Patent Number: 044406738
Section: description

SPECIFIC DESCRIPTION The apparatus shown in the drawing comprises an evaporator 1 surmounted upon a storage tank 2 and receiving waste water containing dissolved solids, especially boric acid, from nuclear electricity-generating power plant N. The outlet 4 of the evaporator 1 which may be fluid powered or electrically energized as represented by the coil 11, opens into the storage tank 2 at the head 5 thereof. In the upper half 6 of this storage tank, there is provided an outlet 7a through which the liquid (decantate) is recirculated vial line 7 to the inlet 8 of the evaporator 1. A pump 7b can displace the liquid along this line. The sludge 12 sedimenting from the clear liquid 13 in tank 2 can be discharged via an immersion pump 9 for packaging it at a station 14 in which the sludge is mixed with portland cement and allowed to set in sealable receptacles. A pipe 10 feeds solid radioactive wastes, e.g. diatomaceous earth or other filter aids, in the form of a slurry or sludge to the tank 2. In operation, the radioactive waste water containing dissolved boric acid is fed via line 3 to the evaporator 1 in which the solution is concentrated, the vapor phase being discharged at 15. The concentration of the water admitted to the storage vessel 2 is below the saturation level at the evaporation temperature and the temperature at which the solution is passed into the storage vessel (at least 50.degree. C.) but above the saturation level at room temperature. Thus in the evaporator 1 and in the connecting duct 4 no solids pass out of the solution. In the storage vessel 2 the waste water concentrate is cooled to room temperature and solids deposit and sediment so that clear liquid can be decanted and recycled to the evaporator with renewed concentration in the manner described. When the tank is more or less filled with the sludge it can be discharged via the pump 9 for processing as described, the sludge having in the interim undergone the long-term storage described.