GB2178588A - Method and apparatus of treatment of radioactive liquid waste - Google Patents

Method and apparatus of treatment of radioactive liquid waste Download PDF

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Publication number
GB2178588A
GB2178588A GB08618470A GB8618470A GB2178588A GB 2178588 A GB2178588 A GB 2178588A GB 08618470 A GB08618470 A GB 08618470A GB 8618470 A GB8618470 A GB 8618470A GB 2178588 A GB2178588 A GB 2178588A
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GB
United Kingdom
Prior art keywords
radioactive
liquid waste
chamber
solvent
freezing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB08618470A
Other versions
GB8618470D0 (en
Inventor
Osamu Takanobu
Isao Kondoh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Doryokuro Kakunenryo Kaihatsu Jigyodan
Original Assignee
Doryokuro Kakunenryo Kaihatsu Jigyodan
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Doryokuro Kakunenryo Kaihatsu Jigyodan filed Critical Doryokuro Kakunenryo Kaihatsu Jigyodan
Publication of GB8618470D0 publication Critical patent/GB8618470D0/en
Publication of GB2178588A publication Critical patent/GB2178588A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
    • G21F9/04—Treating liquids
    • G21F9/06—Processing
    • G21F9/08—Processing by evaporation; by distillation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • F26B5/06—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum the process involving freezing

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Molecular Biology (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Heat Treatment Of Water, Waste Water Or Sewage (AREA)
  • Removal Of Specific Substances (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Abstract

Radioactive liquid waste is subject to freezing and then only the solvent is sublimated to separate it from the radioactive solute so that the radioactive solute remains as a dried material or a concentrate. The invention provides also an apparatus for carrying out the treatment of the radioactive liquid waste.

