Radioactive sludge treatment by the centrifugal dehydration method

The radioactive sludge produced after chemical treatment of radioactive liquid waste usually contains 0.3 to 3% of solid by weight. The gross β activity of sludge produced at the Institute of Nuclear Energy Research (INER) varies 10-1 to 10-3 μCi/g, and the use of centrifugal method for dehydration is justified. The effluent from the decanter goes through the precipitation and concentration stage and then the supernatant is pumped so that a stable concentration of liquid waste can be maintained during separation stage. The decanter used at INER for treating low level radioactive waste is a Westfalia SDB230 decanter which is of solid-bowl type. The liquid waste from a 40MW(th) Taiwan Research Reactor (TRR) and its associated hot laboratories is described in this report. The treatment capacity is about 2m3/h and the characteristics of the separator and the associated systems are discussed. As a result of improvement the solid in concentrated sludge is about 20% by weight, and the production rate is about 240 to 250 kg/h. Furthermore, no water is added to the concentrated sludge. The solidification can be done in a closed type sludge-cement premixing system, and the homogeneous concrete can be obtained