Evaluation on 131I production based on molten salt reactor off-gas extraction

Isotope extraction methods based on molten salt reactor off-gas treatments can provide a new solution for the shortage of medical isotopes. Current research work involves only static estimation, which does not consider the influence of the variation of parameters brought about by the actual reactor operation and may lead to inaccurate estimation of the yield and cooling time. In this work, a model of species migration is developed, and a corresponding program based on Mathematica is constructed to estimate the above problem. Results reveal 2.50 TBq of 131I was delivered to the off-gas system after 50 days of routine operation. This accounts for only 0.041 % of the total 131I in the reactor, which is sufficient to support 4,000 doses of hyperthyroidism treatment. Compared to the extraction based on the main loop salt, 133I remains the main radioactive impurity and product would meet the medical limit for radioactivity impurity after 8 days of cooling. Changes in fuel composition due to normal reactor operation have a small impact on isotope production. The power and flow rate variations due to peak load operation and the corresponding changes in helium bubble surface area due to temperature-pressure fluctuations have essentially no effect on the cooling time of the product but partially affect the production in the off-gas system. Bubble removal efficiency has a large perturbation on the results, but this needs to be investigated in the future. The stability of the cooling time indicates that nuclide production can follow an established scheme, suggesting that a molten salt reactor tail gas-based production scheme is stable and a promising production method.