Highly enriched uranium: Less is more


A number of high-profile initiatives seek to reduce the possibility of nuclear proliferation and terrorism by minimizing the use of highly enriched uranium (HEU) in civilian applications. Operators of research reactors understand the rationale for reducing HEU use, but converting to low-enriched uranium can involve serious financial, technical, and political challenges -- all of which may seem more vivid to the manager of a research reactor than to faraway bureaucrats and nonproliferation specialists. In this Roundtable, Charles Piani of South Africa, Pablo Cristini of Argentina, and Alexandr Vurim of Kazakhstan share their experience of minimization and answer the question: "How might developed countries best incentivize HEU-minimization programs in the emerging and developing worlds?"

Round 1

Conversion in Kazakhstan: A multiplayer game

International initiatives to reduce the use of highly enriched uranium (HEU) deserve unconditional support, but conversion to low-enriched uranium (LEU) is often a difficult project. Research reactors employ a variety of designs and are used for wide-ranging purposes, and different countries have different views on how conversion should be accomplished. In my own nation of Kazakhstan, preliminary plans are in place to convert three research reactors to LEU fuel. But progress has not been as fast as it might have been.

Why? To answer this, one must understand the bureaucracy surrounding Kazakhstan's research reactors, all of which are owned and operated by government entities. Two of the country's four research reactors, known as IVG and IGR, are owned by the National Nuclear Center and operated by one of the center's divisions, the Institute of Atomic Energy, which is also my employer. A third reactor is owned by the Institute of Nuclear Physics, which is separate from the National Nuclear Center. A fourth reactor is in extended shutdown, with its fuel unloaded, and is of no interest from a conversion perspective.

Conversion to LEU must be approved by two government bodies — the Atomic Energy Agency, which regulates reactors and oversees issues like licensing and safety, and also the Ministry of Industry and New Technologies. The ministry has given its approval for conversion at the IVG and IGR reactors. But the Atomic Energy Agency (soon to be reorganized as the Committee of Atomic Energy) has not. The agency will only give its approval for conversion if the facilities' chief designer and research manager approve changes to the reactors; Kazakh laws and regulations require, for decisions such as LEU conversion, the involvement of each reactor's chief designer and research manager.

And here things get even more complicated, because the reactors' chief designer and research manager are not Kazakh entities. Rather, because of the reactors' Soviet origins, they are government-owned Russian entities that now play a minimal role in the reactors' operation. More to the point, the actions of the chief designer and research manager have, up until now, not been coordinated by any single entity in Russia, leaving the Institute of Atomic Energy to coordinate among them. But it is beyond the institute's capacity to coordinate the actions of entities in another country.

It is useful here to recall the organizational structure that was utilized when research reactors were first established in Kazakhstan. All work was carried out under the unified leadership of the Soviet ministry in charge of nuclear science, energy, and industry. The research manager, chief designer, and operating organization were all part of this ministry, and were connected to one another through a clear set of obligations and responsibilities. This system of interaction helped create the most advanced scientific and industrial sector in the Soviet Union, and one of the most advanced nuclear power industries in the world. Unfortunately, the Kazakh government in general, not to mention the Institute of Atomic Energy itself, lacks the capabilities that the former Soviet ministry possessed.

Faced with all this, representatives of the Global Threat Reduction Initiative, a US project involved in HEU minimization, have attempted to engage with yet another entity, the Russian manufacturer of the reactors' fuel. The idea is that the fuel provider could develop an LEU fuel that would enable the reactors to convert. But this, though it might solve some technical problems, would not solve the bureaucratic problems. The full involvement of the chief designer and research manager would still be required.

The Institute of Atomic Energy is now attempting to circumvent these problems by negotiating with the reactors' fuel provider, in the hope that the fuel provider will take responsibility for coordinating among all Russian entities involved. Indeed, at the Kazakh research reactor operated by the Institute of Nuclear Physics, the conversion effort is proceeding more smoothly, precisely because a Russian, state-owned fuel producer is coordinating among all the relevant Russian entities.

