The uranium conversion facility (UCF) located at KAERI was operated from 1982 to 1992. After the localization of nuclear fuel fabrication technol­ogy, it was shut down in 1993. UCF decommissioning began in 2001 and radioactive waste from UCF has been stored in a temporary storage build­ing in the conversion facility. All the wastes are contaminated mainly with natural uranium. Currently, the dismantling of 26 out of 27 rooms at UCF has been conducted (Fig. 21.14) , including decontamination of concrete surfaces, removal of contaminated soil, and completion of treatment of sludge waste in a lagoon.

Research achievements to date are:

• development of volume reduction technology for large amounts of radi­oactive concrete wastes

• development of soil decontamination technology for remediation of nuclear sites after decommissioning

• development of melting technology for decontamination of a hundred tons of slightly contaminated metallic wastes generated from KRR-1 and 2 and UCF

• development of technologies for safe management of irradiated graph­ite arising from decommissioning of KRR-1 and 2

• development of a database system for management and data assessment from D&D activities

• development of chemical decontamination technology applicable to metal wastes contaminated with UN (uranium nitride), AUC (ammo­nium uranyl carbonate), and UO2 generated by dismantling UCF

• development of the safety assessment methodology of the decommis­sioning process

• simultaneous remote measurement of alpha/beta contamination in highly contaminated facility

• decontamination technology development

• waste treatment technology development.

Major R&D activities are now concentrated on development of the decommissioning waste reduction and recycling technology for commercial NPPs and nuclear facilities.

21.5 Conclusion

Given the scarcity of Korea ’s primary energy resources, nuclear power is vitally important as an engine of growth for the nation. Korea has followed a set of consistent policies and executed steady plans to expand nuclear power. With a significant share of nuclear power in the energy mix, the disposal of RAW and SF is looming large as a high-visibility national issue. A low-and intermediate-level waste disposal site has been selected and the facilities are currently under construction with its full operation expected in 2014. Spent fuel management has also become imminent. Although no satisfactory resolution is in sight in the foreseeable future, various options are being studied with the government ’s keen interest and full support. Korea has also designed a rigorous process for decontaminating waste materials.

TRIGA Mark-II, the first Korean research reactor (KRR-1), started opera­tion in 1962, and the second, TRIGA Mark-III (KRR-2) located in Seoul, has been operational since 1972. These two research reactors, located at the former KAERI site in Seoul, were permanently shut down at the end of 1995. As a replacement for the TRIGA research reactors, the 30 MWth multipurpose HANARO research reactor was constructed in 1995 located at KAERI in Daejeon and has operated successfully since then. The D&D of KRR-1 and 2 research reactors was started in January 1997. The decommissioning plan, environmental impact assessment and decommis­sioning design were carried out in 1998. In July 1998, all SF from the TRIGA Mark-II and III reactors was safely transported to the US. At the end of 1998, the decommissioning plan was submitted to the Ministry of Educa­tion, Science, and Technology for licensing, and the Korea Institute of Nuclear Safety (KINS) reviewed it in 1999. The report of their review was considered in January 2000 by the Expert Group for Environmental Radia­tion, one of the four groups of the Nuclear Safety Commission, and the recommendation made by that Expert Group was submitted to the Com­mission for its final approval. At the moment, KRR-2 has been completely dismantled, whereas the decommissioning of KRR-1 was started in 2011 and will be completed by the end of 2014.

Radioactive wastes from the decommissioning of KRR-1 and 2 were classified according to their characteristics and radioactivity levels, packed into 200 L drums or 4 m3 containers and stored in the reactor hall of the KRR-2 according to the process scheme of radioactive waste treatment from decommissioning sites, shown in Fig. 21.12 Radioactive waste gener­ated from KRR-1 and 2 contains 60Co and 152Eu as major radionuclides in the activated waste and 60Co and 137Cs in the case of the contaminated waste. The current status of KRR-1 and 2 is shown in Fig. 21.13, and complete D&D of both will be performed within a few years later.