Description

SPECIFICATION Method and apparatus of treatment of radioactive liquid waste The present invention relates in general to decontamination of radioactive liquid waste, and more particularly, to a method and an apparatus for decontaminating various kinds of radioactive liquid waste such as a liquid waste produced in reprocessing and conversion steps of spent nuclear fuel and a liquid waste produced in the refining step of nuclear fuel materials and in the fabricating step of nuclear fuel.
In the conventional method for decontaminating, or removing plutonium from a nitric acid liquid waste containing plutonium which has been produced the conversion step of plutonium nitrate, the so-called evaporation-neutralization-precipitation method has been applied in which the liquid waste is treated such that a solute of plutonium is concentrated by an evaporator and admixed with a neutralizing agent such as sodium hydroxide to precipitate the plutonium in the form of hydroxide, and then subject to solid-liquid separation, followed by addition of a flocculant such as ferric nitrate and high molecular flocculant to subject again to sold-liquid separation.
In the conventional decontamination method, the structural material of the evaporator used for heat-concentration of the nitric acid liquid waste is exposed to a high corrosive environment and consequently the life time of the apparatus is shortened. Further, addition of neutralizing agent and flocculant defectively increases the quantity of the material to be treated as the operational process progresses.
Moreover, at the time of heat-evaporation of the liquid waste by the evaporator, the liquid waste is splashed due to boiling and entrained in vapor and accordingly, the solute (plutonium) moves into a condensate of the vapor.
Consequently, the decontamination factor (solute concentration of volume of pre-processed liquid relative to solute concentration or volume of processed liquid) is restricted to the order of 103-105. Thus, in order to obtain such concentration of plutonium in the liquid waste that the waste can be released to the environment, the above-described treatment must be carried out repeatedly and therefore it requires additional apparatus and complex operations.
In addition to the above, since the liquid waste to be treated contains radioactive material, the treatment apparatus must be installed within a glove box equipped with a ventilating/exhaust device. Thus, operation and maintenance of the treatment apparatus must be carried out indirectly. Especially in the case of replacement of the apparatus and parts thereof, the glove box must be entirely shielded by a special enclosure called a "green house" and, at the same time, working personnel must be protected by special protective clothing. Consequently, a great amount of radioactive waste is produced and considerable manpower and cost are required.
Therefore, it is strongly expected that the treatment apparatus in the glove box has sufficient service durability and is sufficiently simple in structure that operation and maintenance can be readily carried out.
A general object of a preferred embodiment of the present invention is to provide an improvement in decontamination of a radioactive liquid waste.
Another object of a preferred embodiment of the present invention is to provide a method for decontamination of a radioactive liquid waste, which permits an improvement in service durability with corrosion protection of the apparatus by excluding a high-temperature treatment such as heat-evaporation and also permits an increase of a decontamination factor without an entrainment phenomenon caused by boiling of the liquid waste in the high-temperature treatment.
Another object of a preferred embodiment of the present invention is to provide an improved method for decontamination of a radioactive liquid waste, which permits an easy operation and does not need addition of flocculant and neutralizing agent.
A further object of a preferred embodiment of the present invention is to provide an apparatus for decontamination of a radioactive liquid waste, which is suitable for carrying out the above-described method and has a simple structure for easy maintenance.
The objects described above can be realized by a preferred embodiment of the present invention in which a radioactive liquid waste is subject to freezing and then only a solvent is sublimated to separate the solvent from the solute, rather than the conventional method which employs heat-evaporation of the liquid waste.
Accordingly, there is provided a method of treatment of a radioactive liquid waste containing a solvent and a radioactive solute, comprising the steps of freezing the radioactive liquid waste to produce a frozen material, heating in a vacuum said frozen material to sublimate the solvent so that said radioactive solute is separated from said solvent and remains as a dried material or a concentrate.
There is further provided an apparatus for the treatment of a radioactive liquid waste containing a solvent and a radioactive waste, comprising a freezing-sublimating chamber for freezing the radioactive liquid waste to produce a frozen material and heating the frozen material to sublimate the solvent in the frozen material, a condensating chamber for cooling and condensating the sublimated solvent, a pipe connecting said freezing-sublimating chamber to said condensating chamber for di recting the sublimated solvent from said freezing sublimating chamber to said condensating chamber, and a vacuum device, connected to said condensating chamber, for vacuumize said freezing sublimating chamber and said condensating chamber.
A preferred embodiment of the present invention will now be described in detail, by example only, with reference to the accompanying drawing which is a partly sectioned view of an apparatus for decontamination of a radioactive liquid waste.
Referring to the drawing, the apparatus has a freezing sublimating chamber 1, a condensating chamber 2 and a pipe 3 which connects those two chambers 1 and 2. In the freezing-sublimating chamber 1, a tray 5 for receiving a liquid waste 4 to be treated containing a solvent and a radioactive solute is placed on a stage 6 for cooling or heating the liquid waste 4 which has been fed from an inlet 7 into the tray 5.
In the condensating chamber 2, a trap device 8 is disposed for cooling the sublimated component, that is the solvent, from the freezing-sublimating chamber 1 and condensating it to be recovered. The condensating chamber 2 is connected to a vacuum device 9 and a liquid (condensate) recovery chamber 10.
The apparatus has a heater 11 for heating the stage 6 in the freezing-sublimating chamber 1, and refrigerator 12 for cooling the stage 6 and the trap device 8 in the condensating chamber 2.
An operational mode of the apparatus and the method of the present invention will now be explained. A liquid waste 4 to be treated which contains a solvent and a radioactive solute such as neuclear fuel materials is fed from the inlet 7 to the tray 5 in the freezing sublimating chamber 1, and then cooled by the refrigerator 12 so that the liquid waste 4 is frozen in the tray. In the case of a liquid waste produced by the plutonium nitrate conversion facilities, the freezing temperature is about 230 "K. The trap 8 in the condensating chamber 2 is also cooled by the refrigerator 12. As the temperature of the trap becomes lower, the recovery of the condensate generally becomes higher.In a preferred embodiment of the present invention, the trap temperature is set to be about 200"K which is lower than the freezing temperature described above.
