Gamma spectrometry to determine burnup based on short half-life nuclides

A gamma spectrometry method used to determine burnup based on the equilibrium concentration of short half-life nuclides is proposed. Spent fuel is irradiated under constant neutron flux for a period time to make the short half-life indicator isotopes reach the equilibrium concentration, burnup value can be obtained based on the relationship between the equilibrium concentration and residual 235U content. The theoretical simulation results and fuel irradiation experiment on the LR-0 research reactor show that the characteristic peaks of short half-life nuclides 88Kr and 92Sr can be significantly distinguished when fuel is irradiated for a short period of time, thus confirming the feasibility of using 88Kr and 92Sr as indicator isotopes for burnup measurement. This paper simulates the burnup of 20% enriched spent fuel under different experimental conditions, the experimental result shows that the characteristic peaks of indicator isotopes 88Kr, 92S and the corresponding interfering isotopes 132I, 88Rb can be distinguished in the corresponding energy range, and the gamma spectrum measurement should be carried out within 11 hours after discharge. Finally, the calculated burnup values consistent with the theoretical values can be obtained via 88Kr and 92Sr. Compared with other methods, this burnup measurement method is not affected by the irradiation history, fuel enrichment and cooling time before re-irradiation.