The annual technical review group meetings of key NEA experimental data evaluation and preservation projects, the International Criticality Safety Benchmarks Evaluation Project (ICSBEP) and the International Reactor Physics Experiments Evaluation Project (IRPhE) Technical Review Group (TRG) were held on 13-17 April 2026 in Boulogne-Billancourt, France. The two meetings brought together over 80 experts – experimentalists, practitioners, and modellers – from 13 countries to review candidate evaluations, discuss emerging issues, and enhance data accessibility.
The ICSBEP conditionally approved nine new criticality benchmark evaluations for inclusion in the next edition of the ICSBEP Handbook, pending final comment resolution. The approved experimental benchmarks include:
- HEU-MET-FAST-086, which is a revision of the previous Godiva-IV benchmark. Godiva-IV is a HEU critical experiment located at the National Criticality Experiments Research Center (NCERC), which is operated and managed by Los Alamos National Laboratory (LANL) in the United States (US). This revision includes an improved uncertainty analysis and addresses the concerns in the previous errata and was evaluated by LANL.
- HEU-MET-FAST-108, which is an evaluation of the Prompt Fission Uranium Neutron Spectrum (PFUNS) experiment using highly-enriched uranium (HEU) hemishells. The experiment was conducted at NCERC and evaluated by LANL in the US.
- LEU-COMP-THERM-113, which includes an experiment that was part of the Matériaux Interaction Réflexion Toutes Epaisseurs (MIRTE) programme, conducted at the Commissariat à l’Energie Atomique (CEA) Valduc Center. The experiment was evaluated by the Autorité de Sûreté Nucléaire et de Radioprotection (ASNR), France.
- IEU-COMP-THERM-007, which is a configuration of the Instituto de Pesquisas Energéticas e Nucleares (IPEN)/MB-01 research reactor facility located in the city of São Paulo, Brazil. The IPEN/MB-01 is a water-moderated reactor with 19.75% enriched U3Si2-Al plate fuel. This evaluation was done by Oak Ridge National Laboratory (ORNL) in the US and IPEN (Brazil).
- IEU-COMP-THERM-017, which is an evaluation of the PROTEUS critical experiment facility of the Paul Scherrer Institute (PSI) in Switzerland, performed within the framework of an international collaboration. This evaluation is an extension of a previous IRPhE evaluation, and this revision was done by Idaho National Laboratory (INL), University of Michigan, and JFoster & Associates in the US.
- IEU-COMP-THERM-018, which is an evaluation of a recent HALEU experiment (i.e., DEIMOS) with TRISO kernels that was reflected by graphite and beryllium. This experiment was conducted at NCERC and evaluated by LANL in the US.
- ALARM-CF-PERC-SHIELD-001, which is the evaluation of a measurement of the fast neutron leakage flux from a sphere filled with C2Cl4 (Perchlorethylene) using a stilbene detector and the surface distribution of reaction rates of dosimetry foils when a 252Cf(spontaneous fission) neutron source was placed in the center of the sphere. The experiment and evaluation were conducted by Research Centre Řež (RCR, Centrum Výzkumu Řež) in Czechia.
- FUND-SNL-U-HE3-MULT-001, which is an evaluation of a subcritical experiment of neutron multiplicity measurements of a water-moderated and -reflected low-enriched uranium oxide fuel lattice. The experiment was conducted at Sandia National Laboratories and evaluated by Lawrence Livermore National Laboratory (LLNL) in the US.
- FUND-NCERC-CF-HE3-MULT-001, which is an evaluation of configurations that were part of the Measurement of Uranium Subcritical and Critical (MUSiC) campaign (HEU-MET-FAST-104), which used a set of highly-enriched hemishells. The experiment was conducted at NCERC and evaluated by LANL in the US.
In addition to these 9 evaluations, the next addition of the ICSBEP Handbook will include an evaluation that did not meet current acceptance criteria, but is being retained for its historical significance and value. FUND-NCERC-NP-HE3-MULT-001 is a subcritical evaluation of a neptunium sphere that is part of the NCERC nuclear material inventory.
During the IRPhE Project meeting, a new benchmark and revision were conditionally approved for the next edition of the IRPhE Handbook, pending final comment resolution. The approved and revised benchmarks include:
- The new evaluation that was approved is a series of reactor physics experiments which were carried out to study the effect of iron in the form of low-alloy steel or copper on criticality. The measurements were carried out from October 2023 to January 2025 at the zero-power LR-0 reactor operated by the Research Center Řež (RCR, Centrum Výzkumu Řež) in Czechia.
- A revision to the Zero Energy Deuterium (ZED-2) Reactor was discussed and approved. The ZED-2 reactor is a heavy-water moderated, tank-type reactor currently operated by Canadian Nuclear Laboratories in Chalk River, Ontario, Canada. The revision includes improved descriptions of reactor components.
In addition, minor revisions to the SNEAK-7A and -7B were discussed as well as upcoming experiments for inclusion in the IRPhE Handbook.
