The use of Neutron Resonance Transmission Analysis for the

characterization of nuclear materials is discussed. The method, which relies on resonance structures in neutron-induced reaction cross sections, can be applied as a non-destructive method to characterise complex nuclear materials such as melted fuel resulting from a severe nuclear accident. Results of a demonstration experiment at the GELINA facility reveal that accurate data can be obtained at a compact facility even in the case of strong overlapping resonances

Alaerts, G.

Becker, B.

Harada, H.

Heyse, J.

Kitatani, F.

Koizumi, M.

Kopecky, S.

Moens, A.

Mondelaers, W.

Paradela, C.

Schillebeeckx, P.

Tsuchiya, H.

Wynants, R.

English

Scientific Open-access Literature Archive and Repository

DOI 10.1393/ncc/i2015-15176-0Colloquia: UCANS-VIL NUOVO CIMENTO 38 C (2015) 176Characterization of nuclear material by Neutron ResonanceTransmission AnalysisC. Paradela(1), G. Alaerts(1), B. Becker(1)(∗), J. Heyse(1), S. Kopecky(1),A. Moens(1), W. Mondelaers(1), P. Schillebeeckx(1), R. Wynants(1),H. Harada(2), F. Kitatani(2), M. Koizumi(2) and H. Tsuchiya(2)(1) European Commission, Joint Research Centre, Institute for Reference Materialsand Measurements - Retiesewg 111, B-2440 Geel, Belgium(2) Japan Atomic Energy Agency (JAEA) - Tokai-mura, Naka-gun, Ibaraki-ken, Japanreceived 22 February 2016Summary. — The use of Neutron Resonance Transmission Analysis for thecharacterization of nuclear materials is discussed. The method, which relies onresonance structures in neutron-induced reaction cross sections, can be applied asa non-destructive method to characterise complex nuclear materials such as meltedfuel resulting from a severe nuclear accident. Results of a demonstration experimentat the GELINA facility reveal that accurate data can be obtained at a compactfacility even in the case of strong overlapping resonances.PACS 81.70.-q – Methods of materials testing and analysis.PACS 24.30.-v – Resonance reactions.PACS 28.20.Fc – Neutron absorption.PACS 28.41.Te – Protection systems, safety, radiation monitoring, accidents, anddismantling.1. – IntroductionNeutron Resonance Transmission Analysis (NRTA) and Capture Analysis (NRCA)are non-destructive methods to determine the elemental and isotopic composition withoutthe need of any sample preparation [1, 2]. They are based on the presence of resonancestructures in neutron induced reaction cross sections [2] and rely on well establishedmethodologies for neutron induced reaction cross section measurements [3].NRCA has been used extensively at the time-of-flight facility GELINA of JointResearch Centre at Geel (BE) [4] to study objects of cultural heritage interest [1, 3].(∗) Permanent address: Gesellschaft fu¨r Anlagen- und Reaktorsicherheit, Schwertnergasse 1,50667 Ko¨ln, Germany.Creative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 C. PARADELA et al.The use of NRCA for the characterisation of reference samples including nuclear mate-rial is discussed in [5]. The potential of NRTA as a NDA method for the quantification ofSpecial Nuclear Material (SNM), i.e. Pu-isotopes and 235U, in fresh and spent fuel hasbeen demonstrated by Priesmeyer and Harz [6] and Behrens et al. [7]. Noguere et al. [8]applied NRTA to characterize a PbI2 sample that was produced from a solution of nu-clear waste from the reprocessing facility in Le Hague. An extensive overview of NRTAand NRCA applications is given in [2].Neutron Resonance Densitometry (NRD) is being developed as a method to quantifyrock- and particle-like debris of melted fuel formed in severe nuclear accidents [9, 10].NRD is based on NRTA combined with NRCA. The quantification of SNM is based onNRTA, while NRCA using a detector with a good γ-ray energy resolution is applied todetermine the amount of impurities. A conceptual design of a NRD facility has beenpresented by Harada et al. [9]. The analysis of rock- and particle-like debris samplesis challenging due to the