from the reactor core through the cooling system. The gases are quickly dispersed by the atmosphere. While nuclear critics raise the issue of radioactive gases as an issue in justifying their opposition to nuclear power, nuclear critics often display a strange inconsistency. Radon, a radioactive gas, is also released by coal burning coal fired power plants. In addition natural gas contains radon. More radioactive gas is released into the environment by the use of fossil than by nuclear power plants, yet nuclear critics rarely raise their voices in concern about radioactive gases released by the use of fossil fuels. In fact, many supposedly pro-environmental, anti-nuclear organizations, accept funds from foundations with ties to fossil fuel produces, sometimes with stipulations that the funds will be used to promote fossil fuel use. Needless to say, these organizations never raise talk about the association of radon gas with fossil fuel use.
I will in a later post discuss a methods of preventing or at least limiting the release of radioactive gases associated with the development of the LFTR.
A Primer on Nuclear Safety:
2.0 Defense in Depth
In 1964, Ralph Nader had no reason to question that nuclear power was a clean, safe, cost-efficient technology. Then he attended a conference at the Oak Ridge National Laboratory. Over lunch, Nader began asking nuclear engineers some penetrating questions. “They couldn’t answer them, or the answers weren’t satisfactory,” Nader recalls. “‘What could happen if a system goes wrong?’ I asked. They avoided any such descriptions or said, ‘we’ve got defense in depth’ — and other jargon.”
– David Bollier (Citizen Action and Other Big Ideas)
The concept of defense in depth is fundamental to nuclear safety. The defense in depth approach applies not only to reactor design but also to safety management. Defense in Depth assumes that human judgment is flawed, designs are imperfect, constructors can fail to follow plans, and that things can go wrong in numerous ways. Thus a defense in depth approach assumes that things can go wrong in with reactor, and there must be back up systems if things go wrong. But things can go wrong with the back up system, and they must also have back up plans.
Defense in depth assumes that the potential causes of nuclear accidents are in many instances controllable. One object of nuclear safety research would be the identification of potential causes of accidents, and the design systems to control those causes. The most fundamental causes of nuclear accidents are hidden in reactor design. Western reactor scientists knew immediately the cause of the Chernobyl accident. It was a fundamental design flaw in the RBMK reactor design. The existence of the problem, was what is called a large positive void coefficient, which lead to positive reactor feedback to increased heat.
What does this mean? It means that the cooling water in the RBMK reactor acts as a brake on the chain reaction. If the cooling water is removed from the reactor, the chain reaction will start to run away. Furthermore water can be removed from the reactor by heat. If the cooling water inside the reactor gets hot enough, it starts to boil. As the cooling water boils, the steam forces water outside the reactor, thus removing the nuclear break, increasing reactor heat, which in turn boils more water, etc. So the basic design of the RBMK is flawed and dangerous. Alvin Weinberg, who was an expert on reactor safety noted that when reactors that were similar to the RBMK were designed in the United States during World War II, American scientists were aware of their safety flaw.
Therefore it must be understood that nuclear safety must begin with the recognition that not all reactor designs are equally safe. Some reactor designs are much safer than others, and some reactor designs are inherently safer and perhaps can be even made inherently safe. Other reactors have potentially unsafe design features that can be worked around.
Thus reactor safety is the primary level of nuclear safety, and the defenses against accidents in a reactor may feature both redundancy and a many leveled safety defense system. The current generation of Light Water Reactors have high levels of safety built in to their designs. Nuclear safety engineers have calculated that the General Electric Evolutionary Simple Boiling Water Reactor is so safe that it would experience a core meltdown once every 29 million years. In contrast the Yellowstone Super volcano, which is capable of killing millions of people with an eruption, erupts every 600,000 to 800,000 years. It has been 640,000 years since the last eruption of the Yellowstone super volcano. The likelihood of a major reactor accident and its consequences, ought to be placed in the context of far more likely natural disasters.
