Abstract:

With the development of fast reactor technology in China，the dry reprocessing technology has attracted more and more attention.The dimitrovgrad dry process（DDP） has become one of the most studied dry post⁃processing technologies because it can co⁃deposit uranium and plutonium to directly produce MOX fuel.In the electrolytic separation process of the DDP process，the partial pressure ratio of chlorine to oxygen needs to be precisely controlled to ensure the presence of uranium in the state of uranyl ions and the existence of plutonium in the state of plutonium ions，to achieve efficient co⁃deposition of uranium and plutonium.To grasp the dependence of uranium and plutonium ions on the partial pressure ratio of chloride and oxychloride，the relationship between the minimum partial pressure of oxychloride and temperature and the interaction between the partial pressures of the two gases were studied through the diagram of the double dominant region of uranium⁃plutonium and plutonium ions.It was found that the minimum partial pressure of chlorine was increased slowly with the increase of temperature，while the partial pressure of oxygen was increased rapidly with the increase of temperature.As the oxygen concentration increased，the minimum concentration of chlorine remained unchanged at first，and the partial pressure of chlorine began to increase slowly after the oxygen concentration reached a certain level，and the oxygen pressure began to increase immediately as the chlorine pressure increased.The results of this study had guiding significance for the partial pressure control of chlorine and oxygen in the process of oxide electrolytic deposition.

Key words: spent fuel reprocessing, oxide electrodeposition, partial pressure of oxychloride and oxygen, dominant area map