Study on Measurements of Nuclear Data for Transmutation of Actinide Elements

利用日本京都大学的铅慢化光谱仪（KULS）和46 MeV电子直线加速器（linac）对镎-237和镅-241的裂变截面进行了测量。通过MCNP程序和中子共振滤波器实验，首先得到了KULS的特性(1)中子慢化时间与能量的关系，(2)能量分辨率，(3)中子能谱。然后，将KULS应用于Np-237和Am-241相对于U-235的裂变中子截面测量，测量范围从约1 eV到约10 keV，能量分辨率（dE/E）约为40%。尽管Np-237目前的截面形状与platard等人的测量结果以及ENDF/B-VI和JENDL-3中的测量结果一致，但上述三者的绝对值比目前的数据要小3 - 4倍。然而，Hoffman等人的测量结果更接近于目前的结果。对于Am-241，评估数据和Dabbs测量值的绝对值比现有数据低3倍，与Gayther等人和Bowman等人的测量值相当接近，在几十eV以上。对于^<237>Np(n, γ)^<238>Np反应，热中子截面(158(]SY.+-。[)3 b]和共振积分(652 []SY.+-。[)24 b)分别用标准麦克斯韦和1/E中子能谱场测量。在ENDF/B-V和JENDL-3中出现的热中子截面比当前值大7 ~ 15%。对于共振积分，计算值与现值吻合较好。

Studies on fission cross section measurements of Np-237 and Am-241 for tranmutation were performed through the Kyoto University Lead Slowing-down Spectrometer (KULS) coupled to the 46 MeV electron linear accelerator (linac). The characteristics of the KULS were firstly obtained for (1) the relation between neutron slowing-down time and energy, (2) energy resolution, and (3) neutron energy spectrum, by the MCNP code and by the experiments using neutron resonance filters. Then, the KULS was applied to the fission neutron cross section measurements of Np-237 and Am-241 relative to that of U-235 from about 1 eV to about 10 keV with energy resolution (dE/E) of about 40 %. Although the shape of the present cross section of Np-237 agrees with that measured by Plattard et al. and with those in ENDF/B-VI and JENDL-3, the absolute values of above three are from 3 to 4 times smaller than those of the present data. However, the measurement by Hoffman et al.is rather closer to the present result. For Am-241, the absolute values of the evaluated data and the Dabbs' measurementare are 3 times lower than the present data, which are rather closer to those measured by Gayther et al.and Bowman et al.above a few tens of eV.For the ^<237>Np(n, gamma)^<238>Np reaction, thermal reutron cross section (158(〕SY.+-.〔)3 b) and the resonance integral (652(〕SY.+-.〔)24 b) were measured with the standard Maxwellian and the 1/E neutron spectrum fields, respectively. Thermal neutron cross sections appeared in ENDF/B-V and JENDL-3 are larger by 7 to 15 % than the present value. For the resonance integral, the evaluated data are in good agreement with the present value.