Scope and objectives

The Working Party on Nuclear Criticality Safety (WPNCS) deals with technical and scientific issues relevant to criticality safety. Specific areas of interest include (but are not limited to) investigations of static and transient configurations encountered in the nuclear fuel cycle. These include fuel fabrication, transport and storage. The WPNCS's objectives are to:

• exchange information on national programmes in the area of criticality safety;
• guide, promote and coordinate high-priority activities of common interest to the international criticality safety community and to establish co-operation;
• monitor the progress of all activities and report to the Nuclear Science Committee (NSC);
• publish databases, handbooks and reports;
• facilitate communications within the international criticality safety community through relevant websites;
• co-ordinate the ongoing series of International Conferences on Nuclear Criticality Safety (ICNC), to be held every four years;
• co-ordinate WPNCS activities with other working groups within the NEA and in other international organisations to avoid duplication of activities;
• provide a technical basis for the activities of other international organisations (e.g. International Organizations for Standardization (ISO), International Atomic Energy Agency (IAEA)).

Currently, the WPNCS co-ordinates multiple rotating subgroups, the ICSBEP Project and the SFCOMPO project.

Active Subgroups

If interested in joining any WPNCS subgroup activity, please contact the WPNCS Secretariat (Kelsey Amundson).

SG-17: Subgroup on critical and subcritical values for Nuclear Criticality Safety (NCS) 

The goal of this sub-group is to compile critical values for several fissile materials fully reflected by water. This work is a continuation of the work performed in 2006 by the WPNCS (NEA report n°5433) with up-to-date codes and nuclear data libraries. The resulting report will present the best-estimate critical and subcritical values taking into account the uncertainties due to nuclear data libraries (and possible bias if simple codes are used, such as multigroup energy code).

Coordinator: Thomas Albert (ASNR, France)

SG-18: International Exercise on Nuclear Criticality Safety Evaluation

The objective is to share best practices of each participant country regarding the methodology used to analyse and prevent inadvertent criticality, using a fictional application case. This subgroup will focus on defining the fictional application case.

Coordinator: Michael Prigniau (CEA, France)

SG-19: Subgroup On Burnup Estimation Definitions and Methods for Nuclear Fuel

The work will focus on the quantity called “burnup”, primarily in the context of nuclear fuel irradiated in Light Water Reactors. A review of the different methods to estimate the burnup will be provided, based on the expertise and experience of participants. No specific calculations will be required, and a report will be the main outcome of the SG (both a NEA summary report and another extended document).

Coordinator: Dimitri Rochman (NAGRA, Switzerland)

SG-20: Subgroup to Establish Best Practices for Neutron Noise Methods for Criticality Assay

The subgroup will analyse previous FUND ICSBEP benchmarks (i.e. ICSBEP benchmarks related to fundamental physics measurements) with a variety of neutron noise methodologies. We will present an intercomparison of derived integral parameters (prompt decay constants, criticality) with each institution’s current approach. The analysis will target specific issues in the ICSBEP community like effective uncertainty quantification, the treatment of deadtime, the effect of electronics noise, the various analysis methods (Rossi-alpha, Feynman-alpha, frequency domain, etc.), and best practices for reproducing noise measurements with Monte Carlo codes. 

Coordinator: Daniel Siefman (UC-Berkeley, United States)

Upcoming Meetings

2027 Virtual Meeting (36th Meeting of the WPNCS & Subgroups)

Date: 25 - 29 January 2027

Registration: to be provided later

Current WPNCS Leadership

Chair: Greg O'Connor (ONR, United Kingdom)

Vice-Chair: Coralie Carmouze (CEA, France) & Alexander Vasiliev (PSI, Switzerland)

Members' area

WPNCS members' area (password protected | reminder)