Influence of thermomechanical exposure on the structure of hydrides in irradiated E110 alloy cladding pipes under the conditions of long-term dry storage of spent nuclear fuel

Abstract

The penetration of atomic hydrogen into the cladding material of fuel elements of WWER-1000 reactors due to interaction with the coolant during operation can subsequently significantly reduce their plasticity characteristics with a decrease in temperature during long-term dry storage of spent nuclear fuel (SNF) due to the formation of brittle hydrides. The morphology of hydrides influenced by the hydrogen content, storage temperature and circumferential stresses plays a decisive role in the embrittlement of the fuel cladding material. Associated radial hydrides are of particular danger; they constitute the most favorable path for crack propagation.In the present work, thermomechanical tests of irradiated fuel claddings samples made of the E110 alloy were carried out, simulating normal and emergency conditions of long-term dry storage. It was shown that under the conditions considered, the formation of a significant amount of radially oriented hydrides was observed, leading to degradation of mechanical properties (embrittlement) fuel cladding.