中子诱发241Pu裂变缓发γ光子谱的计算

Calculation of the beta-delayed fission gamma spectrum for n+241Pu

开发了裂变缓发γ光子谱计算程序,利用燃耗计算程序获得裂变产物核的积存量,然后对产物核发射的缓发γ求和得到随时间变化的缓发光子谱。通过对n+235U裂变缓发光子谱计算,并与现有国际评价核数据库、现有实验数据比较,验证了程序的正确性。利用该程序计算了入射为热能中子和裂变谱中子诱发的241Pu裂变缓发光子谱,出射缓发光子能量范围为0~7 MeV,并转换为ENDF/B-Ⅵ格式的数据库,补充了中国评价核数据(CENDL-3.X)。由于采用了最新核数据,与国际数据比较,具有一定的先进性。计算结果表明,热中子和裂变谱中子诱发241Pu裂变产生的光子谱比较相似,但有区别,剂量随时间变化的曲线几乎相等,经过3 h剂量衰减到小于0.1%。时间积分的总剂量略有差别,分别为1 667和1 670 keV-bq-s。

A program is developed to calculate the beta-delayed fission gamma(BDFG)spectrum, which uses the inventory data computed by burn-up code, and the make up the summation of the gammas emitted when the products beta decays. It is verified comparing the n+235U results with evaluated data in ENDF/B-Ⅶ.1 library, as well as the measured data. The program is applied to calculate the BDFG of 241Pu fission induced by thermal-and fission-neutrons(~0.5 MeV). The BDFG spectra are presented as function of cooling time, covering the outgoing energy range of 0~7 MeV. They are converted into ENDF/B-Ⅵ format, and contributed to Chinese nuclear evaluation data library(CENL-3.X). It is a progress since the most recent nuclear data were used. The results show that the BDFG spectra are similar but not same which are induced by the thermal-and fission-neutron. The time dependencies of the dose are almost equal, after about 3 hours, they decayed to less than 0.1%. The integral doses are very close, which are 1 667 and 1 670 keV-bq-s respectively.