Murataite. A matrix for immobilizing waste generated in radiochemical reprocessing of spent nuclear fuel

Incorporation of waste from spent nuclear fuel pyrochemical reprocessing and calcines from the decontamination of glove box and hot cell equipment into murataite-based ceramics was studied. The phase and chemical compositions of the ceramics containing precipitates simulating fission products in molten chlorides were examined. The radiation stability of murataite matrices was studied by incorporating ²⁴⁴Cm isotope (1.8 wt%). In the ceramics produced by melting at 1325 and 1350 °C the murataite phases was rendered to be X-ray amorphous at doses of 2.46 × 10¹⁸ and 2.53 × 10¹⁸ α-decay/g (0.21 dpa), while for the sample sintered at 1250 °C the amorphization dose was found to be 2.73 × 10¹⁸ α-decay/g (0.21 dpa). The murataite structure was recovered after the annealing at 1250 °C for 5 h in air. Both the pristine and amorphized samples had very low leachability of Cm and major elements. Production of highly durable murataite-based ceramics containing waste surrogate after spent nuclear fuel (SNF) pyrochemical reprocessing and calcine after the evaporation of decontamination solutions were demonstrated. (author)