characteristics of the samples: i.e. the diversity in shapeand size of the particle like samples, the radioactivity and temperature of the sample,presence of unknown matrix material including strong neutron absorbers and overlappingof resonances [10]. The impact of the diversity in particle size has been investigatedby Becker et al. [11]. They implemented the Levermore-Pomraning model [12] in theresonance shape analysis (RSA) code REFIT [13] and validated this method for NRTAby Monte Carlo simulations and experiments at GELINA [11]. A method to account forthe contribution of strong absorbing light matrix materials that do not have resonancesin the low energy region has been proposed and validated in [3].For industrial applications a compact NRTA system is considered. In this contributionthe performance of NRTA as an absolute NDA method for the characterization of complexnuclear materials at a short flight path station is demonstrated.2. – Basic principles of NRTAThe quantity of interest for NRTA is the fraction of the neutron beam traversing thesample without any interaction. For a parallel neutron beam that is perpendicular to aslab of material, this fraction or transmission T is given by(1) T = exp[−∑knkσtot,k],where σtot,k is the Doppler broadened total cross section and nk is the number of atomsper unit area of nuclide k. When the total cross sections are known, a measurement ofthe transmission can be used for elemental and isotopic analysis.The experimental transmission Texp is derived from the ratio of the counts of a sample-in measurement and a sample-out measurement, both corrected for losses due to the deadtime in the detector and electronics chain and their background contributions. Hence,the experimental transmission is independent of the detector efficiency and incomingneutron flux and no additional calibration measurements are needed. In addition, theexperimental transmission is a direct measure of the theoretical transmission eq. (1) if themeasurements are performed in a good transmission geometry, which can be achieved bya proper collimation of the neutron beam at both the sample and detector position [3].A good transmission geometry results in a small solid angle subtended by the sample andneutron detector such that the background due to the radioactivity of the sample andCHARACTERIZATION OF NUCLEAR MATERIAL BY NRTA 3Fig. 1. – Transmission through a blind sample with the composition given in table I. Theexperimental transmission is compared with the result of a RSA. The contribution due to thedifferent elements present in the sample is also shown.fission neutrons produced by (n, f) reactions in the sample can be neglected. Finally, theareal density of the nuclides present in the sample can be derived by a least squares fitto the experimental data. Such a fit relies on a theoretical estimate of the transmissionwhich is derived from a folding of the theoretical transmission in eq. (1) with the responsefunction of the TOF-spectrometer [3].3. – ResultsTo investigate the potential of NRTA for complex nuclear materials at a compacttransmission station a demonstration experiment was organized at a 10m station ofGELINA. An inventory of 18 different samples of medium-weight (Cu, Co, Mn, Nb andRh) and heavy elements (W and Au) in the form of metallic discs were made available.These elements were chosen to mimic the resonance structures of elements present innuclear fuel assemblies. In addition, strong neutron absorbing B4C samples were madeavailable. A sample box was constructed that could host up to 8 samples. A nuclearinspector from DG-ENER and a staff member of ORNL (US) were asked to assemble atest sample. The box was closed and sealed by the DG-ENER inspector.After a one night measurement the transmission data were analysed by REFIT usingTable I. – Results of a NRTA analysis of a blind sample. The measurements were performedat a 10m GELINA station. The uncertainties on the NRTA data are only