Risk of Japanese PWR plants by shutting off forced core cooling in an accident requiring safety injection system

https://doi.org/10.1016/j.nucengdes.2020.110822Get rights and content
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Abstract

Westinghouse type plants in the United States (US) and Europe have a manual trip procedure of the reactor coolant pumps (RCP) in the case of a small break Loss of Coolant Accident (LOCA) with the high pressure injection (HPI) system functioned. This is in response to the Three Mile Island (TMI) accident in order to maintain as much the forced core cooling as possible. On the other hand, the initial design of Japanese pressurized water reactor (PWR) plants were designed to shut off the non-safety power supply buses on receiving of safety injection (SI) actuation signals and to handle an accidents only with safety facilities. But other part of design of Japanese PWR plants had basically same as Westinghouse type plants in the US and Europe. Although it was modified to no shut off the non-safety power supply buses in all Japanese PWR plants after the Mihama Unit 2 steam generator tube rupture (SGTR) accident, but it was added an automatic RCP trip logic on receiving of SI actuation signals. Therefore Japanese PWR plants shutting off the forced core cooling using SI actuation signals. As the results, Japanese PWR plants have disadvantages such as increased risk of pressurized thermal shock (PTS) by rapid cooling of the reactor coolant system (RCS), reducing operational margin in transient events, and increase of radioactive release by SGTR.

Keywords

Three Mile Island Accident
PWR
Small break LOCA
Forced core cooling
Reactor Coolant Pumps

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