US 3293151 A
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Description (OCR text may contain errors)
Dec. 20, 1966 s, HOLZER ET AL AQUEOUS RADIOACTIVE WASTE CONCENTRATOR Filed March 29, 1965 2 Sheets-Sheet 1 m m S fiZ OLAA W E H A l W Y I R W E T E w Sw Z mmm R L F H W ATTORNEY Dec. 20, 1966 F. s. HOLZER ET AL AQUEOUS RADIOACTIVE WASTE CONCENTRATOR Filed March 29, 1963 a Sheets-Sheet 2 INVENTORS FRANZ STEPHEN HOLZER ROSCOE KAY VASSAR BYWILLIAM RODGER WILLIAMSON ATTORNEY United States Patent Oiiice 3,2 93,15 1 Patented Dec. 20, 1966 Conn, .assignors to American Machine & Foundry H 7 Company, a corporation of New Jersey Filed Mar. 29, 1963, Ser. No. 268,915 6 Claims. (Cl. 202-181) This invention relates to disposal apparatus for wastes and, more particularly, to a concentrator for radioactive wastes in aqueous solutions.
An object of this invention is to provide a simple, easily installed and easily operated concentrating apparatus for constituents in aqueous radioactive wastes.
Another object of this invention is to provide apparatus for concentrating aqueous radioactive wastes which provides a distillate with a very high degree of purity.
A further object of this invention is to provide a concentrator for aqueous wastes which may operate for a longer period of time without scale formation and which is subjected to corrosive attack to a lesser degree.
Yet another object of this invention is to provide a concentrator for radioactive waste in which the possibility of foaming with resulting carryover of radio-active material into the distillate is almost entirely eliminated.
A still further object of this invention is to provide an aqueous radioactive waste concentrator which requires no special energy source so that it may be easily used in connection with a variety of experimental installations for simple operation at a greatly reduced cost.
Many other objects advantages and features of invention reside in the construction, arrangement and combination of parts involved in the embodiments of the invention and its practice as will be understood from the following description and accompanying drawing wherein:
FIGURE 1 is a longitudinal vertical section through the apparatus of this invention which is partially shown in schematic and diagrammatic form;
FIGURE 2 is a vertical section taken on line 22 of FIGURE 1; and
FIGURE 3 is a schematic and diagrammatic representation of a modification of this invention.
Referring to the drawing in detail FIGURES 1 and 3 show a pipe 19 which extends to an existing facility raw waste storage tank 11. Motor 12 may be activated to drive pump 13 and draw raw waste through pipe and discharge it through pipe 14 to fill the batch tank 15. The aqueous radioactive waste 16 is continuously drawn from tank through pipe 17 by pump 18 which is driven by motor 19. This waste is then forced through pipe 20 which leads through eductor 21 from which the bulk of the radioactive waste flows through pipe 22 to be returned to tank 15.
An evaporator and condenser 23 has an upright cylindrical, tank 24. Valve 25 allows some of the aqueous radioactive waste to flow through pipe 26 into the bottom of tank 24. A fluid level control 27 opens valve 25 when the level of the radioactive waste 16 in the bottom of tank 24 falls below a desired level. Eductor 21 continuously draws the waste 16 through pipe 28 from the bottom of tank 24. A heating coil 29 extends through a cylindrical extension 30 into the bottom of tank 24 to heat the radioactive waste 16 within it. A temperature sensing element 31 activates a unit 32 to close at least partially valve 33 to reduce the amount of hot water flowing through the heating coil 29. Heating coil 29 may be connected to any existing hot water line.
A conical wall 34 divides the evaporator from the condenser of unit 23. A fluid return line 35 extends from the base of wall 34 below the level of the fluid 16. Two mesh drop separators 36 and 37 extend across the base and the apex of the conical wall 34. Water vapor passes through the drop separators 36 and 37 into contact with the cooling coils 38. Disposed directly below the cooling coils 38 within tank 24 is the semi-circular trough 39. The cooling coils 38 enter tank 24 through the cylindrical extension of the trough 39 which projects from the upper portion of tank 24. Extending downward from the extension 40 is the condensate collection trap 41 into which condensate dripping from the cooling coils 38 flows. The coils 38 may be connected to any existing cold water source the fiow from which may be regulated by the valve 42.