The ideal solution for Kazakhstan's conversion process might have been for representatives of the US government to liaise more with officials in Russia, encouraging the Russian government to take a real interest in the work — to take responsibility for all aspects of the conversion process that involve the competencies of the Russian research manager, chief designer, and fuel manufacturer. In the end, conversion may go forward without that sort of intergovernmental cooperation. But in any event, the Kazakh conversion experience provides an example of the problems that reactors can face while attempting to minimize their use of highly enriched uranium.

How to dispense with highly enriched uranium

About 85 percent of all diagnostic nuclear medical procedures, amounting to 30 million procedures a year, utilize technetium 99, a metastable medical isotope. This is the decay product of molybdenum 99, which is considered the most important radioisotope employed in nuclear medicine.

Molybdenum 99 can be produced in several ways, but the most efficient means for medical applications is the fission route — using thermal neutrons produced in a nuclear reactor to irradiate targets that contain uranium. This results in the splitting (or fission) of uranium atoms into various stable and radioactive isotopes, one of them being molybdenum 99. This isotope is ultimately transported to manufacturers of technetium 99 generators, which deliver the generators to nuclear medicine centers. There, technetium 99 is employed to label molecules for use in diagnostic procedures.

Either highly enriched uranium (HEU) or low-enriched uranium (LEU) can be used as the target (the material at which neutrons are fired to induce fission in the reactor core). Use of HEU carries inherent risks for nuclear proliferation and terrorism. Using LEU reduces these risks significantly.

High to low. Argentina's National Atomic Energy Commission (CNEA), which is responsible for carrying out nuclear research and development and also for applications and services like radioisotope production, began producing molybdenum 99 in 1985, using targets enriched to more than 90 percent in the isotope 235. During 1988 and 1989, the commission's RA-3 reactor — then as now the most important reactor in Latin America for producing radioisotopes — was converted to rely on LEU fuel in order to address international proliferation concerns. The next step in HEU minimization was to develop a procedure for molybdenum production using low-enriched uranium targets.

The first challenge was to develop a suitable LEU target that would yield at least as much molybdenum as was obtained using the HEU target. Toward that end, a joint project was carried out by the groups at CNEA responsible for fuel elements, target manufacturing, and chemical processing of targets for separation and purification of molybdenum. Several uranium compounds were tested until, finally, an LEU target was developed with geometry similar to that of the former HEU target but with higher uranium content.

To begin using these new targets, several changes were required in the facility's separation and purification processes, but only slight modifications in infrastructure were needed. In 2002, commercial production of molybdenum 99 from LEU targets began. The entire conversion project had been carried out by the commission's staff, with no external technical or financial support. Today, CNEA produces high-quality molybdenum 99 that meets all of Argentina's demand and one-third of Brazil's. Additionally, around 15 percent of the molybdenum 99 produced is exported to the Latin American region beyond Brazil in the form of technetium 99 generators.

The Argentine experience with conversion from HEU to LEU has often been presented internationally as evidence that conversion is technically and economically feasible. Examples include a 2009 study mandated by the US Congress, "Medical Isotope Production without Highly Enriched Uranium"; the publications of the High-Level Group on Security of Supply of Medical Radioisotopes, an initiative that addresses global supply issues and also conversion to LEU targets in fission radioisotope production; and the US Energy Department program known as Reduced Enrichment for Research and Test Reactors.

CNEA's current efforts to build a new research and production reactor, as well as a new fission radioisotope production plant with a higher capacity, will help increase the availability of medical radioisotopes produced with LEU targets. This will help avert supply crises for technetium 99 — in 2009, problems at a Canadian technetium facility helped spark such a crisis — and will also contribute to the global initiative for minimization of highly enriched uranium.

Encouraging conversion. International efforts to minimize the use of HEU in the civilian sector are moving in the right direction. Several initiatives mentioned above are powerful instruments for publicizing the feasibility and importance of conversion to LEU; so are efforts by the International Atomic Energy Agency to coordinate meetings and establish research projects on this subject. On a national level, countries with a strong demand for fission molybdenum products should demonstrate a preference for suppliers that use LEU and impose restrictions on products based on HEU.

CNEA has contributed strongly to the conversion process — not only by converting its RA-3 and RA-6 reactor cores and its molybdenum 99 production process to LEU, but also by successfully transferring to entities abroad its LEU production technology. These include the Australian Nuclear Science and Technology Organisation and the Atomic Energy Authority of Egypt.

