[en] Independent peer review should be an integral part of any Probabilistic Safety Assessment (PSA). The value of the benefits of a valid PSA may be many times the cost of the study, as demonstrated by a recent report in the United States (EPRI NP-5664) based on utility experience and USNRC perspectives in the practical application of probabilistic risk assesssment (PRA). Independent peer review and revisions, as necessary, give a degree of assurance of validity. The basic disciplines typically covered in a review include event tree analyses, systems analyses, human reliability analyses, data analyses, quantification and uncertainty propagation and external event analyses (if these are included in the PSA). This document is intended to serve as guidelines both for the conduct of an independent peer review of a PSA and for the IPERS programme. The document gives guidance on how an IPER service is conducted, the procedure and steps needed for preparation of an IPER and the technical areas normally covered. 4 tabs