Best Estimate Safety Analysis for Nuclear Power Plants: Uncertainty Evaluation. IAEA Safety Report Series

Abstract

Deterministic safety analysis (frequently referred to as accident analysis)\n\nis an important tool for confirming the adequacy and efficiency of provisions\n\nwithin the defence in depth concept for the safety of nuclear power plants.\n\nRequirements and guidance pertaining to the scope and content of accident\n\nanalysis have been described in various IAEA publications. To a certain extent,\n\naccident analysis is covered in several publications of the revised Safety\n\nStandards Series, mainly in the Safety Requirements on design (Safety of\n\nNuclear Power Plants: Design, Safety Standards Series No. NS-R-1) and in the\n\nSafety Guide on Safety Assessment and Verification for Nuclear Power Plants\n\n(Safety Standards Series No. NS-G-1.2). More detailed guidance has been\n\nincluded in the IAEA safety report on Accident Analysis for Nuclear Power\n\nPlants (Safety Reports Series No. 23). The safety report covers all the steps\n\nrequired for accident analyses (i.e. selection of initiating events and acceptance\n\ncriteria, selection of computer codes and modelling assumptions, preparation\n\nof input data and presentation of the calculation results).\n\nThe aforementioned safety standards and safety report recommend as\n\none of the options for demonstrating the inclusion of adequate safety margins\n\nthe use of best estimate computer codes with realistic input data in\n\ncombination with the evaluation of uncertainties in the calculation results. For\n\nthe evaluation of uncertainties, the sharing of experience and provision of\n\nguidance are elements of vital importance.\n\nThis report has therefore been developed to complement the safety\n\nstandards and the safety report referred to above. It provides more detailed\n\ninformation on the methods available for the evaluation of uncertainties in\n\ndeterministic safety analysis for nuclear power plants and provides practical\n\nguidance in the use of these methods. This report is directed towards analysts\n\ncoordinating, performing or reviewing best estimate accident analysis for\n\nnuclear power plants, both on the utility side and on the regulatory side. It also\n\nprovides background material for relevant IAEA activities such as seminars,\n\ntraining courses and workshops.\n\nThanks are due to V. Landauer for the preparation of the manuscript. The\n\nIAEA officer responsible for this publication was S. Lee of the Division of\n\nNuclear Installation Safety.