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June 1, 2018
Dealing With South Korea’s Spent Fuel Challenges Without Pyroprocessing

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Ferenc Dalnoki-Veress and Miles A. Pomper

Seeking to head off a potential rupture in bilateral nuclear trade, the U.S. and South Korean governments agreed in April to extend their current nuclear energy cooperation agreement for two years, until March 2016. If the two countries’ legislatures endorse the agreement, it will provide Seoul and Washington with some breathing space to agree on new terms for nuclear trade to replace their previous agreement from the early 1970s.

The two countries will seek to use this opportunity to overcome the key stumbling block in the talks: U.S. resistance to South Korean demands for advance consent to alter U.S.-obligated nuclear material through uranium enrichment or spent fuel reprocessing.[1] In particular, South Korea had been hoping to win support to engage in pyroprocessing, a form of reprocessing developed in the 1960s that has never been commercialized.[2]

The technology has appealed to some South Korean scientists because of the country’s problems in storing spent fuel. Many of South Korea’s reactors will likely reach their capacity for storing highly radioactive waste in their pools by the end of this decade, but the South Korean government has yet to designate additional storage capacity that would ensure continued operation of the reactors. The prospect of shipping the material to a new pyroprocessing facility is seen as a means of responding to that concern.

The United States has objected because of regional and global nonproliferation concerns. Regionally, Washington fears that a South Korean pyroprocessing program could undermine efforts at convincing North Korea to abandon its nuclear weapons program; reprocessing technology is at the heart of Pyongyang’s nuclear weapons program. During a time of heightened tension on the Korean peninsula, given the launch of a long-range missile last December and the underground nuclear test in February, Washington also worries that Seoul might be motivated to use the technology to provide fissile material for its own nuclear weapons program. Globally, the United States is concerned that South Korean acquisition of this sensitive fuel-cycle technology runs counter to U.S. efforts to limit the spread of such technologies. The U.S.-South Korean dispute has become politicized and at times heated, with some South Korean politicians objecting to U.S. efforts to limit their “peaceful nuclear sovereignty.”[3]

The disagreement is unnecessary and misplaced, failing to meet the true interests of either side. South Korea’s most pressing needs are to identify short-term measures for storing its spent fuel and to initiate a long-term plan for a spent fuel repository, neither of which requires pyroprocessing or raises the kind of nonproliferation concerns that pyroprocessing does. The two countries should take advantage of the anticipated extension of their agreement to address these immediate challenges, leaving aside further resolution of the pyroprocessing issue until more research is carried out into this still-experimental technology.

Pyroprocessing treats spent fuel by removing the extremely radioactive but relatively short-lived constituents, such as strontium and cesium, and storing these separately from the spent fuel. It then burns the remaining material, including the comparatively long-lived transuranic elements plutonium and other actinides, in fast-neutron reactors.[4] South Korean researchers point to the potential benefits of pyroprocessing in reducing the overall quantity and heat load of waste requiring permanent storage. Other experts point to the added management challenges that arise from increasing the number of waste streams, developing still-conceptual and expensive fast-neutron reactors, and qualifying a new type of fuel for these reactors, while saying that long-term interim storage can provide many of the same benefits.

The inability of Seoul to acquire additional storage capacity is largely a result of domestic politics. Public opposition to previous attempts to resolve the issue has left South Korea’s politicians reluctant to make politically or diplomatically risky decisions to address the problem. The political issues are exacerbated by South Korea’s high population density and lack of free space for storage, which makes identifying and building a permanent repository even more complicated than in most other countries with nuclear power plants. Local populations worry that any interim storage facilities ultimately will become permanent.

South Korean officials argue that pyroprocessing should not be considered equivalent to traditional reprocessing, which originated in weapons programs. These officials say that South Korea does not plan to separate pure plutonium from the spent fuel and, in any case, that pyroprocessing cannot produce a product suitable for nuclear weapons. U.S. officials disagree and consider pyroprocessing to be equivalent to reprocessing, with corresponding nonproliferation challenges.

