Abstract

In the thermal neutron–induced fission of ²³²U, cumulative and independent yields of various fission products within the mass ranges of 72 to 107 and 123 to 158 have been measured using an off-line gamma-ray spectrometric technique. The fission yields were determined relative to the yield of a monitor product ⁹²Sr. Charge distribution correction was applied on the cumulative yields to obtain the post-neutron mass yield distribution. Mass yield distribution parameters such as full-width at tenth-maximum of light and heavy mass wings, average light mass number <A_L> and heavy mass number <A_H>, and average number of emitted neutrons <ν> were obtained. Data from the present and earlier work on the ²³²U(n_th,f) reaction were compared with similar data of the ²³⁵U(n_th,f) reaction. It was found that the mass chain yield distribution in the ²³²U(n_th,f) reaction is asymmetric with two major humps as in the case of the ²³⁵U(n_th,f) reaction. Besides this, in the ²³²U(n_th,f) reaction, the mass yield distribution shows a small third hump for the symmetric fission products. It was also found that the standard II asymmetric mode of fission is favorable in the ²³²U(n_th,f) reaction whereas the standard I asymmetric mode of fission is favorable in the ²³⁵U(n_th,f) reaction.

摘要

在²³² U 的热中子诱发裂变中，使用离线伽马射线光谱技术测量了 72 到 107 和 123 到 158 质量范围内各种裂变产物的累积和独立当量。裂变产率是相对于监测产品⁹² Sr 的产率确定的。电荷分布校正应用于累积产率以获得中子后质量产率分布。得到了轻、重质量翼的第十大全宽、平均轻质量数<A _L >和重质量数<A _H >、平均发射中子数<ν>等质量当量分布参数。²³² U(n ) 现在和早期工作的数据_th ,f) 反应与²³⁵ U(n _th ,f) 反应的类似数据进行了比较。发现²³² U(n _{th ,f) 反应中的质量链产率分布与}²³⁵ U(n _th ,f) 反应的情况一样，具有两个主要的驼峰不对称。除此之外，在²³² U(n _th ,f) 反应中，质量产率分布显示出对称裂变产物的小第三峰。还发现标准 II 不对称裂变模式有利于²³² U(n _th ,f) 反应，而标准 I 不对称裂变模式有利于²³⁵U(n _th ,f) 反应。