Subsequently, the vacuum device 9 is driven to evacuate both the condensating chamber 2 and the freezing-sublimating chamber 1, the latter being connected to the former through the pipe 3 as described above. As the degree of vacuum in the system increases, only the solvent in the frozen material is sublimated due to the difference betwen inherent vapor pressure (sublimation pressure) of the solvent and that of the solute. The sublimated component is directed through the pipe 3 into the condensating chamber 2 and condensated on the surface of the trap device 8 to be recovered. As sublimation proceeds, sublimation heat is taken away from the frozen material in the tray 5 and, accordingly, a corresponding quantity of heat is supplied to the frozen material by the heater 11 so that the temperature of the frozen material is maintained to be slightly lower than the freezing temperature.
When the solvent in the frozen material is sublimated completely to an extent that no slvent remains, only the solute in the frozen material remains in a dried state, and the degree of vacuum in the system increases. At the same time, the heat to be taken away due to sublimation (sublimation heat) runs out and therefore a temperature of the frozen material becomes higher. Consequently, when sublimation is finished, an increase in the degree of vacuum and the increase of temperature of the frozen material are observed. As a matter of course, if operation of the apparatus is shutdown during sublimation, a concentrate is obtained in which the solute is concentrated in the solvent.
The solvent such as water and nitric acid in the liquid waste to be treated is thus sublimated and condensated on the trap device 8, and then collected in the liquid recovery chamber 10 to be recovered. On the other hand, the solute such as plutonium which remains in the tray 5 as a dried material or a concentrate can be recovered.
According to the present invention, since the liquid waste to be treated is not subject to boiling and evaporation, entrainment of the solvent containing a solute component into the vapor due to boiling of a liquid does not occur. Consequently, the quantity of the solute which moves into the solvent recovered by the trap device 8 in the condensation chamber 2 is extremely small and, accordingly, a desired decontamination factor as high as 107 and more can be obtained.
In order to improve further the decontamination capability, a filter 13 can be disposed in the pipe 3 between the freezing-sublimating chamber 1 and the condensating chamber 2.
Alternatively, a suitable thickening agent may be added to the liquid waste before the liquid waste is treated.
As the heater, an electric heater or any other desirable heating medium may be used.
Preferably, at least an inner surface of the tray 5 is made of silicon carbide which can be easily heated by high frequency heating so that the liquid waste is indirectly heated.
Example A nitric acid liquid waste mixture comprising a condensate produced from a denitrating step and a washing liquid waste produced from an exhaust gas-washing step in conversion facilities was evaporated to produce a concen trated liquid waste to be treated having the following composition.
Radioactive concentration (T-a) 54.5 (mci/l) Fe 0.63 (g/l) Cr 0.17 (g/l) Ni 0.13 (g/l) Acid concentration (H+) 7.3 (M) This concentrated liquid waste was treated by the method according to the present invention using the apparatus as shown in the drawing.
1 ml of the concentrated liquid waste was introduced to the tray in the freezing-sublimating chamber, and then both the freezing-sublimating chamber and the condensating chamber were cooled to about -70"C by driving the refrigerator to freeze the concentrated liquid waste. Thereafter, by driving the vacuum device, both the freezing-sublimating chamber and the condensating chamber were evacuated to about 10 3 Torr.The temperature in the freezing-sublimating chamber was then adjusted near -43"C by using the heater and the refrigerator, while the temperature in the condensating chamber was kept at about -700C. In this condition, sublimation of solvent (HNO3) occured in the freezing-sublimating chamber, while condensation of the sublimated solvent occured in the condensating chamber, with the degree of vacuum in the system being 1 X 10 2-3X10 2 Torr. After completion of the treatment, the condensating chamber was heated to recover the condensed and trapped solvent as a solution. 0.9 ml of solution having radioactive concentration (T-a) of 1 X 10 6 mci/l was recovered.Thus, decontamination factor, i.e. [(Amount of liquid waste treated)X (Radioactive concentration in liquid waste)]/[(Amount of solution recovered) X(Radioactive concentration in recovered solu- tion)] was 6X107. 10'.
According to the present invention, the following advantages can be expected.
(1) Since the treatment temperature of liquid waste is very low, i.e. below a freezing temperature, corrosive thinning e.g. thickness-reduction by corrosion of the structural material of the apparatus, which has occurred in the conventional method employing an evaporator, scarcely occurs. Thus, the life time of the apparatus can be prolonged. Further, the present invention greatly contributes towards reduction of cost since an expensive non-corrosive material is not needed.
(2) Separation between solvents (water, nitric acid, etc.) and solutes is made by sublimation and, accordingly, an entrainment which generally occurs in an evaporation procedure is not present at all, with the result of a large improvement of a decontamination factor. For example, a decontamination factor as high as 107 and more can be obtained, in comparison with the fact that a decontamination factor of the conventional evaporation method is about 103-105.
(3) Sublimation of solvent and drying or concentration of solute can be carried out by the same apparatus, and a high decontamination capability can be obtained. Consequently, a treatment process of the liquid waste can be simplified.
(4) Even in the case that combustible or explosive materials are contained in the liquid waste, the treatment temperature is very low and, accordingly, there is little danger of fire and explosion, resulting in a high degree of safety.
(5) The decontamination factor of volatile eie- ments e.g. ruthenium can be heightened in the present invention, whereas it is not possible in the conventional evaporation method.
Although the present invention is primarily related to the treatment of a liquid waste which contains radioactive materials, the principles of separation of solvents and solutes as used in the present invention is extensively applicable to treatment of a liquid which has a difference in a vapor pressure (sublimation pressure) between solvents and solutes when the liquid is frozen, regardless of the nature of liquid being radioactive or otherwise non-radio- active in a technical field of, for example, re moval or recovery of heavy metal components in a metal plating liquid waste.

