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

TL;DR

This paper develops a method to accurately calculate the antineutrino flux from spent nuclear fuel, accounting for various isotopes and operational parameters, to improve reactor neutrino flux predictions.

Contribution

It introduces a comprehensive simulation-based approach to quantify the SNF antineutrino contribution, considering over 2000 isotopes and time-dependent spectra.

Findings

SNF contributes about 0.26%~0.34% to total flux

SNF causes a 20% impact during shutdown

Maximum SNF contribution is about 3.0% with an 18% difference between evaluation methods

Abstract

Spent nuclear fuel (SNF) antineutrino flux is an important source of uncertainties for a reactor neutrino flux prediction. However, if one want to determine the contribution of spent fuel, many data are 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 the isotopes in the spend fuel. A method to calculate the contribution of SNF is proposed in this study. In this method, reactor simulation code verified by experiment have been used to simulate the fuel depletion by taking into account more than 2000 isotopes and fission products, the quantity of SNF in each six spend fuel pool, and the antineutrino spectrum of SNF varying with time after SNF discharged from core. Results show that the contribution of SNF to the total antineutrino flux is about 0.26%~0.34%, and the shutdown impact is about 20%. The SNF spectrum would distort the softer part of antineutrino spectra, and the maximum contribution from SNF is about 3.0%, but there is 18\% difference between line evaluate method and under evaluate method. In addition, non-equilibrium effects are also discussed, and the results are compatible with theirs considering the uncertainties.