Solidification of cesium containing magnetic zeolite sorbent by spark plasma sintering

The possibility of effective solidification of spent sorbents containing radioactive cesium by spark plasma sin -tering (SPS) technology for their safe and long-term disposal was studied. The kinetics of consolidation spent sorbent based on magnetic zeolite after adsorption saturation with cesium (similar to 23 wt %) under SPS conditions in the range of 700-950 degrees C was carried out. The structural, elemental and phase composition changes during high-rate (minutes) heating of zeolite powder saturated with Cs+ ions was studied by SEM, EDX and XRD methods. As a result, ceramic samples with mineral-like structure of Fe-substituted pollucite CsFeSi2O6 were successfully obtained. It was determined that the optimal temperature of SPS consolidation was 900 degrees C, at which the for-mation of CsFeSi2O6 ceramics with a relative density of 91.2%, compressive strength of 497.6 MPa, Vickers microhardness of 1019 HV, rate of cesium leaching of 2.33 x 10-8 g/cm2 x day was reached. It was found that the mechanism of cesium diffusion from the volume of ceramics corresponded to flushing from the available surface of the sample, the lowest diffusion coefficient was 2.71 x 10-16 cm2/s, as well as the lowest penetration depth of the solution into the volume of ceramics was 1.04 x 10-5 cm. The adsorbents prepared by SPS up to 900 degrees C retained the magnetization, and at higher temperature the magnetization decreased, which was caused by phase and structural changes of ceramics. The characteristics of ceramic obtained from spent adsorbent complied with the requirements of GOST R 50926-96 and ISO 6961:1982 for solidified Cs-containing radioactive waste.

Automated summary

The possibility of solidifying spent sorbents containing radioactive cesium by spark plasma sintering (SPS) technology was studied. Ceramic samples with a Fe-substituted pollucite CsFeSi2O6 structure were successfully obtained at an optimal SPS consolidation temperature of 900 degrees C. The obtained ceramic met the requirements for solidified Cs-containing radioactive waste. The mechanism of cesium diffusion in the ceramics was determined and the characteristics of the ceramics were analyzed.