Status of the NEA international activities on nuclear criticality safety

More than 20 years have passed since the establishment of the Working Party on Nuclear Criticality Safety (WPNCS), in the Organisation for Economic Cooperation and Development (OECD)/ Nuclear Energy Agency (NEA). WPNCS has continued to investigate concerns related to static and transient configurations encountered in the nuclear fuel cycle, such as fuel fabrication, transport, reprocessing, storage and geological disposal. The WPNCS and its associated expert groups hold annual meetings to discuss various issues related to criticality safety. Also, WPNCS supervises the updates to the Database for the International Handbook of Evaluated Criticality Safety Benchmark Experiments (DICE) and the release, maintenance, and update of the Spent Fuel Isotopic Composition database of experimental assay measurements, SFCOMPO-2.0. The current structure of WPNCS is composed of 2 Technical Review Groups (TRGs) and 7 subgroups (SG-1: Role of integral experiment uncertainties and covariance data in criticality safety validation; SG-2: Blind benchmark on MOX damp powders; SG-3: The effect of temperature on the neutron multiplication factor for PWR fuel assemblies; SG-4: Analysis of past criticality accidents; SG-5: Experimental needs for criticality safety purpose; SG-6: Statistical tests for diagnosing fission source convergence and under-sampling in Monte-Carlo criticality calculations; and SG-7: On the definition of a benchmark on sensitivity/uncertainty analysis on used fuel inventory. The recent activities of TGRs and of the SGs are reviewed.