The Korea Atomic Energy Research Institute (KAERI) has developed geological repository systems for the disposal of high-level wastes and spent nuclear fuels (SNFs) in South Korea. The purpose of the most recently developed system, the improved KAERI Reference Disposal System Plus (KRS+), is to dispose of all SNFs in Korea with improved disposal area efficiency. In this paper, a system-level safety assessment model for the KRS+ is presented with long-term assessment results. A system-level model is used to evaluate the overall performance of the disposal system rather than simulating a single component. Because a repository site in Korea has yet to be selected, a conceptual model is used to describe the proposed disposal system. Some uncertain parameters are incorporated into the model for the future site selection process. These parameters include options for a fractured pathway in a geosphere, parameters for radionuclide migration, and repository design dimensions. Two types of SNF, PULS7 from a pressurized water reactor and Canada Deuterium Uranium from a heavy water reactor, were selected as a reference inventory considering the future cumulative stock of SNFs in Korea. The highest peak radiological dose to a representative public was estimated to be 8.19×10-4 mSv‧yr-1, primarily from 129I. The proposed KRS+ design is expected to have a high safety margin that is on the order of two times lower than the dose limit criterion of 0.1 mSv‧yr-1.

1. Introduction
2. Methodology
    2.1 Repository System of KRS+
    2.2 Conceptual Model
    2.3 Computational Model
3. Input Parameters for the Assessment
4. Results and Discussion
    4.1 Major Radionuclides Contributing RadiologicalImpact
    4.2 Contribution by Source Terms
    4.3 Comparison between KRS and KRS+:CANDU-V and CANDU-H
5. Conclusion
REFERENCES

• Heejae Ju(Korea Atomic Energy Research Institute) Corresponding Author
• In-Young Kim(Korea Atomic Energy Research Institute)
• Youn-Myoung Lee(Korea Atomic Energy Research Institute)
• Jung-Woo Kim(Korea Atomic Energy Research Institute)
• Yongsoo Hwang(Korea Atomic Energy Research Institute)
• Heui-joo Choi(Korea Atomic Energy Research Institute)
• Dong-Keun Cho(Korea Atomic Energy Research Institute)