Both sides of the discussion continue to see pyroprocessing as being in the developmental stage and do not have sufficient information to determine if it is appropriate for the larger throughput required to minimize South Korea’s spent fuel inventories effectively. Despite the ongoing debate, the discussion of pyroprocessing remains somewhat premature. Seoul and Washington acknowledge that they lack sufficient information to determine whether pyroprocessing, which is only now being tested on an engineering scale, makes technical or economic sense on an industrial scale. They also are working with the International Atomic Energy Agency to see if they can develop appropriate safeguards to prevent proliferation—a difficult challenge in all reprocessing facilities. Higher, industrial-scale throughput levels would be required if pyroprocessing were to be used for minimizing South Korea’s growing stockpile of spent fuel.

At the end of 2010, the two sides agreed to a joint study to evaluate the technical, economic, and nonproliferation feasibility of the process. The ongoing joint study, which the two sides formally began in 2011, is supposed to look at safe and comprehensive ways of dealing with spent fuel and examine pyroprocessing within that context.[5] Although the 10-year study was supposed to consider a wide range of “back-end” alternatives, South Korea has been willing to support work only on pyroprocessing.[6] Moreover, that part of the study effectively had ground to a halt amid the clash over the nuclear cooperation agreement. In any case, even under the most optimistic scenario, pyroprocessing and the associated fast-neutron reactors will not be available options for dealing with South Korea’s spent fuel on a large scale for several decades. Seoul will need to find other options, most urgently for managing spent fuel in the short to medium term. In the long term, it will have to find a permanent answer to the question of properly managing its spent fuel or the high-level waste[7] that will remain after pyroprocessing.

South Korea’s new government has the opportunity to do better. Its first priority should be to seek broad and open discussion with the public and other relevant stakeholders. A year ago, the Ministry of Knowledge and Economy (now the Ministry of Trade, Industry, and Energy) promised to set up a Stakeholder Engagement Commission by March of this year. However, the establishment of this commission, which would be similar to the recent U.S. Blue Ribbon Commission on America’s Nuclear Future, has been delayed for several months.

This commission, which would include technical and social science experts, as well as representatives of nongovernmental organizations and communities near nuclear power plants, is a useful step in widening the public discourse in South Korea. Until now, that discourse has been dominated by engineers and scientists with a vested interest in one technological approach or the other. In addition, South Korea should consider the following particular policies over the short, medium, and long terms.

Shorter-Term Storage Options

The building of short- to medium-term storage facilities at reactors or at other locations should be a major focus of the South Korean nuclear authorities in the immediate future. With or without pyroprocessing, South Korea will need additional storage capacity. South Korean nuclear authorities already have instituted several procedures to boost spent fuel storage capacity in existing pools. These methods include increasing fuel burn-up so such spent fuel remains in the reactor longer before entering a pool, and reracking spent fuel to pack fuel into the pools more tightly.

The nuclear utilities also have moved spent fuel within plants from older, saturated pools to newer reactors with more storage capacity, actions recommended by the Korean Nuclear Society.[8] These techniques, however, have their limitations, and the pools will likely reach their capacity within a decade, and the Korean nuclear industry has recommended the construction of new interim storage facilities no later than 2024.[9] Furthermore, densely packing spent fuel pools raises nuclear safety and security concerns.[10]

Fundamentally, the obstacles to finding additional storage space are political, not technical, and could be overcome if South Korean policymakers were willing to tackle political challenges. Spent fuel from South Korea’s light-water reactors (LWRs) could be stored in dry casks at current reactor sites or at a central site for 60 years or more, as advocated last year by South Korea’s Atomic Energy Commission (AEC).[11] Dry casks are modular units designed to cool spent nuclear fuel with air rather than with water, and in this sense, the casks are less vulnerable to external conditions.

At South Korea’s Wolsong plant, dry-cask storage units have been built for that plant’s spent fuel. South Korea should consider using similar technology at additional plants, and the United States could provide important technical assistance in this regard.[12] The option of safely relying on dry-cask storage for longer periods than previously thought possible has raised the possibility that this technology could be used to prolong the operating lifetime of current South Korean facilities.

