EP0610153B1 - Procédé de décontamination de surfaces métalliques radioactives - Google Patents

Procédé de décontamination de surfaces métalliques radioactives Download PDF

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Publication number
EP0610153B1
EP0610153B1 EP94810037A EP94810037A EP0610153B1 EP 0610153 B1 EP0610153 B1 EP 0610153B1 EP 94810037 A EP94810037 A EP 94810037A EP 94810037 A EP94810037 A EP 94810037A EP 0610153 B1 EP0610153 B1 EP 0610153B1
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EP
European Patent Office
Prior art keywords
aqueous solution
process according
bath
radioactive
stoichiometrically
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Expired - Lifetime
Application number
EP94810037A
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German (de)
English (en)
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EP0610153A1 (fr
Inventor
Jozef Dr. Dipl. Chem. Ing. Eth Hanulik
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Deco Hanulik AG
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Deco Hanulik AG
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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
    • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
    • G21F9/002—Decontamination of the surface of objects with chemical or electrochemical processes
    • G21F9/004—Decontamination of the surface of objects with chemical or electrochemical processes of metallic surfaces

Definitions

  • the present invention relates to a method for the decontamination of radioactive metal surfaces by means of an aqueous solution containing formic acid.
  • Various methods are known for decontamination of radioactive metal surfaces.
  • the use of fluoroboric acid for the decontamination of radioactive contaminated surfaces is known from US Pat. No. 5,008,044.
  • the method described therein is suitable for the decontamination of surfaces made of metallic and mineral substances.
  • the advantage of this method lies in the high absorption capacity of the decontamination agent used and enables a large removal depth, which is why this method is particularly suitable for cleaning medium and strongly radioactive contaminated objects made of different materials. Accordingly, this process is also used in the decontamination work in Chernobyl.
  • the high proportion of metals allows them to be electrolytically regenerated.
  • the decontaminant pyrolyzes to toxic borofluoride in particular at higher temperatures of over 130 ° C.
  • decontamination agents Since all decontamination takes place in a closed circuit, decontamination agents must either be inoculated continuously, since these are used up stoichiometrically, or high concentrations of the acid are used. On the other hand, there is no need to dispose of a bath. However, if the entire coolant of the circuit also has to be cleaned and disposed of, this is extremely problematic because of the formaldehyde present as the reducing agent. Complete free decontamination below A free limit of, for example, 0.37 Bq / cm is hardly possible. However, this is also not in demand within the cooling circuits of reactors.
  • a method of the type mentioned at the outset which is characterized in that the radioactive contaminated metal objects are placed in a first bath with radioactive, contaminated, 0.05 to 5.0% by volume aqueous solution containing formic acid, in which the metal objects remain until the formic acid is at least approximately completely stoichiometrically consumed, whereupon the metal objects are placed in a second, identical bath, which in turn is at least approximately completely stoichiometrically consumed, and this step is repeated until the metal objects have residual radioactivity below the permissible free limit, and that from the stoichiometrically consumed, aqueous solutions the radioactively contaminated metal oxides and metal hydroxides are sedimented out and solidified in a manner known per se, whereupon the radioactively unpolluted aqueous solution after the addition of formic acid for a further decontamin atiosbad is usable.
  • radioactive contaminated metal objects are those made of lead or nickel or of alloys containing lead or nickel, it is advantageous to add an oxidizing agent, especially hydrogen peroxide, to the aqueous solution containing formic acid.
  • an oxidizing agent especially hydrogen peroxide
  • a test carried out in a laboratory is described in detail below.
  • An approximately 200 kg heavy radioactive contaminated metal object in this example a crane hook, was placed in an empty polypropylene tank with a capacity of around 300 l. The entire metal surface of the crane hook was estimated to be around 2 m 2 .
  • 150 l of 0.5% formic acid were added to the bath.
  • the crane hook was left in the bathroom for several hours. This time varied between 5 and 16 hours at room temperature. Subsequently the stoichiometrically used solution was pumped out. Thereupon the radioactivity of the decontamination agent used and the remaining radioactivity of the metal object were measured and the above-mentioned steps were repeated.
  • the decontaminant used was treated electrolytically in the same bath.
  • the remaining sludge consisting mainly of Fe, Fe (OH) x , as well as other impurities including the absorbed radioactivity, was solidified with cement and disposed of after sedimentation.
  • the remaining water was then passed through an ion exchanger in a final step and then fed to the sewage treatment plant.
  • the removal rate was determined.
  • the experiments were carried out on a sample of 200 g and the size of 50 x 100 x 5 mm. It was found here that metal removal at very low concentrations of formic acid, for example of 0.3 mol / l, can be controlled very precisely by changing the temperature. For example, it was found that the removal rate was 1.1 mg / cm 2 h at a bath temperature of 19 ° C., while a removal rate of 35 mg / cm 2 h was found at 80 ° C. Also here the used solution, which was loaded with activity, was anodically oxidized again by means of electrolysis. The iron hydroxide sludge formed has absorbed the activity. After sedimentation, the water was used for further decontamination.
  • the described method can be used for the decontamination of large quantities of radioactive metal parts as well as for smaller decontamination work. Especially for larger work it will stoichiometrically spent solution again use by the dissolved metals and nuclides to beirace an oxidizing agent, preferably H 2 0. 2 This ensures that the insoluble complexes sediment out of the solution, which still has an acidity of around 3 - 3.5 pH.
  • Fe (COOH) 2 is known to be soluble and therefore cannot bind radioactivity. With the addition of H 2 0 2 , the trivalent water-insoluble compounds are formed: Fe 2+ (COOH) 2nd + H 2nd 0 2nd ⁇ Fe (OH) 3rd and or Fe 3+ (OH) 2nd (COOH)
  • Both Fe (OH) 3 and Fe + (OH) 2 (COOH) have a very large absorption surface and are therefore particularly suitable for binding radioactivity.
  • the sludge thus formed can be separated by means of sedimentation and / or decantation and / or filtration and then solidified and disposed of.
  • Fe 3+ (OH) 2 (COOH) can also be heated to approximately 150 ° C., so that it breaks down into the parts Fe 2 0 3 + radioactivity and H 2 0 and C0 2 .
  • Formic acid is now added to the now largely radioactivity-free aqueous solution until the aqueous solution has the initial concentration again, after which the metal part to be decontaminated is added again. So one step after the other can be carried out in the same tub with the same water content only with the addition of HCOOH and the process can be repeated as often as necessary until the decontamination work is done.
  • aqueous solution After completing decontamination work, the aqueous solution must of course also be disposed of. In the method according to the invention, this will again be done with the addition of H 2 0 2 . But still a minor one
  • a solution is also added to the aqueous solution after a short waiting time. NaOH and Ca (OH) 2 are particularly suitable for this, depending on which nucleides are predominantly present, namely Co-60, Cs-134, Cs-137 or U or Pu isotopes.
  • the sludge is then separated as before and the approximately neutral, aqueous solution is preferably passed over a resin ion exchanger and then passed into the sewage treatment plant free of radioactivity.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Food Science & Technology (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

