WPNCS Expert Group on Criticality Excursions

This expert group was created with the aim of providing scientific knowledge on criticality excursions (accidents, experiments and simulation). Three main areas were identified by the expert group members as being of high relevance to the criticality-safety community.

Under the guidance of the Working Party on Nuclear Criticality Safety, the major assignments of the expert group include:

• identifying and compiling criticality transient data from experimental programmes and from accident data;
• evaluatingthe main transient experimental programmes and creating a database to store and disseminate the data;

• identifying and highlighting experimental needs for criticality accidents analyses;
• identifying and compiling available models and computer codes for transient analyses;
• defining benchmark exercises to compare the computer codes used for criticality accidents analyses;
• identifying modelling needs.

Current programme of work

The expert group's work currently addresses the following areas:

• The evaluation of criticality excursion experiments. A draft format (MS word file 186 kb) was designed by extending and adapting the International Criticality Safety Benchmark Evaluation Project evaluation format.
• The organisation of inter-code comparison exercises. Benchmark proposals based on experiments performed in SILENE and TRACY solution reactors have been prepared. A report on these benchmark exercises is currently being finalised. A further four phases of this exercise are envisaged. The expert group is examining preliminary results from the second phase of the benchmark exercise, which covers slow transients from the TRACY experimental reactor. A third phase will study code performances to simulate long-duration experiments, whilst a fourth phase will examine the dilute Pu-solution. A final fifth phase will be a detailed analysis of postulated accident conditions.
• The development of a web-based information resource on criticality excursions (experimental programmes, existing modelling capabilities, criticality accidents).

Phase I report discuss the performances of four transient codes: AGNES, CRITEX, INCTAC, and TRACE to simulate experimental results from two experimental facilities SILENE and TRACY (final report is on publication)

Related links

NEA Working Party on Nuclear Criticality Safety

Nuclear Science Committee

Working area (password required)

E-mail contact: Yolanda Rugama (rugama@nea.fr)

Last updated: 20 September 2007