NEA Mandates and Structures

Working Party on Nuclear Criticality Safety (WPNCS)

Mandate (Document reference):

• Agreed at the 7^th Meeting of the Nuclear Science Committee in June 1996 [NEA/SEN/NSC(96)3]
• Summary Record of the 15^th meeting of the Nuclear Science Committee [NEA/SEN/NSC(2004)3]
• Summary Record of the 18^th meeting of the Nuclear Science Committee [NEA/SEN/NSC(2007)3]
• Extended at the 21^th meeting of the Nuclear Science Committee in June 2010 [NEA/SEN/NSC(2010)3]
• Extended at the 24^th meeting of the Nuclear Science Committee, June 2013 [NEA/SEN/NSC(2013)]
• Extended and revised for one year at the 27^th meeting of the Nuclear Science Committee in June 2016 [NEA/SEN/NSC(2016)2]
• Mandate extended and approved under the written procedure by the WPNCS [NEA/SEN/NSC/WPNCS(2017)1]
• Summary record of the 31^st meeting of the Nuclear Science Committee in September 2020 [NEA/SEN/NSC(2020)20]
• Mandate of the Working Party on Nuclear Criticality Safety (WPNCS) extended and approved by the WPNCS [NEA/SEN/NSC/WPNCS(2020)1]

Mandate (Document extract):

Extract from document [NEA/SEN/NSC/WPNCS(2020)1]

Scope

Under the guidance of the Nuclear Science Committee (NSC), the WPNCS will deal with technical and scientific issues relevant to criticality safety. Specific areas of interest include, but are not limited to, investigations concerning static and transient configurations encountered in the nuclear fuel cycle, such as fuel fabrication, transport, separation processing and storage. Areas of activities include:

• evaluation of available experimental data, including critical integral experiments and spent nuclear fuel assay data of spent nuclear fuel;
• assessment of experimental needs ;
• code and data inter-comparison, co-ordination of international benchmark exercises;
• development of codes and models, assessment of uncertainties;
• development of criticality methodologies and data (including the application of burn-up credit);
• study of uncertainty propagation and quantification analyses for criticality safety assessments;
• study of advanced Monte Carlo techniques (including transfer of best practices to practitioners, and the development of convergence, undersampling metrics);
• study of criticality of used nuclear fuel (including investigations on degraded fuel, degraded poisons); and
• study of criticality excursions and criticality accident analyses methodologies.

Objectives

The objectives of the WPNCS are to:

• exchange information on national programmes in the area of criticality safety;
• guide, promote and co-ordinate high priority activities of common interest to the international criticality safety community, establish co-operations;
• develop databases and tools, publish handbooks and reports;
• facilitate communications within the international criticality safety community through relevant websites;
• co-ordinate WPNCS activities with other working parties within the NEA and in other international frameworks to avoid duplication of activities;
• provide a technical basis for other international activities [e.g. International Organisation for Standardisation (ISO), IAEA, …];
• co-ordinate the series of international conferences on nuclear criticality safety (ICNC), held every four years;
• monitor the progress of all activities mentioned above and report to the NSC.

Working methods

The WPNCS will report to the Nuclear Science Committee. The WPNCS will meet once per year, with additional meetings in support of particular activities, as needed.

Interactions

The WPNCS will liaise closely with other relevant NSC bodies, in particular the Working Party on International Nuclear Data Evaluation Co-operation (WPEC) and the Working Party on Scientific Issues and Uncertainty Analysis of Reactor Systems (WPRS). The WPNCS will also coordinate as appropriate with the Committee on the Safety of Nuclear Installations (CSNI) and the relevant working parties under its cognizance. The objective will be to ensure that the respective programmes are complementary and to provide advice and support where required and undertake common work where appropriate.

Deliverables

The deliverables of the WPNCS are the following:

1. Integral Experiments, Databases and Tools

• new editions of the International Handbook of Criticality Safety Benchmark Evaluation Project (ICSBEP), including updated or new evaluations;
• updates to the Database for the International Handbook of Evaluated Criticality Safety Benchmark Experiments (DICE).
• maintenance and update of the new Spent Fuel Compositions (SFCOMPO) experimental post irradiation experiment (PIE) assay database and evaluation of several experiments.

2. Benchmark Reports (Provisional Titles)

• finalisation of the summary report of the now closed Expert Group on Criticality Excursions Analyses (EGCEA);
• finalisation of the summary report of now closed Expert Group on Advanced Monte Carlo Techniques (EGAMCT);
• finalisation of the summary report of the now closed Expert Group on Criticality Analysis of Used Nuclear Fuel (EGUNF);
• report on the uncertainty analysis for criticality safety assessment Phase IV benchmark – role of Integral Experiment Covariance Data for Criticality Safety Validation [Sub-group (SG)- 1];
• report on the analysis of the benchmark on criticality of MOX damp powders (SG‑2);
• report on the effect of temperature on the neutron multiplication factor for PWR fuel assemblies (SG-3);
• report on the benchmark of number of fissions, peak power, profile of power and temperature among different codes/methods based on past criticality accident (SG‑4);
• report on the experimental needs for criticality safety purpose (SG-5);
• report on the statistical tests for diagnosing fission source convergence and undersampling in Monte-Carlo criticality calculations (SG-6);
• report on benchmark specification for sensitivity/uncertainty analysis of used fuel inventory (SG-7); and
• report on a methodology for collecting and disseminating feedback on evaluations from qualified experts to better serve users of the ICSBEP benchmarks (SG-8).