Taken together, national and multilateral efforts are helping to create a better understanding of the importance of eliminating HEU in civilian applications. This contributes to making the world a safer place.

Minimizing danger, maximizing headaches

Controlling access to fissile material is among the most important measures that can be taken to prevent nuclear weapons proliferation, and it is widely recognized that highly enriched uranium (HEU) poses proliferation threats whether it is used in military or civilian applications. This accounts for the international drive to favor low-enriched uranium (LEU) over highly enriched uranium. But what challenges face developing countries that elect to pursue HEU minimization?

In the developing world, highly enriched uranium is put to two uses that are relevant to minimization initiatives: as fuel for research reactors that have not yet been, or cannot be, converted to LEU, and as targets that bear fissionable uranium for the production of medical radioisotopes. (Two other uses may come under discussion in the future: fuel for naval reactors and fuel for fast reactors.)

Organizations that promote conversion to low-enriched uranium, such as the US National Nuclear Security Administration (NNSA) and the International Atomic Energy Agency (IAEA), sometimes employ a carrot-and-stick approach to encourage developing nations to convert. As a stick, these organizations might brandish the idea that developing countries will lose their supplies of enriched uranium if they don't convert to LEU. As a carrot, they might offer developing nations support for research and development initiatives or the chance to export radioisotopes. Many developing countries, in response to political pressure or commercial restrictions, and in an effort to be internationally cooperative, are attempting to reduce their use of HEU as much as is feasible. A complication for developing-world research reactors, however, is that facility managers often face pressure to reduce stakeholder costs — and conversion to LEU, whether for fuel or targets, carries significant financial implications.

Costs too high? Several research reactors that use highly enriched uranium as fuel face no urgency to convert to LEU — they have on hand sufficient fuel inventories for many operational cycles. But for reactors that do require fresh supplies of fuel, a twofold question presents itself: Can the reactor feasibly be converted to LEU; and can conversion be carried out in an efficient, economical way? If management does decide to convert, it must find suitable financial support to ensure that the transition to LEU is smooth, guaranteeing the facility's operational sustainability.

Converting to LEU targets for the production of medical radioisotopes presents a different set of issues. Radioisotope production is a major international industry; molybdenum 99 and more particularly its decay product technetium 99 (a metastable medical isotope) play a role in about 30 million patient applications per year. Historically, the industry has been based on irradiating HEU-bearing targets (often uranium 235 enriched to more than 90 percent). Converting to LEU targets requires that the target's uranium content be increased by a factor of two or more. This presents a technical challenge. In addition, if production of radioisotopes is to remain constant, more targets are required and larger volumes of waste are produced.

Another obstacle is that converting facilities to LEU, whether it is fuel or targets undergoing conversion, often requires a lead time of several years, during which nuclear licenses and permission to engage in medical applications must be updated. All of this implies substantial up-front costs, to be borne either by the reactor or its isotope producer, or by a major stakeholder (for example, the government). In addition, research reactors and isotope production facilities must concern themselves with loss of sales during any changeover, meaning that conversion often needs to be carried out even as existing production processes continue. This has significant implications for capacity and costs.

For research reactors in the developing world that are faced with these issues, financial options are often limited. They can seek assistance from supportive stakeholders like the government. They can try to manage with the funding that is available from commercial isotope production. Or, when it is available, they can seek assistance from developed countries — incentives. (The best results are often achieved by combining all three of these methods.) Significant technical and financial assistance from developed countries has come through, among other sources, the US Energy Department and the NNSA initiative known as the Reduced Enrichment for Research and Test Reactors Program (RERTR), as well as the Russian Research Reactor Fuel Return Program; both of these have received substantial organizational and financial support from the IAEA.

