Regular Article

The 0E2 benchmarks for PWR UO₂ decay heat: an analysis from the NEA WPNCS

¹ Paul Scherrer Institute (PSI), Villigen, Switzerland
² Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain
³ OECD Nuclear Energy Agency (NEA), Paris, France
⁴ JFoster & Associates, LLC (JFA), Idaho Falls, ID, USA
⁵ Nuclear Safety and Radiation Protection Authority (ASNR), Fontenay-aux-Roses, France
⁶ Universidad Politécnica de Madrid (UPM), Madrid, Spain
⁷ Commissariat à l’énergie atomique et aux énergies alternatives (CEA), Cadarache, France
⁸ Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
⁹ Belgian Nuclear Research Centre (SCK CEN), Mol, Belgium
¹⁰ Subatech (CNRS/IN2P3, IMT Atlantique, Université de Nantes), Nantes, France
¹¹ ENRESA, Madrid, Spain
¹² Gesellschaft für Zwischenlagerung (BGZ), Essen, Germany
¹³ Bundesamt für die Sicherheit der nuklearen Entsorgung (BASE), Salzgitter, Germany
¹⁴ VTT Technical Research Centre of Finland (VTT), Espoo, Finland
¹⁵ EPFL, Lausanne, Switzerland
¹⁶ Svensk Kärnbränslehantering AB (SKB), Solna, Sweden
¹⁷ Jožef Stefan Institute (JSI), Ljubljana, Slovenia
¹⁸ Commissariat à l’énergie atomique et aux énergies alternatives (CEA), Saclay, France
¹⁹ ORANO, Beaumont Hague, France
²⁰ ORANO, Montigny-le-Bretonneux, France
²¹ National Nuclear Laboratory (NNL), Seascale, UK
²² Oak Ridge National Laboratory (ORNL), Oak Ridge, TN, USA
²³ Central Research Institute of Electric Power Industry (CRIEPI), Nagasaka, Japan
²⁴ Science Engineering Associates, Madrid, Spain
²⁵ Studsvik Scandpower, Inc., Newton, MA, USA
²⁶ Nagra, Wettingen, Switzerland

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Received: 11 February 2026
Received in final form: 30 March 2026
Accepted: 8 April 2026
Published online: 19 June 2026

Abstract

This paper presents the work performed in the subgroup 16 of the Working Party for Nuclear Criticality Safety (WPNCS) of the OECD Nuclear Energy Agency. The main goal was to define two decay heat benchmarks for Spent Nuclear Fuel (one pincell and one assembly), perform calculations and compare and analyze the results in light of existing calorimetric measurements. The selected case is the PWR UO₂ assembly 0E2, irradiated at the Ringhals-3 reactor and measured at the Clab facility in Sweden. In total, 21 institutes worldwide participated to the exercise, leading to 55 calculated results (named C). It was found that the measured decay heat values (E) can be satisfactorily reproduced with two-dimensional assembly calculations, leading to an average C/E value of 0.99, with an uncertainty (or one standard deviation) of ±0.01.