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The Current Status of Spent Nuclear Fuel in Korea

Hyun-Soo Park and Jongwon Choi

Korea Atomic Energy Research Institute

Despite the slowdown of the nuclear energy industry in western countries, Korea is steadily promoting the nuclear power generation business in response to Korea’s increasing electricity demand, seeking new sites for nuclear power plants, and supporting the development of commercial technology. Nuclear energy has certainly been a great contribution to the energy supply in Korea because of the shortage of natural energy resources. In 2002 nuclear power was the primary energy source, with a 29.2 percent share of the total, followed by bituminous coal (27.4 percent), gas (25.3 percent), and oil (8.7 percent). The only domestic energy resources were anthracite coal and hydropower, which had a share of 2.2 percent and 7.2 percent of the total, respectively. In gross power generation nuclear power produced a share of 38.9 percent over other energy sources, such as coal (38.5 percent), oil (8.2 percent), gas (12.7 percent), and hydro (1.7 percent).

Since the first nuclear power plant, Gori Unit 1, a pressurized water reactor (PWR), was commissioned in Korea in April 1978, the nuclear power generation capacity has grown steadily and remarkably in Korea. By the end of 2002, 18 nuclear power plants with 14 PWRs and 4 CANDU (Canada deuterium uranium) reactors were in operation with a total capacity of 15.7 GWe (see Table 1). In addition, 2 PWRs produced by the Korean Standard Nuclear Plant (KSNP) of 2 GWe are under construction. The construction of an additional 4 PWRs produced by KSNP and 4 evolutionary PWRs (Korean next-generation reactors, 1.4 GWe each) is planned by 2015. A total of 26 nuclear power plants will be in commercial operation by the year 2015, after the potential retirement of the two oldest units (Gori Unit 1 and Wolsung Unit 1). The total installed nuclear power capacity is then expected to reach 26.1 GWe.



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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop The Current Status of Spent Nuclear Fuel in Korea Hyun-Soo Park and Jongwon Choi Korea Atomic Energy Research Institute Despite the slowdown of the nuclear energy industry in western countries, Korea is steadily promoting the nuclear power generation business in response to Korea’s increasing electricity demand, seeking new sites for nuclear power plants, and supporting the development of commercial technology. Nuclear energy has certainly been a great contribution to the energy supply in Korea because of the shortage of natural energy resources. In 2002 nuclear power was the primary energy source, with a 29.2 percent share of the total, followed by bituminous coal (27.4 percent), gas (25.3 percent), and oil (8.7 percent). The only domestic energy resources were anthracite coal and hydropower, which had a share of 2.2 percent and 7.2 percent of the total, respectively. In gross power generation nuclear power produced a share of 38.9 percent over other energy sources, such as coal (38.5 percent), oil (8.2 percent), gas (12.7 percent), and hydro (1.7 percent). Since the first nuclear power plant, Gori Unit 1, a pressurized water reactor (PWR), was commissioned in Korea in April 1978, the nuclear power generation capacity has grown steadily and remarkably in Korea. By the end of 2002, 18 nuclear power plants with 14 PWRs and 4 CANDU (Canada deuterium uranium) reactors were in operation with a total capacity of 15.7 GWe (see Table 1). In addition, 2 PWRs produced by the Korean Standard Nuclear Plant (KSNP) of 2 GWe are under construction. The construction of an additional 4 PWRs produced by KSNP and 4 evolutionary PWRs (Korean next-generation reactors, 1.4 GWe each) is planned by 2015. A total of 26 nuclear power plants will be in commercial operation by the year 2015, after the potential retirement of the two oldest units (Gori Unit 1 and Wolsung Unit 1). The total installed nuclear power capacity is then expected to reach 26.1 GWe.

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop TABLE 1 Status of Nuclear Power Plants in Korea as of December 2002   Reactor Sites Gori Yonggwang Uljin Wolsung Number in operation 4 6 4 4 Number under construction — — 2 — Reactor type PWR PWR PWR CANDU Korea’s demand for uranium and nuclear fuel cycle service has continuously increased. The radioactive waste and spent fuel has also been rapidly accumulated, and radioactive waste management is one of the important concerns in the Korean nuclear community. A new radioactive waste management plan was proposed by the Ministry of Commerce, Industry, and Energy in January 1997 and was approved by the Atomic Energy Commission in September 1998. According to the new plan, a low- and intermediate-level radioactive waste repository will be constructed by 2008, and spent fuel will be stored at each nuclear power plant site until interim storage facilities are constructed in 2016.The site-securing program is currently underway. SPENT FUEL MANAGEMENT The effective management of spent fuel remains a challenge for the future of the nuclear industry. The current at-reactor (AR) storage capacities of PWRs and CANDUs are 4996 tU and 4807 tU, respectively. The cumulative amount of spent fuel by the year 2002 reached about 2893 tU from the existing PWRs and 3089 tU from the CANDUs. Using the above to generate a long-term projection, it can be estimated that approximately 11,000 tU and 20,000 tU of spent fuel would be accumulated by the years 2010 and 2020, respectively. The accumulated amount of spent fuel and the expected year of losing full core reserve in each power station in Korea are shown in Table 2, as of December 2002. The policy for spent fuel management in Korea is based on the guidelines provided by the Korea Atomic Energy Commission (AEC), which is the nation’s top policy-making body on nuclear energy. The government has not yet established a definite policy on whether to recycle or to permanently dispose of its spent fuel for long-term management. The AEC set a goal for spent fuel interim storage as a mid- and long-term expedient. The government effort to construct a centralized interim storage facility for spent fuel and a repository for radioactive waste packages had come to nothing due to strong dissension about the site acquisition from the local communities. After the Guleop Island Project was

