权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Study on Molten Core Behavior in Severe Accidents using Particle Method

严重事故中熔芯行为的粒子法研究

基本信息

批准号：
11480120
负责人：
OKA Yoshiaki
金额：
$ 9.02万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Test experiments, SWISS-2 and MACE-MO, of molten core-concrete interaction (MCCI) were analyzed by a particle method. In both cases, crust was formed at the top of the melt pool and the heat removal to the upper water pool was suppressed. The heat removal to the water pool and the ablation speed in the concrete agreed well between the calculations and the experiments in two cases. An unlimited geometry was also analyzed. The upper crust was formed and the heat removal was suppressed as well. However, the heat removal was enhanced when the crust was broken by the dissolved gas release and the old crust sank in the melt pool.Formation of the molten core debris was analyzed by the particle method. This is an additional subject which had not been described in the initial research plan. Behavior of a single droplet of the melt in water was investigated. Neglecting the vapor film, we could reproduce the critical Weber number which had been obtained in experiments without the phase change. If the vapor film was considered, the critical Weber number increased and the droplet size was enlarged. The critical heat flux of the debris bed was assessed as IMW/m^2, which showed enough capabilities of the decay heat removal.Pressure wave propagation processes in vapor explosions were analyzed using a one-dimensional finite volume method considering water, steam, melt droplets and fragments. Based on the past studies using the particle method, a thermal fragmentation model for the melt droplets was developed and incorporated into the code. The mechanical energy conversion ratio achieved 5 % when the thermal fragmentation took place, while it remained less than 1% when the hydrodynamic fragmentation took place. In large-scale vapor explosions, the hydrodynamic fragmentation becomes dominant, so that 1 % is proper to employ as the conversion ratio.As described above, the present study progressed beyond the initial goal as well as reached it.

通过粒子法分析了熔融核心-混凝土相互作用（MCCI）的测试实验 SWISS-2 和 MACE-MO。在这两种情况下，熔池顶部都形成了硬壳，并且抑制了向上水池的散热。在两种情况下，水池的排热和混凝土中的烧蚀速度与计算结果和实验结果吻合良好。还分析了无限的几何形状。上地壳形成，散热也受到抑制。然而，当地壳由于溶解的气体释放而破裂并且旧地壳沉入熔池时，热量的排出增强。用粒子法分析了熔融核心碎片的形成。这是最初的研究计划中没有描述的额外主题。研究了水中熔体的单个液滴的行为。忽略蒸汽膜，我们可以重现在没有相变的实验中获得的临界韦伯数。如果考虑蒸汽膜，临界韦伯数增加，液滴尺寸增大。碎片床的临界热通量评估为IMW/m^2，显示出足够的衰变热排除能力。采用考虑水、蒸汽、熔滴和碎片的一维有限体积方法分析了蒸气爆炸中的压力波传播过程。基于过去使用粒子方法的研究，开发了熔体液滴的热破碎模型并将其纳入代码中。热破碎时机械能转化率达到5%，而水动力破碎时机械能转化率仍低于1%。在大规模蒸气爆炸中，流体动力破碎占主导地位，因此采用1％作为转化率是合适的。如上所述，本研究进展超出了最初的目标，并且达到了目标。