Safeguards impacts of antineutrinos from activation of structural elements in power and research reactors

Recent experiments have demonstrated the capability of antineutrino detectors to gain insight into the reactor operational status and fissile inventory. However, current gaps in physics knowledge challenge the accuracy and timeliness of antineutrino detection as an effective safeguards measure. Few of the experiments that measured the reactor antineutrino flux have focused on antineutrinos produced from other structural materials. Reactor antineutrinos are produced from the decay chains of fission products and other beta-decay reactions such as activation. The purpose of this study is to quantify structural activation as an additional source of antineutrino uncertainty within various nuclear reactor designs. The modeling and simulation results should inform the antineutrino and safeguards communities about the technological issue of precisely measure fission antineutrinos in research reactors. Reactor simulation in MCNP calculated fission and activation rates in one commercial (PWR) and two research reactors (HFIR and NBSR) to examine perturbations in the antineutrino source. The ratio of aluminum activation to uranium fission rates in the two research reactors differed by a factor of five. The findings suggest that each research reactor requires separate simulation and analysis to quantify systematic uncertainties in antineutrino production. The design of monitoring protocols using antineutrino detectors must consider such uncertainties for all relevant reactor types.