A study of ²³⁹Pu production rate in a water cooled natural uranium blanket mock-up of a fusion–fission hybrid reactor

Abstract

The 239 Pu production rate is important data in neutronics design for a natural uranium blanket of a fusion-fission hybrid reactor, and the accuracy and reliability should be validated by integral experiments. The distribution of 239 Pu production rates in a subcritical natural uranium blanket mock-up was obtained for the first time with a D-T neutron generator by using an activation technique. Natural uranium foils were placed in different spatial locations of the mock-up, the counts of 277.6 keV γ-rays emitted from 239 Np generated by 238 U capture reaction were measured by an HPGe γ spectrometer, and the self-absorption of natural uranium foils was corrected. The experiment was analyzed using the Super Monte Carlo neutron transport code SuperMC2.0 with recent nuclear data of 238 U from the ENDF/ B-VII.0, ENDF/B-VII.1, JENDL-4.0u2, JEFF-3.2 and CENDL-3.1 libraries. Calculation results with the JEFF-3.2 library agree with the experimental ones best, and they agree within the experimental uncertainty in general with the average ratios of calculation results to experimental results (C/E) in the range of 0.93 to 1.01.