Catalytic Effects of Silver in Iodine Reactors for Dissolved Used Nuclear Fuel

• Published in: Nuclear technology Vol. 208; no. 12; pp. 1867 - 1875
• Main Authors: Gogolski, Jarrod M., Taylor-Pashow, Kathryn M. L., Rudisill, Tracy S., Restivo, Michael L., Pareizs, John M., Lascola, Robert J., O'Rourke, Patrick E., Daniel, William. E.
• Format: Journal Article
• Language: English
• Published: La Grange Park Taylor & Francis 02.12.2022; American Nuclear Society
• Subjects: gases; hydrogen recombination; Iodine reaction; NOx gases; NUCLEAR FUEL CYCLE AND FUEL MATERIALS
• ISSN: 0029-5450; 1943-7471
• DOI: 10.1080/00295450.2022.2092358

The dissolution of used nuclear fuel generates a variety of off-gasses including flammable hydrogen and other species that are a concern for environmental release. The H-Canyon facility at the Savannah River Site is currently dissolving aluminum-clad research reactor fuel from material test reactors and the High Flux Isotope Reactor (HFIR) using a mercury-catalyzed nitric acid flowsheet. Savannah River National Laboratory recently developed and deployed a Raman spectrometer to monitor the off-gas stream from the dissolution process. Results from these measurements indicated a lack of the expected hydrogen, nitrous oxide, and nitric oxide in the off-gas stream. It was proposed that the silver on the silver nitrate-coated berl saddles present in the reactors for iodine capture were acting as a catalytic hydrogen recombiner. Nitric oxide is readily oxidized to nitrogen dioxide under normal conditions, but it was unclear what happened to the nitrous oxide. A laboratory-scale iodine reactor was assembled and filled with silver nitrate-coated berl saddles to help ascertain the fate of nitrous oxide and hydrogen. Testing with this laboratory-scale reactor observed the recombination of hydrogen when a simulated dissolver off-gas was passed through the reactor containing silver nitrate-coated berl saddles at the approximate temperatures seen in H-Canyon. However, the nitrous oxide concentration was unchanged, suggesting a more complex process occurring within the off-gas stream before it reaches the iodine reactors at H-Canyon.