Claims (7)

1. A method of treatment of a radioactive liquid waste containing a solvent and a radioactive solute, comprising the steps of freezing the radioactive liquid waste to produce a frozen material, heating in a vacuum said frozen material to sublimate the solvent so that said radioactive solute is separated from said solvent and remains as a dried material or a concentrate.
2. The method according to claim 1, wherein said frozen material is heated by high frequency heating.
3. The method according to claim 1, wherein a thickening agent is added to said radioactive liquid waste before said liquid radioactive waste is treated.
4. An apparatus for the treatment of a radioactive liquid waste containing a solvent and a radioactive waste, comprising a freezing-sublimating chamber for freezing the radioactive liquid waste to produce a frozen material and heating the frozen material to sublimate the solvent in the frozen material, a condensating chamber for cooling and condensating the sublimated solvent, a pipe connecting said freezing sublimating chamber to said condensating chamber for directing the sublimated solvent from said freezing-sublimating chamber to said condensating chamber, and a vacuum device, connected to said condensating chamber, for vacuumize said freezing sublimating chamber and said condensating chamber.
5. The apparatus according to claim 4, wherein a filter is disposed in said pipe to improve decontamination of the radioactive liquid waste.
6. A method of treatment of a radioactive waste containing a solvent and a radioactive solute substantially as herein described with reference to the particular example.
7. An apparatus for the treatment of a radioactive waste containing a solvent and a radioactive solute substantially as herein described and as illustrated in the accompanying drawing.
GB08618470A 1985-07-29 1986-07-29 Method and apparatus of treatment of radioactive liquid waste Withdrawn GB2178588A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP16703185A JPS6227697A (en) 1985-07-29 1985-07-29 Method and device for processing waste liquor containing radioactive substance

Publications (2)

Publication Number Publication Date
GB8618470D0 GB8618470D0 (en) 1986-09-03
GB2178588A true GB2178588A (en) 1987-02-11

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ID=15842104

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08618470A Withdrawn GB2178588A (en) 1985-07-29 1986-07-29 Method and apparatus of treatment of radioactive liquid waste

Country Status (4)

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JP (1) JPS6227697A (en)
DE (1) DE3625602A1 (en)
FR (1) FR2585502A1 (en)
GB (1) GB2178588A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0347255A1 (en) * 1988-06-17 1989-12-20 Doryokuro Kakunenryo Kaihatsu Jigyodan Method of treating high-level radioactive waste liquid
EP0358431A1 (en) * 1988-09-05 1990-03-14 Doryokuro Kakunenryo Kaihatsu Jigyodan Spent fuel treatment method
EP0831286A2 (en) 1996-09-19 1998-03-25 The Boc Group, Inc. Freeze drying method and apparatus

