An Investigation on the Persistence of Uranium Hydride during Storage of Simulant Nuclear Waste Packages

Abstract

Synchrotron X-rays have been used to study the oxidation of uranium and uranium hydride when encapsulated in grout and stored in de-ionised water for 10 months. Periodic synchrotron X-ray tomography and X-ray powder diffraction have allowed measurement and identification of the arising corrosion products and the rates of corrosion. The oxidation rates of the uranium metal and uranium hydride were slower than empirically derived rates previously reported for each reactant in an anoxic water system, but without encapsulation in grout. This was attributed to the grout acting as a physical barrier limiting the access of oxidising species to the uranium surface. Uranium hydride was observed to persist throughout the 10 month storage period and industrial consequences of this observed persistence are discussed.

Evaluating laser-driven Bremsstrahlung radiation sources for imaging and analysis of nuclear waste packages

“…Important corrosion characteristics of uranium metal were determined using this method, for example, formation of UH 3 on uranium encapsulated in grout was observed to initiate and propagate in large, protruding, blisters instead of forming a continuous layer across the metal surface (which is the typical case with unenclosed uranium metal). Furthermore, it was shown that these blisters persisted whilst submersed in water for at least 10 months [14,15]. However, due to uranium's high density (18.95g.cm −3 ), the x-ray attenuation was too great to analyse samples thicker than 1mm, even utilising the highest beam energy achievable at the synchrotron (130keV).…”

The effect of work-hardening and thermal annealing on the early stages of the uranium-hydrogen corrosion reaction

“…Upon deuterium admittance to the reaction cell, an almost immediate and continuous drop in gas pressure was observed signifying the onset of hydride nucleation and growth. The reaction was ceased after a measured drop in deuterium pressure of 1.4 mbar (140 Pa) was recorded, equivalent to 0.00263 mmol of D 2 consumed to form UD 3 . That quantity was considered appropriate to initiate hydride formation and growth without reaching the bulk stage of the reaction.…”

“…Hydrogen corrosion of metallic U may occur during various stages of the nuclear fuel cycle, however, it is predominantly observed to occur during waste disposal [1][2][3]. The formed corrosion product, uranium hydride (UH 3 ), is a highly pyrophoric and unstable substance and, therefore, classed as a potential hazard due to the potential for enhanced radionuclide release and dispersion of gas/solid fission products arising from the spent nuclear fuel (SNF) material (fire, smoke containing fission products, etc.)…”

“…The formed corrosion product, uranium hydride (UH 3 ), is a highly pyrophoric and unstable substance and, therefore, classed as a potential hazard due to the potential for enhanced radionuclide release and dispersion of gas/solid fission products arising from the spent nuclear fuel (SNF) material (fire, smoke containing fission products, etc.) [4,5].…”

Engineering Science at the I12 Beamline at Diamond Light Source

“…This pyrophoric compound reacts vigorously with oxygen to make UO 2 and, as such, is thought to exist only fleetingly. Stitt et al [26,27] investigated the risk posed by an accumulation of pyrophoric uranium hydride. For these experiments, UH 3 was stored underwater after being artificially formed on a uranium rod and encased in the grout used at nuclear waste facilities.…”