Low-temperature Swelling in LWR Internal Components: Current Data and Modeling Assessment

Recent experimental observations have made it clear that cavity formation can occur in light-water reactor internal components fabricated from austenitic stainless during the course of their service life. In order to assess the potential for cavity swelling in these components at end-of-life doses, it is necessary to develop a validated computational model that incorporates the relevant physical mechanisms and accounts for recent experiment data. Such a modeling activity is underway; the model development and some preliminary results are described. For the relatively low temperatures involved, cavity formation is shown to be sensitive to both the temperature and the rate of helium production by nuclear transmutation reactions. This report includes a brief review of the relevant microstructural data, discussion of the current model s status and planned further development, and a description of the microstructural modeling that is planned to fully define the potential for cavity evolution under light water reactor operating conditions.