Validation of Thermalhydraulic Computer Codes Used in Safety Analysis: Regulatory Perspective

Abstract of the technical paper/presentation presented at:
ASME Verification and Validation Symposium (V&V)
May 3-5, 2017

Prepared by:
Janusz E. Kowalski
Canadian Nuclear Safety Commission


The Canadian Nuclear Safety Commission (CNSC) and the Canadian Standards Association (CSA) frameworks specify the requirements for validation activities applicable to the computer codes used in the design and safety analyses of nuclear power plants [1, 2]. The regulatory framework requires that thermalhydraulic codes’ capabilities and limits, as well as the quantification of code accuracy, must be assessed during the validation process.

During the past three decades, considerable resources have been devoted in Canada to establish and conduct validation of the computer codes used in safety analysis. The validation effort was primarily phenomena-based and did not fully quantify the code prediction accuracy of key safety parameters.

Recently, CNSC staff have indicated the need to change the validation approach and conduct future validation using key parameters such as trip parameters and figure of merit (FOM). In this new approach, the identification of important phenomena and parameters is directly linked to the acceptance criteria and FOM, forming an essential step of the parameter-based validation process.

This paper describes the regulatory approach used in the review of code validation submissions, including the assessment approach and the review acceptance criteria. CNSC expectations on the code validation process are discussed, with a focus on the data qualification and methodology used for determining the code accuracy.

The scope of the review performed by CNSC staff may be different from case to case. It may consist either of a comprehensive evaluation of the validation program or a more detailed assessment of specific validation activities (e.g., qualification of the data used for validation exercises).


  • 1) Deterministic Safety Analysis, regulatory document REGDOC-2.4.1, Canadian Nuclear Safety Commission, May 2014.
  • 2) Quality Assurance of Analytical, Scientific, and Design Computer Programs, Canadian Standard Association, N286.7-16, January 2016.

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