Enhanced Polymer Hydrogen Getters for Use in the TRUPACTT-II

Abstract

Addressing the needs to safely and more efficiently ship Transuranic (TRU) wastes that may generate flammable levels of hydrogen, polymer getters were previously evaluated for deployment in the TRUPACT-II. Subsequently, enhanced polymer getters, collectively known as ''TRUGETTER,'' were formulated and pelletized, then tested against the challenging conditions defined for transport of TRU wastes. Reaction rate, reversibility, compatibility, structure/shape, passivity and capacity were evaluated. The effects of temperature extremes, radiation exposure, poisons, pressure, and free liquids were quantified. The manufacturing parameters for production of getter powder and pellets were determined. The TRUGETTER hazards have been characterized and flammability studies completed demonstrating it is not regulated as a hazardous material by DOT. TRUGETTER is commercially available on a multikilogram scale. The precious metal content of the getters is easily recycled. The optimum formulation of TRUGETTER pellets has a hydrogen capacity of 6.3 mol kg{sup -1}. The hydrogenation rate at 5% hydrogen, ambient temperature and 50% getter loading is 1.2 x 10{sup -3} mol s{sup -1} kg{sup -1}, and the rate is proportional to the hydrogen concentration (i.e., partial pressure). Therefore, the amount of getter required to meet the performance specification of 1.2 x 10{sup -5} mol s{sup -1} for 60 days at ambient temperature is determined by the getter capacity rather than rate. About 20 kg of getter will provide 2X the required hydrogen capacity. Reducing the temperature to -20 F reduces the hydrogenation rate at 5% hydrogen and 50% getter loading to 1.4 x 10{sup -5} mol s{sup -1} kg{sup -1}. The rate of hydrogen removal from air at -20 F is about 10 times faster. Therefore, based on initial results 20 kg of getter should be sufficient to maintain the hydrogen concentration in the ICV below 0.4% by volume even at the low temperature extreme. Codeployment of the getter with zeolite and Hopcalite' catalyst mitigates the effects of all getter poisons evaluated. The gettering reaction is not reversible under transport conditions, and increasing the total pressure from 0 psig to 50 psig has minimal impact on absorption rate. Exposure to 2.5 x 10{sup 4} rad gamma radiation has minimal impact on hydrogen absorption rate and capacity. Based on the tests conducted during Phase 2 TRUGETTER will be able to maintain a safe environment within the TRUPACT-II under the defined conditions of transport. The TRUGETTER is now ready for Phase 3 of this project, which will involve evaluation of the engineered getter assembly in its deployed form.