Examination of Spent PWR Fuel Rods After 15 Years in Dry Storage

Abstract

b Argonne-West, Idaho Falls, ID, USA Virginia Power Surry Nuclear Station Pressurized Water Reactor (PWR) fuel was stored in a dry inert atmosphere Castor V/21 cask at the Idaho National Environmental and Engineering Laboratory (INEEL) for 15 years at peak cladding temperatures decreasing from about 350 to 150°C. Prior to the storage, the loaded cask was subjected to extensive thermal benchmark tests. The cask was opened to examine the fuel for degradation and to determine if it was suitable for extended storage. No rod breaches had occurred and no visible degradation or crud/oxide spallation were observed.Twelve rods were removed from the center of the T11 assembly and shipped from INEEL to the Argonne-West HFEF for profilometric scans. Four of these rods were punctured to determine the fission gas release from the fuel matrix and internal pressure in the rods. Three of the four rods were cut into five segments each, then shipped to the Argonne-East AGHCF for detailed examination. The test plan calls for metallographic examination of six samples from two of the rods, microhardness and hydrogen content measurements at or near the six metallographic sample locations, tensile testing of six samples from the two rods, and thermal creep testing of eight samples from the two rods to determine the extent of residual creep life. The results from the profilometry (12 rods), gas release measurements (4 rods), metallographic examinations (2 samples from 1 rod), and microhardness and hydrogen content characterization (2 samples from 1 rod) are reported here. The tensile and creep studies are just starting and will be reported at a later date, along with the additional characterization work to be performed.Although only limited prestorage characterization is available, a number of preliminary conclusions can be drawn based on comparison with characterization of Florida Power Turkey Point rods of a similar vintage. Based on this comparison, it appears that little or no cladding thermal creep and fission gas release from the fuel pellets occurred during the thermal benchmark tests or storage. Measurements of the cladding outer-diameter, oxide thickness and wall thickness are in the expected range for cladding of the Surry exposure. The measured hydrogen content is consistent with the oxide thickness. The volume of hydrides varies azimuthally around the cladding, but there is little variation across the thickness, of the cladding. It is most significant that all of the hydrides appear to have retained the circumferential orientation typical of prestorage PWR fuel rods.

Evolution of the Hydride Structure in Irradiated E110 Alloy in the Process of Thermomechanical Treatment Simulating Supercritical Dry Storage Conditions

“…Стоит отметить, что определение механических характеристик проводилось при ком натной температуре, достижение которой в условиях сухого хранения ОЯТ возможно через достаточно длительный срок (более 70 лет) [18]. В ряде работ показано, что с повышением температуры [2] пластичность наводороженных циркониевых оболочек восстанавливается и что критическая температура изменения характера разрушения в зависимости от содержания водорода и ориентации гидридов не превышает 150°С.…”

Spent nuclear fuel in dry storage conditions – current trends in fuel performance modeling

“…It points out that the cladding creep in normal storage conditions will not lead to gross rupture of the cladding for two reasons. First, according to the post-storage tests carried out by Einziger et al, SNF exhibits a high creep capacity even after 15 years of dry storage [52] . Second, creep is selflimiting: progressing creep increases the rod volume which decreases RIP, which is the main force driving the cladding creep; as the driving force is lower, the creep rate decreases.…”

High-Velocity Oxy-Fuel (HVOF) Spray Coating of Inconel, Colmonoy, and Aluminum on AISI 316L Stainless Steel: A Comparative Investigation of the Microstructure and Corrosion Resistance of Coatings

“…Stainless steels show better corrosion resistance than carbon steels, thanks to the formation of an inherent passive oxide film on their surfaces [4,5]. Nevertheless, there are some serious concerns regarding the corrosion resistance of stainless steel in sea waters and chlorine-containing aqueous environments [6][7][8]. In marine environments, severe localized corrosion and pitting in stainless steel are always critical issues, especially when the temperature increases and the humidity rises.…”