Korean decommissioning and decontamination (D&D) work on the retired research reactors KRR-1 and 2 and the uranium conversion facility (UCF) at KAERI is under way. Hundreds of tons of metallic and concrete wastes are expected from the D&D of these facilities. Therefore, countermeasures are being taken to deal with the amount of waste generated by dismantling these retired nuclear facilities. Recycling or volume reduction of the large quantities of metallic and concrete wastes are key waste management options due to the difficulty in securing a waste disposal site in Korea and the capacity limitation of the temporary waste storage facility at KAERI. Recycling or volume reduction through application of appropriate treat­ment technologies has merits from the viewpoint of resource recycling as well as a decrease in the amount of waste to be disposed of resulting in reduced disposal cost and enhanced disposal safety.

The international nuclear community recognizes the potential of nuclear energy systems to cope with increasing energy demand and international protocol for climate change even after the Fukushima accident. Interna­tional cooperative programmes have been initiated to develop new systems that secure stable energy supply and have improved public acceptance, safety, and cost-effectiveness. The Republic of Korea is actively participat­ing in these programmes currently, such as the Generation IV International Forum (GIF) and the International Project on Innovative Nuclear Reactors and Fuel Cycle (INPRO).

Korea has been a chartered member of GIF since 2000 and plays a sig­nificant role in the development of Gen-IV. GIF was organized for collabo­rative development of new generation nuclear energy systems aiming for 2030 that can be accepted by the public and the energy market with excel­lent technical features and competitive economics, with 13 members leading nuclear utilization and development in the world taking part in GIF. GIF selected six systems of the most promising concepts as the Generation IV nuclear energy systems (Gen-IV) in 2002 and has been conducting collabo­rative R&D for each system through multilateral agreements since 2005. Korea focuses on SFR (sodium-cooled fast reactor-see Fig. 21.10) and

VHTR (very high temperature reactor) among the six Gen-IV systems. SFR is expected to use and recycle uranium resources effectively and mini­mize high-level radioactive waste with proliferation resistant fuel cycles. Korea is participating in six collaborative projects, tackling safety and oper­ation, advanced fuels, and component design and balance of plant in SFR. Korea’s Long-term Development Plan for Future Nuclear Energy Systems, approved in December 2008, also presents a milestone and deliverables of SFR and pyro-processing technology.

KAERI has been developing pyro-processing technology (Fig. 21.10) for recycling useful resources from spent fuel since 1997. The process includes pre-treatment, electro-reduction, electro-refining, electro-winning, and a waste salt treatment system. The removal of transuranic elements (TRU), Cs, and Sr from spent fuel allows the repository burden to be reduced by a factor of 100, compared with the case without removal. Fission products (FP) are recovered and transferred to a repository. As a result of pyro — processing, both repository efficiency and uranium usage are increased up to 100-fold with strong proliferation resistance.

According to the analysis of KAERI, spent nuclear fuel stock at the end of this century can be maintained at a level lower than that of today by introducing SFRs coupled with pyro-processing technology in the 2030s (Fig. 21.11 ).

to be renewed in 2014. In 2008, the IAEA approved an electro­refining laboratory — the Advanced Spent Fuel Conditioning Process Facil­ity (ACPF) at KAERI which is to be built by 2011 and expanded to engineering scale by 2012. This is envisaged as the first stage of a Korea Advanced Pyro-processing Facility (KAPF) to start experimentally in 2021 and become a commercial-scale demonstration plant in 2025. In connection with renewal of the US-ROK agreement in or by 2014, discussions are proceeding on pyro-processing.

Spent fuel generated from NPPs is stored in the spent fuel storage facility in each unit. The storage capacity for spent fuel has been expanded as a consequence of the delayed construction schedule of the away-from-reactor (AFR) interim storage in accordance with the conclusions of the 249th and the 253rd meetings of the AEC. Taking into consideration the sufficiency of spent fuel storage capacity beyond 2016, the national policy for spent fuel management, including the construction of the interim storage facility for spent fuel, shall be decided in a timely manner through national con­sensus by public consultation among the stakeholders.

