Coprecipitation of 239Np with BaSO4 in experiments on uranium content determination

Activation-chemical method of analysis based on 239Np and BaSO4 coprecipitation is developed to determine uranium content in samples with wide varying of chemical composition which have been used for the seach of superheavy elements in the nature. 239Np is formed from 238U in the course of sample irradiation with thermal and epithermal neutrons. It is shown that insignificant part of neptunium remains in solution after precipitation. For complete coprecipitation it necessary to reduce neptunium, carefully to tetravalent state. The presence of cadmium in the solution increases neptunium capture with barium sulfate, and Rb and Cs deteriorate its coprecipitation. Neptunium desorption from barium sulfate proceeds slowly (for 2 hours concentrated HNO3 leaches only 22% of neptunium). The known data do not contradict the notions of isomorphic coprecipitation of tetravalent neptunium with BaSO4