Limit too low? Often, when developed and developing countries discuss HEU minimization, the first issue on the agenda is converting reactors to low-enriched uranium. The second is timely removal and disposal of nuclear materials from facilities that no longer use these materials. To assist in reactor conversion, developed countries often provide subsidized computational evaluations of the feasibility of operating reactors using LEU and of expected increases in costs for producing isotopes after conversion. Removal and disposal of nuclear materials raise issues including the secure storage of used fissile materials until they can be suitably processed or repatriated. Significant progress has been made in recent years regarding the return of used fissile material from research reactors to the United States and Russia, but problems remain — like how to repatriate residual materials associated with fuel that did not originate in the United States or Russia. In addition, the Gap Material Program, an initiative of the US Global Threat Reduction Initiative that is intended to address high-risk materials not addressed through other programs, seems to be stagnating.

All this aside, the question posed in this Roundtable — "How might developed countries best incentivize HEU minimization programs in the emerging and developing worlds?" — begs that the term "HEU minimization" be clarified.

The entire drive for HEU minimization is related to the Nuclear Non-Proliferation Treaty, and to efforts by nearly 200 signatory nations to prevent the spread of nuclear weapons. Minimizing the use of HEU in civilian applications is a natural outgrowth of the treaty. But despite regular discussions on the issue, no universal consensus exists regarding what HEU minimization, as opposed to HEU elimination, is. Moreover, considerable skepticism surrounds the idea that all levels of HEU utilization represent a real proliferation problem.

By definition, HEU has more than 20 percent concentrated uranium 235; LEU is less than 20 percent concentrated uranium 235. I present a question here, perhaps confrontational but nonetheless deserving consideration: Why can't the cut-off for LEU be raised to something greater than 20 percent, in order to help research reactors around the developing world overcome the technological and financial challenges they face in the conversion process?

Round 2

Minimization at any cost?

In their essays so far, my colleagues Pablo Cristini and Charles Piani have expressed very different views on some aspects of minimizing the use of highly enriched uranium (HEU). Cristini has taken what I would call a conventional position on the issue, while Piani has expressed views that are somewhat more controversial. I find myself more in sympathy with the controversial outlook.

From the conventional perspective, converting reactors from HEU to low-enriched uranium (LEU) is universally practicable. This belief is mostly based on successful conversions of reactors that produce medical radioisotopes like molybdenum 99 — and indeed, in such conversions, production of molybdenum 99 has been maintained and reactors have not suffered in the commercial radioisotope market. A lot of experience has been gained in converting this kind of reactor; relevant fuel fabrication techniques have been perfected over the years; and conversions have become increasingly routine. The success of such conversion projects is by this time predictable, and depends only on proper planning, appropriate management, and adequate funding.

But reactors that produce medical radioisotopes are generally similar to one another, while reactors with other uses often have unique designs that are inextricable from the features of a reactor's fuel. Generally belonging to this category are pulse reactors, in which uranium enriched to a high level allows high neutron flux density in a relatively small reactor core, and also allows reactors to be operated for a long time without refueling. Designing a low-enriched fuel appropriate for such facilities can be a very difficult problem. It is precisely for these reasons that I tend to sympathize with Piani's controversial views on conversion — which, in my opinion, really amount to a balanced attitude toward conversion.

Monument to achievement. Kazakhstan's IGR research reactor, which I play a role in managing, is the highest-powered research pulse reactor in the world. Preliminary studies have shown that conversion to LEU is theoretically possible, but a number of difficult technical problems remain, and it is impossible to test how the reactor will perform over the long term if it is converted.

Taking into account circumstances like these, must research reactors really be converted to LEU at all costs? What if conversion is so difficult that it is essentially equivalent to constructing a new reactor, as may be the case with the proposed IGR conversion? (It is doubtful that even the building that houses IGR, not to mention the reactor's major systems, could be retained after conversion.) Must fuel that is already present in a reactor, and that remains capable of providing excellent performance for years, be replaced? And if it is clear, as is the case with IGR, that a converted reactor will not perform at the same level as the existing reactor, the question becomes: How much effort and expense should be devoted to creating a converted reactor that is inferior to an existing unit?

IGR has been in operation for more than 50 years, and over that time it has proven itself very safe. It is equipped with all the standard instruments and procedures that protect against unauthorized access — and it is located in the former Semipalatinsk nuclear test site, an especially secure area. Moreover, IGR is in high demand because of its suitability for studying the behavior of test fuels in conditions that simulate severe accidents in the cores of power reactors.

