EP0047978A2 - Méthode de traitement d'un liquide résiduaire radioactif - Google Patents

Méthode de traitement d'un liquide résiduaire radioactif Download PDF

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Publication number
EP0047978A2
EP0047978A2 EP81107102A EP81107102A EP0047978A2 EP 0047978 A2 EP0047978 A2 EP 0047978A2 EP 81107102 A EP81107102 A EP 81107102A EP 81107102 A EP81107102 A EP 81107102A EP 0047978 A2 EP0047978 A2 EP 0047978A2
Authority
EP
European Patent Office
Prior art keywords
oxine
activated charcoal
water
filter elements
adsorbent
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Withdrawn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
EP81107102A
Other languages
German (de)
English (en)
Other versions
EP0047978A3 (fr
Inventor
Kenji Motojima
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.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
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 Hitachi Ltd filed Critical Hitachi Ltd
Publication of EP0047978A2 publication Critical patent/EP0047978A2/fr
Publication of EP0047978A3 publication Critical patent/EP0047978A3/fr
Withdrawn legal-status Critical Current

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    • 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
    • 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
    • G21F9/12—Processing by absorption; by adsorption; by ion-exchange

Definitions

  • the present invention relates to a method for treating a radioactive waste liquid which contains colloidal and suspended solid substances.
  • radioactive impurities have been removed by filtration using a demineralizer in which hundreds of filter elements are pre-coated with a mixture of powdery anion-exchange resin and powdery cation-exchange resin such as known "Powdex”. (trade name of Graver Water Conditioning Co.).
  • Powdex powdery anion-exchange resin
  • Powdery cation-exchange resin such as known "Powdex”.
  • the above system is very effective for refining water, since it captures not only colloidal substances or suspended solids but also captures even anions and cations dissolved therein. This method, however, presents defects as will be mentioned below.
  • the powdery anion-exchange resin and the powdery cation-exchange resin tend to swell or contract when they are subjected to the ion-exchange operation, and further tend to be deformed when they are placed under pressure con - ditions. Therefore, the filter layer composed of powdery ion-exchange resins becomes gradually densified. The difference in the filtering pressure, therefore, is increased when a flat filter element is used, such as of a stainless-steel gauze.
  • a filter element obtained by winding a nylon yarn or a polypropylene yarn on a hollow metal pipe to a thickness of 10 to 15 mm, or a fibrous ion-exchange resin, has been used.
  • oxine-impregnated activated charcoal is employed as a pre-coating material in stead of powdery ion exchange resin for the demineralizer.
  • the invention comprises a method for treating a radioactive waste liquid containing colloidal substances and suspended solids by adsorbing on filter elements precoated with a powdery adsorbent comprising precoating the filter elements with oxine-impregnated activated charcoal, passing the waste liquid through the filter elements to adsorb the colloidal substances and suspended solids, removing the spent adsorbent from the filter elements and incinerating the removed spent adsorbent in order to reduce the volume of the waste adsorbent.
  • the oxine-impregnated charcoal is originally developped by the applicant as an adsorption material for radiocobalt ion. The details of the material are described for example in U.S. Patent 4,222,892.
  • the oxine-impregnated activated charcoal By the use of the oxine-impregnated activated charcoal, the final volume of the used precoating material can be greatly reduced to less than 5 % of the original volume, because the used oxine-impregnated charcoal can be easily burned to ash. Also, by the use of the oxine-impregnated activated charcoal, it is possible to eliminate troublesome operations such as regeneration of the ion exchange resin and counter-current washing operations.
  • the powdery activated charcoal having a particle size distribution over a range of 5 to 200 ⁇ m, or the powdery activated charcoal which is impregnated with oxine in an amount of up to 35 % by the method described in U.S. Patent 4,222,892, or a mixture thereof is dispersed in water, and the dispersion is passed through a filter element to form a filter layer of a thickness of 5 to 15 mm (pre- coating).
  • Water to be treated is then passed through the filter layer, whereby radioactive impurities contained in water are removed and, when oxine is used, ions of cobalt and ions of heavy metals dissolved in water are also removed.
  • the difference in the filtering pressure is not increased by the deformation which is a serious defect inherent in the use of ion-exchange resin powders. Therefore, a metal gauze made of a stainless steel can simply be used for the filter element.
  • the amount of oxine which is eluted is negligibly small even when the water temperature is as high as about 100 0 C, provided the amount of oxine does not exceed 10 % with respect to the amount of activated carbon.
  • the filter layer which produces increasing difference in the filtering pressure during the use can be easily and completely peeled off from the filter element by applying a small reverse pressure.
  • the filter layer which is peeled off is dehydrated, dried, and is then gradually incinerated, so that its volume is reduced to less than several percent of its initial volume. In this case, no radioactive substance is emitted, and no harmful gas is generated.
  • the filter layer is formed on the surface of the filter element in the following manner.
  • the powdery activated charcoal, the powdery activated charcoal impregnated with oxine, or a mixture thereof is thrown into water in the pre-coating tank, and is aggitated and dispersed.
  • the dispersion is then passed to the filter element so that it is pre-coated as uniformly as possible. Fine powdery activated charcoal which leaks out first when water is circulated, is also captured by the filter layer.
  • the powdery activated charcoal may be dispersed in water beforehand with stirring followed by the addition of a predetermined amount of oxine powder, or the filter element may be pre-coated with the activated charcoal followed by the flow of water in which is dispersed oxine powder.
  • oxine is strongly adsorbed by the activated charcoal, and ions of heavy metals such as of cobalt are removed in the same manner as by the use of oxine-adhered activated charcoal.
