Integral experiment of ¹²⁹I(n, γ) reaction using fast neutron source in the 'YAYOI' reactor

The present study analyzes an integral experiment performed in the fast-neutron reactor 'YAYOI' of the University of Tokyo to validate the ¹²⁹I (n,γ) cross-section. An iodine-129 sample and 15 neutron flux monitors were irradiated with fast neutrons in the Glory hole of the reactor. Capture reaction rates of ¹²⁹I were obtained by measurement of gamma rays emitted through the decay of ¹³⁰I, and the 15 neutron flux monitors helped validate the computed fast-neutron flux spectrum in the Glory hole. By comparing the experimental and calculated reaction rates for ¹²⁹I, the present study reveals that the ¹²⁹I (n,γ) cross-section of JENDL-4.0 should be reduced by 18% in the 10 keV-3 MeV energy range and supports the data by Noguere et al. below 100 keV. (author)