It would be sad if the IGR reactor, due to a well-intentioned conversion effort, proved unable to maintain its current capabilities, and if knowledge and technology that have existed for more than five decades were effectively lost. Therefore I pose a question, to which I do not have a precise answer myself. Might it be appropriate to preserve the IGR reactor as a monument to human achievement, and as a symbol of one aspect of humanity's cultural heritage?

Finally, I would add that even if IGR and all facilities like it are converted to LEU, highly enriched uranium will not disappear from the world. For example, naval propulsion reactors fueled by HEU seem unlikely to disappear any time soon.

Conversion to LEU: Petals and thorns

As the essays published in this Roundtable so far have established, converting research reactors and fission radioisotope production facilities to the use of low-enriched uranium (LEU) can involve a number of difficult challenges. Some are purely technical, some are financial, and others, as is often the case with medical isotopes, are related to safety and medical regulations.

Experience has shown that technical challenges to conversion at facilities producing molybdenum 99 can usually be overcome. Facilities using targets based on highly enriched uranium (HEU) often have the independent expertise to develop new LEU-based processing methods or to adapt their existing HEU processes. Where sufficient expertise is lacking, projects like the Global Threat Reduction Initiative may provide assistance that enables conversion to proceed.

In some cases, financial challenges are larger than technical ones. These challenges are best overcome when every stakeholder in the fission radioisotope supply chain becomes convinced that conversion is highly important to global security. Convincing everyone of this can be difficult in itself, as the supply chain contains numerous links: manufacturers of uranium targets, research reactors themselves, processors of molybdenum 99, manufacturers and distributors of technetium 99 generators, and nuclear medicine centers. But gaining the cooperation of all these stakeholders — as well as that of local governments and international minimization initiatives — seems the most satisfactory way to finance the costs of conversion.

Alexandr Vurim's first Roundtable essay describes a situation in which regulatory issues are paramount to the success of a research reactor's conversion process; indeed, regulation plays a large role in many conversion scenarios. Gaining regulatory approval for LEU conversion can take a long time (and it can take even longer for new facilities). Also, partly for regulatory reasons, facilities undergoing conversion may need to maintain parallel production processes for a while — the existing HEU process to produce medical radioisotopes until conversion is complete, and an LEU process that, as it is being refined, provides a demonstration for regulatory authorities.

So far I have mostly discussed facilities that are already in operation. But I believe it is clearly desirable that newcomers to fission radioisotope production use LEU targets from the very beginning, even if HEU is produced locally. Some new producers will be able to develop LEU-based processing methods on their own; if not, they can draw on programs such as a project of the International Atomic Energy Agency known as Small-Scale Indigenous Production of [Molybdenum 99] Using LEU Targets or Neutron Activation, which has been useful for some countries embarking on small-scale production of molybdenum 99. Or, as Australia and Egypt have done, nations may import LEU-based technology directly from a country like Argentina.

Defining the cut-off. My colleague Charles Piani has asked why the cut-off between low-enriched and highly enriched uranium can't be increased to something greater than 20 percent uranium 235, and he suggests that 30 percent might be a more reasonable dividing line. Others have raised the same issue — after all, cut-offs are often somewhat arbitrary. And from the perspective of some research reactors, economic factors argue for a cut-off higher than 20 percent.

I believe, however, that the 20-percent limit makes sense. Alexander Glaser, a Princeton University professor and a member of the Bulletin's Science and Security Board, has argued, in effect, that the existing definition represents a good compromise between competing nonproliferation imperatives. That is, when research reactors use uranium enriched to higher levels, uranium-based proliferation risks grow, in the sense that diversion or theft represents a greater security concern; but when facilities use uranium enriched to lower levels, plutonium-based proliferation risks grow (larger amounts of plutonium are produced when uranium enriched to lower levels is irradiated). I tend to agree with Glaser that the existing cut-off "represents a reasonable and even optimum choice as a conversion goal for research reactors" — and, I would add, for fission radioisotope production.

Better to control than eliminate?