Steps that can be taken to prevent reactor accidents include:
A. good design based on an up to date understanding of reactor safety,
B. An exhaustive follow through of all safety related reactor features in the procurement of manufacturing materials and replacement parts, The actual manufacture and maintenance of the reactor, and reactor operations
C. systematic faults detected in procurement, manufacture and operation, with a prompt and complete follow up.
D. Redundant or fall back systems in the event of the failure of a reactor system.
E. Automatic system response that relies on the laws of nature, rather than operator intervention.
F. Reactor siting consistent with reactor safety issues. Experimental reactors placed in remote locations.
G. Reactor staff should be both well trained and highly motivated to follow all safety guidelines.
unit placed in safe state by well-trained staff using approved procedures
The second level of nuclear safety is accident mitigation. These would include those elements of reactor design that would tend to diminish the effects of a nuclear accident on the public. Mitigation would include both internal reactor design features, and design features of the reactor facility that would tend to mitigate the effects of a major nuclear accident. Mitigation defenses can be in depth. Hence in the event of a core meltdown in a light water reactor, the reactor pressure vessel would pose a significant defense against the escape of solid fission products. The reactor containment dome would form another layer of defense against fission product release, while the isolation of the reactor would lead to the dissipation of radioactive gases, and the precipitation of solid radioactive particles escaping the reactor containment facility prior to contacts with human communities.
Accident mitigation would include, the automatic shutdown of a reactor after a partial system failure, the automatic initiation of back up cooling and/or emergency cooling in the event of a primary cooling system failure. The design of reactor monitoring panels and system alerts to give clear and concise information about what is happening without creating an overwhelming flow of information. Staff training in accident management. Well defined accident response procedures to be included in staff training. The management of initial recovery after accident related shut down, Well defined accident cleanup and recovery procedures.
A third level of defense would be the management of public consequences after a nuclear accident. These would include the notification of the NRC, as well as Federal, State and Local officials. Steps which might be taken to manage the consequences of a serious accident include evacuations, bans on the use of potentially contaminated food and/or water. Provisions for safe sheltering of at risk populations, and the distribution of KI pills, as well as other pre-planned interventions by the federal, state and local governments.
Normal accounts of nuclear safety defense in depth stop at this point. There are however other levels of nuclear safety, A fourth level would be a well informed public. Nuclear safety is a genuine matter for public concern. The public should demand the safest nuclear technology possible, and both support nuclear safety research and for monitoring of observance of safety rules and procedures by demanding that reactor operators comply with them, and that the NRC vigorously enforce them.
One of the great flaws of the anti-nuclear movement has been to dis-empower the public on nuclear safety issues. Figures like Ralph Nader failed to avail themselves of opportunities to learn more about nuclear safety. Had Ralph Nader really wanted to understand the safety concerns that Alvin Weinberg discussed with Claire Nader and with Ralph himself, had Ralph Nader tried to understand what the ORNL nuclear safety engineer was telling him about defense in depth, the history of the first nuclear era might have ended differently. Had there have b
een a public outcry for nuclear safety in the 1970′s rather than an anti-nuclear movement, the owners of the Three Mile Island reactor, would not have been allowed to get away with the safety errors they committed. Had there been a public outcry for safety research, staff safety training, and safe design of reactor control panels, there would have been no Three Mile Island accident. By convincing the public of the ill intentions of safety advocates within the nuclear community, and by convincing the public that nuclear safety was impossible, and therefore it had no stake in the development of nuclear safety improvements, the anti nuclear movement, dis-empowered the public on nuclear safety issues. It is up to the public to take its power back from the anti-nuclear movement, and assert its right to demand the highest levels of nuclear safety possible. Such a public demand would be a fourth level of nuclear safety defense.
The fifth level of of nuclear safety defense is nuclear safety research, and safe reactor design coupled with the actual replacement with reactors designed to current safety standards by reactors designed with even higher levels of safety. Nuclear safety is something that happens in time. Nuclear safety has a history. It has evolved during its history, and can be expected to continue to do so. It is perhaps unfortunate that the Light Water Reactor emerged early on as the predominant power reactor type. Light Water Reactors have inherent safety flaws. Those flaws can be largely worked around, by engineering reactor modifications, but those modifications are expensive. Too much of the history of nuclear safety has been the history of increasingly expensive safety developments for the light water reactor.
