PNNL

Abstract

The U.S. Department of Energy Office of Nuclear Energy, Office of Fuel Cycle Technology established the Used Fuel Disposition Campaign (UFDC) to conduct research and development activities related to storage, transportation, and disposal of used nuclear fuel (UNF) and high-level radioactive waste. Within the UFDC, the storage and transportation task has been created to address issues of extended storage and transportation. One gap in knowledge identified as high priority by UFDC includes hydrogen effects in zirconium alloy cladding and reorientation of cladding hydrides. During reactor operations, hydrogen is generated from the oxidation of the surface of zirconium alloy materials in the coolant of light water reactors can be absorbed into the cladding and form zirconium hydrides. At high temperatures and hoop stresses, these normally circumferential oriented hydrides in high burnup UNF (HB-UNF) may reorient in the radial direction and affect the mechanical properties of the cladding. Understanding these changes in mechanical properties will aid in analyzing how UNF will perform during storage and transportation. Separate effects testing to measure the mechanical properties of un-hydrided, pre-hydrided, and irradiated HB-UNF is currently underway at Pacific Northwest National Laboratory (PNNL). In order to measure these mechanical properties, staff at PNNL are employing tensile, compression, and burst testing. Systems have been developed to pre-hydride cladding and reorient cladding hydrides. The development of these systems and the testing methods are described herein.