By study on separation behavior of actinides in the fluoride volatility process

To know the behavior of plutonium in the fluoride volatility process (FLUOREX PROCESS) for the spent nuclear fuel, both UO2 and PuO2 are fluorinated by fluorine forming volatile UF6 and PuF6, respectively. Then PuF6 is separated and recovered from UF6 by using adsorption materials such as uranyl fluoride UO2F2. In this paper, volatilization and separation behavior of Pu, Np and Am was examined by the use of their tracers such as 236Pu; 239Pu and 241Am. First, UO2F2 was synthesized by the reaction of UO3 with HF at 350degC and the stability of UO2F2 in F2 atmosphere was analyzed by TG-DTA method showing that uranium volatilized completely over 350degC by the formation of UF6. The behavior of PtF6 as a chemical analogue of PuF6 was also conducted for comparison and it showed that the deposition of PtF4 on UO2F2 at 200degC. When the U3O8 doped with actinide tracers was reacted with 10%F2-He gas at 600degC, adsorption of 236Pu and 239Np on UO2F2 was observed by α and γ ray measurements. However, gamma ray of 241Am was observed in the residue showing that Am formed non-volatile fluoride. The adsorption mechanism of Pu and Np on UO2F2 was discussed with experimental data and thermodynamical consideration. (author)