Claims (12)

  1. Procédé pour la décontamination de surfaces métalliques radioactives au moyen d'une solution aqueuse contenant de l'acide formique, caractérisé en ce que les objets métalliques ayant une contamination radioactive sont introduits dans un premier bain comportant une solution aqueuse n'ayant pas de contamination radioactive, contenant de l'acide formique à raison de 0,05-5,0 % en volume, où les objets métalliques restent jusqu'à ce que l'acide formique soit stoechiométriquement au moins presque totalement consommé, après quoi les objets métalliques sont introduits dans le second bain identique, qui à son tour est stoechiométriquement au moins presque totalement épuisé, et en ce que cette étape est réitérée jusqu'à ce que les objets métalliques présentent une radioactivité résiduelle inférieure à la limite d'autorisation permise, et en ce que les oxydes métalliques et hydroxydes métalliques à charge radioactive sont extraits à partir des solutions aqueuses utilisées stoechiométriquement par sédimentation et solidifiés de manière connue en soi, après quoi la solution aqueuse n'ayant pas de contamination radioactive peut être utilisée après addition d'acide formique pour un autre bain de décontamination.
  2. Procédé selon la revendication 1, caractérisé en ce que la solution aqueuse utilisable pour une autre décontamination est totalement purifiée au moyen d'une résine échangeuse d'ions contre de l'eau désionisée.
  3. Procédé selon la revendication 1, caractérisé en ce que la solution aqueuse du dernier bain est soumise à une électrolyse.
  4. Procédé selon la revendication 1, dans lequel les objets métalliques ayant une contamination radioactive sont en plomb ou en nickel ou contiennent du plomb ou du nickel, caractérisé en ce qu'on ajoute à la solution aqueuse contenant de l'acide formique un agent d'oxydation, en particulier du peroxyde d'hydrogène.
  5. Procédé selon la revendication 1, caractérisé en ce que les bains sont maintenus à une température comprise entre la température ambiante et 80°C.
  6. Procédé selon la revendication 1, caractérisé en ce que la concentration de l'acide formique dans la solution aqueuse est de 0,1 à 1,0 mol/l et la vitesse d'extraction est pilotée par la température du bain.
  7. Procédé selon la revendication 1, caractérisé en ce qu'on ajoute un agent d'oxydation à la solution au moins presque totalement épuisée stoechiométriquement, avec les métaux qui y sont dissous et les nucléides radioactifs, et on élimine la boue insoluble dans l'eau.
  8. Procédé selon la revendication 1, caractérisé en ce que, une fois le travail effectué, après la dernière utilisation stoechiométriquement au moins presque complète de la solution aqueuse avec les métaux qui y sont dissous et les nucléides radioactifs, on ajoute d'abord un agent d'oxydation et ensuite une lessive alcaline, après quoi la boue précipitée est séparée par filtration et/ou décantation et/ou sédimentation et est solidifiée pour être entreposée, tandis que la solution aqueuse restante est envoyée dans la canalisation.
  9. Procédé selon la revendication 7, caractérisé en ce qu'on utilise de préférence H2O2 comme agent d'oxydation.
  10. Procédé selon la revendication 8, caractérisé en ce qu'on utilise H2O2 comme agent d'oxydation et on utilise comme lessive alcaline NaOH et/ou Ca(OH)2.
  11. Procédé selon la revendication 7, caractérisé en ce que la solution aqueuse régénérée est amenée à la concentration initiale par addition d'acide formique et le bain suivant est introduit.
  12. Procédé selon la revendication 11, caractérisé en ce que toutes les étapes de décontamination sont effectuées dans le même bain.
EP94810037A 1993-02-01 1994-01-20 Procédé de décontamination de surfaces métalliques radioactives Expired - Lifetime EP0610153B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH285/93 1993-02-01
CH28593 1993-02-01

