Improvement of low radioactive waste immobilisation process at the nuclear power plant of Doel

A problematic family of liquid nuclear waste streams containing tritium and carbon 14 isotopes are mixed waste streams containing toxic or inflammable organic components such as oils, LSC cocktails, HPLC effluents and solvents. Different methods for solidification or immobilization were tested. Direct solidification by novel absorbent polymers was the first option. N935 was tested for the solidification of alcoholic solvents and N910 for the solidification of a naphta petroleum liquid, but none were successful.. Next the encapsulation of alcoholic solvents using a Portland cement matrix was studied. The porosity and weight loss increased with increasing ethanol content. It is hypothesized that the ethanol is not strongly bound to the matrix. The third treatment route is incineration followed by immobilization of tritiated water and 14CO2 from the off gas. Tritium can be removed by condensation as tritiated water. The absorption of water by the N960 polymer product was studied. Further encapsulation is needed to improve immobilization and compressive strength. For the immobilization of 14CO2 the packed bed process using solid calcium hydroxide or barium hydroxide octahydrate was investigated. The decontamination factor of both processes is at least 900.