PAMELA: Predictability of long-term Ageing MEchanisms of reactor components based on modelling and LAboratory experiments

Général

In nuclear power plants, reactor materials undergo ageing and subsequent degradation in physical and mechanical properties, due to severe in-service neutron irradiation. In order to guarantee the safety and improve the economics of the plants, it is vital to gain full knowledge of the kinetics of the processes leading to materials degradation, so as to estimate reliably the component lifetime. Costly replacements of in-core parts can in this way be properly planned, within full respect of safety. In addition, by properly assessing the lifetime of irreplaceable components, such as the pressure vessel, the period of operation of the plant can be safely extended.

For this purpose, experimental data concerning the behaviour of materials beyond the standard lifetime of the component must be produced. These are necessarily accelerated experiments, in which materials are irradiated at higher dose rates, so as to reach faster the end-of-life dose, and also exceed it. These experiments should mimic as closely as possible the operational conditions in terms of temperature, pressure, presence of flowing water (for corrosion), etc. These irradiation experiments can be conducted in test reactors using neutrons, but in order to make it affordable to explore more operating conditions also ion irradiation can be used. The issue then arises of being sure that the higher dose rates and sometimes the different impinging particles used in these experiments do not alter the ongoing physical processes, to the extent of invalidating the relevance of the results obtained. Clearly, a deep understanding of the fundamental physical processes and the consequent development of models, of empirical, mechanistic and especially physical type, is expected to guide the assessment of the relevance of these accelerated experiments. The goal is to ensure that the predictions remain acceptable, when applied to real components.

The aim of this workshop is to address the issue of the transferability of data - from accelerated experiments performed in the laboratory, to the conditions met by the material when in operation - based on advances in modelling and on a proper analysis and correlation of existing data, from both laboratory experiments and surveillance.