POLYMER-BASED HYDROGEN GETTERS FOR TRANSPORT PACKAGINGS

Polymer-based hydrogen getters are described and their effectiveness for reducing hydrogen levels in radioactive materials (RAM) packagings is demonstrated. These Sandia National Laboratories patented getters have been characterized, in United States Department of Energy Office of Environmental Management programs (National Transportation Program and TRU & Mixed Waste Focus Area), for hydrogen mitigation under conditions existing in RAM packagings. The decomposition of radioactive waste produces non-radioactive gaseous by-products, including hydrogen. Additional gases and vapors (getter “poisons”) may be present in sealed waste containers. The accumulation of hydrogen within waste packages presents a safety hazard. Regulatory limits on the hydrogen concentration in RAM packagings may require costly repackaging (and more shipments) or waste treatment unless hydrogen accumulation can be mitigated. The use of hydrogen getters is a promising mitigation technology. The Sandia getters consist of a mixture of organic polymers containing carbon-carbon double bonds and a palladium or platinum catalyst on a carbon support. In the absence of oxygen, hydrogen is removed by reaction with the carbon-carbon double bonds (i.e., hydrogenation). When oxygen is present, the polymer-based getter functions primarily as a recombination catalyst until the oxygen is consumed, after which the hydrogenation mechanism takes over. The polymer-based getters have demonstrated favorable hydrogen gettering characteristics relative to the requirements for specific packaging applications, such as the DDF-1 packages at the Savannah River Site and the TRUPACT-II for the Waste Isolation Pilot Plant. The polymer-based getters are non-pyrophoric, recombine H2 and O2 regardless of capacity, require no activation, remove hydrogen in a variety of atmospheres, are compatible with a wide range of materials, have demonstrated resistance to many “poisons” (e.g., carbon tetrachloride) and radiation, are effective over a wide temperature range, and are commercially available at relatively low cost. The getters have been shown to perform effectively in terms of Nuclear Regulatory Commission criteria which include capacity, pressure, “poisons”, reversibility, temperature, humidity, and thermal output.