Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Level 1 probabilistic safety assessment of supercritical-CO2-cooled micro modular reactor in conceptual design phase

  • So, Eunseo (Department of Energy Systems Engineering, Chung-Ang University) ;
  • Kim, Man Cheol (Department of Energy Systems Engineering, Chung-Ang University)
  • Received : 2020.02.28
  • Accepted : 2020.07.22
  • Published : 2021.02.25
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Abstract

Micro reactors are increasingly being considered for utilization as distributed power sources. Hence, the probabilistic safety assessment (PSA) of a direct supercritical-CO2-cooled fast reactor, called micro modular reactor (MMR), was performed in this study; this reactor was developed using innovative design concepts. It adopted a modular design and passive safety systems to minimize site constraints. As the MMR is in its conceptual design phase, design weaknesses and valuable safety insights could be identified during PSA. Level 1 internal event PSA was carried out involving literature survey, system characterization, identification of initiating events, transient analyses, development of event trees and fault trees, and quantification. The initiating events and scenarios significantly contributing to core damage frequency (CDF) were determined to identify design weaknesses in MMR. The most significant initiating event category contributing to CDF was the transients with the power conversion system initially available category, owing to its relatively high occurrence frequency. Further, an importance analysis revealed that the safety of MMR can be significantly improved by improving the reliability of reactor trip and passive decay heat removal system operation. The findings presented in this paper are expected to contribute toward future applications of PSA for assessing unconventional nuclear reactors in their conceptual design phases.

Keywords

Acknowledgement

This research was supported by the Chung-Ang University Graduate Research Scholarship in 2018. This work was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT), Republic of Korea (2017M2B2B1071973). We thank Professor Jung Ik Lee and Mr. Bong Seong Oh of Korea Advanced Institute of Science and Technology for sharing the input model for MMR used in the transient analysis.

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