An experimental investigation was conducted for gas generation in contact-handled transuranic(CH-TRU) wastes subjected for several years to conditions similar to those expected to occur at the WasteIsolation Pilot Plant (WIPP) should the repository eventually become inundated with brine. Varioustypes of actual CH-TRU wastes were placed into 12 corrosion-resistant vessels. The vessels were looselyfilled with the wastes, which were submerged in synthetic brine having the same chemical composition asthat in the WIPP vicinity. The vessels were also inoculated with microbes found in the Salado Formationat WIPP. The vessels were sealed, purged, and the approximately 750-ml headspace was pressurized withnitrogen gas to approximately 146 atmospheres to create anoxic conditions at the lithostatic pressureexpected in the repository were it inundated. The temperature was maintained at the expected 30 C. Thetest program objective was to measure the quantities and species of gases generated by metal corrosion,radiolysis, and microbial activity. These data will assist in the specification of the rates at which gases areproduced under inundated repository conditions for use in the WIPP Performance Assessment computermodels.These experiments were very carefully designed, constructed, instrumented, and performed.Approximately 6-1/2 years of continuous, undisturbed testing were accumulated. Several of the vesselsshowed significantly elevated levels of generated gases, virtually all of which was hydrogen. One vesselmeasured over 4.2% hydrogen, by volume. Two other vessels generated well over 1% hydrogen, andanother was at nearly 1%. Only small quantities of other gases, principally carbon dioxide, weredetected.Gas generation was found to depend strongly on the waste composition. The maximum hydrogengeneration occurred in tests containing carbon steel. Average corrosion penetration rates in carbon-steelof up to 2.3 microns per year were deduced. Conversion of carbon to carbon dioxide was calculated to beup to 4.7 μg-mol/yr/g-carbon.
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