due to countingstatistics.Element Areal number density (at/b) RatioDeclared (C) NRTA (E) (C/E)Mn 1.901(0.002)× 10−2 1.886(0.002)× 10−2 1.008(0.002)Co 4.585(0.005)× 10−3 4.550(0.066)× 10−3 1.008(0.015)W 1.337(0.001)× 10−2 1.334(0.002)× 10−2 1.002(0.002)Au 6.844(0.007)× 10−3 6.862(0.005)× 10−2 0.997(0.001)4 C. PARADELA et al.the cross section data in the JEFF-3.2 library. The result of a least squares fit to the datais shown fig. 1. A comparison of the areal density derived by NRTA and the declaredvalues is shown in table I. These data reveal that the amount of the elements present inthe sample was predicted within 1%. Evidently the accuracy of NRTA strongly dependson the quality of the nuclear data [3,14]. It should be noted, that for the analysis of NRTAdata only total cross sections are required and the uncertainties on total cross sections aremostly considerably smaller compared to uncertainties on partial cross sections. SinceNRTA can also be considered as an absolute method, it is one of the most accurate NDAmethods for the characterization of nuclear materials.∗ ∗ ∗This work is part of a collaboration between the Japan Atomic Energy Agency andthe Joint Research Centre (JRC). The experiments at GELINA were supported by the327-ARI-ET project (EUFRAT) of the JRC.REFERENCES[1] Postma H. and Schillebeeckx P., Neutron Resonance Capture and TransmissionAnalysis, in Encyclopedia of Analytical Chemistry, edited by Meyers R. A. (John Wiley& Sons Ltd.) 2009, chapt. a9070.[2] Schillebeeckx P., Becker B., Harada H. and Kopecky S., Neutron ResonanceSpectroscopy for the Characterization of Materials and Objects, in JRC Science and policyreports, EUR 26848 EN (2014).[3] Schillebeeckx P., Becker B., Danon Y., Guber K., Harada H., Heyse J.,Junghans A. R., Kopecky S., Massimi C., Moxon M. C., Otuka N., Sirakov I.and Volev K., Nucl. Data Sheets, 113 (2012) 3054.[4] Mondelaers W. and Schillebeeckx P., Notiziario Neutroni e Luce di Sincrotrone, 11(2006) 19.[5] Schillebeeckx P., Borella A., Drohe J. C., Eykens R., Kopecky S., Massimi C.,Mihailescu L. C., Moens A., Moxon M., Siegle P. and Wynants R., Nucl. Instrum.Methods Phys. Res. A, 613 (2010) 378.[6] Priesmeyer H. G. and Harz U., Atomkernenergie, 25 (1975) 109.[7] Behrens J. W., Johnson R. G. and Schrack R. A., Nucl. Technol., 67 (1984) 162.[8] Noguere G., Cserpak F., Ingelbrecht C., Plompen A. J. M., Quetel C. R. andSchillebeeckx P., Nucl. Instr. Meth. Phys. Res. A, 575 (2007) 476.[9] Harada H., Kitatani F., Koizumi M., Tsuchiya H., Takamine J., Kureta M.,Iimura H., Seya M., Becker B., Kopecky S. and Schillebeeckx P., Proposal ofNeutron Densitometry for Particle Like Debris of Melted Fuel using NRTA and NRCA inProceedings of the 35th ESARDA Symposium, edited by Sevini F., 2013, pp. 547–553.[10] Schillebeeckx P., Abousahl S., Becker B., Borella A., Emiliani F., Harada H.,Kauwenberghs K., Kitatani F., Koizumi M., Kopecky S., Moens A., Moxon M.,Sibbens G. and Tsuchiya H., ESARDA Bull., 50 (2013) 9.[11] Becker B., Kopecky S., Harada H. and Schillebeeckx P., Eur. Phys. J. Plus, 129(2014) 58.[12] Levermore C. D., Pomraning G. C., Sanzo D. L. and Wong J., J. Math. Phys., 27(1986) 2526.[13] Becker B., Kauwenberghs K., Kopecky S., Harada H., Moxon M. andSchillebeeckx P., Implementation of an analytical model accounting for sampleinhomogeneities in REFIT, in JRC Scientific and Policy Reports, JRC 86936, 2013, ISBN978-92-79-35095-5.[14] Tsuchiya H., Harada H., Koizumi M., Kitatani F., Takamine J., Kureta M.,Iimura H., Kimura A., Becker B., Kopecky S., Kauwenberghs K., MondelaersW. and Schillebeeckx P., Nucl. Instrum. Methods Phys. Res. A, 767 (2014) 364.

Characterization of nuclear material by Neutron Resonance

Transmission Analysis

http://eprints.bice.rm.cnr.it/19166/1/ncc11076.pdf

Characterization of nuclear material by Neutron Resonance Transmission Analysis

Abstract

Similar works

Full text

Available Versions

Scientific Open-access Literature Archive and Repository