事故容错燃料安全性能初步分析

事故容错燃料（ATF）是通过提高燃料材料热物性或包壳材料抗高温氧化性能来加强核燃料的事故容错能力，从而使核燃料能长期忍受严重事故。使用二次开发适用于ATF的RELAP5程序，对UO₂-FeCrAl、FCM-FeCrAl这两种ATF和传统核燃料UO₂-Zir-4进行大破口失水事故安全分析。对比事故分析结果可知：相较于传统UO₂芯块，稳态运行工况下，热导率高的FCM芯块具有更低的燃料中心温度和更小的燃料径向温度梯度，同时在瞬态事故工况下，FCM芯块具有更低的瞬态初始温度和更小的燃料温度增长速率。相较于传统Zir-4包壳，在瞬态事故工况下，FeCrAl的包壳峰值温度更小，达到的时间更晚，同时由于FeCrAl包壳具有良好的抗高温氧化性能，事故过程中产生的氢气质量更小。

Preliminary Analysis of Safety Performance for Accident-tolerant Fuel

Accident-tolerant fuel (ATF) is to enhance the accident-tolerant capacity of nuclear fuel by improving the thermal properties of fuel materials or the high temperature oxidation resistance of cladding materials, so that nuclear fuel can endure serious accidents for a long time. Using RELAP5 program developed for ATF, safety analysis of UO₂-FeCrAl, FCM-FeCrAl and conventional nuclear fuel UO₂-Zir-4 was carried out. Compared with conventional UO₂ pellets, FCM pellets with higher thermal conductivity have lower fuel center temperature and smaller radial fuel temperature gradient under steady state operating conditions. FCM pellets also have lower transient initial temperature and lower fuel temperature growth rate under transient accident condition. Compared with conventional cladding Zir-4, the peak cladding temperature of FeCrAl is smaller and reaches later under transient accident condition. Meanwhile, due to the better high temperature oxidation resistance of FeCrAl cladding, the smaller hydrogen mass production is produced during the accident progress.