PNNL

Abstract

The operating life of nuclear reactors is often dictated by material performance. Reactor components subjected to a neutron flux will undergo radiation-induced changes that impact their ability to function as designed. Typically the materials comprising these components undergo changes in dimensions (swelling and creep) and changes in mechanical properties (yield strength, ultimate tensile strength, ductility and fracture toughness) that are an irradiation effect and cannot be simulated in the laboratory. In order to predict future performance of components in operating reactors, or for the design of new reactors, materials test reactors (MTRs) have been utilized over many years to perform accelerated materials evaluations. The main value from testing in MTRs comes from the higher neutron fluxes and radiation damage production rates. Not only does the MTR provide the researcher with the ability to obtain information on materials degradation in advance of operating reactors, but also one can test material properties using standardized test specimens in controlled conditions. Often the most critical reactor components are complex and, until the advent of nano-scale testing capabilities allowing test specimens to be extracted directly from the irradiated component, information on property changes had to be gleaned from irradiating standardized test specimens. Such specimens would be made from the same material and subject to the same thermo-mechanical processing as applied in preparing the reactor component of interest.