EP0610153A1 - Process for decontaminating radioactive contaminated metallic surfaces - Google Patents

Process for decontaminating radioactive contaminated metallic surfaces Download PDF

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EP0610153A1
EP0610153A1 EP94810037A EP94810037A EP0610153A1 EP 0610153 A1 EP0610153 A1 EP 0610153A1 EP 94810037 A EP94810037 A EP 94810037A EP 94810037 A EP94810037 A EP 94810037A EP 0610153 A1 EP0610153 A1 EP 0610153A1
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aqueous solution
bath
formic acid
radioactive
decontamination
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EP0610153B1 (en
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Jozef Dr. Dipl. Chem. Ing. Eth Hanulik
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Deco Hanulik AG
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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
    • G21F9/001—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 great depth of removal, which is why this method is particularly suitable for cleaning medium and highly 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. However, the disposal of the baths is complex and generates a large proportion of waste because of the acid residues present. Another problem is the toxicity of the decontaminant.
  • 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, in particular hydrogen hydroxide, to the aqueous solution containing formic acid.
  • an oxidizing agent in particular hydrogen hydroxide
  • 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 at around 2 m2.
  • 150 liters 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 the removal rate was 35 mg / cm 2 h 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.
  • the stoichiometrically used solution will be used again by adding an oxidizing agent, preferably H202, to the metals and nucleids dissolved therein. This ensures that the insoluble complexes sediment out of the solution, which still has an acidity of around 3 - 3.5 pH.
  • an oxidizing agent preferably H202
  • Fe (COOH) 2 is soluble and consequently cannot bind radioactivity.
  • H202 the trivalent water-insoluble compounds are formed:
  • 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.
  • Fe3+ (OH (2 (COOH) can also be heated to about 150 ° C, so that it breaks down into Fe203 + radioactivity and H20 and C02.
  • 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 process according to the invention, this will again be done with the addition of H202. 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)

Abstract

To decontaminate radioactively contaminated metal objects, these were introduced into a first bath comprising a radioactively uncontaminated aqueous solution of formic acid. The metal objects were left in the bath for several hours until the formic acid was stoichiometrically completely consumed. Thereupon the metal objects were introduced into a second bath of the same chemical composition. This too was stoichiometrically completely consumed. The concentration of the aqueous formic acid solution was about 0.3 mol/l. These steps were repeated until the residual contamination of the metal objects was below the outdoor limit of 0.37 Bq/cm<2>. The radioactively contaminated metal oxides were sedimented out and the sludge was consolidated with cement and thereafter disposed of.

Description

Die vorliegende Erfindung betrifft ein Verfahren zur Dekontamination von radioaktiven Metalloberflächen mittels einer ameisensäurehaltigen, wässerigen Lösung. Zur Dekontamination von radioaktiven Metalloberflächen, sind verschiendene Verfahren bekannt. Aus der US-A-5'008'044 ist der Einsatz von Fluoroborsäure zur Dekontamination von radioaktiv kontaminierten Oberflächen bekannt. Das darin beschriebene Verfahren eignet sich sowohl zur Dekontamination von Oberflächen aus metallischen und mineralischen Stoffen. Der Vorteil jenes Verfahrens liegt in der hohen Aufnahmefähigkeit des verwendeten Dekontaminationsmittels und ermöglicht eine grosse Abtragtiefe, weshalb sich jenes Verfahren insbesondere zur Reinigung von mittel und stark radioaktiv kontaminierten Gegenständen aus verschiedensten Materialien eignet. Entsprechend wird auch jenes Verfahren bei den Dekontaminationsarbeiten in Tschernobyl eingesetzt. Der hohe Anteil an Metallen erlaubt die elektrolytische Regenerierung derselben. Die Entsorgung der Bäder ist jedoch aufwendig und erzeugt einen grossen Anteil an Abfällen, wegen der vorhandenen Säurenreste. Ein weiteres Problem stellt die Giftigkeit des Dekontaminationsmittels dar.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 great depth of removal, which is why this method is particularly suitable for cleaning medium and highly 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. However, the disposal of the baths is complex and generates a large proportion of waste because of the acid residues present. Another problem is the toxicity of the decontaminant.

Insbesondere bei höheren Temperaturen von über 130°C pyrolisiert das Dekontaminationsmittel zu giftigem Borofluorid.The decontaminant pyrolyzes to toxic borofluoride in particular at higher temperatures of over 130 ° C.

