PNNL

Abstract

Molten salt reactors offer a wide range of potential benefits but pose challenges separate from those of traditional light water reactors, particularly designs where the fuel is in a liquid salt form and uncladded. This will result in the evolution of fission gases into the headspace of the reactor core where a cover gas is passed to maintain an inert atmosphere and remove fission products. The cover gas leaving the reactor core is expected to contain both noble and non-noble gases, aerosols, volatile species, tritium, radionuclides, and their daughters. Development of a robust off-gas system for molten salt reactors is critical to ensure safe operation is maintained. To remove the off-gas constituents from the stream prior to recirculating the gas back to the core, various treatment systems must be staged in series. Treatment options vary greatly depending on what they are designed to remove from the gas stream. This paper reviews the anticipated composition of a molten salt reactor off-gas stream and subsequently the available resources that could be employed to remove these species from the gas stream. An example off-gas system, along with several design considerations, is detailed exemplifying the necessity for high fidelity modelling. Lastly, the need for further property research and the employment of advanced sensor technology for treatment component testing is discussed.