Development of preliminary event trees for loss of coolant accident and loss of load event in autonomous micro modular reactor

초록

In order to make nuclear power plants (NPPs) safer and more economical, many advanced reactors are under development in many countries around the world. Several reactors have some common features such as small size, modular design, and passive safety systems. Autonomous micro modular reactor (MMR), whose conceptual design is currently ongoing in Korea, also has these design features. MMR is a direct supercritical CO2 cooled modularized fast reactor which is designed to supply power to small villages in an isolated inland area. There are many advanced features to achieve such a goal. It adopts active and passive air-cooled decay heat removal system and autonomous load following operation feature. As MMR is in its conceptual development stage, preliminary probabilistic safety assessment (PSA) may give insights for design improvements. As the first step of PSA, possible initiating events of MMR are identified by the review of other reactors with similar features. As representative cases among the initiating events, thermal-hydraulic analysis is performed for loss of coolant accident (LOCA) and loss of load (LOL) event and preliminary event trees for the accidents are developed. After development of the event trees and fault trees for all the initiating events of MMR, it is expected that core damage frequency can be estimated and design improvements can be identified. Copyright © 2019 European Safety and Reliability Association.

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