RASCAL程序严重事故源项计算方法研究及应用

Study and Application of Severe Accidents Source Term Method in RASCAL

福岛事故发生后,NRC通过研究发现RASCAL 4版本不能满足长期厂外断电(LTSBO)事故源项的计算要求,并在RASCAL4.3.1版本中加入了针对LTSBO事故的源项计算方法。应用RASCAL 4.3.1程序,建立了某电厂机组的LTSBO事故和LOCA事故模型,计算了两种事故工况下释放到环境的源项及距电厂中心不同距离处的公众受到的剂量,并对两种事故工况下的计算结果进行对比分析。研究结果表明:(1)8小时后,与LOCA事故相比,LTSBO事故下释放到环境的碘和其他核素的活度较大,惰性气体的活度较小;(2)LTSBO事故下的有效剂量和甲状腺当量剂量均大于LOCA事故。因此,使用针对LTSBO事故序列的源项计算方法能够更加准确的反映LTSBO事故后果。

After Fukushima accident,NRC found that RASCAL 4 version cannot meet the demand of the calculation of LTSBO,and add the source term calculation method under LTSBO accident sequence to RASCAL.RASCAL 4.3.1 was applied for modeling LTSBO and LOCA accident,and source term released to environment and dose of different distance far away from the center of the site was calculated.Besides,the results of LTSBO and LOCA was compared and analyzed.Results show that:(1)8 hours later,the release activity of iodine and other nuclide under LTSBO was larger than the activity under LOCA,but the release activity of noble gas was smaller;(2)The total effective dose equivalent(TEDE)and thyroid committed equivalent dose(CED)under LTSBO was larger than the doses under LOCA.Consequently,it is necessary to use the calculation method of source term under LTSBO accident,which will reflect the accident consequence more accurately.