This paper explains the procedure for evaluating RPV material degradation in WWER-type reactors during operation. Because no legal document existed in the former Soviet/Russian codes and rules, the VERLIFE project within the European research activities started with the aim of elaborating such a document, which had to be consistent with the original Soviet/Russian codes and rules and incorporate PWR approaches and the most current developments in fracture mechanics. This document was finalized as IAEA-NULIFE-VERLIFE “Procedure for Evaluation of Integrity and Lifetime of Components and Piping in WWER NPPs during Operation” with participation of experts from all countries operating WWERs, as well as some countries in the European Union. This procedure has been accepted as Section IV in the normative technical documentation of the Czech Association of Mechanical Engineers and is continuously updated.