Immobilisation of Radwaste in Synthetic Rock: An Alternative to Cementation

SOGETER is a waste conditioning process for Low Level radwaste (LLW) or Intermediate Level radwaste (ILW) such as sludge, soil, ashes, evaporator concentrate, concrete rubble, asbestos or sand. Such radioactive waste is usually solidified into a cement matrix, resulting in a 2 to 5 times volumetric waste increase, i.e. 1 m³ of initial raw waste generates 2 to 5 m³ of solidified waste. Sogeter melts the waste at high temperature - up to 2000 K, and produces a synthetic rock. The main component of the matrix is the waste itself; therefore 1 m³ of initial raw waste generates only 0.2 to 0.5 m³ of solidified waste. Compared to cementation, synthetic rock decreases the volume to be disposed of by a factor of 4 up to a factor of 25. By mixing different types of waste, or using additives, the composition of the waste is adjusted so that a fluid melt is obtained at temperatures less than 2000 K and the final 200 L ingot can be cooled within 2 days, without shattering or disaggregating. A wide range of compositions have been tested demonstrating that almost every type of waste can be conditioned with Sogeter. An industrial facility has been designed based on very robust and proven heating and off-gas treatment technology. Industrial tests have been carried out on more than 2 tons of simulated, non-radioactive waste, producing blocks of treated matter weighing up to 250 kg. During these tests all process parameters, including electrical consumption, throughput and robustness, have been checked.