My colleagues, in their first-round essays, described quite different experiences of converting research reactors, or attempting to convert them, to low-enriched uranium (LEU) from highly enriched uranium (HEU). Pablo Cristini's account of conversion in Argentina is representative of a situation in which a developing country possesses the independent ability to convert a reactor to LEU: Local expertise is sufficient to carry out the project, and the nation's government offers adequate support. Alexandr Vurim's essay on conversion in Kazakhstan presents a situation in which a nuclear facility is willing to undergo conversion but restrictions of a national or international nature may prevent it from doing so. Obstacles such as those faced in Kazakhstan can be very difficult to surmount unless decision makers become convinced of conversion's benefits.

South Africa's experience with conversion to LEU at its SAFARI-1 research reactor is more similar to the Argentine than the Kazakh situation. In South Africa, as in Argentina, it was possible to address all technical issues on a local level, and South African conversion efforts benefitted from strong governmental cooperation in the legal and regulatory realms. Financial circumstances in the two countries, however, appear to have been quite different.

To begin with, South Africa's exports of molybdenum 99 are significantly larger than Argentina's, so commercial considerations played a very large role in South Africa's deliberations. Also, though the nation's energy department provided significant funding for conversion, South Africa also welcomed US assistance in research and development. This came in the form of evaluating local processes for manufacturing LEU products and providing suggestions for improvement, as well as in performing theoretical computations regarding fuel and target plate efficiencies. (This help was provided by, for example, Argonne National Laboratory.)

There is, however, a continuing problem. SAFARI-1 completed its conversion to LEU fuel in 2009 and LEU targets in 2010, but regulatory authorities have not yet authorized the South African Nuclear Energy Corporation's HEU fuel and target manufacturing facilities to begin producing LEU versions. Thus, the nuclear energy corporation currently must import LEU plates for targets and for fuel and control rod assemblies. This represents a commercially undesirable loss of self-sufficiency.

Not so convincing. As I discussed in my first essay, research reactors in the developing world face a complex set of considerations when deciding whether to convert to LEU, and facilities at which HEU fuel and targets remain available will in some cases continue to delay conversion, unless very strong international persuasion is brought to bear. Reactors can be offered help in exporting radioisotopes, and decision makers understand this sort of commercial incentive readily enough. But less convincing at times are the nonproliferation arguments that developed countries employ in favor of conversion. This is especially true when converting a reactor would be very difficult. An example (admittedly not in the developing world) is Germany's Forschungsreaktor Munchen-II. There, conversion appears impossible unless difficult technical issues involving fuel density can be overcome. When obstacles of this sort complicate reactor conversions, surely it becomes appropriate to take into consideration the security systems that a nation employs for its nuclear material, rather than attempting to force conversion in all cases. Also, a question that I posed in my first essay is relevant here: Why can't the cut-off between low-enriched and highly enriched uranium be increased to something greater than 20 percent uranium 235? In my view, an enrichment level of 30 percent would be quite safe from a nonproliferation perspective.

Additional questions present themselves. What constitutes effective HEU minimization to begin with? How much HEU, in the possession of a particular country or facility, is considered unacceptable? How is that question answered when the fuel is fresh, and how is it answered when the fuel is spent?

And wouldn't developed countries contribute more to nonproliferation by focusing their efforts and funding on adequately controlling highly enriched uranium — whether at their own facilities or at more risk-prone facilities in the developing world — than by attempting to eliminate all uranium enriched above a particular threshold?

Round 3

Taking a fresh look

This Roundtable discussion has been very thought-provoking, and has encouraged me to look with new eyes at certain issues that surround the conversion of Kazakhstan's research reactors from highly enriched uranium (HEU) to low-enriched uranium (LEU).

The two active research reactors owned by Kazakhstan's National Nuclear Center (NNC) don't require refueling very often. Partly for this reason, Kazakhstan has never developed the capability to manufacture reactor fuel. If Kazakh research reactors convert to low-enriched uranium, this dependence on foreign fuel manufacturers seems likely to persist. At first glance, then, it would seem natural for the Russian firm that now manufactures fuel for the center's reactors to provide LEU fuel after conversion occurs.

