Chang-Lak Kim

Deterministic performance assessment for a conceptual repository for low- and intermediate-level wastes in Korea

The release of radionuclides from the conceptual low- and intermediate-level radioactive waste (LILW) repository in Korea is analyzed by establishing a multicompartment model. The model takes into account the vault-array configuration consisting of multiple waste types, multimember radioactive decay chains, and radionuclide transport through the water-unsaturated regions and water-saturated aquifer. Observations of the repository performance have been made with the radiological exposure dose rates and with the radiotoxicities in the environment. Numerical results show that, among all the radionuclides in the waste, 129I is the predominant contributor to the overall peak exposure dose rate. The peak exposure dose rate of 129I can be affected by a migration distance in the geosphere and the vault-array configuration. Reducing the initial inventory of 129I stored in the waste vaults or spreading its release over a longer time period by modification of the engineered barrier system would effectively reduce the exposure dose rate because the release rate of 129I from the repository is reduced. The total radiotoxicity in the environment is dominated by 129I at early times and by 238U and its daughters after 106 yr. Because of the long half-lives of these nuclides, the radiotoxicity in the environment is insensitive to the vault-array configuration or to the transport distance in the geosphere.

An Integrated Safety Assessment System for Near-Surface Disposal of Low- and Intermediate-Level Radioactive Waste in Korea

An integrated safety assessment system to be used for evaluation of near-surface disposal concept has been developed within the framework of safety assessment methodology taken for low- and intermediate-level radioactive waste disposal in Korea. It is to provide an evaluation of the safety of the disposal system in a clear, comprehensive and well-documented manner, and to integrate the results into a defensible package showing reasonable assurance of compliance with regulatory requirements for licensing application. This system is made up of two key components, a system-level safety assessment code and an input database/quality assurance module for safety assessment, which both are interfaced with each other.Copyright

U.S. Policy and Current Practices for Blending Low-Level Radioactive Waste for Disposal

In the near future, many countries, including the Republic of Korea, will face a significant increase in low level radioactive waste (LLW) from nuclear power plant decommissioning. The purpose of this paper is to look at blending as a method for enhancing disposal options for low-level radioactive waste from the decommissioning of nuclear reactors. The 2007 U.S. Nuclear Regulatory Commission strategic assessment of the status of the U.S. LLW program identified the need to move to a risk-informed and performance-based regulatory approach for managing LLW. The strategic assessment identified blending waste of varying radionuclide concentrations as a potential means of enhancing options for LLW disposal. The NRC’s position is that concentration averaging or blending can be performed in a way that does not diminish the overall safety of LLW disposal. The revised regulatory requirements for blending LLW are presented in the revised NRC Branch Technical Position for Concentration Averaging and Encapsulation (CA BTP 2015). The changes to the CA BTP that are the most significant for NPP operation, maintenance and decommissioning are reviewed in this paper and a potential application is identified for decommissioning waste in Korea. By far the largest volume of LLW from NPPs will come from decommissioning rather than operation. The large volumes in decommissioning present an opportunity for significant gains in disposal efficiency from blending and concentration averaging. The application of concentration averaging waste from a reactor bio-shield is also presented.

The Study for Reducing the Borrowing Cost for LILW Disposal

The repository for the disposal of LILW which is generated from nuclear power plants and industries is expected to be completed in 2014. For the disposal of LILW, it is important to secure a disposal facility itself, but it is also very important to establish a reasonable charging system which all shareholders are satisfied with. Korea’s disposal fee for LILW is higher than other countries’ fee, which is a burden to waste generators as well as the waste management organization. The partial reason for the high disposal fee is put on the high social and construction cost when compared with other countries. However the major reason is put on the excessive borrowing cost that is used for the construction of the LILW disposal facility. In this study, we proposed the way to reduce the excessive borrowing cost for sustainable project managements of LILW disposal by analyzing a cost structure.

Development of Disposal Option for Radioactive Waste

The development of a lasting solution to radioactive waste management is a critical issue for future nuclear applications. When assessing radioactive waste disposal options factors such as volume of waste and sustainability of the plan must be considered. This paper describes basic plans for the disposal of Low- and intermediate-level radioactive wastes (LILW) expected to be generated from nuclear power plants for countries starting nuclear power program for the first time. The purpose of this paper was to develop a disposal option for Low- and intermediate level radioactive wastes for new comer countries planning to build at least two nuclear power units. A LILW disposal plan was developed by considering countries’ radioactive waste generation data from pressurized water nuclear reactors. An on-site storage facility of 1,000 m3 for LILW at NPPs sites for a period 10 years pending final disposal was recommended. It was concluded that storage and disposal processes are complementary with each other, therefore; both programs should be complemented for effective management and control of radioactive wastes. This study is important as an initial implementation of a national Low- and intermediate level wastes (LILW) disposal program for countries planning to build nuclear power plants for the first time.© 2013 ASME