Contents lists available at ScienceDirect Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene Evaluation of the criticality and reaction rate benchmark experiments utilizing UO 2 F 2 aqueous solution of intermediate enrichment in spherical geometry at ORNL Tanja Goričanec a,b , Bor Kos a,b , Gašper Žerovnik a,1 , Margaret A. Marshall c , Ivan A. Kodeli a , Igor Lengar a , Žiga Štancar a,b , John D. Bess c , David P. Heinrichs d , Soon S. Kim d , Michael L. Zerkle e , Luka Snoj a,b,∗ a Jožef Stefan Institute, Jamova cesta 39, SI-1000, Ljubljana, Slovenia b Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, SI-1000, Ljubljana, Slovenia c Idaho National Laboratory, 1955 N. Fremont Ave., Idaho Falls, ID, 83415, USA d Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA e Bettis Atomic Power Laboratory, PO Box 79, West Mifin, PA, 15122, USA ARTICLEINFO Keywords: Benchmark experiment Spherical geometry UO 2 F 2 ICSBEP IRPHEP MCNP ABSTRACT An evaluation of the criticality and relative fssion rate radial distribution experiments in an 69.2-cm diameter aluminium sphere flled with intermediately enriched UO 2 F 2 aqueous solution is presented. An evaluation of the total experimental uncertainty has been performed within the framework of the International Criticality Benchmark Evaluation Project (ICSBEP) and International Reactor Physics Benchmark Evaluation Project (IRPhEP). In addition, the uncertainty due to the uncertainties in the nuclear data is evaluated in this paper. It has been determined that the highest contribution to the overall uncertainty in the efective multiplication factor k ef is due to the uncertainty in the uranium enrichment ( 550 pcm in k ef due to the 4% uncertainty in 235 U enrichment). The highest experimental uncertainties in the relative fssion rate profle in terms of the relative standard uncertainty (Lrs) are 0.032, 0.016, and 0.020 due to the uncertainty in guide tube diameter, flling tubes position, and detector position, respectively. It is estimated that the uncertainty in the nuclear data contributes approximately 400 pcm–1200 pcm to the uncertainty in k ef depending on the covariance data library used. k ef and radial fssion rates have been calculated with MCNP and COG Monte Carlo neutron transport codes and have been compared to the experimental benchmark values. In general, the various Monte Carlo codes have given similar results with deviations within uncertainties. 1. Introduction Thousands of experiments in diferent reactors and fssile systems have been performed since 1940. Considerable knowledge, experience, equipment and fnancial resources were needed to execute these ex- periments. Their results are of great importance for nuclear technology, because they are a reference for the validation of the modern computer codes and nuclear data. To preserve this data, the Nuclear Energy Agency within the Organisation for Economic Co-Operation and Development (OECD/NEA) launched several projects aiming to collect, preserve and disseminate benchmark data. The aim of the International Criticality Safety Benchmark Evaluation Project (ICSBEP, 2016) is to collect the information of all criticality experiments (Briggs and Bess, 2011; Briggs et al., 2014; Dean, 2003), while the International Reactor Physics Experiment Evaluation Project (IRPhEP, 2017) is evaluating various physical parameters from fssile experiments: reaction rate distribution, neutron fux distribution, neutron energy spectrum, re- activity coefcient measurements, etc. Their goal is to compile ex- perimental benchmark data into standardized format that allows ana- lysts to easily use data to validate computer tools and nuclear data. In the ICSBEP and IRPhEP evaluations great efort is put into the de- termination of experimental uncertainties and the efect of each https://doi.org/10.1016/j.pnucene.2018.10.024 Received 15 June 2018; Received in revised form 17 September 2018; Accepted 29 October 2018 ∗ Corresponding author. Jožef Stefan Institute, Jamova cesta 39, SI-1000, Ljubljana, Slovenia. E-mail addresses: tanja.goricanec@ijs.si (T. Goričanec), bor.kos@ijs.si (B. Kos), gasper.zerovnik@ijs.si (G. Žerovnik), margaret.marshall@inl.gov (M.A. Marshall), ivan.kodeli@ijs.si (I.A. Kodeli), igor.lengar@ijs.si (I. Lengar), ziga.stancar@ijs.si (Ž. Štancar), john.bess@inl.gov (J.D. Bess), heinrichs1@llnl.gov (D.P. Heinrichs), kim53@llnl.gov (S.S. Kim), michael.zerkle@unnpp.gov (M.L. Zerkle), luka.snoj@ijs.si (L. Snoj). 1 Currently at Institute for Reference Materials and Measurements, EC-JRC-IRMM, Retieseweg 111, B-2440 Geel, Belgium. Progress in Nuclear Energy 111 (2019) 97–108 Available online 11 November 2018 0149-1970/ © 2018 Elsevier Ltd. All rights reserved. T