Swelling of 316 stainless steel and D9 cladding in FFTF

A data base of cladding swelling measurements from post-irradiation examinations of Fast Flux Test Facility (FFTF) 316 stainless steel clad fuel pins has been developed, which is now sufficiently large to compare to previously published cladding swelling data. This comparison of data was motivated by the observation, in the early cycles of FFTF operation, that design swelling correlations had to be adjusted to account for the observed length increases for driver assembly ducts. These original correlations had been developed from nonfueled EBR-II irradiation tests. The recent data indicate that FFTF and EBR-II cladding, from actual fuel pins with similar heats of steel, behave almost identically with respect to fast fluence. The FFTF data further suggest that, above --4900C, 316 stainless steel (SS) swells in a manner that is essentially independent of irradiation temperature. A comparison of immersion density measurements with the length increases the FFTF driver fuel pins has also shown the 316 SS cladding swelling behavior to be essentially isotropic. D9 cladding (a titanium modified variant of 316 SS) has also been irradiated in FFTF. The data base here is limited but is large enough to establish the superiority of D9 over 316 SS as an FFTF fuel pin cladding from a swelling point of view