At the start of the operation of this apparatus, a distillate holding tank 43 is at least partially filled with pure water 44. The water 44 is pumped from tank 43 through pipe 45 by pump 46 which is driven by motor 47. This water is forced by pump 46 through pipe 48 and eductor 49 to return to tank 43 through pipe 50. Pipe 51 leads from eductor 49 to the upper portion of the cylindrical extension 40 to draw a vacuum within tank 24 of less than 1 p.s.i.a. In operation, eductor 49 removes noncondensible gases from tank 24 and eductor 49 also draws distillate from the bottom of the condensate collection trap 41 through pipes 52 and 53 and the three-way valve 54. A purity sensing element 55 is installed on pipe 53. Purity sensing element 55, which may be a conductivity cell, activates a mechanism 56 if the condensate is not of a desired degree of purity. Mechanism 56 then activates the valve 54 so that the condensate is drawn through pipe 57 by eductor 21 to be returned to the batch tank 15. When the purity of the distillate reaches a desired level, element 55 actuates mechanism 56 so that valve 54 allows the condensate to be drawn through pipe 52 by eductor 49 to be discharged into the distillate holding tank 43. Distillate may flow from tank 43 through pipe 58 and valve 59 to the drain 60 which may lead to a distillate storage tank, a reactor pool makeup water storage tank, or to a sewage line (not shown).
If it is desired, valve 61 may be opened and valve 59 closed to pass the distillate through an ion exchange column 62 containing demineralizing resins 63 behind a glass cylindrical wall 64. Since the water from the evaporator and condenser 23 has already been high-1y purified, with a solids content as low as 2 ppm, the demineralizer resins 63 will last through thousands of gallons of distillate. The ion exchange resins 63 are visible to an operator through the glass wall 64 and change color when they are exhausted. They can then be easily removed and replaced. If extreme purity is not required, the demineralizer 62 may be bypassed.
One radioactive waste concentrator, built according to that shown in FIGURE 1, was supplied with hot water to coil 29 at a great variety of temperatures and flow rates. With a fiow rate of hot water of 11 gallons per minute at 165 F. the same rate of evaporation was produced as with a flow rate of 25 gallons per minute at F. The amount of cooling water required to be supplied to coils 38 to condense distillate varied with the temperature of the cold water supply. One unit has performed satisfactorily with a cold water supply at 57 F. and a flow rate of approximately 20 gallons per minute.
Because the evaporator and condenser 23 is operated at a high degree of vacuum, there is no possibility of contaminating the heating and cooling Water which may be further recirculated for conventional "building service use. Should the coils 29 or 38 develop a leak, cooling or heating water would flow into the high vacuum so that radioactive materials could not possibly enter coils 29 or 38 against their higher internal line pressures.
When operating the apparatus shown in FIGURE 1 with a hot water supply at the rates and temperatures heretofore mentioned with the vacuum at 27 in. Hg and the temperature of the boiling liquid at 100 F., the rate of evaporation varied from 25 to 28 gallons per hour. Two types of waste were processed. The first type of waste was a low level activity waste with an extremely high solids content. The performance characteristics obtained while processing this waste without the use of the de-ionizer 62 are listed below.
Average activity of raw waste approximately 10 uc./cc.;
Average activity of distillate approximately 10 uc./cc.;
Decontamination factor-approximately 100,000 to 1 reduction in activity;
Average solids in distillate-5 ppm.
The second type of waste contained a higher activity and had a low solids content as compared with the first type. The radioactive constituent Was Mn as MnSO dissolved in tap water. The performance characteristics obtained while processing this waste without the de-ionizer 62 are listed below.
Activity of the raw waste 49x10" uc./cc.;
Activity of the distillate 5.1 x u.c./cc.;
Decontamination factor960,000 to 1 reduction in activity;
Average solids content in distillate--insignificant.
Additional tests show that the de-ionizer 62 will further reduce the activity of the distillate by a factor of 10 with the types of wastes which were tested.
As shown in FIGURE 1, aqueous radioactive wastes 16 are withdrawn from the batch tank by pump 18. Some of these wastes pass through pipe 26 into tank 24 to be heated by coil 29 and then withdrawn through tube 28 and reintroduced into tank 15. Thus the radioactive waste material 16 is constantly recirculated between the batch tank 15 and the bottom of the evaporator and consenser 23. When the radioactive waste 16 reaches a desired degree of concentration, valve 65 in drain pipe 66 maybe opened to drain the concentrated waste to a sludge storage or radioactive waste drumming station.
