Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbH

GRS provides, as scientific-technical expert and research organisation, interdisciplinary knowledge, advanced methods and qualified data for assessing and improving the safety of technical facilities and for further developing the protection of man and the environment against technical hazards and risks, which cannot be excluded during operation of such facilities. GRS’ activities are mainly focused on the area of nuclear safety and waste management, where it is Germany´s leading expert institution and the main technical support organisation to the federal government of Germany on nuclear safety and research. GRS is a founding member of the European TSO network (ETSON), and a member of NUGENIA and ESReDA. Via GRS’s subsidiary RISKAUDIT, jointly owned with IRSN, GRS’s experts support several international regulatory authorities and TSOs in projects financed by the European Commission or other international institutions.

In APAL, GRS contributes to WP1 state-of-the-art of thermalhydraulic as well as to probabilistic PTS analysis, where GRS performs thermal hydraulic calculations on postulated leak transients with the sytem code ATHLET in connection with the mixing tool GRS-MIX to determine the uncertainties of the loading conditions for structure and fracture analyses, especially the pressure profile, the temperature distribution of the fluid in the downcomer and the heat transfer coefficient dependent on position and time. In WP3 temperature distributions and stresses are computed in the RPV wall based on thermal hydraulic loading conditions. In WP4 the crack initiation probability (CIP) of a postulated fixed crack is computed with the PROST code. Uncertainties in the thermal hydraulic loading conditions as well as in the embrittlement related data are considered. Minor extensions to the PROST code are performed to ease the use and to ensure the validity in this application case. Based on the conclusions of the benchmark activities on assessment of the considered uncertainties GRS contributes to the proposal of a European methodology for probabilistic RPV integrity assessment (WP5). Like all partners, GRS contributes also to WP6 and WP7.