Abstract In this paper, first, MELCOR calculations for a conventional high power pressurized water reactor are performed to obtain the geometrical configurations and remaining fraction of the fission products in the degraded reactor core during the early phase of a severe accident. Then, based on the coupling between MELCOR and Serpent 2 code, sensitivity analyses on the criticality are performed for various water levels, burnup, and release of fission products with whole-core modelling on the degraded reactor. Sub-critical boron concentrations are obtained on the configuration of the degraded reactor core showing the largest criticality. The sub-critical boron concentrations are compared to critical boron concentrations of the intact reactor core to quantify additional boron concentrations required to make the reactor sub-critical during the early phase of the severe accident. Effects of control rod degradation and fission product release are also presented in terms of boron concentrations from the results of sensitivity analyses.

中文翻译：

---

韩国常规大功率压水堆严重事故早期再临界全堆芯分析

摘要 在本文中，首先对常规大功率压水反应堆进行了MELCOR计算，以获得严重事故早期退化反应堆堆芯中裂变产物的几何构型和剩余部分。然后，基于 MELCOR 和 Serpent 2 代码之间的耦合，对退化的反应堆进行全堆芯建模，对各种水位、燃耗和裂变产物的释放进行临界敏感性分析。亚临界硼浓度是在退化的反应堆堆芯的配置上获得的，显示出最大的临界性。将亚临界硼浓度与完整反应堆堆芯的临界硼浓度进行比较，以量化在严重事故的早期阶段使反应堆亚临界所需的额外硼浓度。根据敏感性分析的结果，控制棒降解和裂变产物释放的影响也以硼浓度的形式呈现。