PSAM 16 - Paper Overview

PSAM 16 Conference Paper Overview

Welcome to the PSAM 16 Conference paper and speaker overview page.

Lead Author: Gyunseob Song Co-author(s): Man Cheol Kim - charleskim@cau.ac.kr

An estimation method for heat pipe cascading failure frequency for micro modular reactor PSA
Initiating event analysis is one of essential elements in probabilistic safety assessment (PSA) to estimate core damage frequency (CDF) or large early release frequency (LERF) as risk metrics. As several types of reactors have been developed which are so called Generation Ⅳ reactor, it is expected that several types of initiating events which are not considered in traditional reactors exist. The frequency of an initiating event is generally estimated using historical data from operating reactors. However, there is no observed experience about expected initiating events for developmental stage reactors and hence methodologies to estimate frequencies of expected initiating events should be developed. In Generation Ⅳ reactors, heat pipe is widely considered as heat removal system because of its passive property. Even if a heat pipe is designed to have enough capability in normal operating conditions, the performance of a heat pipe may depend on heat load. Therefore, it is possible that individual failures of heat pipes cause cascading failure of other heat pipes due to the increase in heat load resulted from failed heat pipes. When the cascading failure of heat pipes occurs, the heat removal capability of the system decreases and hence the integrity of the reactor can be threatened. Therefore, the analysis should be performed to estimate occurrence frequency of heat pipe cascading failure. Previous researches on estimating cascading failure frequency of heat pipes mainly use Monte Carlo analysis based on defined failure probability within a time step which depends on increased heat load due to failure of adjacent heat pipes. However, the time step size is restricted by computational cost and hence the defined failure probability may be underestimated because the failure of adjacent heat pipe cannot be instantly reflected. Furthermore, the frequency is simply estimated as a point value, the ratio of the number of cascading failures to the number of simulations. In this research, we model the failures of heat pipes as a stochastic process and approximate the analytic distribution for occurrence time of heat pipe cascading failure. Then, the estimated frequency of heat pipe cascading failure event is mathematically calculated.

An estimation method for heat pipe cascading failure frequency for micro modular reactor PSA

Initiating event analysis is one of essential elements in probabilistic safety assessment (PSA) to estimate core damage frequency (CDF) or large early release frequency (LERF) as risk metrics. As several types of reactors have been developed which are so called Generation Ⅳ reactor, it is expected that several types of initiating events which are not considered in traditional reactors exist. The frequency of an initiating event is generally estimated using historical data from operating reactors. However, there is no observed experience about expected initiating events for developmental stage reactors and hence methodologies to estimate frequencies of expected initiating events should be developed. In Generation Ⅳ reactors, heat pipe is widely considered as heat removal system because of its passive property. Even if a heat pipe is designed to have enough capability in normal operating conditions, the performance of a heat pipe may depend on heat load. Therefore, it is possible that individual failures of heat pipes cause cascading failure of other heat pipes due to the increase in heat load resulted from failed heat pipes. When the cascading failure of heat pipes occurs, the heat removal capability of the system decreases and hence the integrity of the reactor can be threatened. Therefore, the analysis should be performed to estimate occurrence frequency of heat pipe cascading failure. Previous researches on estimating cascading failure frequency of heat pipes mainly use Monte Carlo analysis based on defined failure probability within a time step which depends on increased heat load due to failure of adjacent heat pipes. However, the time step size is restricted by computational cost and hence the defined failure probability may be underestimated because the failure of adjacent heat pipe cannot be instantly reflected. Furthermore, the frequency is simply estimated as a point value, the ratio of the number of cascading failures to the number of simulations. In this research, we model the failures of heat pipes as a stochastic process and approximate the analytic distribution for occurrence time of heat pipe cascading failure. Then, the estimated frequency of heat pipe cascading failure event is mathematically calculated.

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Author and Presentation Info

Presentation only, a full paper is not available.

Lead Author Name: Gyunseob Song (dyrnfmxm678@cau.ac.kr)

Bio:

Country: South Korea
Company: Chung-Ang university
Job Title: