Neutron inelastic scattering of 232Th: measurements and beyond

Eliot Party,Grégoire Henning,Xavier Doligez,Alexandru Negret,Arjan Plompen,Maëlle Kerveno,Catalin Borcea,Adina Olacel,Markus Nyman,Philippe Dessagne

doi:10.1051/epjconf/201921103005

Abstract

Gamma production cross sections have been obtained for 81 transitions in 232Th from (n,n’γ), 11 in 231Th from (n,2nγ) and 7 in 230Th from (n,3nγ) reactions using prompt gamma spectroscopy. Incident neutron energies were determined using the neutron time-of-flight technique. Sources of uncertainty have been examined and their correlations have been computed. Total uncertainty on cross sections ranges from 4 to 20%. Obtained cross sections are in agreement with prior experiments, but are not well reproduced by the TALYS 1.8 reaction code using default parameters. During analysis, discrepancies between our findings and the Evaluated Nuclear Structure Data File (ENSDF) were noted. Future work related to the present experiment includes: improving theoretical models, quantifying the influence of the 232Th inelastic neutron cross section on reactor core parameters, and conducting additional measurements.

Highlights

Today, the lack of precision in nuclear data affects our capability to predict accurately some phenomena in nuclear reactors
Gamma production cross sections have been obtained for 81 transitions in 232Th from (n,n’γ), 11 in 231Th from (n,2nγ) and 7 in 230Th from (n,3nγ) reactions using prompt gamma spectroscopy
The main result of this work is the measurement of 81 232Th(n,n’γ) cross sections, on a large incident neutron energy range, up to 20 MeV

Summary

Introduction

The lack of precision in nuclear data affects our capability to predict accurately some phenomena in nuclear reactors. Inelastic scattering off 238U is the main source of uncertainty due to nuclear data in power distribution of large reactor [1]. To answer to the need of lower uncertainties in nuclear data for applications, new precise measurements of cross sections are necessary. Measurements of neutron inelastic scattering off 232Th using prompt gamma spectroscopy are presented. Two studies used gamma spectroscopy to determine partial cross sections in 1980’s, one by Dave et al [3], the other by Filatenkov et al [4]. A few of these measurements, and none using gamma detection, extended beyond 3 MeV in incident neutron energy, as shown on Fig. 1. This work provides new and precise measurements on a range of incident neutron energy extending to 20 MeV

Methods

Results

Conclusion