This report describes the rapid determination of 90Sr in highly radioactive solutions from a nuclear fuel reprocessing plant. The majority of fission products (FPs) including 90Y are precipitated in an alkaline medium, leaving 90Sr in the supernatant in the presence of inactive strontium as the hold-back carrier. 90Y freshly grown-in from the 90Sr is measured by utilizing a Cerenkov radiation counting technique with stainless steel shielding 0.2 mm thick that cuts off any low energy /3-particles, after strontium is recovered as a carbonate precipitate from the supernatant. Only two hours is sufficient for 90Y grow-in because large amount of 90Sr can be present in the final precipitation. The concentration of 90Sr is calculated from the 90Y detected and its grow-in time. The nuclides potentially interfering with this method, 106Ru, 134Cs , 137Cs, 144Ce, 144pr, 147pm, 154Eu, 123Sn and 125Sb, are quantitatively removed by coprecipitation with iron(II) hydroxide during the alkaline precipitation stage. The relative standard deviation (n=5) is better than 5%. The time required for one determination is less than 3 h.
KeywordsStrontium-90, highly radioactive liquid waste, reprocessing, precipitation, Cerenkov radiation countingIn the PUREX (plutonium-uranium refining by extraction) reprocessing process for spent nuclear fuel, most 90Sr would pass into the highly radioactive liquid waste (HRLW) solutions. 90Y, the daughter nuclide of 90Sr in radiative equilibrium , is regarded as a predominant exothermic nuclide, bearing nearly half of the energy evolved in the typical HRLW solution. Determination of 90Sr for the calorific evaluation due to 90Y in HRLW solutions and for the estimate of the radioactivity in vitrification product is of importance. A simple and rapid determination for 90Sr in HRLW solutions is required as a routine analysis method for controlling the processes related to HRLW.Numerous methods have been reported for the determination of radio-strontium in biological/ environmental samples. Very few methods for determining 90Sr in HRLW solutions, however, have been published. Many efforts have been made for the separation and purification of Sr. Those that showed satisfactory results needed long processing times. The precipitation methods1'2 require repeated operations for good recovery of Sr, while ion exchange procedures34, moreover, require careful pH adjustment. Extractions5-14 are frequently used for the separation of radiostrontium, although use of an organic solvent in a hot cell is undesirable for remotely controlled analytical operations with a manipulator.Most of these procedures are to separate Sr from calcium which may interfere with the subsequent /3-counting. Recently, the use of dicyclohexano-l8-crown-65-9 and dibenzo-l8-crown-69 have been proposed for Sr separation from calcium. However, these can not be applied to highly acidic solution samples. In addition, Sr picrate used in these methods is restricted in nuclear facilities from a safety viewpoint. An improvement has been made by Horwitz e...