Jong-Youl Lee

Concept of a Korean Reference Disposal System for Spent Fuels

A deep geologic disposal system for the spent fuels from nuclear power plants has been developed since this program was launched in 1997 in Korea. In this paper, the concept of a Korean reference high-level waste (HLW) vertical disposal system (KRS-V1) is described. Though no site for the underground repository has yet been specified in Korea, a generic site with a granitic rock is considered for a reference spent fuel repository design. The depth of the repository is assumed to be 500 m. The repository consists of a disposal area, a controlled area, and an uncontrolled area. The disposal area consists of disposal tunnels, panel tunnels, and a central tunnel. In the controlled area and the uncontrolled area, there are technical rooms and tunnels and/or shafts to connect them to the ground level, respectively. The repository will be excavated, operated, and backfilled in several phases including an underground research laboratory (URL) phase. The result of this concept development will be used for an evaluation of its feasibility, analyses of its long-term safety, information for public communication, and a cost estimation, among others.

Characteristics of a Geological Disposal System for the Increasing Burn-up of Spent Nuclear Fuel in Korea

The characteristics of a geological disposal system that can accommodate increasingly higher burn-up levels of spent fuel were assessed based on the Korea reference disposal system concept. First, a status investigation that included a projection of spent fuel quantity versus burn-up was carried out to demonstrate the trend toward higher burn-up levels. Next, the main features of the Korea reference disposal system were introduced. Finally, the disposal tunnel length, excavation volume, and raw materials (e.g., a cast insert, copper, bentonite and backfill) necessary for a disposal system were comprehensively analyzed to define the characteristics and overall effects on geological disposal at increasingly higher burn-up levels. Our study determined that it is reasonable to use a canister containing 4 spent fuel assemblies with burn-up levels up to 50GWD/MTU, while a canister containing 3 spent fuel assemblies can accommodate burn-up levels beyond 50GWD/MTU. A remarkable increase of 33% in disposal tunnel length and that of 30% in excavation volume were observed as the burn-up increased from 50 to 60GWD/MTU. However, this was offset by a reduction of 17% in raw materials used in canister fabrication. Therefore, it seems that spent fuel at increasingly higher burn-up levels is not a serious concern for deep geological disposal in Korea.

PYROPROCESS WASTE DISPOSAL SYSTEM DESIGN AND DOSE CALCULATION

PWR spent fuels produced in the Republic of Korea are expected to be recycled by pyroprocess in the long term future. Even though pyroprocess waste amounts can be smaller than that of PWR spent fuel assembly in case of direct disposal, this process essentially will produce various and unique radioactive wastes. The goals of this article are to characterize these wastes, calculate the amount of wastes, design disposal systems for each waste and evaluate the radiation safety of each system by dose assessment. The absorbed dose results of the metal and ceramic waste for the engineering barrier system (EBS) showed 2.21 x 10 -2 Gy/h and 1.15 x 10 -2 Gy/h, which are lower than the recommended value of 1 Gy/h. These results confirmed that the newly proposed disposal systems have a safety margin for the radiation produced from each waste.

Implementation of a virtual environment for development of a spent fuel disposal process

Since the program for the development of a deep geological disposal system for the spent fuel from nuclear power plants was launched in 1997 as a national program in KOREA, a pre-conceptual design of a disposal system for spent fuel in a deep geological host rock formation was carried out and the Korean reference spent fuel vertical disposal system (KRS-VI) is concurrently being developed. In this study, a virtual environment system for developing a spent fuel disposal system and reviewing and analyzing the process for an optimization was implemented. This system consisted of a 3-D graphic simulation module and an analysis module, and was developed in three stages. To develop this system, the design bases like the fuel canisters, the production rate and the functions of the facility, and the detailed processes were reviewed. With the graphic simulation module, the disposal processes were simulated in a virtual work cell according to a process scenario. Also, with the analyses module, the spent fuel disposal processes were preliminarily analyzed. It is necessary to verify this system more specifically and analyze the disposal process in detail. This virtual system can be effectively used for developing a process and the process equipment, as well as optimizing the process for a spent fuel disposal in a deep geological host rock.

A Study on the Conceptual Development for a Deep Geological Disposal of the Radioactive Waste from Pyro-processing

A long-term R&D program for HLW disposal technology development was launched in 1997 in Korea and Korea Reference disposal System(KRS) for spent fuels had been developed. After then, a recycling process for PWR spent fuels to get the reusable material such as uranium or TRU and to reduce the volume of radioactive waste, called Pyro-process, is being developed. This Pyro-process produces several kinds of wastes including metal waste and ceramic waste. In this study, the characteristics of the waste from Pyro-process and the concepts of a disposal container for the wastes were described. Based on these concepts, thermal analyses were carried out to determine a layout of the disposal area of the ceramic wastes which was classified as a high level waste and to develop the disposal system called A-KRS. The location of the final repository for A-KRS is not determined yet, thus to review the potential repository domains, the possible layout in the geological characteristics of KURT facility site was proposed. These results will be used in developing a repository system design and in performing the safety assessment.

A Graphic Simulator for the Development of a Spent Fuel Encapsulation Process in a Disposal Canister

The development of a deep geological disposal system for the spent fuel from nuclear power plants in Korea has been carried out since this program was launched in 1997 and a pre-conceptual design of the Korean Reference HLW vertical disposal system (KRS-VI) is being developed. In this study, a graphic simulator for a spent fuel encapsulation process in a disposal canister is developed to review and analyze the process for an optimization and to develop the process equipment. The process equipment for handling high level radioactive materials like spent fuels is operated in a hot cell, due to the high radioactivity. Thus, this equipment should be maintained and repaired optimally by remotely operated maintenance tools. To do this, the design bases like the fuel canisters, the production rate and the functions of the facility are reviewed. Also, the detailed processes from receiving the spent fuel to a shipping of the disposal canister to an underground facility are described. The facilities and parts of the equipment are modeled graphically in three dimensions, and they are assembled as a virtual work cell. The encapsulation processes are simulated in a virtual work cell according to a process scenario. This simulator will be used for analyzing and optimizing the spent fuel encapsulation process and developing the process equipment