Reactor scientists have known since the 1940′s that it is possible to eliminate the very possibility of the most serious of reactor accidents, the core meltdown. Reactors designs developed over 50 years ago posses inherent safety feature that far surpass those of light water reactors. Furthermore one of those two advanced reactor designs, the Liquid Fluoride Thorium Reactor, relies on an abundant nuclear fuel, Thorium, which it uses so efficiently that it will provide sustainable nuclear power for millions of years to come. Because of its efficient use of the Thorium fuel cycle, the LFTR also virtually eliminates the long term nuclear waste. Developing and implementing the LFTR reactor designs would not be inordinately expensive, or require an extensive period of time. The development cost for either reactor design would cost less than the cost of two light water reactors, or less than the cost of the imported oil the United States consumes in one week. The manufacturing cost for the LFTR would also be lower that the current cost of building Light Water Reactors. Thus at a relatively small cost the United States could acquire a fifth level of nuclear defense, one which would make the most serious reactor accident impossible, and solve other problems related to the use of nuclear energy in the generation of electrical power.
The following legislation has been introduced in the US Senate today by Senator Orrin Hatch and Senator Harry Reid:
To amend the Atomic Energy Act of 1954 to provide for thorium fuel cycle nuclear power generation.
IN THE SENATE OF THE UNITED STATES
introduced the following bill; which was read twice
and referred to the Committee on
To amend the Atomic Energy Act of 1954 to provide for thorium fuel cycle nuclear power generation.
Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled,
SECTION 1. SHORT TITLE.
This Act may be cited as the “Thorium Energy Independence and Security Act of 2008″.
SEC. 2. FINDINGS.
Congress finds that—
(1) the United States and foreign countries will require massive and increasing quantities of energy during the 20-year period beginning on the date of enactment of this Act to support economic growth;
(2) nuclear power provides energy without generating unacceptable quantities of greenhouse gasses;
(3) the generation of nuclear power in the United States and many foreign countries has been discouraged by concerns regarding—(A) the proliferation of weapons-useable material; and (B) the proper disposal of spent nuclear fuel;
(4) nuclear power plants operating on an advanced thorium fuel cycle to generate nuclear energy—(A) could potentially produce fewer weapons-useable materials than uranium-fueled plants; and (B) would produce less long-term waste as compared to other nuclear power plants;
(5)(A) thorium is more abundant than uranium; and (B) the United States possesses significant domestic quantities of thorium to ensure energy independence;
(6)(A) thorium fuel cycle technology was originally developed in the United States; and (B) cutting-edge research relating to thorium fuel cycle technology continues to be carried out by entities in the United States; and
(7) it is in the national security and foreign policy interest of the United States that foreign countries seeking to establish or expand generation and use of nuclear power should be provided—(A) access to advanced thorium fuel cycle technology; and (B) incentives to reduce the risk of nuclear proliferation.
SEC. 3. THORIUM FUEL CYCLE NUCLEAR POWER GENERATION.
Chapter 19 of title I of the Atomic Energy Act of 1954 (42 U.S.C. 2015 et seq.) is amended by inserting after section 244 the following:
“SEC. 251. THORIUM FUEL CYCLE NUCLEAR POWER GENERATION.
“(a) DEFINITIONS.—In this section:
“(1) CHAIRMAN.—The term “Chairman” means the Chairman of the Nuclear Regulatory Commission.
“(2) OFFICE.—The term “Office” means an office established under subsection (b)(1).
“(3) SECRETARY.—The term “Secretary” means the Secretary of Energy.
