A satisfactory ion-exchange-polarographic method was developed for the determination of either chromium(VI) or total chromium in Homogeneous Reactor fuels. Total chromium is determined as chromium (VI) , i.e., chromate, and in the same way as is chromium(VI), after chromium in the lower valence states is oxidized to chromate by potassium permanganate. Chromate is separated from all interfering metal ions in the fuel by ion exchange on a Dowex 50 resin column. The Chromate in the effluent is determined polarographically in approximately 0.75 M sodium hydroxide solution as supporting electrolyte. A well polarographic wave is obtained for the chromium (VI) chromium (III) reduction at a half-wave potential of -0.85 volt vs. the S.C.E. The relative standard deviation of the data for 2 μg of chromium (VI) per ml was 2%; for 4 μg of total chromium per ml, it was 3%. An ion-exchange-polarographic method was developed also for the determination of chromium(III). Chromium (III) is separated from all interfering ions in the fuel by ion exchange on a Dowex 1 resin column. The chromium (III) in the effluent is determined polarographically in a 1M ammonia-1M ammonium chloride supporting electrolyte. The wave obtained at a half-wave potential of -1.42 volt vs. the …

Release of fission products from UO2 with emphasis on fuel elements operated at higher surface temperatures and lower external pressures than those for pressurized-water systems.