Apparatus for subjecting a radioactive sodium borate waste solution to volume reduction and solidification

• US 4,710,266 A
• Filed: 03/20/1986
• Issued: 12/01/1987
• Est. Priority Date: 08/09/1983
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Mizushima, Toyoshi, Hayashi, Tadamasa
• Primary Examiner(s): Bashore, S. Leon
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/841,036
• Time in Patent Office: 621 Days
• Field of Search: 159/5, 159/7, 159/25.1, 159/DIG. 12, 252/628, 252/629, 252/632, 219/10.55 R, 219/10.55 A, 65/144, 55/DIG. 9, 422/159, 422/903
• US Class Current: 159/7
• CPC Class Codes: C03C 1/002 Use of waste materials, e.g. slags
• CPC Class Codes: G21F 9/305 Glass or glass like matrix C03B5/005 takes precedence; compositional aspects C03C
• CPC Class Codes: Y10S 159/12 Radioactive
• CPC Class Codes: Y10S 422/903 Radioactive material apparatus

Abstract

An apparatus is disclosed for producing a vitric solid solution comprising mainly the solid content of a radioactive waste solution of sodium borate discharged from a pressurized water reactor, the apparatus comprising a waste solution feed tank equipped with a hopper for stabilizing agent in water, a thin film evaporator, a heating type dehydrator, a powder drier connected with a microwave generator through a microwave guide tube and equipped with a stirrer, and a melting furnace connected with a microwave generator through a microwave guide tube, the above units being combined by pipes or a powder-transferring means.

Claims

1. An apparatus for producing a vitric solid solution comprising (a) the solid content of a radioactive waste solution of sodium borate discharged from a pressurized water reactor, having a Na₂ O to B₂ O₃ molar ratio of 0.1 to 0.06 and (b) 10 to 40 mole % of ZnO or 10 to 40 mole % of ZnO plus 3 to 10 mole % of Al₂ O₃ and/or CaO so that the total content of ZnO plus Al₂ O₃ and/or CaO does not exceed 43 mole %,

the apparatus comprising:

(A) a waste solution feed tank equipped with a hopper for stabilizing agent in water, a stirrer for stirring the sodium borate waste solution and the stabilizing agent in water added thereto from said hopper;

(B) a waste solution circulation pump for circulating a part of the resulting mixture to the waste solution feed tank and another part of the resulting mixture to an evaporator through a waste solution supply pump;

(C) the evaporator for evaporating and concentrating the waste solution fed from the pump to remove water by a heating fluid so as to form an evaporator residue;

(D) a heating type dehydrator for heating the evaporator residue sent from the evaporator by a heating fluid while being stirred by a stirrer, for further evaporation;

(E) a powder dryer for removing the crystal water of the evaporation residue, thereby rendering said residue as a porous lump, by heating with a microwave generator through a microwave guide tube, and a stirrer for grinding the lump into a powder provided therein;

(F) discharger means for forcible batch delivery of said residue to said powder dryer;

(G) a melting furnace for melting into a vitric melt the dried power sent from the powder dryer by irradiation with microwaves transmitted from a microwave generator through a microwave guide tube, said melt being charged in a solid solution container;

(H) a condenser for condensing the evaporated water generated from the evaporator and the heating type dehydrator;

(I) a prefilter for filtering the off-gas from the powder dryer and the melting furnace to remove solids;

(J) an off-gas cooler for removing the residual water of the off-gas from the waste solution feed tank, the condenser and the prefilter;

(K) an off-gas treater for purifying the off-gas from the off-gas cooler to discharge it from an off-gas exhaust fan.

2. An apparatus for producing a vitric solid solution according to claim 1, wherein a cooler is attached to the melting furnace for cooling the melt successively discharged from the melting furnace to the vitric solid solution and wherein the off-gas from the cooler is sent to the prefilter for filtering said off-gas to remove solids.

3. An apparatus for producing a vitric solid solution according to claim 1, wherein, at the outlet side of the melting furnace for a vitric solid solution melt, there are provided a heater for prevention of rapid cooling of containers filled with the vitric melt as well as a slow cooling chamber for the containers 24.

4. An apparatus for producing a vitric solid solution according to claim 1, wherein the melting furnace includes a container as a lower half for receiving said vitric melt.