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

Molybdenum-99 (99Mo) 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 99Mo. In this work, the feasibility of fluoride volatility process as a potential technique for selective extraction of trace amount of 99Mo from fuel salt in the form of volatile MoF6 by nitrogen trifluoride (NF3) is illustrated. The results showed that in the case of using LiF-BeF2-ZrF4-UF4-MoF3 (64.4–29.7–5.0–0.5–0.4 mol.%) molten salt as the simulated fuel salt, MoF3 reacted with NF3 to form MoF6 at or above 570℃, while the conversion of UF4 to volatile UF6 required higher temperatures (≥650℃), when both exposed to 20 % NF3/Ar mixture. Based on above “cold” experiments, fluoride volatility process in LiF-BeF2-ZrF4 molten salt containing irradiated UF4 was carried out, and the extraction rate of 99Mo was determined by detecting the change of its γ activity in the molten salt. The results indicated that 99Mo 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 99Mo product was only 0.9 wt%.