Nuclear Power Technology Development

IAEA Coordinated Research Projects (CRP)

Benchmarking Severe Accident Computer Codes for Heavy Water Reactor Applications


Consideration of severe accidents at a nuclear power plant (NPP) is an essential component of the defence in depth approach used in nuclear safety. Severe accident analysis involves very complex physical phenomena that occur sequentially during various stages of accident progression. Computer codes are essential tools for understanding how the reactor and its containment might respond under severe accident conditions.

This CRP promotes international collaboration among IAEA Member States through the benchmarking exercise to improve severe accident analysis capability for Heavy Water Reactors (HWRs). The CRP scope includes defining the severe accident sequence and conducting benchmark analyses for HWRs, simulating phenomenological experiments(s) relevant to severe accidents and comparing the results with experimental data, and evaluating the capabilities of existing computer codes to predict important severe accident phenomena and suggesting necessary code improvements and/or new experiments to reduce uncertainties. The CRP has been planned on the advice and with the support of the IAEA Nuclear Energy Department's Technical Working Groups on Advanced Technologies for HWRs (the TWG-HWR). The CRP will be conducted by IAEA's Nuclear Power Technology Development Section, in cooperation with the Division of Nuclear Installation Safety.

Overview of the CRP

Computer codes used for the analysis of design basis events have been validated against integral and/or separate effects tests, whereas in the case of severe accident computer codes it is rather impossible, or at least quite expensive, to carryout a validation exercise against integrated experiments. Consequently, the code capabilities have to be assessed based on benchmarking against other severe accident computer codes. In view of this, a benchmarking exercise becomes necessary to assess the results from various computer codes to provide an improved understanding of modelling approaches, strengths and limitations. The exercise could also suggest ways to overcome code limitations and thereby increase the confidence in severe accident code predictions. A benchmarking exercise encompassing the various severe accident codes in use within the HWR community is important not only for providing confidence in the overall performance of the codes but also for the reduction of uncertainties in their predictions.

Planned activities within the CRP include:

  • collection and evaluation of existing models, correlations, experiments, and computer codes applicable to HWR severe accident analysis,

  • determination of reference design and severe accident scenario for benchmarking analysis considering operating HWRs and available computer codes in Member States,

  • establishment of criteria for fuel failure, fuel channel failure, fuel channel disassembly, core collapse, calandria vessel failure and containment failure, and reactor vault failure,

  • benchmark analysis for Phase 1 (accident initiation to fuel channel dryout), Phase 2 (fuel channel dryout to core collapse), Phase 3 (core collapse to calandria vessel failure), and Phase 4 (calandria vessel failure to containment failure),

  • benchmark analysis for experiment.

The expected outcomes from this CRP are:

  • improved understanding of the importance of various phenomena contributing to event timing and consequences of a severe accident,

  • improvement of emergency operating procedures or severe accident management strategies,

  • advanced information on computer code capabilities to enable the analysis of advanced HWR designs.


The following institutions are participating in this CRP:

Korea Atomic Energy Research Institute (Rep. of Korea), Shanghai Jiao Tong University (China), Politehnica University of Bucharest (Romania), Atomic Energy of Canada, Ltd. (Canada), Bhabha Atomic Research Centre (India), and Nuclear Power Corp. of India Ltd. (India)

Research Coordination Meetings

The First Research Coordination Meeting (RCM) of the CRP was held at IAEA Headquarters, Vienna, Austria, 25-27 February 2009. During this first RCM the participants developed an Integrated Research Plan (IRP) that indicated how the participating organizations were to collaborate during the CRP and that specified their contributions to the various activities of the CRP.

The Second Research Coordination Meeting (RCM) of the CRP was held at NPCIL Headquarters, Mumbai, India, 4-7 May, 2010.

The Third Research Coordination Meeting (RCM) of the CRP was held at KAERI, Daejeon, Rep. of Korea, 30 August - 2 September 2011

CRP Results


Please contact NENP Technology Development Section - Contact Point if you have any questions.