Storage of spent fuel in dry casks appears to be safe and secure for decades more than originally thought and is a proven technology used at numerous sites around the world. In the 1980s, the U.S. Nuclear Regulatory Commission (NRC) estimated that spent fuel “could be stored safely for at least 30 years after a reactor’s operating license expired.” That estimate was pushed further out in 1990, when the NRC stated that it was safe “30 years beyond a 40-year initial license and a 30-year license renewal period, for a total of at least 100 years.”[13]

Additional storage sites could be available if South Korean policymakers were willing to overcome the political obstacles against shipping fuel from a plant site in one jurisdiction to a plant site in another. Currently, political uncertainties even could block the shipment of fuel from parts of the Kori site to the adjacent Shin-Kori site because the two groups of reactors are in different jurisdictions.[14]

Overcoming these political obstacles will require efforts by the political and technical communities to inform the public of the safety and security benefits that might come from dry-cask storage. Previous efforts to win public support have tended to be top-down approaches that did not involve substantial public input or explanation of relative risks and benefits. Continuing this tradition by claiming that pyroprocessing represents a technical solution to what is inherently a political problem, rather than an intriguing if still untested research program, is unlikely to be successful.

Moreover, the various strands of South Korea’s spent fuel management system need to be integrated into a comprehensive approach with decisions on fuel burn-up, storage of spent fuel at reactors or offsite facilities, and possible long-term solutions tied together to provide plausible paths forward, while providing South Korean policymakers and the public with the maximum range of policy options. By contrast, South Korean policy to date has been hampered by bureaucratic infighting and confined to an unnecessarily narrow set of choices.

Long-Term Storage Options

As noted above, South Korea is interested in reprocessing, particularly pyroprocessing, as a means of long-term spent fuel management. As part of this plan, South Korea needs to develop reactors capable of burning the fuel created in pyroprocessing. Seoul’s current efforts build on the considerable experience that the United States has had in developing the Integral Fast Reactor.[15] Fast-neutron reactors have been under development in many countries for decades, but have yet to be successfully commercialized. Their use also would require South Korea to develop, qualify, license, and fabricate commercially a new type of fuel.

South Korea partly justifies its push for reprocessing by citing the need for nuclear “sovereignty” and energy self-sufficiency. Yet, the development of a reprocessing capability in South Korea might not be economically feasible. The research is not at a stage where a definitive decision can be made about the viability of these techniques. Therefore, South Korea should favor an approach that will leave options open and give it time to investigate various technologies before making any decisions about commercial-scale deployment.

Among the notions that could be explored is “extended storage” beyond the many decades currently envisioned by the South Korean AEC, the U.S. NRC, and others. Due to delays in many countries in siting repositories for final disposition of spent fuel or high-level waste, interest has grown in possibly extending storage for periods lasting centuries or more. To be sure, this concept, known as “indefinite,” or extended, storage, has a number of problems in comparison to other long-term options because safety and security are guaranteed only if continuing maintenance is assured in perpetuity, an assurance that is nearly impossible to give. Nevertheless, extended storage has its benefits. These include postponing the high costs of developing reprocessing facilities or disposal sites and the political problem of siting a disposal location while still safely storing these materials for a long period of time. Extended storage also would allow for the continued availability of other future options, including reprocessing. In any case, South Korea would benefit from participating in research aimed at assessing the technical feasibility of extended storage.

Even without extended storage, spent fuel will need to be stored in South Korea for decades because of the period required for cooling of the spent fuel before further treatment of it or because advanced treatments, such as pyroprocessing, cannot be implemented on a large scale for many years. If spent fuel is to be stored for a long time, then various conditioning methods are available to reduce the volumes to be stored and ultimately disposed of and to avoid unacceptable long-term degradation of the spent fuel or its packaging.