To expand the spent fuel storage capacity, the utility company, Korea Hydro & Nuclear Power Co. (KHNP), is installing high density storage

racks, transferring spent fuel between units and building dry storage. High density storage racks have been installed in Kori 3 and 4, Ulchin 1, 2, 3 and 4, and Yonggwang 3 and 4. Dry storage facilities have been installed on the Wolsong site for Wolsong 1, 2, 3 and 4 units which are CANDU reactors. By adding 100 canisters in 2006, 300 canisters are installed on site. In addi­tion to the canisters, seven modules of MACSTOR (Modular Air-Cooled STORage)-400 with 3,175 mtu total capacity have been installed and in operation since May 2010.

The spent fuel storage pool of the HANARO reactor is a heavy concrete structure, lined with stainless steel plate. The vault comprises three storage lattices. The vault has enough capacity for temporarily storing new fuel as well as spent fuel to be generated during normal operation of HANARO for 20 years.

The Korean government has striven to secure a spent fuel management site since the early 1980s. However, the national policy for spent fuel man­agement including construction of the centralized spent fuel interim — storage facility was to be decided in view of domestic and international technology developments later on. The national policy for spent fuel man­agement will be decided later in consideration of domestic and interna­tional technology developments. Reprocessing activities have not been conducted in Korea.

21.1.1 Spent fuel inventory

Spent fuels can be categorized into those from commercial NPPs and those from research reactors. Spent nuclear fuels from commercial NPPs are

stored on site in spent fuel storage (water) pools or in a dry storage facility. All the spent fuels from the 17 PWRs in Korea are stored in pools on site. About half of the spent fuels from the four CANDU reactors is stored in pools and the other half is stored in dry silos or dry casks on site. As of September 2011, 5,408 tons of spent fuel from PWRs and 6,431 tons of spent fuel from CANDU reactors are stored at four sites: three sites for PWRs, one site for CANDUs (NSSC, 2011). The annual addition to the amount of spent fuel is about 690 mtu. After 2045, spent fuel stores from the CANDU reactors will be full because of decommissioning of the CANDU reactors. The capacities, inventories and types of spent fuel in storage are given in Table 21.3 (NSSC, 2011).

Spent fuel and irradiated fuel from the HANARO research reactor are stored in the storage pool on site at the Korea Atomic Energy Research Institute (KAERI). Up to 20 PWR fuel assemblies can be stored in the storage pool after irradiation tests. As of September 2011, 4 tons of spent fuel from HANARO was stored in the pool on site (NSSC, 2011). HANARO is a multi-purpose research reactor used for fuel performance testing, material irradiation testing, radio isotope (RI) production, and basic science and applications studies.

A small-scale underground research laboratory, KAERI Underground Research Tunnel (KURT) at KAERI in Daejeon, was constructed to develop a Korean disposal system for the HLW repository, including spent fuels, between March 2005 and November 2006. The KURT, with an access tunnel and two research modules, as shown in Fig. 21.8 , is located in a mountainous area inside the KAERI territory. The KURT, has a total length of 255 m with a 180 m long access tunnel and two research tunnels 75 m long in total. The maximum depth of 90 m could be effectively achieved by select­ing the tunnel direction to the peak of a mountain. The horseshoe shaped tunnel, 6 m wide and 6 m high, is located in a granite rock body (Fig. 21.8). Regardless of limited applications of KURT, which only handles naturally occurring radionuclides, the KURT facility will be a major infrastructure for validating the safety and feasibility of the suggested disposal system by various in-situ experiments:

1. Single hole heater test in rock.

2. THM (thermal-hydraulic-mechanical) behavior of engineered barrier systems (EBS).

3. EDZ (excavation disturbed zone) characteristics and mechanical stabil­ity of rock.

4. Retardation of solute migration through fractured rock.

5. Site investigation techniques.

6. Hydrogeological and geochemical baseline data (Kwon et al., 2009 ).

The current 10-year plan for mid — and long-term nuclear R&D on HLW disposal was accepted by the AEC in 1997. This plan includes a program for development of a Korean repository for HLW disposal and for the associated system performance assessment. After completion of the

combined research output of this 10-year study, the Korean government will define the direction and prioritization of further R&D activities for HLW disposal. Since 1997, KAERI has been developing a permanent dis­posal facility for HLW and a total system performance assessment (TSPA). Its current R&D activities are focused on the preliminary conceptual design of the Korean Reference Disposal System (KRS), development of the key technologies, and geo-environmental studies to confirm the KRS’s safety, as shown in Fig. 21.9. Currently, the four major projects underway at KAERI are:

1. repository system development;

2. a TSPA;

3. geo-environmental science research; and

4. construction and operation of a KAERI underground research tunnel (KURT) to demonstrate the KRS ’s performance relevant to the func­tional criteria established in the disposal concept (Fig. 21.8).

