Reactor components and structures degrade by exposure to heat, environmental conditions and radiation. It is vital to understand ageing processes to ensure that safety criteria continue to be met.
An essential part of the safety of nuclear facilities is ensuring that components and systems continue to meet their performance criteria, recognising that in many cases they will degrade over time due to exposure to environmental conditions (temperature, radiation, corrosive elements). Since the 1960s, one of the larger areas of co-operation on nuclear safety for the NEA is research and experience with ageing mechanisms. The current lead in this area is the Committee on the Safety of Nuclear Installations’s (CSNI’s) Working Group on Integrity and Ageing of Components and Structures (WGIAGE). There are two main types of components and structures considered by WGIAGE. First, there are metallic components such as vessels, piping and valves, which are essential to the operation of a reactor. Second, there are concrete structures such as reactor buildings and containment. In both cases, experience has shown that there are mechanisms that lead to slow degradation over the long term, and faster-acting threats, such as environmental assisted cracking, which can lead to more rapid failure. WGIAGE members share experience with the ageing of components and structures, and co-operate on research to monitor the integrity of structures and investigate ageing mechanisms. WGIAGE also considers seismic engineering and the response of reactor structures to earthquakes as a particular focus – read more under external hazards and nuclear safety.
The main mission of the Working Group on Integrity and Ageing of Components and Structures (WGIAGE) is to advance the current understanding of the relevant aspects related with ensuring the integrity of components, systems and structures (SSC), and to propose general principles on the optimal ways of dealing with respective challenges facing operating and new nuclear power plants as well as other nuclear facilities, and to make use of an integrated approach to design safety and plant life management.