Precise Rb92 and Y96 yields for thermal-neutron-induced fission of U235 and Pu239,241 determined using calorimetric low-temperature detectors

Santwana Dubey,Pascal Scholz,Stefan Stolte,Gregoire Kessedjian,Patrick Grabitz,Aurelien Blanc,Friedrich Gönnenwein,Saskia Kraft-Bermuth,Peter Egelhof,Werner Lauterfeld,Ulli Köster,Artur Echler,Manfred Mutterer,Olivier Serot

doi:10.1103/physrevc.102.044602

Abstract

The novel technology of calorimetric low-temperature detectors (CLTDs) was applied to determine isotopic yields of fission fragments using the passive absorber method for thermal-neutron-induced fission reactions at the LOHENGRIN mass spectrometer at the Institut Laue-Langevin in Grenoble, France. Precise yields were determined for $^{92}\mathrm{Rb}$ and $^{96}\mathrm{Y}$. These fission products are the dominant contributors to the high-energy portion of the reactor antineutrino spectra. Our new measurements resolve inconsistencies between previous yield measurements and fission data libraries and reduce the nuclear data uncertainties in the computation of reactor antineutrino spectra by the summation method.

Highlights

The so-called reactor antineutrino anomaly [1], an apparent ≈2.5σ deficit in antineutrino rate, has been derived by comparing measured antineutrino rates from nuclear reactors with those computed from integral fission product beta spectra measured previously by Schreckenbach et al with the BILL spectrometer at the Institut Laue-Langevin (ILL) [2,3,4,5]
From a conversion of integral beta spectra, the expected antineutrino spectra can be computed by the summation method where the contributions of all known decay branches of fission fragments are summed weighted with their fission yields [9,10,11]
Computing the reactor antineutrino anomaly based on the yields reported by Tipnis et al for 92Rb, the high-energy part of the antineutrino spectra would further increase the anomaly by 8%

Summary

Introduction

The so-called reactor antineutrino anomaly [1], an apparent ≈2.5σ deficit in antineutrino rate, has been derived by comparing measured antineutrino rates from nuclear reactors with those computed from integral fission product beta spectra measured previously by Schreckenbach et al with the BILL spectrometer at the Institut Laue-Langevin (ILL) [2,3,4,5]. From a conversion of integral beta spectra, the expected antineutrino spectra can be computed by the summation method where the contributions of all known decay branches of fission fragments are summed weighted with their fission yields [9,10,11]. A few fission products with very high Q value for beta decay contribute to the high-energy part of the antineutrino spectra.

Methods

Results

Conclusion