# Nuclear Science and Techniques

《核技术》(英文版) ISSN 1001-8042 CN 31-1559/TL     2019 Impact factor 1.556

Nuclear Science and Techniques ›› 2019, Vol. 30 ›› Issue (8): 130

• NUCLEAR ENERGY SCIENCE AND ENGINEERING •

### A study of PFBR auxiliary neutron source strength activation and its variability with respect to the neutron spectrum and Sb123 capture cross section

G. Pandikumar, D. Sunilkumar, M.M. Shanthi, Bagchi Subhrojit, A. John Arul, D. Venkatasubramanian, Prasad Rajeev Ranjan

1. Reactor Shielding and Data Division, Department of Atomic Energy, Nuclear Systems Design Group, Reactor Design Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, India
• Received:2018-07-23 Revised:2019-02-22 Accepted:2019-04-06
• Contact: G. Pandikumar E-mail:pkg@igcar.gov.in
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G. Pandikumar, D. Sunilkumar, M.M. Shanthi, Bagchi Subhrojit, A. John Arul, D. Venkatasubramanian, Prasad Rajeev Ranjan. A study of PFBR auxiliary neutron source strength activation and its variability with respect to the neutron spectrum and Sb123 capture cross section.Nuclear Science and Techniques, 2019, 30(8): 130

Abstract: In fast reactors, the inherent neutron source strength is often insufficient for monitoring the reactor start-up operation with ex-core detectors. To increase the subcritical neutron flux, an auxiliary neutron source subassembly (SSA) is generally used to overcome this problem. In this study, the estimated neutron source strength and detector count rate of an antimony–beryllium-based SSA are obtained using the deterministic transport code DORT and Monte Carlo calculations. Because the antimony activation rate is a critical parameter, its sensitivity to the capture cross section and neutron flux spectrum is studied. The reaction cross section sensitivity is studied by considering data from different evaluated nuclear data files. It is observed that, because of the variation in the cross sections from different evaluated nuclear data files, the values of the saturation gamma ([1.67 MeV) activity and neutron strength predicted by ORIGEN2 lie within ± 2%. The obtained antimony activation rate and sensitivity to the neutron flux are partially validated by irradiating samples of antimony in the KAMINI reactor. The average onegroup capture cross sections of bare and cadmium-covered 123Sb samples obtained by the ratio method are 4.0 and 1.78b, respectively. The results of the calculation predicting the activated neutron source strength as a function of operating time and sensitivity to the neutron spectrum in the irradiation region are also presented.