Exploring Current Constraints on Antineutrino Production by $^{241}$Pu and Paths Towards the Precision Reactor Flux Era

TL;DR

This paper analyzes current constraints on antineutrino production from $^{241}$Pu and explores future measurement strategies across various reactor types to improve the precision of reactor neutrino flux models.

Contribution

It provides the first direct bound on $^{241}$Pu IBD yield and investigates how future measurements can refine knowledge of multiple isotope yields.

Findings

$^{241}$Pu IBD yield is 8.16 ± 3.47 cm²/fission, about 135% of models.

Fast reactors can measure $^{240}$Pu IBD yield directly.

Multiple reactor measurements can surpass current theoretical prediction accuracy.

Abstract

By performing global fits to inverse beta decay (IBD) yield measurements from existing neutrino experiments based at highly $^{235}$U enriched reactor cores and conventional low-enriched cores, we explore current direct bounds on neutrino production by the sub-dominant fission isotope $^{241}$Pu. For this nuclide, we determine an IBD yield of $\sigma_{241}$ = 8.16 $\pm$ 3.47 cm$^2$/fission, a value (135 $\pm$ 58)% that of current beta conversion models. This constraint is shown to derive from the non-linear relationship between burn-in of $^{241}$Pu and $^{239}$Pu in conventional reactor fuel. By considering new hypothetical neutrino measurements at high-enriched, low-enriched, mixed-oxide, and fast reactor facilities, we investigate the feasible limits of future knowledge of IBD yields for $^{235}$U, $^{238}$U, $^{239}$Pu, $^{241}$Pu, and $^{240}$Pu. We find that the first direct measurement of the $^{240}$Pu IBD yield can be performed at plutonium-burning fast reactors, while a suite of correlated measurements at multiple reactor types can achieve precision in direct $^{238}$U, $^{239}$Pu, and $^{241}$Pu yield knowledge that meets or exceeds that of current theoretical predictions.