Reorientation of Hydrides in Unirradiated Clad Tubes Made of Alloy E110 under Conditions Simulating Long-Term Dry Storage of Spent Nuclear Fuel

Abstract

Reorientation of hydrides in the course of dry storage of spent nuclear fuel is a possible mechanism for the degradation of the properties of fuel claddings made of alloy E110 (Zr–1% Nb) based on spongy zirconium in VVER reactors. To determine the degree of reorientation of hydride precipitates in fuel claddings under conditions that simulate the conditions of dry storage, a series of tests have been performed for unirradiated samples with a hydrogen content of 100 and 200 wppm at various levels of circumferential stresses up to 100 MPa for 40 days. The orientation of hydride precipitates is determined using metallographic measurements. To assess the mechanical characteristics, the ring specimens have been tested for static uniaxial tension. The hydrides are analyzed using transmission electron microscopy and X-ray diffraction analysis. It is shown that test conditions lead to partial reorientation of hydride precipitates, which contributes, in turn, to a decrease in the plasticity.