During tests of the apparatus as shown in FIGURE 1, a concentration of approximately 471,000 ppm. of solids was obtained. At room temperature, this resulted in precipitated solids by volume. Naturally, during the operation of the apparatus, the recirculation of the radioactive waste material between the tank 24 and tank 15 about the heating coil 29 caused the radioactive waste material 1 6 in both tanks to become heated. As shown in FIGURE 3, a precipitator 67 may receive the concentrated waste material from bat-ch tank 15 when valve 65 is opened. The precipitated solids 68 may then be removed for disposal and the liquid returned to the radioactive waste storage tank 11 to again be concentrated in the apparatus.
FIGURE 3 shows a further modification of this invention wherein heating and cooling coils 80 and 81 within the evaporator and condenser 23 are connected by means of the tubes 82, 83 and 84 to an expansion valve 85 and a refrigerant compressor 86 which is driven by a motor 87. Any suitable refrigerant, such as freon, is compressed and thereby heated by the compressor 86 to deliver heat to the heating coil 80. The refrigerant then passes through tube 83 to flow through the throttling valve 85 to cool and absorb heat within the condensing coils 81. The refrigerant then passes through tube 82 for return to compressor 86. If it is required, a small additional heat sink may be provided to remove heat generated in the pump 86 from the refrigeration circuit so that all the water vaporized may be condensed. The particular characteristics of a given apparatus will determine whether or not an additional heat sink is required.
A heat sensing element 88 activates a control unit 89 which, in turn, controls the refrigeration cycle to maintain the heating coil at a desired temperature. The control unit 89 may, through a lead 95, regulate the speed of motor 87 or it may control the refrigeration circuit in any other conventional manner.
The apparatus shown in FIGURE 3 is particularly adaptable in its installation as only a current source is required to operate the motors 12, 19, 47 and 87. If hot and cold water supplies are available, as in normal building service, then the apparatus shown in FIGURE 1 may be easily installed.
What is claimed is:
1. Apparatus for the concentration of aqueous radioactive wastes comprising, in combination,
(a) a batch storage tank,
(b) means to fill said batch storage tank with radio active Waste,
(c) a first pump drawing waste from said batch tank,
(d) a first eductor through which said pump forces waste which returns to said batch tank,
(e) an evaporator and condenser having a heating coil in its lower portion, a condensing coil in its upper portion, means collecting condensate from said con= densing coil, and drop separators between said heat= ing and condensing coils,
(f) a first valve enabling some flow from said first eductor to flow into the bottom of said evaporator and condenser,
(g) means responsive to the waste level in the bottom of said evaporator and condenser closing said first valve,
(h) a first pipe through which said first eductor draws waste from said evaporator and condenser to return with the waste flowing from said first eductor to said 'batch tank,
(i) a distillate holding tank,
(j) a second pump drawing water from said distillate holding tank,
(k) a second eductor through which said second pump forces water which returns to said distillate holding tank,
(1) a second pipe through which said second eductor draws a vacuum in said evaporator and condenser,
(m) a purity sensing device,
(11) a three-way valve actuated in response to said purity sensing device, and
(o) a third pipe leading from said means collecting condensate through said purity sensing device to said three-way valve, said three-way valve directing con densate to said second eductor to pass into said distillate tank and said three-way valve being activated in response to said purity sensing device directing dis tillate of lesser purity to said first eductor to pass into said batch tank.
2. The combination according to claim 1 wherein said second eductor is adapted to draw a vacuum through said second pipe in said evaporator and condenser of about 1 p.s.i.a.
3. The combination according to claim 1 with the addition of a building service supply of hot and cold water wherein said heating and condensing coils of said evaporator and condenser have said building service supply of hot and cold water flow through them.
4. The combination according to claim 3 with the addi# tion of a second valve regulating the flow from said building service supply of hot water through said heating coil, means regulating said second valve, and a temperature sensing element in the bottom of said evaporator and condenser, said temperature sensing element activating said means regulating said second valve.
5. The combination according to claim 1 with the addition of a refrigeration circuit having a refrigerant to flow through said heating coil, and an expansion valve through which said refrigerant expands to pass through said condensing coil.
6. The combination according to claim 5 with the addition of means controlling said refrigeration circuit, and a 1,516,314 11/1924 Sebald 202153 X 2,832,726 4/1958 Norment 202181 3,009,864 11/1961 Webb 202-206 X 3,055,810 9/1962 Skow 202181 X NORMAN YUDKOFF, Primary Examiner.
F. E. DRUMMOND, Assistant Examiner.