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop dealt a final blow in 1995 with the confirmation of active fault zones near and along the island during the site investigation, attempts to secure a site were started again at the beginning of the new millennium. The Nuclear Environment Technology Institute (NETEC) of Korea Hydro and Nuclear Power Co., Ltd. (KHNP) is an organization dedicated to a new site-securing program under governmental supervision. Site selection involves three basic principles: voluntary subscription of local governments, democratic and open procedures for public acceptance, and financial support programs for the local community. In this regard, continuing efforts for the improvement of safety and reliability, which are the most important objectives in the National Radioactive Waste Management Program in Korea, are needed. According to the revised spent fuel management plan announced by the government in September 1998, a centralized interim storage facility will be completed by the year 2016. The storage system, dry or wet, will be determined by considering the circumstances of the facility site and the research and development progress at that time. The facility is to be run on the 2000 tU scale in its early stage and will be expanded gradually to a total scale of 20,000 tU, as needed. Spent fuel generated will be stored at the reactor sites until the year 2016. As shown in Table 2, the current storage capacities at reactor sites are insufficient to meet the target year of 2016 for operation of the centralized interim storage facility. Therefore, the expansion of AR storage capacity is being implemented at each site, taking into consideration an appropriate combination of technical and economic factors. For PWRs the AR expansion is currently being carried out by transshipment between neighboring units and re-racking with high-density storage racks, which increase the storage density by using boral or borated stainless steel neutron absorbers, have been installed partially or fully in spent fuel pools. Storage density was increased to about 200 percent by replacing old storage racks with the high-density storage racks. For a while this type of temporary measure will be taken into account to expand the AR storage capacities. In the case of the CANDU reactors, spent fuel bundles, after at least six years of cooling in the spent fuel bay, are put into stainless steel baskets and TABLE 2 Status of AR Spent Fuel Storage in Korea as of July 2002 Site Location No. of Units Storage Capacity (tU) Cumulative Amount (tU) Year of Losing Full Core Reserve Gori 4 1737 1288 2008 Yonggwang 6 1696 895 2008 Uljin 4 1563 710 2007 Wolsung 4 4807 3089 2006 Total   9803 5982  

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop transferred to the onsite concrete silo-type dry storage facility. A silo can hold nine fuel baskets, and each basket accommodates 60 bundles. Additional dry storage facilities for CANDU spent fuel will be constructed as needed. RESEARCH AND DEVELOPMENT STATUS ON FUEL CYCLE BACK-END TECHNOLOGY The Atomic Energy Act of Korea stipulates that the minister of science and technology shall formulate the National Atomic Energy Research and Development Program according to a sector-by-sector implementation plan. Originally the National Mid- and Long-Term Atomic Energy Research and Development Program was launched in June 1992 as a 10-year (1992–2001) program. It was modified into a new research and development program to be implemented for the 1997–2006 term, to take account of the major changes in national and international situations. The program is being carried out and is funded by both the government budget and the atomic energy research and development endowment fund. The back-end fuel cycle area of the Intermediate and Long-Term Research and Development Program covers the following projects: (1) DUPIC (direct use of spent PWR fuel in CANDU reactors); (2) high-level waste disposal; (3) the advanced spent fuel conditioning process (ACP); and (4) the pyro process for partitioning and accelerator-driven systems (ADS) for transmutation. DIRECT USE OF SPENT FUEL Generally, approximately 0.6 percent fissile plutonium and 0.9 percent uranium-235 (U-235) are contained in the spent PWR fuel with a discharge burn-up of 35 MWd/kgU. Hence, spent PWR fuel is potentially an attractive energy resource for recycling in a CANDU reactor. From this context a broad feasibility study was performed from 1991 to 1993 in order to identify any feasibility issues of a fundamental nature for the DUPIC fuel cycle concept. This concept is based on the idea that the spent PWR fuel material is fabricated directly into CANDU fuel without any intentional separation of fissile materials and fission products. The fuel materials always remain highly radioactive to prevent any diversion of sensitive nuclear material. Thus, by taking advantage of Korea’s strategy of using both PWR and CANDU, the DUPIC fuel cycle has been developed with keen interest as an alternative of spent fuel management in a proliferation-resistant way. In 1992 appropriate agencies of Korea and Canada and the U.S. Department of State agreed to cooperate on a study on dry recycling of spent PWR fuel into CANDU reactors in Korea. Seven dry recycling options were investigated. These options, involving only mechanical and/or thermal processes, can be referred to collectively as DUPIC fuel cycle options. Of these options the OREOX (oxida-

