双堆布置核电厂公用设施对双堆超设计基准事故缓解的影响和改进

Impacts and Improvements of Facilities Shared by Twin-reactor Nuclear Power Plants to Mitigate Beyond-Design-Basis Accidents

福岛事故后,同一厂址多台机组同时发生超设计基准事故(包括严重事故)的后果开始受到关注,为此需要从设计上保证核电厂事故应对措施的独立性。我国运行和在建的大部分核电厂为双堆布置的二代改进型核电厂。分析表明,水压试验泵和安全壳过滤排放系统(EUF)为双堆公用,对双堆超设计基准事故的应对能力存在影响。进而研究了这两个公用设施在现有电厂中的潜在改进选项,从尽量减少硬件改动的目的出发提出了最可能的改进方案。其中EUF交替排放仅仅通过操作规程的变化,凭借一套公用系统即可实现双堆的卸压目的。进一步计算也证明,合理选取交替排放的时间窗口,EUF交替排放在最保守及最现实的事故情况下均能确保双堆安全壳的安全。

After Fukushima accident, the consequences of multiple-unit beyond-design- basis accidents （BDBA） at the same site have been paid attention. Therefore, the independence of accident response measures of nuclear power plant （NPP） is required to be guaranteed in design. Most of nuclear power plants in operation and under construction in China are Gen II＋ nuclear power plants with twin-reactor layout. It is shown that hydro-test pump and containment filtration and venting system （EUF） shared by twin reactors would affect the mitigation capability against twin-reactor BDBA. The potential improvement options of the above facilities have been studied for the existing plants, and the most probable improvement solutions have been proposed with the purpose of reducing the hardware changes to the greatest extend. By means oftwin-reactor alternative venting, one single system of EUF is capable to satisfy the depressurization requirements of twin reactors. Further calculations also prove that, with the reasonable time window of alternative venting, the safety of twin-reactor containments can be ensured by EUF alternative venting both in the most conservative conditions and the most realistic conditions.