Still, geological disposal is currently the only recognized long-term strategy guaranteeing safety and security without continual care and maintenance. Regardless of whether South Korea opts for a strategy based on direct disposal of spent nuclear fuel or some reprocessing of its fuel, Seoul definitely faces the challenge of implementing a multiyear program leading to ultimate geological disposal. Yet, experience in numerous national programs has illustrated vividly that geological disposal is a contentious issue that can severely affect the overall public acceptance of a nuclear power program. In some countries, the public will accept nuclear power only if a geological repository is constructed, while in other countries activists oppose the construction of geological repositories in order to prevent the expansion of nuclear power.[16]

One broad question on geological disposal is whether to employ a mined geological repository or deep borehole disposal. Mined geological repositories are located several hundred meters underneath the earth’s surface in stable geological formations and include engineered barriers and natural barriers such as rock, salt, or clay. By contrast, deep borehole disposal involves the emplacement of waste packages in the bottom sections of holes drilled to depths of several kilometers, much deeper than mined geological repositories. The upper kilometers of the holes are not used for disposal, but backfilled and sealed so any nuclear waste is at least three kilometers below the surface.

One advantage of a mined repository is that it is by far the more established technology, with decades of research conducted by numerous countries around the world. South Korea’s program ultimately envisions such a repository. Compared to conventional mined geological repositories, however, deep borehole disposal reduces the need for specific types of geology that are particularly good at containing radionuclides. Also, a greater depth may diminish the likelihood of failure scenarios in which radionuclides are able to mix with groundwater and eventually propagate into the environment.

Moreover, it appears likely that deep borehole disposal would offer benefits similar to the ones that pyroprocessing advocates claim for the reduced-area repository that they say would be sufficient to dispose of the spent fuel. Under some scenarios, placing intact spent fuel in deep boreholes could require one to two times the surface area of a reduced-area repository as conceived by South Korean scientists, but with the added advantage that the high-heat producers do not need to be chemically separated from the fuel.[17]

Deep borehole disposal should be regarded as a viable alternative to the mined repository concept. At this point, however, deep borehole disposal is more expensive and will likely stay so until there are advances in technologies used to drill holes and place waste in them. One critical question for South Korean policymakers in this regard is whether they want materials in the repository to be retrievable, something that is not really possible for deep boreholes but could still be an option with a mined repository.

One of the main tasks when looking at geological disposal is choosing the type of system that best fits the available or appropriate site. Generally, finding a suitable and acceptable site for a geological disposal facility is the most difficult aspect of the whole program. It is important for the geological disposal program to maintain a flexible approach to design before a site or geological environment is identified and to begin public discussion about the need for and nature of such a site as early as possible.


South Korea could take a number of actions that would allow it to tackle its short- and medium-term spent fuel challenges while providing it with flexibility with respect to its ultimate choices in handling spent fuel and high-level waste.

Short- to medium-term approaches. In the short and medium term, the primary focus needs to be on moving older spent fuel out of reactor pools in order to allow continued operation. At the same time, Seoul has to take steps to arm itself with more information on and options for addressing longer-term concerns.

In the short term, South Korea’s planned Stakeholder Engagement Commission is an important step forward. Making this process as transparent as possible is crucial. The commission should seek to educate communities near current reactor sites about the safety and security benefits of dry-cask storage. As an additional benefit to the communities, the commission could offer to establish a clear link between interim storage and the lifetime of nuclear reactors by promising to remove spent fuel from a plant site as soon as that reactor complex shuts down. It is not clear at this point if a forthcoming five-year government plan will call for the construction of new domestic reactors beyond those already planned at existing sites. Should this be the case, however, Seoul could consider tying the winning bid for the next nuclear power plant site to a community’s willingness to host an interim storage facility or at least to accept spent fuel from other sites.

After the Stakeholder Engagement Commission’s two-year mandate expires, current plans envision the establishment of a Site Selection Commission that might pick appropriate future sites for spent fuel. It is essential that the commission undertake an active engagement program with the residents and businesses in the areas considered appropriate for hosting storage facilities so that these communities are involved in the decision-making. In the case of a centralized storage facility, one incentive that some have suggested Seoul could offer, which the U.S. Blue Ribbon Commission on America’s Nuclear Future also proposed, is to pledge that communities hosting such a facility would not also host a geological repository.