Publications (2)

Publication Number Publication Date
EP0610153A1 EP0610153A1 (fr) 1994-08-10
EP0610153B1 true EP0610153B1 (fr) 1996-09-25

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EP94810037A Expired - Lifetime EP0610153B1 (fr) 1993-02-01 1994-01-20 Procédé de décontamination de surfaces métalliques radioactives

Country Status (3)

Country Link
US (1) US5386078A (fr)
EP (1) EP0610153B1 (fr)
DE (1) DE59400707D1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2284702A (en) * 1993-12-10 1995-06-14 British Nuclear Fuels Plc Decontamination of metals
EP0902950A1 (fr) 1996-05-21 1999-03-24 British Nuclear Fuels PLC Decontamination de metal

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE59400707D1 (de) 1993-02-01 1996-10-31 Deco Hanulik Ag Verfahren zur Dekontamination von radioaktiven Metalloberflächen
US5545795A (en) * 1993-02-01 1996-08-13 Deco-Hanulik Ag Method for decontaminating radioactive metal surfaces
US5564105A (en) * 1995-05-22 1996-10-08 Westinghouse Electric Corporation Method of treating a contaminated aqueous solution
JPH09101397A (ja) * 1995-10-02 1997-04-15 Morikawa Sangyo Kk 放射性の金属イオンを有する有機処理液の分解方法及び装置並びにそれを用いた放射性金属の採取方法及び装置。
GB2319259A (en) * 1996-11-15 1998-05-20 Babcock Rosyth Defence Limited reducing radionucleide contamination of a metallic component
US20030052063A1 (en) * 2001-03-30 2003-03-20 Motoaki Sakashita Decontamination method and apparatus
JP3809577B2 (ja) * 2001-04-03 2006-08-16 株式会社日立製作所 放射性物質除染方法及び放射性物質除染装置
FR2826355B1 (fr) * 2001-06-22 2003-08-15 Commissariat Energie Atomique Procede de traitement d'un effluent, notamment radioactif, contenant des matieres organiques
KR100724710B1 (ko) * 2002-11-21 2007-06-04 가부시끼가이샤 도시바 방사화 부품의 화학적 오염제거 시스템 및 방법
JP2010101762A (ja) * 2008-10-24 2010-05-06 Chubu Electric Power Co Inc 放射性金属廃棄物の除染方法

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1136398A (fr) * 1979-12-10 1982-11-30 William A. Seddon Reactifs de decontamination pour systemes radioactifs
CH653466A5 (de) * 1981-09-01 1985-12-31 Industrieorientierte Forsch Verfahren zur dekontamination von stahloberflaechen und entsorgung der radioaktiven stoffe.
US4587043A (en) * 1983-06-07 1986-05-06 Westinghouse Electric Corp. Decontamination of metal surfaces in nuclear power reactors
JPS61231496A (ja) * 1985-04-05 1986-10-15 日立プラント建設株式会社 放射性金属廃棄物の除染方法
DE3676962D1 (de) * 1985-05-28 1991-02-21 Recytec Sa Verfahren zur dekontamination von radioaktiv kontaminierten gegenstaenden aus metall oder aus zementhaltigem material.
US5024805A (en) * 1989-08-09 1991-06-18 Westinghouse Electric Corp. Method for decontaminating a pressurized water nuclear reactor system
DE59400707D1 (de) 1993-02-01 1996-10-31 Deco Hanulik Ag Verfahren zur Dekontamination von radioaktiven Metalloberflächen
GB9325323D0 (en) 1993-12-10 1994-02-16 British Nuclear Fuels Plc Decontamination of metals

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2284702A (en) * 1993-12-10 1995-06-14 British Nuclear Fuels Plc Decontamination of metals
EP0902950A1 (fr) 1996-05-21 1999-03-24 British Nuclear Fuels PLC Decontamination de metal

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Publication number Publication date
US5386078A (en) 1995-01-31
EP0610153A1 (fr) 1994-08-10
DE59400707D1 (de) 1996-10-31

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