Qualification of scientific computing tools used in the nuclear safety case - 1. barrier. Guide No. 28, Version of 25/07/2017

Some of the studies used in the nuclear safety case for basic nuclear installations (BNI) are based on the use of scientific computing tools (SCT). Article 3.8 of the order in reference [3] requires the use of 'validated' methods and of SCTs that have been qualified for the performance of these studies. The licensee must thus have adopted formal approaches to establishing the validation of the methods and the qualification of the SCT. The examinations by ASN and IRSN of the file concerning a method and that concerning the qualification of an SCT used for application of this method, are generally separate; however, if the method and the SCT are linked, these two files are generally examined jointly. These files are examined prior to the examination of the studies performed using these methods and SCTs. In this guide, the qualification of an SCT implies recognition by the licensee that an SCT is able to provide results that are usable for a nuclear safety case. This recognition is established on the basis of data produced by verification, validation, quantification of uncertainties and transposition operations. These operations are part of an overall process described in chapters 3, 4 and 5 ensuring that the SCT is capable of calculating the variables of interest with the uncertainties appropriate to the requirements, within the intended scope of utilisation. This guide presents the ASN and IRSN recommendations for these operations and this process. Its purpose is to provide a coherent set of recommendations to be implemented in order to ensure that an SCT is qualified in accordance with ASN's requirements. It aims to facilitate the preparation and assessment of the files establishing the qualification of the SCTs, by specifying the contents of the file to be produced by the licensee for transmission to ASN. It takes account of international reference texts. In the studies contributing to the nuclear safety case, this guide applies to the SCT used to demonstrate compliance with the technical acceptance criteria associated with the fuel behaviour in normal operation or in the event of incidents or accidents affecting pressurised water reactors, research reactors, or spent fuel or fuel storage pools. The technical areas concerned are fuel neutronics, thermohydraulics, thermomechanics and the physical chemistry of the fuel. This guide applies to the SCT used in the initial design of basic nuclear installations (BNIs), during their periodic safety reviews, for modifications or in the additional substantiation files, during operation or for shutdown and decommissioning. This guide was produced by ASN and IRSN, with the participation of representatives from industry and the licensees during certain steps. It was submitted for consultation to industry and the licensees and then to the public, from 31 March 2017 to 4 May 2017. After recalling the context of qualification (see chapter 1.2), the guide deals with the following in turn: - the intended scope of utilisation of the SCT in the safety case (chapter 2), which must be defined before the processes of verification, validation and transposition subsequently presented; - the process of verification and validation (chapter 3) of the SCT, which lies at the heart of qualification; - the process of transposition of the validation cases to the intended scope of utilisation (chapter 4); - the declaration of qualification (chapter 5); - several particular points concerning certain software (pre- and post-processing, coupling, etc.) and certain uses of the SCT (chapter 6); - the description of the content of the qualification file to be submitted to ASN (chapter 7)