The ongoing operability relies on being able to understand and predict how the mechanical properties and dimensional stability change over extended periods of operation. The internal structures of the LWRs operate at temperatures between approximately 270 and 320 ☌ although some parts can be hotter (more than 400 ☌) because of localised nuclear heating. For fast reactors, operating temperatures vary from 400 to 550 ☌ for the internal structures and up to 650 ☌ for the fuel cladding. This paper describes a rate-theory model for void swelling of 316 stainless steel irradiated in the EBR-2 reactor as a function of irradiation temperature and neutron dose.Īustenitic stainless steels are used for core internal structures in sodium-cooled fast reactors (SFRs) and light-water reactors (LWRs) because of their high strength and retained toughness after irradiation (up to 80 dpa in LWRs), unlike ferritic steels that are embrittled at low doses (<1 dpa). By using published data on: (i) yield strength as a function of dose and temperature (to establish an empirical expression for dislocation density evolution) (ii) cavity number densities as a function of temperature and (iii) freely migrating defect (FMD) production as a function of primary knock-on atom (PKA) spectrum, the necessary parameter and microstructure inputs that were previously unknown can be used in model development.

With reasonable estimates of key microstructure parameters, a standard rate theory model can be applied, and the model parameter space explored, in connection with historical swelling data. Whereas the lack of microstructure information is still an issue for historical swelling data, in the past 10–20 years data have been published on the evolution of the microstructure (point defect yields from collision cascades, cavity number densities, and dislocation densities/yield strengths) allowing certain gaps in information to be filled when considering historic swelling data. A rigorous validation of the models has not been possible because of the dearth of information concerning the microstructures that correspond with the swelling data. Many rate theory models of cavity (void) swelling have been published over the past 50 years, all having the same, or similar, structures.

Precipitate examples