Preliminary research on selective extraction of 99Mo from fuel salt for molten salt reactor

Molybdenum-99 ( 99 Mo) is one of the most important radionuclides for nuclear medicine. This isotope of molybdenum is mainly produced as a result of fission and decay processes occurring in nuclear reactors. Molten salt reactors (MSRs), a unique reactor with the fuel dissolved in a molten salt , have attracted attention as a source of 99 Mo. In this work, the feasibility of fluoride volatility process as a potential technique for selective extraction of trace amount of 99 Mo from fuel salt in the form of volatile MoF 6 by nitrogen trifluoride (NF 3 ) is illustrated. The results showed that in the case of using LiF-BeF 2 -ZrF 4 -UF 4 -MoF 3 (64.4–29.7–5.0–0.5–0.4 mol.%) molten salt as the simulated fuel salt, MoF 3 reacted with NF 3 to form MoF 6 at or above 570℃, while the conversion of UF 4 to volatile UF 6 required higher temperatures (≥650℃), when both exposed to 20 % NF 3 /Ar mixture. Based on above “cold” experiments, fluoride volatility process in LiF-BeF 2 -ZrF 4 molten salt containing irradiated UF 4 was carried out, and the extraction rate of 99 Mo was determined by detecting the change of its γ activity in the molten salt. The results indicated that 99 Mo could be extracted from the molten salt containing a quantity of uranium with the extraction rate of 98 % under current experimental conditions, and the content of uranium in collected 99 Mo product was only 0.9 wt%.