Incorporation of advanced accident analysis methodology into safety

FOREWORD Safety analysis reports (SARs) represent the most comprehensive compilation of specific information relevant to the safety of a nuclear power plant (NPP). They serve as the basis for assessment of the overall NPP safety status, as well as for modifications and improvements of plant hardware, procedures and operation. For the regulatory body the SAR is the essential document for the licensing process. Deterministic safety analysis (frequently referred to as accident analysis) is an essential part of any SAR. Due to the close interrelation between accident analysis and safety, an analysis that lacks consistency, is incomplete, or of poor quality, is considered a safety issue for a given NPP. Developing IAEA guidance for accident analysis is thus an important step towards resolving this issue. Requirements and guidance pertaining to the scope and content of accident analysis have, in the past, been partially described in various IAEA technical publications. Accident analysis is also covered in several IAEA Safety Standards, for example in the Safety Requirements on Design and in the Safety Guide on Safety Assessment and Verification. In consistence with these publications, the IAEA has developed a detailed Safety Report on Accident Analysis for Nuclear Power Plants, which is aimed at providing practical guidance for performing accident analysis. The report covers all the steps required for accident analyses, i.e. selection of initiating events and acceptance criteria, selection of computer codes and modelling assumptions, preparation of input data and presentation of the calculation results. Advanced best estimate computer codes are suggested in all IAEA guidance publications to be used for safety analysis. The current TECDOC complements the Safety Report on Accident Analysis for Nuclear Power Plants and presents additional guidance for specific application of advanced computer codes in accident analysis needed for the SARs. It provides an overview of presently available advanced computer codes for various technical disciplines relevant for reactor accidents and discusses the application of such codes for various categories of accidents. The report is intended for use primarily by the developers or reviewers of deterministic safety analysis for the SAR of a NPP, both on the utility as well as on the regulatory side. The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of names …