Aus der US-A- 4'508'641 ist ein weiteres Dekontaminationsverfahren bekannt, welches als Dekontaminationsmittel Ameisensäure und/oder Essigsäure und wenigstens ein Reduktionsmittel, wie Formaldehyd und/oder Acetaldehyd verwendet. Es handelt sich hierbei um ein Dekontaminationsverfahren für Reaktorkühlkreisläufe, mittels dem Stahloberflächen mit relativ kleinen Mengen an Chemikalien und Spülwasser gereinigt werden können und wobei die gebrauchte Dekontaminationslösung wieder aufbereitet wird. Dank der Beigabe des Reduktionsmittels verbleiben die Eisenionen stabil in der Lösung und gehen somit keine Verbindung ein. Dies ist in einem System mit geschlossenen Kreislauf wesentlich, damit keine Sedimentation ausfällenden Verbindungen entstehen. Erst in einem zweiten Verfahrensschritt werden zur Entsorgung die Eisenverbindungen aus der Dekontaminationslösung ausgefällt. Da die gesamte Dekontamination in einem geschlossenen Kreislauf stattfindet, muss entweder kontinuierlich Dekontaminationsmittel eingeimpft werden, da dieses sich stöchiometrisch verbraucht oder mit hohen Konzentrationen der Säure gearbeitet werden. Hingegen erübrigt sich hier das Problem der Entsorgung eines Bades. Muss jedoch das gesamte Kühlmittel des Kreislaufes ebenfalls gereinigt und entsorgt werden, so ist dieses wegen des vorhandenen Formaldehyds als Reduktionsmittel äusserst problematisch. Eine vollständige Freidekontamination bis unter die Freigrenze von beispielsweise 0,37 Bq/cm ist kaum möglich. Dies ist jedoch auch innerhalb der Kühlkreisläufe von Reaktoren nicht gefragt.Another decontamination process is known from US Pat. No. 4,508,641, which uses formic acid and / or acetic acid and at least one reducing agent, such as formaldehyde and / or acetaldehyde, as the decontamination agent. It is a decontamination process for reactor cooling circuits, by means of which steel surfaces can be cleaned with relatively small amounts of chemicals and rinsing water and the used decontamination solution is reprocessed. Thanks to the addition of the reducing agent, the iron ions remain stable in the solution and therefore do not form a compound. This is essential in a closed-loop system so that no compounds precipitating sedimentation occur. Only in a second process step are the iron compounds precipitated from the decontamination solution for disposal. 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.

Es war folglich die Aufgabe der vorliegenden Erfindung ein Dekontaminationsverfahren zu schaffen, welches einerseits mittels einem möglichst ungiftigen und preiswerten Dekontaminationsmittel arbeitet und bei dem insbesondere die Menge an Sekundärabfällen besonders gering ist.It was therefore the object of the present invention to provide a decontamination process which, on the one hand, works with a decontamination agent which is as non-toxic and inexpensive as possible and in which the amount of secondary waste is particularly low.

Diese Aufgabe löst ein Verfahren der eingangs genannten Art, das sich dadurch auszeichnet, dass die radioaktiv kontaminierten Metallobjekte in ein erstes Bad mit radioaktiv unbelasteter, 0,05 bis 5,0 Volumen % ameisensäurehaltiger, wässeriger Lösung gegeben wird, worin die Metallobjekte verbleiben, bis die Ameisensäure stöchiometrisch mindestens annähernd vollständig verbraucht ist, worauf die Metallobjekte in ein zweites, gleiches Bad gegeben werden, welches wiederum stöchiometrisch mindestens annähernd vollständig verbraucht wird, und dass dieser Schritt so lange wiederholt wird, bis die Metallobjekte eine Restradioaktivität unterhalb der zulässigen Freigrenze aufweisen, und dass aus den stöchiometrisch verbrauchten, wässerigen Lösungen die radioaktiv belasteten Metalloxide und Metallhydroxide aussedimentiert und in an sich bekannter Weise verfestigt werden, worauf die radioaktiv unbelastete wässerige Lösung nach Zugabe von Ameisensäure für ein weiteres Dekontaminatiosbad verwendbar ist.This problem is solved by 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.

Ein solches Verfahren hat den Vorteil, dass die Bäder nicht nach jeder Verwendung vollständig gereinigt werden müssen und somit der Anteil an sekundären Abfällen äusserst gering ist. Erst wenn die Dekontaminationsarbeit abgeschlossen ist, wird man dann mit an sich bekannten Mitteln die verbleibende wässerige Lösung vollständig reinigen.Such a process has the advantage that the baths do not have to be completely cleaned after each use and the proportion of secondary waste is therefore extremely low. Only when the decontamination work has been completed will the remaining aqueous solution be completely cleaned by means known per se.