Since the creation of the legal grounds for the implementation of the project by the 1986 revision of the Atomic Energy Act (AEA), the Korean government has actively implemented the selection of the sites for radioac­tive waste disposal facilities. There have been nine failed attempts to secure a disposal site from 1986 to 2004 due to: [35] local residents voluntarily petitioned to host the facilities in ten areas, but site selection ultimately halted due to the absence of preliminary applica­tions by local government leaders. In March 2005, MKE organized the Site Selection Committee (SSC) in order to guarantee the transparency and fairness of the site selection process. The SSC, consisting of 17 civilian experts from diverse fields, managed and supervised the entire site selection process. In addition, the ‘Special Act on Support for Areas Hosting Low and Intermediate Level Radioactive Waste Disposal Facilities’ (MKE Notice No. 2005-146) was legislated and announced in March 2005 to stipu­late support for areas hosting LILW disposal facilities, including special financial support, entry fees, and relocation of the KHNP headquarters. The act also stipulated the following to enhance the democracy and transpar­ency of the selection process:

• the host area was to be selected through resident voting in accordance with the Referendum Act,

• the selection plan, site survey results, and selection process were to be implemented openly and transparently,

• open fora and discussions were to be held for local residents.

Accordingly, in June 2005, the MKE announced the candidate site selection method and procedures as well as the support to be provided to the host areas and initiated the process through an announcement regarding LILW disposal facility candidate site selection. Regarding candidate site selection procedures, as shown in Fig. 21.4, the local governors must apply to host the facilities with consent from local councils. Then, in accordance with the results of the site suitability assessment, the MKE requested local governors to conduct local referenda in appropriate regions as required by the Ref­erendum Act. Local governors proposed and held the referenda. Based on the results of local referenda, areas with the highest percentage of favorable responses were selected as the final candidate sites. Local governments that had appropriately applied to host the LILW disposal facility by August 31, 2005 were in the four areas of Gunsan, Gyeongju, Pohang, and Yeongdeok County, and these four local governments conducted referenda. In accord­ance with the results of local referenda (Table 21.2), the city of Gyeongju was selected as the final candidate site (MKE Notice No. 2005-133).

The area of the disposal site accommodates a total of 800,000 drums of LILW, and, as the first stage of construction, a rock cavern type of repository for up to 100,000 drums was chosen. However, the disposal method for further expansion will be decided depending on the nature of the site condi­tion. The disposal facility to be constructed in Gyeongju was named ‘Wolsong Low — and Intermediate-level Radioactive Waste Disposal Center’ operated by KRMC under the jurisdiction of MKE which was established on January 1,2009 (Figs 21.5 and 21.6). As of June 2012, the disposal facility is almost 90% complete (Fig. 21.7) and the date for initial operation is mid — 2014, taking into account the construction period.

In the main review phase, after completion of three rounds of Q&A, a few key technical issues (KTIs) were brought out and profiled for further intense deliberation. The KTIs that needed to be taken into consideration throughout the later part of the main review phase can be summarized as follows:

1 SILO REPOSITORY

2 CONSTRUCTION TUNNEL © OPERATING TUNNEL

© PORTAL © ACCESS SHAFT (6 RADWASTE RECEIPT/ STORAGE BLDG © RADWASTE BLDG ® SERVICE BLDG.1 UNDERGROUND (9 SERVICE BLDG.2 ‘ DISPOSAL AREA 10 OFFICE

11 GARAGE

12 SUBSTATION BLDG

13 WASTE WATER TREATMENT © BLDG.

1 14 GUARD HOUSE

^ 15 SUPER COMPACTOR BLDG.

