Post-Neutron Mass Yield Distribution in the Thermal Neutron Induced Fission of ²³²U

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.

Keywords:

• ²³²U(n,f) reaction
• measured fission product yields
• mass chain yield distribution
• off-line gamma-ray spectrometric technique.

Acknowledgments

We are thankful to R. H. Iyer, Bhabha Atomic Research Centre (BARC), for his keen interest and support during this work. The authors are also thankful to the members of the staff of the reactor APSARA at BARC for their help in providing the irradiation facility and successfully carrying out the irradiations during the experiment.