In Korea, two types of spent nuclear fuels (SNFs) are generated, pressurized light water reactor type (PWR) and pressurized heavy water reactor type (PHWR; CANDU), that differ greatly in size, decay heat, and radioactive characteristics. Technology development for the disposal of SNFs has mainly focused on PWR SNFs that are large in size and have extremely high decay heat and radioactivity. However, CANDU SNFs should be considered differently from PWR SNFs in deep geological disposal systems because their characteristics significantly differ from those of PWR SNFs in terms of their dimensions, number of SNF bundles, and handling systems in nuclear power plant sites. In this paper, after reviewing the status of the CANDU SNF disposal concept by Canada and Korea, concepts related to the direct geological disposal of CANDU SNFs were described, and two concepts were proposed based on the results of the development. The engineered barrier systems developed using these two concepts were comparatively analyzed in terms of disposal safety, disposal efficiency, and technical maturity. Based on the results of the comparative analyses, a vertical-type emplacement disposal concept was determined as a reference concept for the deep geological disposal of CANDU SNFs.

I. Introduction
2. Status on Development of DisposalConcepts for CANDU SNFs
    2.1 Status in Canada
    2.2 Status of CANDU SNF Disposal ConceptDevelopment in Korea
3. Proposal of Two Disposal Concepts forCANDU SNFs
    3.1 Characteristics of CANDU SNFs and StorageBasket
    3.2 Disposal Concept of Vertical EmplacementType
    3.3 Disposal Concept of Horizontal EmplacementType
4. Comparative Analysis of Two DisposalConcepts
    4.1 Disposal Container Lifespan
    4.2 Radionuclide Migration in BentoniteMaterial
    4.3 Disposal Efficiency
    4.4 Technology Maturity
    4.5 Selection of Reference Disposal Conceptfor CANDU SNFs
5. Conclusions
Conflict of Interest
Acknowledgements
REFERENCES

• Jongyoul Lee(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea) Corresponding author
• Heuijoo Choi(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Changsoo Lee(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Jung-Woo Kim(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Sunghoon Ji(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)
• Dongkeun Cho(Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 34057, Republic of Korea)