21.5 View of the Wolsong LILW disposal center.

Gaseous RAW is mainly generated from degassing of the primary system and ventilation systems in the radiation controlled area of NPPs. Gaseous waste from the primary system is treated by gas decay tank or charcoal decay bed to reduce radioactivity, and released into the atmosphere through a radiation monitor. Gaseous waste from the building ventilation system is also exhausted under continuous monitoring through high-efficiency par­ticulate (HEPA) and charcoal filters into the environment.

The MEST addresses the maximum radioactivity concentration, ECL, for gaseous effluent being released into the atmosphere at the restricted area boundary (MEST Notice No. 2008-31). The licensee must conduct a peri­odic evaluation of the anticipated off-site dose due to gaseous effluent released into the environment, and routinely report results to the KINS. The Enforcement Decree of the AEA and the MEST Notice No. 2008-31 (Standards on Radiation Protection, etc.) prescribe discharge limits of gaseous and liquid radioactive effluents to be released from nuclear facili­ties into the environment, along with annual dose constraints of the popula­tion living around nuclear facilities.

In practice, nuclear facilities are operated with targets which are more restrictive than the discharge limits. In addition, some facilities also apply the derived release limits based on a small fraction of the dose limits for convenience for a field application. Whether related limits are met is veri­fied by periodic inspection or the examination of regular reports submitted to the regulatory body.

The radiation dose and its effect on individuals around nuclear facilities are assessed monthly by using the Off-site Dose Calculation Manual (ODCM, Reg. Guide 1.109) [US-NRC, 1977]. The assessments are based on the radioactivity of released liquid and gaseous effluents, atmospheric con­ditions, metabolism, and social data including agricultural and marine prod­ucts of the local community within a radius of 80 km.

The Korea Atomic Energy Research Institute (KAERI) in Daejeon and KHNP carry out R&D on RAW management. Treatment and disposal of HLW/SF is studied by KAERI. KHNP studies the treatment and disposal of LILW and interim storage of spent fuel. Technological developments are currently focused on the following topics: [34]

• LILW disposal and safety assessment technology

• improvement of existing technology for spent fuel storage and transpor­tation, and development of advanced spent fuel storage technology.

In addition to current use of conventional treatment methods such as evap­oration, compaction, drying and cementation, advanced technology for LILW treatment is being developed. Vitrification has been identified as the most promising innovative technology from the point of view of being environmentally sound and of being able to substantially reduce the volume of LILW, to improve the waste stability and to enhance the public accept­ance of its disposal. Vitrification immobilizes the radionuclides in a stable solid glass form and the associated volume reduction should result in effi­cient and prolonged use of a repository, which is most important for a small, densely populated country.

A feasibility study of the vitrification process was initiated in 1994 and a pilot-scale vitrification facility was installed in July 1999. This facility con­sists of an induction heater, cold crucible melter (CCM) for combustible waste, a plasma torch melter (PTM) for non-combustible waste, and an off-gas treatment system. KHNP’s research center (CRI) located in Daejeon has developed the technology with a target for commercialization of the process from 2005. The Ulchin Vitrification Facility (UVF) is the world ’s first commercial facility for the vitrification of LILW generated from NPPs using CCM technology. The construction of the facility began in 2005 and was completed in 2007. From December 2007 to September 2009, all key performance tests, such as the system functional test, the cold test, the hot test, and actual waste testing, were performed successfully. The UVF started commercial operation in October 2009 for the vitrification of LILW waste (Jo et al, 2010).

Liquid RAW can be divided into process drains, floor drains and laundry drains based on the sources of waste generation. It is mainly generated from the clean-up and maintenance processes of reactor coolant and related systems containing radioactivity. In general, liquid RAW is treated with evaporators, demineralizers, and/or filters. The effluent is released to the sea after monitoring whether the radioactivity of liquid effluent is lower than regulatory limits. It is also common for liquid wastes to be treated with ultracentrifugation, ion exchange, and reverse osmosis.

The Ministry of Education, Science, and Technology (MEST Notice No. 2008-31) prescribes the effluent control limit (ECL) for liquid effluent being discharged into the environment at the restricted area boundary. Operators
must conduct periodic assessments for the expected off-site dose due to the liquid effluent discharged into the environment, and routinely report results to the regulatory body (Korea Institute of Nuclear Safety, KINS).