Development of Component Specific Ageing Management Programmes for Mechanical Components at the NPP Paks

The plant’s current ageing management practice is based on designer’s specifications and the more than 20 years of operation and maintenance experience. This practice meets the established rules and requirements in depth. In accordance with local regulations for long term operation the implementation of a comprehensive ageing management system for a defined scope of nuclear (safety classes 1–3+) components is required. As part of the comprehensive system, type ageing management programmes (TAMP) are developed, from which component specific programmes (SAMP) shall be developed and executed for the passive components of the concerned scope. This presentation summarizes the specific ageing management programmes of the WWER main components (reactor pressure vessel, steam generator, pressurizer, main coolant pump, main circulation pipeline, main gate valve) and of some other mechanical equipment (ECCS heat-exchangers, main steamline valves, steam generator drain expander tanks and emergency feedwater pumps). The development of the SAMPs is based on the TAMPs that describe the degradation processes (low-cycle fatigue, thermal ageing, irradiation damage, stress corrosion, boric acid corrosion, wear, local corrosion, irradiation assisted stress corrosion, loosening of threaded fasteners, swelling, high-cycle fatigue, general corrosion, thermal stratification fatigue, erosion, erosion-corrosion, water hammer, ground water corrosion, microbiological corrosion, deposition). The format and content of the SAMP comply with the domestic regulatory system and essentially follow the attributes of the US NRC’s 10 element ageing management programme (scope, prevention, parameters to be inspected, detection, monitoring-trending, acceptance criteria, corrective actions, feedback, administrative control, utilization of operating experience). During programme development, the review and, based on specific aspects, the examination of compliance of each established programme (technical review plan, ISI programme, ISI acceptance standards, maintenance instructions, water chemistry programmes, operational manuals, other inspection programmes etc.) dealing with the given component and affecting its ageing management were carried out, also taking account of the Aging Management (AM) review reports produced as part of the service life extension project. On the one hand the evaluation of the SAMP confirmed the effectiveness of the programmes currently applied, from ageing management aspects, and on the other hand, the recommended developments and enhancements help establish and strengthen the Comprehensive Ageing Management system.