A simplified flowsheet for pyroprocessing commercial spent fuel is proposed in which the only salt treatment step is actinide drawdown from electrorefiner salt. Actinide drawdown can be performed using a simple galvanic reduction process utilizing the reducing potential of gadolinium metal. Recent results of equilibrium reduction potentials for Gd, Ce, Nd, and La are summarized. A description of a recent experiment to demonstrate galvanic reduction with gadolinium is reviewed. Based on these experimental results and material balances of the flowsheet, this new variant of the pyroprocessing scheme is expected to meet the objectives of minimizing cost, maximizing processing rate, minimizing proliferation risk, and optimizing the utilization of geologic repository space.

The US Department of Energy’s Idaho National Laboratory (INL) has been operating a molten salt electrorefiner at their facility since 1996. The baseline method for disposal of the radioactive salt is the ceramic waste process which generates glass bonded sodalite loaded with chloride salts. This process starts with the high temperature absorption of the salt into zeolite-4A. The salt-loaded zeolite is then blended with glass frit and heated to form a sintered, glass-bonded sodalite. INL is currently assessing alternatives for disposal of the ER salt because of the lengthy processing times, costly equipment and large volume of waste associated with the baseline process. An alternative process was studied, where protonated zeolite was used instead of alkali metal-substituted zeolite. It was found that the metals contained in the salt can replace the protons in the zeolite which are evolved via formation of HCl. From the standpoint of generating a nuclear waste form, the evolution of HCl gas should reduce the weight of the final waste. It has been estimated that the volume of waste produced from immobilizing the INL electrorefiner salt could be reduced by a factor of three using this process followed by sintering the fission product loaded zeolite. Equipment requirements in the hot cell would be significantly simplified, and the time to process all of the waste salt would be reduced by almost a factor of 4. An investigation into the new process has been presented here.