Instrumentation effects on U and Pu CBNM standards spectra quality measured on a 500 mm³ CdZnTe and a 2×2 inch LaBr₃ detectors

Nuclear Research Center SCK-CEN, B-2400 Mol, Belgium yaroslav.meleshenkovskii@sckcen.be
Nuclear Research Center SCK-CEN, B-2400 Mol, Belgium alessandro.borella@sckcen.be; klaas.van.der.meer@sckcen.be; michel.bruggeman@sckcen.be
Université libre de Bruxelles, Servicede Métrologie Nucléaire (CP/165/84), nipauly@ulb.ac.be; pelabeau@ulb.ac.be
European Commission Joint Research Center, Retieseweg 111, B-2440 Geel, Belgium Peter.SCHILLEBEECKX@ec.europa.eu

Published online: 10 January 2018

Abstract

Nowadays, there is interest in developing gamma-ray measuring devices based on the room temperature operated medium resolution detectors such as semiconductor detectors of the CdZnTe type and scintillators of the LaBr₃ type. This is true also for safeguards applications and the International Atomic Energy Agency (IAEA) has launched a project devoted to the assessment of medium resolution gamma-ray spectroscopy for the verification of the isotopic composition of U and Pu bearing samples. This project is carried out within the Non-Destructive Assay Working Group of the European Safeguards Research and Development Association (ESARDA). In this study we analyze medium resolution spectra of U and Pu standards with the aim to develop an isotopic composition determination algorithm, particularly suited for these types of detectors. We show how the peak shape of a CdZnTe detector is influenced by the instrumentation parameters. The experimental setup consisted of a 500 mm³ CdZnTe detector, a 2×2 inch LaBr₃ detector, two types of measurement instrumentation – an analogue one and a digital one, and a set of certified samples – a ²⁰⁷Bi point source and U and Pu CBNM standards. The results of our measurements indicate that the lowest contribution to the peak asymmetry and thus the smallest impact on the resolution of the 500 mm3 CdZnTe detector was achieved with the digital MCA. Analysis of acquired spectra allowed to reject poor quality measurement runs and produce summed spectra files with the least impact of instrumentation instabilities. This work is preliminary to further studies concerning the development of an isotopic composition determination algorithm particularly suited for CZT and LaBr3 detectors for safeguards applications.