But maybe this isn't as natural as it appears at first. This is because LEU fuel, by definition, is enriched to a lower level than HEU fuel; therefore, in order for low-enriched fuel to provide performance approximating that of highly enriched fuel, the density of the uranium in the fuel matrix must be increased. But this carries implications for fuel fabrication — the stage of the process at which enriched fuel is converted into assemblies suitable for use in a reactor. That is, existing technologies for producing HEU fuel may not, even after they are modified for low-enriched uranium, be compatible with existing processes for LEU fuel fabrication. This implies that fabrication techniques for low-enriched fuel would probably have to be designed from scratch.

With conversion requiring so many changes, the firm that now manufactures fuel for Kazakh research reactors would appear to enjoy no advantage over competing firms, other than its history of working with Kazakhstan. Thus it seems appropriate for Kazakh authorities, if conversion goes forward, to make an objective assessment of the entire market for LEU fuel suppliers, and not confer any special status on the existing fuel supplier.

Another issue to which I have devoted thought as a result of this Roundtable is the exact manner in which conversion at Kazakh reactors might be carried out. The reactors owned by the NNC are in constant use for research projects, mostly involving nuclear energy (including fusion). The center has reached agreements with customers on work schedules through 2018, and proposals have come in for projects as far in the future as 2020. These programs, of course, play a significant role in the NNC's budget. Any reactor shutdown would be undesirable because the center would inevitably sustain financial losses during conversion and, even if conversion were very successful, building up the reactors' business again would take time.

Therefore, if conversion is to proceed, disruptions to research projects must be minimized. How could this be achieved? One option, if it proves technically possible, would be to replace HEU fuel with LEU fuel only gradually, during planned refuelings. The NNC might be able to implement this approach at its IVG reactor, where preliminary studies have shown that conversion would not require changes to some of the reactor's systems — for example, to its control and protection systems. However, this approach would require Kazakh authorities and international partners such as Argonne National Laboratory and the US National Nuclear Security Administration to reach agreement on a conversion schedule. Also, these partners would need to make decisions about providing compensation for financial losses associated with conversion.

Not much point. My colleagues Pablo Cristini and Charles Piani have conducted a discussion on whether the widely accepted cut-off between low-enriched and highly enriched uranium should be maintained where it is, at 20 percent uranium 235, or whether it should be increased. To my mind, the existing cut-off is based on reasonable criteria. Any attempt to change the cut-off would have to win acceptance from the international nuclear community and various regulatory bodies — but the chances of this happening are very low, so I see little point in calling for an increase. In my view, then, there is only one option for converting reactors to LEU, and that is to do so with the cut-off of 20 percent in mind.

Difficult, but worth it

In his second Roundtable essay, Alexandr Vurim characterized me as representing a "conventional perspective" toward converting research reactors to low-enriched uranium (LEU) from highly enriched uranium (HEU). From this conventional perspective, he wrote, conversion is seen as "universally practicable." He went on to argue that certain research reactors, if converted to low-enriched uranium, could be difficult if not impossible to operate with the same efficiency that had existed before conversion. And he suggested that conversion should perhaps not be attempted in such cases.

I maintain now, as I have before, that many activities carried out at research reactors, including but not limited to radioisotope production, can be conducted perfectly well after conversion to LEU. But in point of fact, I agree with Vurim that it is irrational to halt useful nuclear applications if, for technical reasons, they cannot be performed with acceptable efficiency after conversion to LEU. In some instances, conversion to low-enriched uranium is simply not a reasonable course of action. In these cases, nuclear activities should not be interfered with.

Charles Piani, in his smart and funny final essay, employed an extended metaphor in which he portrayed conversion to LEU as an elephant that can only be eaten piece by piece, though some parts of this beast might prove to be inedible. This gets at the truth of the matter, but I would go further, and suggest that the animal to be eaten is not just an elephant but an especially large one — and that certain cuts of its meat might cause acute indigestion. Still, the meal is being served, so diners should do their best to clean their plates. At least they can look forward to an enjoyable dessert — the satisfaction of ridding the world, to the greatest extent possible, of civilian HEU.