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop tion and reduction of oxide fuel) option was chosen as the most promising method for the DUPIC fuel cycle, considering technical feasibility, safeguards, and so forth. Based on this feasibility study the experimental verification program has been implemented in tripartite cooperation. In an earlier stage of the program the fundamental works led by Atomic Energy of Canada Limited (AECL) on the DUPIC fuel fabrication process and reactor physics assessment were carried out. Three DUPIC fuel elements were fabricated, and have been irradiated in the NRU research reactor (National Research Universal reactor at AECL’s Chalk River Laboratories). The post-irradiation examination for the two elements removed from NRU at 10 MWd/kgHM and 16 MWd/kgHM burn-up have already been performed. A comprehensive research and development program has been implemented at the Korean Atomic Energy Research Institute (KAERI) to experimentally verify the DUPIC fuel cycle concept in international cooperation with Canada, the United States, and the International Atomic Energy Agency. In Phase II of the Experimental Verification Program, which was carried out in full momentum until 2001, the proliferation-resistant dry process has been developed for direct recycling of spent PWR fuel in CANDU reactors. Following small-scale hot cell experiments at the post-irradiation examination facility (PIEF) to characterize DUPIC powder/pellets using actual spent PWR fuel, a main DUPIC fuel fabrication campaign was started to fabricate the DUPIC fuel pellets and elements for the irradiation test at a research reactor. From the start of this experiment until the year 2002 a total of 10 kg of spent PWR fuel that has undergone a nominal burn-up of 35,500 MWd/tU was fabricated into DUPIC fuel pellets and elements. On the basis of the process conditions developed by the DUPIC powder/pellet characterization study, DUPIC pellets and elements were successfully fabricated in a remote manner. The fabricated DUPIC elements were loaded into the HANARO research reactor for the irradiation test. The major achievements are summarized below. Quality DUPIC fuel has been remotely fabricated in hot cells. The in-reactor performance of DUPIC fuel has been verified through the irradiation tests in research reactors and post-irradiation examinations. The compatibility of DUPIC fuel with a CANDU reactor system has been verified. Significant progress has also been accomplished in developing the DUPIC safeguards system in close collaboration with the United States. The DUPIC fuel cycle has been found to be economically feasible compared with the once-through cycle. During Phase III, scheduled to take place from 2002 to 2007, more intensive works on the symbiotic fuel cycles will be carried out in international cooperation between Korea, Canada, the United States, and the IAEA.

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop High-Level Waste Disposal KAERI initiated research and development activities on high-level waste disposal technology given that it will be required for long-term consideration of the nuclear energy strategy regardless of fuel cycle options. The current research and development activities are focused on the performance assessment in the long-term postclosure period and a study to set up a Korean reference disposal system. At this moment four major projects are underway in KAERI: (1) a total system performance assessment; (2) disposal system development; (3) geoenvironmental science research: and (4) a radionuclide migration study. The Phase III study (approximately 2002 to 2007) is being carried out and covers the following research items: Korea standard reference disposal system reference engineered barrier system (EBS) development through spent fuel characteristics cost and sensitivity analysis strategic national disposal plan and scenario performance assessment multidimensional probabilistic safety assessment (PSA) code development cyber research and development platform development flow visualization lab provision assessment of deep geological environmental condition validation of performance of high-level waste disposal system engineered barrier systems (EBS) performance experiments in engineer ing scale radionuclide migration experiments in large rock block construction and operation of underground research tunnel at KAERI site Advanced Spent Fuel Conditioning Process With the volume reduction perspective of the spent fuels to be stored and/or disposed of, the Advanced Spent Fuel Conditioning Process, a so-called lithium reduction process, has been under development in KAERI since 1997. Technical goals of advanced spent fuel conditioning are divided into three major areas: (1) active demonstration of the lab-scale process system; (2) technical and economic verification of the process concept and development of innovative technologies to simplify process systems and to reduce costs (inactive components have been developed since 1997); (3) and the installation of a lab-scale mockup, which was completed in 2000. Tests and modification of mockup facilities are