“(b) OFFICES FOR REGULATION OF THORIUM FUEL CYCLE NUCLEAR POWER GENERATION.—
“(1) ESTABLISHMENT.—The Secretary, in consultation with the Chairman, shall establish, and provide funds to, an office for the regulation of thorium fuel cycle nuclear power generation in each of—
“(A) the Office of Nuclear Energy, Science and Technology of the Department of Energy; and
“(B) the Nuclear Regulatory Commission.
“(2) REGULATIONS.—Not later than December 31, 2012, the Chairman, in cooperation with the
18 heads of the Offices, shall promulgate regulations for facilities and materials used in thorium fuel cycle nuclear power generation.
“(3) DEMONSTRATION PROJECTS.—The heads of the Offices, in cooperation with the head of the Idaho National Engineering Laboratory, shall carry out demonstration projects for thorium fuel cycle nuclear power generation at the Idaho National Engineering Laboratory.
“(4) INTERNATIONAL PARTNERSHIPS AND INCENTIVES.—The heads of the Offices shall provide recommendations to the Secretary with respect to methods of—
“(A) strengthening international partnerships to advance nuclear nonproliferation through the design and deployment of thorium fuel cycle nuclear power generation; and
“(B) providing incentives to nuclear reactor operators in the United States and foreign
countries to use proliferation-resistant, low waste thorium fuels in lieu of other fuels.
“(c) REPORT.—Not later than 1 year after the date of enactment of the Thorium Energy Independence and Security Act of 2008, and annually thereafter, the Secretary shall submit to Congress a report describing, with respect to the preceding calendar year—
“(1) progress made in implementing this section; and
“(2) activities carried out by the Offices pursuant to this section.
“(d) AUTHORIZATION OF APPROPRIATIONS.—There are authorized to be appropriated to the Secretary to carry out this section $250,000,000 for the period of fiscal years 2009 through 2013.’’.
For immediate release
Contact: Mark Eddington, (202) 224-5251
Heather Barney, (801)524-4380
Oct. 1, 2008
Sens. Orrin Hatch and Harry Reid Push for Thorium Nuclear Fuel Cycle
WASHINGTON – Sen. Orrin G. Hatch (R-Utah) and Harry Reid (D-Nev.) today introduced legislation that would pave the way for thorium nuclear-fuel reactors in the United States.
The Thorium Energy Independence and Security Act of 2008 would establish offices at the Nuclear Regulatory Commission and the Department of Energy to regulate domestic thorium nuclear power generation and oversee possible demonstrations of thorium nuclear fuel assemblies.
Using thorium for nuclear power has a number of potential benefits over conventional uranium. As a resource, thorium is abundant in the U.S. and throughout the world. A thorium fuel rod would remain in the reactor about three times as long as conventional nuclear fuel, cutting the volume of spent nuclear fuel by as much as two-thirds. Also, thorium nuclear fuel would significantly reduce the possibility that weapons-grade material would result from the process. Finally, a thorium fuel cycle could be used to dispose of existing plutonium stockpiles, which is the national security goal.
“Our nation has focused mostly on mixed oxide nuclear fuel cycles, and our regulatory structure reflects that,” Hatch said. “With the growing interest in thorium nuclear power in the world and in the U.S., it’s time we made sure our government has a regulatory infrastructure in place to accommodate this new generation of nuclear power.”
Speaking about the bill, Bruce Blair, president of the World Security Institute said, “This legislation reflects an enlightened grasp of the importance of supporting nuclear power while suppressing nuclear proliferation.”’
Seth Grae, president and CEO of Thorium Power said that the bill “represents a major milestone toward the recognition that the nuclear renaissance can best be achieved by encouraging new and innovative fuels designs. Senators Hatch and Reid have acted today to strengthen American technology and American business to compete in the global marketplace.”
“This bill is a giant step for the United States toward the development of a safe, secure and independent energy future,” said Jack Lifton, business development and corporate communications director of Thorium Energy.
Thorium Energy owns property in Lemhi Pass, Idaho, where it is generally believed that the largest veins of thorium-rich minerals in the world are located. Analysis of the deposits shows them to be either the highest grade or in the top tier of the highest grade known anywhere on Earth.