Antineutrino flux and spectrum calculation for spent nuclear fuel for the Daya Bay antineutrino experiment

Abstract

The antineutrino flux from spent nuclear fuel (SNF) is an important source of uncertainty when making estimates of a reactor neutrino flux. However, to determine the contribution from SNF, sufficient data is needed such as the amount of spent fuel in the pool, the time after discharged from the reactor core, the burnup of each assembly, and the antineutrino spectrum of each isotope in the SNF. A method to calculate this contribution is proposed. A reactor simulation code verified against experimental data has been used to simulate fuel depletion by taking into account more than 2000 isotopes and fission products, the quantity of SNF in each of the six spent fuel pools, and the time variation of the antineutrino spectra after SNF discharging from the core. Results show that the SNF contribution to the total antineutrino flux is about 0.26%-0.34%, and the shutdown impact is about 20%. The SNF spectrum alters the softer part of the antineutrino spectra, and the maximum contribution from the SNF is about 3.0%. Nevertheless, there is an 18% difference between the line evaluate method and under evaluate method. In addition, non-equilibrium effects are also discussed, and the results are compatible considering the uncertainties.

Measurement of the Electron Antineutrino Oscillation with 1958 Days of Operation at Daya Bay

“…[7], the uncertainty of the spent fuel contribution was conservatively set to 100% due to a lack of knowledge of the spent fuel inventory history. An investigation of the history, in collaboration with the nuclear power plant, results in a reduced uncertainty of 30%, now dominated by the calculation of theν e spectrum [16], which sums the β decay spectra of fission isotopes with half-lives longer than 10 hours.…”

Measurement of electron antineutrino oscillation with 1958 days of operation at Daya Bay

“…[7], the uncertainty of the spent fuel contribution was conservatively set to 100% due to a lack of knowledge of the spent fuel inventory history. An investigation of the history, in collaboration with the nuclear power plant, results in a reduced uncertainty of 30%, now dominated by the calculation of the ν e spectrum [16], which sums the beta decay spectra of fission isotopes with half-lives longer than 10 hours.…”

Antineutrino energy spectrum unfolding based on the Daya Bay measurement and its applications *

“…The effect of the SNF was subtracted from the IBD spectrum. The relative uncertainty from SNF was reduced from 100% [37] to 30% [39] using the spent fuel inventory history provided by the nuclear power plant. The relative rate of background is less than 2% and contributes less than 0.15% to the uncertainty on the IBD rate and less than 0.02% to the uncertainty of IBD shape in the 1.5-6.0 MeV prompt energy region.…”