Handelt es sich bei den radioaktiv kontaminierten Metallobjekten um solche aus Blei oder Nickel oder aus Blei oder Nickel enthaltenden Legierungen, so ist es von Vorteil, dass man der ameisensäurehaltigen, wässerigen Lösung ein Oxidationsmittel beigibt, insbesondere Wasserstoffhydroxid.If the 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, in particular hydrogen hydroxide, to the aqueous solution containing formic acid.

Weitere vorteilhafte Merkmale des Verfahrens gehen aus den abhängigen Patentansprüchen hervor.Further advantageous features of the method emerge from the dependent patent claims.

Nachfolgend ist ein labormässig durchgeführter Versuch im Detail beschrieben. Ein rund 200 kg schweres radioaktiv kontaminiertes Metallobjekt, im vorliegenden Beispiel ein Kranhaken, wurde in einen leeren Tank aus Polypropylen, mit einem Fassungsvermögen von rund 300 l gegeben. Die gesamte Metalloberfläche des Kranhakens wurde auf rund 2 m² geschätzt. In einem zweiten Schritt wurden dem Bad 150 1 einer 0,5 %-igen Ameisensäure beigegeben. In einem dritten Schritt wurde nun der Kranhaken über mehrere Stunden im Bad belassen. Diese Zeit variierte bei Raumtemperatur zwischen 5 und 16 Stunden. Anschliessend wurde die stöchiometrisch verbrauchte Lösung ausgepumpt. Hierauf hat man die Radioaktivität des verbrauchten Dekontaminationsmittels, sowie die verbleibende Radioaktivität des Metallobjektes gemessen und die vorgenannten Schritte wiederholt. Je nach der Stärke der radioaktiven Kontamination mussten diese Schritte mehrmals wiederholt werden. Nachdem festgestellt wurde, dass die Restradioaktivität des Kranhakens unterhalb der Freigrenze lag, wurde das verbrauchte Dekontaminationsmittel im selben Bad elektrolytisch behandelt. Der verbleibende Schlamm, vorwiegend bestehend aus Fe, Fe (OH)x, sowie sonstige Unreinheiten inklusive der absorbierten Radioaktivität wurde nach der Sedimentation mit Zement verfestigt und entsorgt. Das verbleibende Wasser wurde danach in einem letzten Schritt über einen Ionentauscher geleitet und danach der Kläranlage zugeführt.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 at around 2 m². In a second step, 150 liters of 0.5% formic acid were added to the bath. In a third step, 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. Depending on the level of radioactive contamination, these steps had to be repeated several times. After it was determined that the residual radioactivity of the crane hook was below the exemption limit, 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.

In einem weiteren experimentellen Versuch an 43 A-Stahl wurde die Abtragsgeschwindigkeit eruiert. Die Versuche wurden an einem Muster von 200 g und der Grösse von 50 x 100 x 5 mm durchgeführt. Hierbei wurde festgestellt, das die Metallabtragung bei sehr niedrigen Konzentrationen der Ameisensäure, beispielsweise von 0,3 Mol/l sich mittels Aenderung der Temperatur sehr genau steuern lässt. So wurde zum Beispiel festgestellt, dass bei einer Badtemperatur von 19°C die Abtragungsgeschwindigkeit 1.1 mg/cm² h betrug, während bei 80°C eine Abtragungsgeschwindigkeit 35 mg/cm² h festgestellt wurde. Auch hier wurde wiederum die verbrauchte und mit Aktivität geladene Lösung mittels einer Elektrolyse anodisch oxidiert. Der gebildete Eisenhydroxidschlamm hat dabei die Aktivität absorbiert. Nach Durchführung einer Sedimentation wurde das Wasser für eine weitere Dekontamination verwendet.In a further experimental test on 43 A steel, 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 the removal rate was 35 mg / cm 2 h 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.

Eine quantitative Gegenüberstellung des bekannten Verfahrens gemäss der US-A-4'508'641 im Vergleich zum erfindungsgemässen Verfahren ergab ein Verhältnis von rund 30:1. Gerade diese quantitative Gegenüberstellung zeigt deutlich die wirtschaftliche Bedeutung des erfindungsgemässen Verfahrens.A quantitative comparison of the known method according to US Pat. No. 4,508,641 in comparison with the method according to the invention gave a ratio of around 30: 1. This quantitative comparison clearly shows the economic importance of the method according to the invention.

