衰变对AP1000核电厂LBLOCA始发严重事故源项的影响

Source Term Evaluation Considering Decay for AP1000 Reactor under Severe Accident Initialed by LBLOCA Condition

文中采用FORTRAN编写了放射性核素的衰变和生成程序(DAIC),并通过燃耗计算程序进行了验证;以AP1000核电厂为研究对象,选取大破口始发的严重事故,采用严重事故分析程序MELCOR模拟事故进程并结合DAIC程序计算释放至安全壳的源项。进行衰变对源项的影响研究。研究结果表明,衰变对^(131)I、^(131m)Xe、^(133)Xe、^(85)Kr和^(134)Cs等半衰期长的核素释放份额影响不大,其结果与不考虑衰变的结果接近,结果曲线整体呈上升趋势,达到最大值后保持不变;衰变对^(134)I、^(135)I、^(138)Xe、^(138)Cs和^(87)Kr等半衰期较短的核素的释放份额影响较大,结果曲线先上升后下降。

In this paper,the decay and ingrowth code(DAIC),which was verified by the burnup calculation code,has been developed by FORTRAN language;MELCOR was utilized to module the severe accident processes initialed by the large break loss of coolant accident(LBLOCA)and calculate the in-containment source term combing the DAIC code for AP1000 NPP.Then,the influence of decay on the fission products release has been studied.The results showed that the decay has little influence on the release fraction of long half-time nuclides,such as^(131)I,^(131m)Xe,^(133)Xe,^(85)Kr,^(134)Cs and so on,whose release fractions are close to those discounting decay.The release fraction is on the rise as a whole along time;the decay has obvious influence on the release fraction of the short half-time nuclides,such as^(134)I,^(135)I,^(138)Xe,^(138)Cs,^(87)Kr and so on,whose release fraction curves rise first and then decrease.