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop being performed. The process system will be optimized by using mockup facilities by 2003. Nuclear materials control and accounting technology for this process is being developed. More detailed research and development items are being performed as follows: optimization of process systems by using mockup facilities experimental verification of oxide reduction chemistry automation and remotization of all unit operations and material transfers between operations development of nuclear materials control and accounting technology establishment of continuous uranium metal casting technology selection and optimization of dry storage systems The planned launch date of the Phase III study of this project is 2004, and the study will cover lab-scale verification of process concepts, demonstration of nuclear material accountability and system safeguardability, verification of technical and economic feasibility of the process concepts, and the establishment of a roadmap for further research and development. Pyroprocess for Partitioning and ADS for Transmutation Pyrochemical partitioning technology development in Korea was initiated on the basic concepts of adoption of the proliferation process and transmutation of transuranium (TRU) and long-lived fission products (LLFP) in the hybrid power extraction reactor (HYPER) system. Key technologies in this area were defined as follows: preparation of metal halides, electrorefining and electrowinning, reductive extraction by solvent metals, and salt regeneration. On the basis of the fundamental study conducted in Phase I, KAERI’s current research and development effort in the Phase II study (2001–2003) is focused on the following items: development electrorefining technology to recover uranium and TRU (surrogate material) in LiCl-KCl molten salt development of electrowinning and cadmium distillation technologies to reduce uranium content further in TRU/RE(U) metal and TRU (surrogate) from liquid cadmium cathode, respectively core optimization in terms of neutronic performance for ADS system corrosion testing of structural material (HT-9, 9Cr-2WVTa steels) against lead-bismuth coolant in static conditions development of fuel fabrication technology using simulated material (uranium-zirconium)

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop The research and development of the phase beginning in 2004 will cover the improvement of liquid metal cathodes to reduce rare earth (RE) content further, update the electrowinning process to minimize uranium content in the recovered TRU/RE(U) metal, complete a conceptual core design for ADS, specifically a Pb-Bi corrosion test in dynamic conditions (using KAERI facility), and irradiation experiments for the transmutation characteristics of FP using the HANARO research reactor. SUMMARY OBSERVATIONS The Republic of Korea has 14 PWRs and 4 CANDUs with a total capacity of 15.7 GWe currently in commercial operation. An ambitious plan has been established to expand the total installed nuclear capacity up to 26.1 GWe by the year 2015. The cumulative amount of spent fuel generated by July 2002 in Korea reached about 6000 tU. Long-term projections indicate that approximately 20,000 tU of spent fuel will be accumulated by 2020. An away-from-reactor interim storage facility, which will be run on the initial capacity of 2000 tU scale, is planned to be completed by the year 2016. The Republic of Korea continues research and development activities in search of an optimal option for spent fuel management, keeping in mind the long-term perspective of nuclear power use, which has been and should be a vital component of a growing economy and environmental protection. According to the National Mid- and Long-term Atomic Energy R&D Program launched in 1992, the back-end fuel cycle area covers DUPIC, high-level waste disposal, advanced spent fuel conditioning process (ACP), pyroprocess for partitioning, and ADS for transmutation. The basic concept of the DUPIC fuel cycle is to directly fabricate the CANDU fuel from the spent PWR fuel by using thermal/mechanical processes at hot cells without the separation of fission products and transuranic elements. Since 1991 KAERI has successfully fabricated several DUPIC fuel elements remotely in the hot cell, and the performance evaluation through the irradiation tests at the HANARO research reactor is under way. The main purpose of the HLW disposal technology development program started in 1997 is to establish a Korean standard reference for HLW disposal systems by 2006. The basic concept is to encapsulate the intact spent fuel in the corrosion resistant container; the packaged spent fuels are then to be disposed of in a mined underground facility located at about several hundred meters below surface in a crystalline rock mass. The concept of the ACP is to convert spent oxide fuel into a metallic form in a high-temperature molten salt in order to reduce the heat power, volume, and radioactivity of the spent fuel. The main objective of the ACP is to treat PWR spent fuel for long-term storage and eventual disposal in a proliferation resistant

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An International Spent Nuclear Fuel Storage Facility: Exploring a Russian Site as a Prototype - Proceedings of an International Workshop and cost effective way. Moreover, the electrolytic reduction method of the ACP can contribute to the innovative nuclear energy system as a key technology for the preparation method of the metallic fuel. The purpose of the study on the pyroprocess for partitioning and ADS for transmutation is to propose a conceptual design of the HYPER system by 2006. In this study, the HYPER system, comprising a proton accelerator and a subcritical reactor, is considered an appropriate one for the Korean situation, with priority given to the nonproliferation attributes of the treatment of nuclear fissile materials in the back-end fuel cycle.