MEASUREMENT OF INTEGRAL CROSS SECTIONS OF SELECTED DOSIMETRY REACTIONS IN LR-0 REACTOR

Martin Schulc,Jan Šimon,Roberto Capote,Andrej Trkov,Michal Kostal,Tomas Czakoj,Vlastimil Juříček,Vojtěch Rypar,Evzen Losa,Martin Mareček

doi:10.1051/epjconf/202124709018

Abstract

The cross section is a fundamental quantity which affects the accuracy of Monte Carlo simulations widely used in nuclear applications. A new dosimetry library IRDFF-II that contains cross section evaluations that include full uncertainty quantification is being developed by the International Atomic Energy Agency and expected to be released in January 2020; a preliminary version IRDFF-1.05 was released in 2014 and is being tested in this work. Validation of the cross-section evaluations proposed for this library is a high priority task. The validation can be realized using integral cross sections measured in standard and/or reference neutron benchmark fields. Integral quantities feature significantly lower uncertainties than differential nuclear data. If the neutron spectrum where the cross section is measured is well characterized, then the Spectrum Averaged Cross Section can be used for validating of existing evaluations.

Highlights

There is an extensive set of integral cross sections of dosimetry reactions measured in high power reactors
The advantage of this approach is that even small foils which do not affect the neutron field are significantly activated so that the gamma spectrum can be measured for the irradiated foils in distant geometry
We have developed an innovative approach using the LR-0 reactor, which is a zero-power reactor with low neutron flux

Summary

INTRODUCTION

There is an extensive set of integral cross sections of dosimetry reactions measured in high power reactors. The advantage of this approach is that even small foils which do not affect the neutron field are significantly activated so that the gamma spectrum can be measured for the irradiated foils in distant geometry. To ensure reliable measurement, enough target nuclei in combination with close measuring geometry must be used. This puts strong requests on the evaluation of measured data. Close geometry is challenging because the precise mathematical model of the detector must be used. Measured Spectrum Averaged Cross Section (SACS) can be used either to validate the evaluated reaction cross section (assuming the neutron spectrum is well known), or to validate the neutron spectrum (assuming that the reaction cross sections are well known)

INSTRUMENTS AND METHODS

Gamma spectrometry of irradiated samples

Flux monitors

Calculations

RESULTS

CONCLUSIONS