  • the filter element used in the method of the present invention can be other than the one which is usually used for the pre- coated filtration.
  • a filter cylinder or a filter plate made of a stainless-steel gauze is preferable since it permits the used filter layer to be easily peeled off by applying a reverse pressure and since it is less loaded or less deteriorated by the radiation. Further, the size of the mesh should be 40 to 50 um.
  • Fig. 1 illustrates the principle of an apparatus of the present invention for removing by filtration colloidal substances and suspended solids from the cooling water or radioactive waste liquid in a nuclear power plant.
  • a cylindrical filter element 2 made of many pieces of stainless-steel metal gauze (having a mesh size of 44 ⁇ 5 ⁇ m) is installed in a filtering tank 1.
  • a purge valve 11 is opened, and pure water is filled in the tank 1 through a pump 15 and a valve 7. Thereafter, the valves 11, 7 are closed, and the pump 15 is stopped to stop the supply of pure water.
  • a predetermined amount of pure water is introduced into a pre-coating tank 3, and powdery activated charcoal or oxine-impregnated powdery activated charcoal which is a pre-coating material is added in a predetermined amount (1 to 4 kg per square meter of the filtering area) followed by stirring so that it is dispersed in pure water.
  • Valves 8, 10 are then opened, a pump 16 is actuated, and pure water in which is dispersed the pre- coating substance is introduced into the filtering tank 1 and is circulated therein. Valves 4, 5, 6 and 7 are closed. The pre-coating material is permitted to precipitate on the outer surface of the filter element 2, thereby to form a filter layer.
  • the pump 16 is stopped, and the valves 8 and 10 are closed. Then, the valves 4 and 6 are opened, a pump 14 is driven, and water to be treated (such as cooling water or radioactive waste liquid of nuclear reactors) is supplied into the filtering tank 1. Water to be treated is filtered through the filter layer (layer of powdery activated carbon). Further, a pump 13 and a valve 5 are provided to constitute a pressurizing system in order to prevent the filter layer from being peeled off when the pumps 14 and 16 are not working.
  • water to be treated such as cooling water or radioactive waste liquid of nuclear reactors
  • the operation is discontinued when the colloidal substances or suspended solids in the water to be treated precipitated on the pre-coating material of the filter layer cause the difference in the filtering pressure to be increased (usually, up to about 2 kg/cm2), and compressed water or compressed water admixed with the compressed air is fed through the valve 11, in order to peel off the pre-coating material applied onto the outer surface of the filter element 2.
  • the pre-coating material which is peeled off is drained out of the filtering tank 1 through a valve 12. Solid portion of the slurry which chiefly consists of the drained powdery activated carbon is separated by the sedimentation method and the filtering method, dried, and is incinerated in an incineration furnace 18 at between 400 to 800 °C.
  • the incineration can be easily controlled by adjusting the blow rate of the air.
  • Waste ash which remains after the incineration includes iron and stable metal oxides.
  • the volume of the solid portion of the waste can therefore be reduced to less than several percent of the initial volume though it may vary depending upon the amount of solid matter that is filtered.
  • FIG. 2 shows a small filtering apparatus used for studying the fundamental requirements of the present invention.
  • a filter 20 consists of a tube 21 made of acrylic resin (having an inner diameter of 36 mm) and a plug made of polytetrafluoroethylene, and has in the bottom portion thereof a metal gauze 29 (mesh size, 44 - 5 ⁇ m) made of a stainless steel which is fixed by packing. Powdery activated charcoal or oxine-impregnated powdery activated charcoal dispersed in water in a pre-coating tank 23 using a magnetic stirrer, is introduced into the filter 20 by a pump 25; in order to form a filter layer 30 composed of activated charcoal or oxine-impregnated activated charcoal on the metal gauze.
  • sample water in a sample- water tank 22 is fed into the filter 20 at a constant flow rate using the pump 25.
  • the pressure difference is measured using pressure gauges 26 and 27.
  • Reference numeral 24 denotes a pure-water tank and 28 denotes a flow meter.
  • the experiment is carried out by using fine powdery iron oxide (Fe 2 O 3 , particle diameter 0.5 to 5 ⁇ m, average particle diameter 3 ⁇ m) as suspended solid substance and cobalt ions (cobalt nitrate whose pH is always maintained at 7.0 - 0.2 using diluted ammonia water) as dissolved ions.
  • Iron oxide in drained water is measured based upon the oxine-extraction absorptiometric method by separating the sample water by a millipore filter (0.45 micron) and dissolving it in hydrochloric acid, and cobalt is measured by the a-nitroso-8-naphthol-extraction absorptiometric method (quantitative sensitivity, 0.002 ppm).
  • curve A represents the measured data of the filtering pressure which rises relative to the amount of water which has passed through the filter layer when water to be treated is permitted to flow at the above-mentioned constant rate
  • curve B represents the amount of cobalt leaked into the drained water.
  • the spent powdery activated carbon can be easily burned in the air. No contaminated gas is produced even when the oxine-impregnated activated carbon is burned.
  • solid lines represent characteristics of the powdery activated charcoal
  • broken lines represent characteristics of the oxine-impregnated powdery activated charcoal
  • one-dot chain lines represent characteristics of the oxine-impregnated powdery activated charcoal admixed with iron oxide (Fe 2 0 3 ) in a mixing ratio of 1 to 1.
  • the activated charcoal and oxine-impregnated activated charcoal exhibit nearly the same weight and same differential thermal analytic curves.
  • the present invention presents no problem even when fibers of cotton or paper are added to the powdery activated charcoal.
  • the radioactive waste liquids can be effectively refined, and the amount of radioactive wastes can be strikingly reduced.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • Filtration Of Liquid (AREA)
  • Filtering Materials (AREA)
  • Treatment Of Water By Ion Exchange (AREA)
EP81107102A 1980-09-12 1981-09-09 Méthode de traitement d'un liquide résiduaire radioactif Withdrawn EP0047978A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP12593880A JPS5750697A (en) 1980-09-12 1980-09-12 Method of treating radioactive liquid
JP125938/80 1980-09-12

