MECHANISMS OF RADIATION-INDUCED DEGRADATION OF REACTOR VESSEL MATERIALS

摘要

Fast neutrons are usually considered the source of various radiation effects caused by atom displacements, such as embrittlement. swelling, and creep. However, other reactions may contribute to atom displacements under certain conditions. These additional sources of displacements include those caused by thermal neutron capture recoils, gamma-induced energetic electrons, and energetic particles emerging from transmutation reactions. In reactor vessels, for example, special circumstances may be encountered where these reactions become significant or even dominant with respect to fast-neutron-induced displacements. Key considerations describing these relative contributions are described. Inequalities are derived giving requirements among materials parameters and irradiation conditions to make each process significant with respect to fast neutrons. An example of the application of these conditions is given, covering the explanation of 'early' embrittlement in the HFIR reactor vessel. [References: 19]