DETERMINATION OF TRACES OF URANIUM IN TUNGSTEN AND MOLYBDENUM BY RADIOCHEMICAL NEUTRON-ACTIVATION ANALYSIS VIA THE FISSION-PRODUCT BA-140

A radiochemical separation procedure has been developed to determine t races of uranium in tungsten and molybdenum. In this procedure the fis sion product Ba-140, indicator nuclide for uranium, is selectively sep arated from the matrix activities and from all other long-lived activa tion and fission products and obtained at high purity. The radionuclid e in the final fraction is sufficiently pure so that it can he measure d with high counting efficiency by beta-counting. The separation proce dure consists of two steps: a cation-exchange separation to separate b arium from the anionic matrix tungstate or molybdate, and many other e lements. In the second step the Ba-fraction is further purified by pre cipitation of barium as barium chloride in 8M hydrochloric acid. The p recipitate is then dissolved in water for beta-counting via the Cerenk ov effect. The chemical yield forbarium is 94.6 +/- 2.6%. When samples of 0.1 g, a thermal neutron flux of 2 . 10(13) n . cm(-2). s(-1), an irradiation time of 10 hours and a measuring time of 2 hours were appl ied, then the detection limit of uranium was 4 ng/g.