Irradiation growth behavior and effect of hydrogen absorption of Zr-based cladding alloys for PWR

Abstract

In order to understand the dimensional stability of the fuel rod during long-term use in commercial LWRs, irradiation growth testing on various Zr-based fuel cladding materials including improved Zr-based alloys was conducted in the Halden reactor in Norway under prototypic irradiation and corrosion environment. The effect of hydrogen absorbed in the cladding tube due to corrosion on the irradiation growth behavior was investigated in this paper. The comparison of specimens with or without pre-charged hydrogen (about 200 and 400 ppm) revealed that the effect of hydrogen absorption, i.e. the acceleration of irradiation growth, became significant when the hydrogen content exceeded the hydrogen solubility limit in the corresponding irradiation temperature. Based on this understanding, the growth acceleration effect was evaluated to be (0.06 ± 0.01)%/100 ppm, with the denominator defined as the amount of absorbed hydrogen involved in hydride precipitation under irradiation as a relevant parameter. Discrimination of hydrogen effect confirmed lower irradiation growth of the improved Zr-based alloys than the conventional Zry-4, which may be attributed to the effect of lower hydrogen absorption property for Nb addition specimens.