Components Qualification for the Safe Operation of Nuclear Power Plants

Abstract

AREVA operates a worldwide unique thermal hydraulic platform to ensure high safety standards in the nuclear industries. This platform is operated as an accredited test and inspection body according to ISO 17025 and 17020 to grant a high and independently confirmed quality standard. The accreditation also ensures the independency of the organization and confidentiality to the individual stakeholders, as for example research centers, utilities, components suppliers, engineering companies, and vendors. Especially for nuclear power plants it is very relevant to consider that reliability depends on the integrity of its components during its life time—from design through construction, operation, and maintenance. For example, a typical nuclear power plant (NPP) has 1000–2000 large valves and 7500–12,500 small valves, of which about 200–400 are designated Safety Class 1. These safety-related components require a higher level of diligence in ensuring that they function properly. The qualification of these Safety Class 1 components is relevant for reactor new builds but also for installed plants. Because replacing worn or malfunctioning safety-related components, especially those that were designed and manufactured decades ago by now-defunct manufacturers, is a challenge, qualification programs for new components have been developed. As regulations have changed over the years, so have the requirements for component qualification. This paper explains newly established qualification tasks, the corresponding testing infrastructure, and the state of the art of testing technology. By way of example, the paper describes the program and possible sequence of qualifying NPP safety-related valves. Depending on the design and operational conditions, such a qualification program may include testing containment environmental effects, sealing capability, end loading, seismic performance, and proper functioning under various conditions, such as high-energy pipe rupture, thermal shock, particle-loaded fluids, to name a few.