Publications (2)

Publication Number Publication Date
EP0047978A2 true EP0047978A2 (fr) 1982-03-24
EP0047978A3 EP0047978A3 (fr) 1982-06-23

Family

ID=14922674

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81107102A Withdrawn EP0047978A3 (fr) 1980-09-12 1981-09-09 Méthode de traitement d'un liquide résiduaire radioactif

Country Status (2)

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EP (1) EP0047978A3 (fr)
JP (1) JPS5750697A (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0059623A1 (fr) * 1981-02-27 1982-09-08 Hitachi, Ltd. Procédé pour purifier un liquide utilisant du charbon actif imprégné d'oxine et appareil pour sa mise en oeuvre
EP0396322A2 (fr) * 1989-05-01 1990-11-07 Westinghouse Electric Corporation Méthode de restauration d'un sol contaminé

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6261688A (ja) * 1985-09-11 1987-03-18 Johoku Kagaku Kogyo Kk オキシン添着活性炭のプレコ−ト法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB831745A (en) * 1956-08-09 1960-03-30 Little Inc A Process for the recovery of dissolved metal values
US3520805A (en) * 1967-05-29 1970-07-21 Union Tank Car Co Method of disposal of radioactive solids
GB1336241A (en) * 1970-02-05 1973-11-07 Osaka Soda Co Ltd Purification process
DE2414728A1 (de) * 1974-03-27 1975-11-27 Licentia Gmbh Verfahren und vorrichtung zur aufbereitung von kontaminiertem waschwasser, insbesondere in kernkraftwerken

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51119500A (en) * 1975-03-26 1976-10-20 Kraftwerk Union Ag Method of purifying filter tower with activated charcoal in reactor facility
JPS6059037B2 (ja) * 1978-08-21 1985-12-23 荏原インフイルコ株式会社 復水処理方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB831745A (en) * 1956-08-09 1960-03-30 Little Inc A Process for the recovery of dissolved metal values
US3520805A (en) * 1967-05-29 1970-07-21 Union Tank Car Co Method of disposal of radioactive solids
GB1336241A (en) * 1970-02-05 1973-11-07 Osaka Soda Co Ltd Purification process
DE2414728A1 (de) * 1974-03-27 1975-11-27 Licentia Gmbh Verfahren und vorrichtung zur aufbereitung von kontaminiertem waschwasser, insbesondere in kernkraftwerken

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0059623A1 (fr) * 1981-02-27 1982-09-08 Hitachi, Ltd. Procédé pour purifier un liquide utilisant du charbon actif imprégné d'oxine et appareil pour sa mise en oeuvre
EP0396322A2 (fr) * 1989-05-01 1990-11-07 Westinghouse Electric Corporation Méthode de restauration d'un sol contaminé
EP0396322A3 (fr) * 1989-05-01 1991-06-05 Westinghouse Electric Corporation Méthode de restauration d'un sol contaminé

Also Published As

Publication number Publication date
EP0047978A3 (fr) 1982-06-23
JPS5750697A (en) 1982-03-25

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Inventor name: MOTOJIMA, KENJI