Looking toward the longer term, the Site Selection Commission should seek to initiate discussions of potential permanent disposal sites and look for hosts for centralized interim storage facilities.

Internationally, South Korea should work with the United States to carry out a more comprehensive 10-year back-end study on new approaches to spent fuel disposition. The focus of this study should go beyond pyroprocessing and include issues such as research and development on fast-neutron reactors, disposal and storage options such as deep borehole disposal and extended storage, and discussions of possibilities for multilateral facilities in or outside of South Korea. In addition, Seoul should study the implications of different fuel-cycle strategies on the timing and the technology needed for final repository implementation and make the results of this analysis a major factor in decisions on future policies.

Long-term approaches. By the end of next year, the Stakeholder Engagement Commission is supposed to provide recommendations on spent fuel management to South Korea’s Ministry of Trade, Industry, and Energy and the AEC. The AEC is then supposed to establish a Basic Plan for Radioactive Waste Management. In this basic plan, Seoul should develop and publicize a national strategy and accompanying road map for a process leading credibly after several decades to a national repository, should no other viable options be developed in the intervening period. Although South Korea’s current preferred strategy is pyroprocessing, Seoul should acknowledge that, for this strategy too, a final disposal solution in a geological repository will be needed.

In addition, South Korea should continue and broaden cooperation on research on deep borehole disposal that it has just begun with Sandia National Laboratories in the United States. Such research could touch on pilot testing of practical boreholes, waste package handling methodologies and technologies, borehole sealing and drilling, development of safety assessment scenario analyses and development of technical requirements for a deep borehole disposal program.


The political tensions and rhetorical battle between South Korea and the United States over pyroprocessing and the renewal of the nuclear cooperation agreement have obscured some of the technical issues involved, particularly when it comes to the handling of spent nuclear fuel. The pending two-year extension could provide an opportunity to reshape the debate on the issue to focus on South Korea’s immediate and long-term spent fuel needs, while deferring discussion on pyroprocessing. At a time of high nuclear tension on the Korean peninsula, it is counterproductive for policymakers to focus on deciding whether to move forward with a process that raises many nonproliferation red flags yet has not proven its technical or economic viability. Both countries should take advantage of the window promised by the expected extension to lower the political temperature on this issue and focus on pragmatic and cooperative spent fuel solutions that can offer benefits today.

Ferenc Dalnoki-Veress is a scientist-in-residence and adjunct professor at the James Martin Center for Nonproliferation Studies (CNS) of the Monterey Institute of International Studies. Miles A. Pomper is a senior research associate at CNS. This article was adapted from “The Bigger Picture: Rethinking Spent Fuel Management in South Korea,” of which Dalnoki-Veress and Pomper were two co-authors.


1. “U.S.-obligated material” includes material transferred from the United States, as well as special nuclear material produced overseas through the use of U.S.-supplied nuclear material or reactors. South Korea’s light-water reactors are largely based on U.S. designs and include important U.S components. Therefore, even though the majority of its reactors were constructed by South Korean companies, those reactors are legally considered to have been supplied by the United States. “Advance consent” or “programmatic consent” means that the United States provides approval for sensitive nuclear activities for the life of a nuclear cooperation agreement rather than considering each case individually. See Fred McGoldrick and Duyeon Kim, “Decision Time: U.S.-South Korea Peaceful Nuclear Cooperation,” KEI Academic Paper Series, March 13, 2013, http://www.keia.org/publication/decision-time-us-south-korea-peaceful-nuclear-cooperation.

2. A form of pyroprocessing was used to reprocess fuel from the Experimental Breeder Reactor II from 1964 to 1969. See Yoon I. Chang, “The Integral Fast Reactor,” CONF-8810155-28, 1988.

3. “Seoul Wants ‘Sovereignty’ in Peaceful Nuclear Development,” Chosun Ilbo, December 31, 2009.

