Improved Hydrogen Gas Getters for TRU Waste -- Final Report

Stone, Mark ; Benson, Michael ; Orme, Christopher ; Luther, Thomas ; Peterson, Eric

Idaho National Laboratory

关键词: Alpha-Bearing Wastes;    12 - Mgmt Of Radioactive And Non-Radioactive Wastes From Nuclear Facilities, 37 - Inorganic, Organic, Physical And Analytical Chemistry;    Radiolysis;    Polymers;    Hydrogen;   

DOI  :  10.2172/911778
RP-ID  :  INL/EXT-05-00805
RP-ID  :  DE-AC07-99ID-13727
RP-ID  :  911778

美国|英语

来源: UNT Digital Library

【 摘 要 】

Alpha radiolysis of hydrogenous waste and packaging materials generates hydrogen gas in radioactive storage containers. For that reason, the Nuclear Regulatory Commission limits the flammable gas (hydrogen) concentration in the Transuranic Package Transporter-II (TRUPACT-II) containers to 5 vol% of hydrogen in air, which is the lower explosion limit. Consequently, a method is needed to prevent the build up of hydrogen to 5 vol% during the storage and transport of the TRUPACT-II containers (up to 60 days). One promising option is the use of hydrogen getters. These materials scavenge hydrogen from the gas phase and irreversibly bind it in the solid phase. One proven getter is a material called 1,4-bis (phenylethynyl) benzene, or DEB, characterized by the presence of carbon-carbon triple bonds. Carbon may, in the presence of suitable precious metal catalysts such as palladium, irreversibly react with and bind hydrogen. In the presence of oxygen, the precious metal may also eliminate hydrogen by catalyzing the formation of water. This reaction is called catalytic recombination. DEB has the needed binding rate and capacity for hydrogen that potentially could be generated in the TRUPACT II. Phases 1 and 2 of this project showed that uncoated DEB performed satisfactorily in lab scale tests. Based upon these results, Phase 3, the final project phase, included larger scale testing. Test vessels were scaled to replicate the ratio between void space in the inner containment vessel of a TRUPACT-II container and a payload of seven 55-gallon drums. The tests were run with an atmosphere of air for 63.9 days at ambient temperature (15-27°C) and a scaled hydrogen generation rate of 2.60E-07 moles per second (0.35 cc/min). A second type of getter known as VEI, a proprietary polymer hydrogen getter characterized by carbon-carbon double bonds, was also tested in Phase 3. Hydrogen was successfully “gettered” by both getter systems. Hydrogen concentrations remained below 5 vol% (in air) for the duration of the tests. However, catalytic reaction of hydrogen with carbon triple or double bonds in the getter materials did not take place. Instead, catalytic recombination was the predominant gettering mechanism in both getter materials as evidenced by (1) consumption of oxygen in the belljars, (2) production of free water in the belljars, and (3) absence of chemical changes in both getter materials as shown by nuclear magnetic resonance spectra.