Abstract

Accident tolerant fuels (ATFs) are new nuclear fuels developed in response to the accident at the Fukushima power station in March 2011. The goal of ATFs is to withstand accident scenarios through better performance compared to currently employed fuels (e.g., small-scale hydrogen generation). This paper targets a method for evaluating and comparing ATF performance from a probabilistic risk assessment (PRA) perspective by employing a newly developed combination of event trees and dynamic PRA methods. Compared to classical PRA methods based on event trees and fault trees, dynamic PRA can evaluate with higher resolution the safety impacts of physics dynamics and the timing/sequencing of events on the accident progression without the need to introduce overly conservative modeling assumptions and success criteria. In this paper, we analyze the impact on the accident progression of three different cladding configurations for two initiating events [a large break loss-of-coolant accident (LB-LOCA) and a station blackout (SBO)] by employing dynamic PRA methods. The goal is to compare the safety performance of ATFs (FeCrAl and Cr-coated cladding) and the currently employed Zr-based clad fuel. We employ two different strategies. The first focuses on the identification of success criteria discrepancies between the accident sequences generated by the classical PRA model and the set of simulation runs generated by dynamic PRA using ATF. The second one, on the other hand, directly uses dynamic PRA to evaluate the impact of timing of events (e.g., recovery actions) on accident progression. By applying these methods to the LB-LOCA and SBO initiating events, we show how dynamic PRA methods can provide analysts with detailed and quantitative information on the safety impact of ATFs.

摘要

事故容忍燃料（ATF）是为响应2011年3月福岛核电站事故而开发的新型核燃料。ATF的目标是通过比目前使用的燃料（例如小规模氢气产生）更好的性能来承受事故情况）。本文的目标是通过采用新开发的事件树和动态PRA方法的组合，从概率风险评估（PRA）角度评估和比较ATF性能的方法。与基于事件树和故障树的经典PRA方法相比，动态PRA可以以更高的分辨率评估物理动力学的安全性影响以及事件的时间/顺序对事故进展的影响，而无需引入过于保守的建模假设和成功标准。在本文中，我们通过采用动态PRA方法，分析了两种始发事件[大的冷却液失速事故（LB-LOCA）和停电事故（SBO）]三种不同覆层结构对事故进展的影响。目的是比较ATF（FeCrAl和Cr涂层包层）与当前使用的Zr基包层燃料的安全性能。我们采用两种不同的策略。第一部分着重于确定经典PRA模型生成的事故序列与动态APR使用动态PRA生成的一组模拟运行之间的成功标准差异。另一方面，第二种方法则直接使用动态PRA来评估事件时间安排（例如，恢复行动）对事故进展的影响。通过将这些方法应用于LB-LOCA和SBO发起事件，