Applied Radiation and Isotopes 156 (2020) 108975 Available online 6 November 2019 0969-8043/© 2019 Elsevier Ltd. All rights reserved. Performance assessment of a 500 mm 3 CZT and a 2x2 inch LaBr 3 (Ce) detectors for the determination of the uranium enrichment using the enrichment-meter method and calibration standards for safeguards applications I. Meleshenkovskii a, b , N. Pauly b, * , P.-E. Labeau b a Belgian Nuclear Research Centre, SCK�CEN; Environment, Health and Safety Institute, Boeretang 200, B-2400, Mol, Belgium b Universit� e libre de Bruxelles, Service de M� etrologie Nucl� eaire (CP/165/84), 1050, Bruxelles, Belgium A R T I C L E INFO Keywords: CdZnTe LaBr 3 (Ce) Room temperature Uranium enrichment Enrichment-meter Safeguards ABSTRACT Determination of the uranium enrichment is an important safeguards verifcation task, routinely carried out using non-destructive assay methods. The enrichment-meter method is one of the most widely used passive non- destructive X- and gamma-ray based methods used for such tasks. Among its advantages is the highly constrained physical nature of its underlying formalism, allowing it to be used with high-resolution HPGe detectors, as well as with low-resolution NaI detectors. Due to attractive features and spectroscopic performance, CdZnTe and LaB- r 3 (Ce) detectors raised interest in their application to such tasks as well. However, their spectroscopic perfor- mance is different to that of the traditional detectors in many ways. Application of the enrichment-meter method requires determination of the net peak areas corresponding to 235 U signature photopeaks. The latter requires an adequate algorithm to select the region-of-interest boundaries, which may be sensitive to asymmetrical photo- peaks of CZT detectors. In this paper we conduct a performance assessment of a 500 mm 3 CZT detector of a quasi- hemispherical design and a 2 � 2 inch LaBr 3 (Ce) scintillator with the enrichment-meter method using a set of certifed uranium standards with enrichment degrees from 0.31% to 4.46% of 235 U atomic abundance. We investigate the impact of different methods used for net peak area determination, statistical quality of acquired spectra and size of region-of-interest boundaries on accuracy and uncertainty. We propose an algorithm for symmetrical/asymmetrical region-of-interest boundaries determination and make recommendations on the best combinations of the region-of-interest size and method used for the net peak area determination for each of the detectors. The underlying routines of the algorithm and analysis procedures are described in detail and results are presented. 1. Introduction Introduction of room temperature medium resolution detectors, such as CdZnTe (CZT) and LaBr 3 (Ce), with superior spectroscopic perfor- mance compared to such traditional room temperature detectors as NaI, has opened new possibilities in many radiation detection applications (Sullivan et al., 2008; Prosper et al., 2012). Indeed, their compact design and absence of cryogenics are an advantage in many practical applica- tions. CZT detectors are prized for their wide energy band gap (E g ~1.6 eV) allowing their room temperature operation, coupled with their high atomic number (Z max ¼ 52) yields a high intrinsic effciency of gamma absorption compared to HPGe (Takahashi and Watanabe, 2001). Besides, CZT detector technologies have rapidly evolved from simple planar designs to advanced co-planar grid and quasi-hemispherical de- signs, yielding energy resolution of 1.3% at 661 keV ( 137 Cs) for a 10 mm � 10 mm x 5 mm device (Ivanov and Dorogov, 1999; Arlt et al., 2000; Ivanov et al., 2014). Nowadays these detectors are commercially available in sizes up to 4000 mm 3 (Ivanov et al., 2014), making them attractive for many practical applications. LaBr 3 (Ce) detectors have a high light output (~60000 photons/Mev), fast response (decay constant <30 ns) and show good energy resolution (~2.2% at 662 keV 137 Cs) (Van Loef et al., 2001; Maghraby et al., 2014; Saint-Gobain detectors leafet 2019). One of the felds where attractive features and spectroscopic * Corresponding author. E-mail address: Nicolas.Pauly@ulb.ac.be (N. Pauly). Contents lists available at ScienceDirect Applied Radiation and Isotopes journal homepage: http://www.elsevier.com/locate/apradiso https://doi.org/10.1016/j.apradiso.2019.108975 Received 3 June 2019; Received in revised form 24 October 2019; Accepted 4 November 2019