LWR Safety Analysis and Licensing and Implications for Advanced Reactors (2011)

The risk-informed approach will be discussed in the light of US plants experience.Approaches in other countries will also be presented and the gained experience will be commented, Kadak & Matsuo (2007). Basic definitionsSafety analysis is the study, examination and description of a nuclear installation expected behavior throughout its life, under normal and transient conditions, and also under postulated events, in order to determine: a) safety margins provided in normal operation and in transient regimes; b) the adequacy of items to prevent the consequences of accidents that may occur.Safety assessment is the systematic and independent evaluation carried out by the regulator on the submitted safety analysis.It is used to support and subsidize the licensing decision on the plant acceptability, once the risk associated with its operation is known.Inspection is the core activity performed by the regulator to verify compliance with its regulatory requirements or expressed in terms of licenses and permits and to implement them through coercive actions.Regulatory inspection is the examination, observation, measuring, testing and verification of documentation executed by the regulator during any stage of the licensing process, to ensure compliance of materials, components, systems, structures, operational activities, processes, procedures and qualification of personnel with pre-established requirements or determined by the regulatory body.Figure 1 displays the general Brazilian licensing process, where the definitions discussed herein play an important role.The Preliminary Safety Analysis Report (PSAR) is one of the reports of the application for a building permit.It aims at demonstrating that the applicant is qualified to manage the construction application by providing design-related technical information to the regulator.The Final Safety Analysis Report (FSAR) presents the final analysis and evaluation of plant design, as constructed, and the behavior of items in order to assess the risk to health and safety of the population as a whole, resulting from the installation and considering the information provided since the presentation of the PSAR.A discussion on PSA meaning will be presented in Section 7 in the context of risk-informed decision making. Defense in depthThe basic philosophy of nuclear power plant design has been described as defense in depth expressed in terms of three safety levels (NRC).These levels cover a variety of considerations that often intertwine, so that the allocation of certain aspects of the project to one level or another is somewhat arbitrary.However, these levels are useful to indicate the various stages in the safety design of a nuclear power plant.NRC defines each safety level through ordinances or rules.The basic purpose of reactor safety is to maintain the integrity of multiple barriers against the release of fission products.This integrity is supported by a defense in depth approach on three safety levels: a) prevention; b) protection; c) mitigation.However, it has been more convenient to subdivide the second safety level (protection) into three new levels.Therefore, the implementation of the defense in depth concept is made through five levels whose objectives and essential means are displayed in Table 1, IAEA www.intechopen.com