Work goes on. As this Roundtable has emphasized, deciding where and how to convert to LEU can be a very difficult project. The difficulties are eased, however, through international cooperation, whether it is in the form of expert meetings or through minimization programs like Global Threat Reduction Initiative and the Reduced Enrichment for Research and Test Reactors program. These powerful resources have proved quite adequate for overcoming a host of technical and financial hurdles to conversion. Over time, I believe, interactions like these will produce a consensus about which nuclear facilities should convert to low-enriched uranium and which must be allowed to continue using HEU. Wherever the use of highly enriched uranium continues, however, security measure to prevent theft or diversion must be maintained at the highest achievable levels.

Meanwhile, the debate over conversion continues. No perfect approach to conversion will be found, if perfection is defined as eliminating all proliferation risks while also overcoming all technical and financial obstacles to conversion. But building awareness of conversion's benefits remains an important project, one that should continue through international initiatives and conferences and, for that matter, fora like this Roundtable.

Conversion will take work. It will require funding and time. In the end, some facilities that use highly enriched uranium will probably continue doing so. But my conviction is that the international effort toward conversion to low-enriched uranium is worth the effort.

Eating the elephant

In my part of Africa, when people are faced with a large, daunting problem, someone often asks, "How do we eat this elephant?" The typical response is: "Piece by piece!" Minimizing the use of highly enriched uranium (HEU) can be seen as an elephant that, indeed, can only be eaten piece by piece. But it may also be the case that certain parts of this animal are simply inedible.

My colleagues Pablo Cristini and Alexandr Vurim have expressed somewhat different views about when it is reasonable to expect that reactors using HEU should convert to low-enriched uranium (LEU). But consensus has emerged on one point: At reactors that produce molybdenum 99, converting fissionable targets to LEU is a feasible project, though possibly a painful one. Much the same determination was reached in a 2012 report by the Nuclear Energy Agency, which concluded that, despite the investments of money and time that conversion entails, "conversion is important and will occur." In any event, as long as only a few nations supply HEU, and these countries continue to exert pressure on molybdenum-producing reactors to convert, these facilities will find that their alternatives to conversion are very limited. Reactors that want to be involved in commercial production of medical isotopes will eventually have to eat their piece of the elephant — or go hungry.

Another portion of the meal involves certain research reactors that use HEU and are engaged in activities beyond isotope production. New research reactors, of course, are generally expected to be designed in such a way that they can function well with low-enriched uranium. But older reactors may find their elephant flesh too tough to swallow. This is mainly because possibilities for reconfiguring reactor cores are often limited at research reactors with older designs. In these cases — for instance at Vurim's IGR reactor in Kazakhstan — conversion in many cases implies reduced performance.

At these facilities, the developed world can provide a sort of meat tenderizer by furnishing technical and financial support for conversion efforts. But even support of this type won't always be sufficient — not as long as the cut-off between LEU and HEU remains defined as 20 percent uranium 235. So in a few instances, the meal simply cannot be served, and any international minimization strategy that aims to make all research reactors completely safe from a proliferation perspective is unlikely to succeed. The International Atomic Energy Agency's database of research reactors gives an indication of the scope of the problem: Many dozens of the reactors listed there have little financial or technical ability to convert on their own. More to the point, they have no real desire to convert. When it comes to eating the elephant, they just aren't hungry enough.

Even if conversion can't be accomplished in all cases, developed countries can contribute to nonproliferation by continuing to carry out risk evaluations of HEU inventories in developing nations, and by helping to improve security and material management programs where appropriate. Inventories that pose the highest risks — for example, stocks of fresh HEU fuel in developing countries with insufficient programs for nuclear material management and security — should be given special priority. Spent fuel, in view of its high radioactivity, to a certain extent provides its own deterrent to theft or diversion.

Nuclear-powered submarines represent perhaps a more alarming problem than research reactors. Submarines are by definition physically isolated much of the time. They will inevitably make ports of call in foreign countries, whether planned or not, and it is not really possible to apply proper security to facilities that are so mobile. And as Vurim indicated in his second essay, HEU for naval applications is unlikely to be eliminated any time soon.

But when it comes to research reactors, conversion to LEU at facilities that produce medical radioisotopes is a meal already on the table, and one that will be consumed fairly quickly. Conversion of all research reactors to LEU, however — this animal may be even harder than an elephant to eat.


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