4. Fast-neutron reactors have a different neutron spectrum then conventional (thermal) reactors. They allow operators to use recycled material from spent fuel more efficiently to generate electricity and if operated in “burner” mode, decrease the quantity of actinides in the fuel.

5. Yonhap News Agency, “South Korea, U.S. Agree to Start Joint Study on Nuclear Fuel Reprocessing,” April 17, 2011.

6. Park Hyong-ki, “South Korea, U.S. Move Forward on Nuclear Pact,” Korea Herald, December 31, 2012.

7. The Nuclear Regulatory Commission defines high-level waste as being “highly radioactive materials produced as a byproduct of the reactions that occur inside nuclear reactors.” High-level waste can take two forms: as waste from the reprocessing of spent nuclear fuel or as the spent nuclear fuel itself. See http://www.nrc.gov/waste/high-level-waste.html.

8. Jungmin Kang, “The ROK’s Nuclear Energy Development and Spent Fuel Management Plans and Options,” NAPSNet Special Report, January 22, 2013, http://nautilus.wpengine.netdna-cdn.com/wp-content/uploads/2013/01/Kang_Nuclear_Energy_Spent_Fuel_ROK_final_11-14-2012.pdf.

9. Korea Radioactive Waste Management Corporation, “Current Status of Spent Fuel Management in Korea” (presentation, Seoul, June 11, 2013).

10. Robert Alvarez et al., “Reducing the Hazards From Stored Spent Power-Reactor Fuel in the United States,” Science and Global Security, Vol. 11, No. 1 (2003): 1-51. See also Gordon R. Thompson, “Handbook to Support Assessment of Radiological Risk Arising from Management of Spent Nuclear Fuel,” Institute for Resource and Security Studies, January 31, 2013, http://nautilus.wpengine.netdna-cdn.com/wp-content/uploads/2013/05/SNF-Risk-Handbook-Rev-1.pdf.

11. Kang, “The ROK’s Nuclear Energy Development and Spent Fuel Management Plans and Options.”

12. Chaim Braun of Stanford University’s Center for International Security and Cooperation has pointed out that the CANDU spent fuel assemblies are small and have low burn-up while the spent fuel assemblies from South Korea’s pressurized-water reactors (PWRs) are large with high burn-up, thus requiring different types of interim storage. He has suggested the United States and South Korea could cooperate on a demonstration program for the PWR assemblies. Chaim Braun, “ROK-U.S. Prospective Nuclear Energy Cooperation Measures” (remarks, Washington, DC, May 17, 2013).

13. Winston and Strawn LLP, “Waste Confidence and Spent Fuel Storage Developments,” Nuclear Energy Practice Briefing, October 2008, http://www.winston.com/siteFiles/publications/Waste_Confidence_Rule.pdf.

14. Ibid.

15. The Integral Fast Reactor was a prototype reactor that was co-located with a pyroprocessing line, fuel fabrication facility, and waste handling facility and that immediately burned recycled spent fuel. Congress ended funding for that effort in 1994.

16. International Atomic Energy Agency, “Factors Affecting Public and Political Acceptance for the Implementation of Geological Disposal,” IAEA-TECDOC-1566, October 2007, p. 43.

17. This calculation simply estimates the number of boreholes needed for a total spent fuel inventory of 53,000 metric tons of spent nuclear fuel in the year 2050. The total area occupied by the borehole field is about 1 square kilometer, corresponding to 520 boreholes. This should be compared to 0.8 square kilometers for the Korean Atomic Energy Research Institute’s proposed reduced-area repository if pyroprocessing is employed. See Seong Won Park, “Why South Korea Needs Pyroprocessing,” Bulletin of the Atomic Scientists, October 26, 2009, http://www.thebulletin.org/why-south-korea-needs-pyroprocessing. See also Jongyoul Lee et al., “Concept of a Korean Reference Disposal System for Spent Fuels,” Journal of Nuclear Science and Technology, Vol. 44, No. 12 (2007): 1565-1573.