Determination of 135Cs concentration and 135Cs/137Cs ratio in waste samples from nuclear decommissioning by chemical separation and ICP-MS/MS

Determination of Cs-135 concentration and Cs-135/Cs-137 atomic ratio is of great importance in characterization of radioactive waste from decommissioning of nuclear facilities. In this work, an effective analytical method was developed for simultaneously determination of Cs-135 and Cs-137 in different types of waste samples (steel, zirconium alloy, reactor coolant, ion exchange filter paper and spent ion exchange resin) by coupling AMP-PAN, AG MP-1M and AG 50 W-X8 chromatographic separation with ICP-MS/MS measurement. Decontamination factors of 7.0 x 10(6) for Co, 6.0 x 10(6) for Ba, 4.2 x 10(5) for Mo, 3.2 x 10(5) for Sn and 2.1 x 10(5) for Sb were achieved using the chemical separation procedure. The overall chemical yields of cesium were higher than 85%. A detection limit of 3.1 x 10(-14) g/g for Cs-135 was achieved for 0.2 g stainless steel sample or spent resin. The developed method was validated by analysis of standard reference materials (IAEA-375) and successfully applied for analysis of zirconium alloy, steel, ion exchange filter paper and spent ion exchange resin from nuclear power reactors. The obtained Cs-135 can be used to evaluate the long-term environmental impact and provide useful information for waste disposal. The measured Cs-135/Cs-137 ratio in reactor coolant, as a characteristic information, might be useful for source identification and localization of leaked fuel element. The neutron flux of the leaked fuel element can be estimated based on the measured Cs-135/Cs-137 atomic ratios in the reactor coolant water. The developed method is simple and rapid (8 samples/day) for the determination of Cs-135 concentrations and Cs-135/Cs-137 ratios in various waste samples from nuclear decommissioning.

Automated summary

The study developed an effective method for simultaneous determination of Cs-135 and Cs-137 in various waste samples. High decontamination factors and chemical yields were achieved, with a detection limit of 3.1 x 10(-14) g/g. The method is simple, rapid, and has been successfully applied in nuclear waste analysis.