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JPH01311296A (en) * 1988-06-09 1989-12-15 Power Reactor & Nuclear Fuel Dev Corp Processing method for waste solvent
JPH01316690A (en) * 1988-06-17 1989-12-21 Power Reactor & Nuclear Fuel Dev Corp Treatment of plutonium and uranium solution
JPH01316695A (en) * 1988-06-17 1989-12-21 Power Reactor & Nuclear Fuel Dev Corp Reprocessing of nuclear fuel by using vacuum freeze drying method
JPH073471B2 (en) * 1988-07-29 1995-01-18 動力炉・核燃料開発事業団 Solvent purification method
CN113461092A (en) * 2021-06-21 2021-10-01 以农环境工程有限公司 Method for treating sewage by using freezing sublimation technology
CN115014047A (en) * 2022-05-30 2022-09-06 南京威尔药业科技有限公司 Method for producing tert-butyl alcohol by using freeze dryer

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GB994156A (en) * 1962-04-27 1965-06-02 Leybold Anlagen Holding Ag Process for treating radioactive substances
GB995930A (en) * 1961-11-28 1965-06-23 Leybold Hochvakuum Anlagen Method of freeze drying
GB1042081A (en) * 1963-03-02 1966-09-07 Leybold Hochvakuum Anlagen Improvements relating to the freeze drying of materials
EP0000181A1 (en) * 1977-06-24 1979-01-10 Ingenieurbüro Stecker Process and apparatus for solidifying toxic and waste materials, in particular radioactive materials.

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FR1333345A (en) * 1961-11-28 1963-07-26 Leybold Hochvakuum Anlagen Freezing drying process
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JPS56128592A (en) * 1980-03-12 1981-10-08 Doryokuro Kakunenryo Method and device for heating with microwave
US4444680A (en) * 1981-06-26 1984-04-24 Westinghouse Electric Corp. Process and apparatus for the volume reduction of PWR liquid wastes
DE3200331A1 (en) * 1982-01-08 1983-07-28 GNS Gesellschaft für Nuklear-Service mbH, 4300 Essen "METHOD AND SYSTEM FOR THE TREATMENT OF DAMP OR WET RADIOACTIVE WASTE MATERIALS"
JPS58191998A (en) * 1982-05-06 1983-11-09 動力炉・核燃料開発事業団 Cyclic tank type microwave heating device

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Publication number Priority date Publication date Assignee Title
GB995930A (en) * 1961-11-28 1965-06-23 Leybold Hochvakuum Anlagen Method of freeze drying
GB994156A (en) * 1962-04-27 1965-06-02 Leybold Anlagen Holding Ag Process for treating radioactive substances
GB1042081A (en) * 1963-03-02 1966-09-07 Leybold Hochvakuum Anlagen Improvements relating to the freeze drying of materials
EP0000181A1 (en) * 1977-06-24 1979-01-10 Ingenieurbüro Stecker Process and apparatus for solidifying toxic and waste materials, in particular radioactive materials.

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0347255A1 (en) * 1988-06-17 1989-12-20 Doryokuro Kakunenryo Kaihatsu Jigyodan Method of treating high-level radioactive waste liquid
EP0358431A1 (en) * 1988-09-05 1990-03-14 Doryokuro Kakunenryo Kaihatsu Jigyodan Spent fuel treatment method
EP0831286A2 (en) 1996-09-19 1998-03-25 The Boc Group, Inc. Freeze drying method and apparatus
EP0831286A3 (en) * 1996-09-19 1998-05-20 The Boc Group, Inc. Freeze drying method and apparatus
US5996248A (en) * 1996-09-19 1999-12-07 The Boc Group, Inc. Freeze drying method

Also Published As

Publication number Publication date
GB8618470D0 (en) 1986-09-03
DE3625602A1 (en) 1987-01-29
JPS6227697A (en) 1987-02-05
FR2585502A1 (en) 1987-01-30

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