Das beschriebene Verfahren lässt sich sowohl für die Dekontamination grösserer Mengen radioaktiver Metallteile verwenden, wie auch für kleinere Dekontaminationsarbeiten. Insbesondere bei grösseren Arbeiten wird man die stöchiometrisch verbrauchte Lösung wieder gebrauchen, indem man den darin gelösten Metallen und Nukleiden ein Oxidationsmittel, vorzugsweise H₂0₂ beigibt. Hierdurch wird erreicht, dass aus der Lösung, die noch einen Säuregrad von circa 3 - 3,5 pH aufweist, die nicht löslichen Komplexe aussedimentieren. Bekanntlich ist Fe (COOH)₂ löslich und kann folglich die Radioaktivität nicht binden. Unter Beigabe von H₂0₂ bilden sich so die dreiwertigen in Wasser unlöslichen Verbindungen:

Figure imgb0001
The described method can be used for the decontamination of large quantities of radioactive metal parts as well as for smaller decontamination work. In particular for larger works, the stoichiometrically used solution will be used again by adding an oxidizing agent, preferably H₂0₂, to the metals and nucleids dissolved therein. This ensures that the insoluble complexes sediment out of the solution, which still has an acidity of around 3 - 3.5 pH. As is known, Fe (COOH) ₂ is soluble and consequently cannot bind radioactivity. With the addition of H₂0₂, the trivalent water-insoluble compounds are formed:
Figure imgb0001

Sowohl Fe(OH)₃ als auch Fe⁺(OH)₂(COOH) weisen eine sehr grosse Absorptionsoberfläche auf und sind folglich zur Bindung der Radioaktivität besonders geeignet. Der sich so bildende Schlamm kann mittels Sedimentation und/oder Dekantation und/oder Filtration abgetrennt und danach verfestigt und entsorgt werden.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.

Selbstverständlich kann aber Fe³⁺(OH(₂(COOH) auch noch auf circa 150°C erhitzt werden, so dass es in die Teile Fe₂0₃ + Radioaktivität, sowie in H₂0 und C0₂ zerfällt.Of course, Fe³⁺ (OH (₂ (COOH) can also be heated to about 150 ° C, so that it breaks down into Fe₂0₃ + radioactivity and H₂0 and C0₂.

Der nun weitgehend radioaktivitätsfreien, wässerigen Lösung setzt man nun wieder Ameisensäure bei, bis die wässerige Lösung wieder die anfängliche Konzentration aufweist, worauf man das zu dekontaminierende Metallteil wieder hineingibt. So kann in derselben Wanne mit demselben Wasseranteil lediglich unter Beigabe von HCOOH ein Schritt nach dem anderen durchgeführt werden und das Verfahren beliebig oft wiederholt werden, bis die Dekontaminationsarbeit erledigt ist.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.

Nach Beendigung einer Dekontaminationsarbeit muss selbstverständlich auch die wässerige Lösung entsorgt werden. Beim erfindungsgemässen Verfahren wird man dies wiederum unter Beigabe von H₂0₂ tun. Um aber noch eine geringfügige Restradioaktivität zu eliminieren, gibt man nach einer kurzen Wartezeit der wässerigen Lösung auch noch eine Lauge bei. Hierzu eignet sich insbesondere NaOH und Ca(OH)₂, je nachdem, welche Nukleide vorwiegend vorhanden sind, nämlich Co-60, Cs-134, Cs-137 oder U bzw. Pu-Isotope. Danach wird wie bisher der Schlamm abgeschieden und die annähernd neutrale, wässerige Lösung vorzugsweise über einen Harzionentauscher geleitet und dann frei von Radioaktivität in die Kläranlage geleitet.After completing decontamination work, the aqueous solution must of course also be disposed of. In the process according to the invention, this will again be done with the addition of H₂0₂. But still a minor one To eliminate residual radioactivity, 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.

Claims (12)

Verfahren zur Dekontamination von radioaktiven Metalloberflächen mittels einer ameisensäurehaltigen, wässerigen Lösung, dadurch gekennzeichnet, dass die radioaktiv kontaminierten Metallobjekte in ein erstes Bad mit radioaktiv unbelasteter, 0.05-5,0 Vol.% ameisensäurehaltiger, wässeriger Lösung gegeben wird, worin die Metallobjekte verbleiben bis die Ameisensäure stöchiometrisch mindestens annähernd vollständig verbraucht ist, worauf die Metallobjekte ins zweite gleiche Bad gegeben werden, welches wiederum stöchiometrisch mindestens annähernd vollständig verbraucht wird und dass dieser Schritt so lange wiederholt wird, bis die Metallobjekte eine Restradiokativität unterhalb der zulässigen Freigrenze aufweisen, und dass aus den stöchiometrisch verbrauchten wässerigen Lösungen die radioaktiv belasteten Metalloxide und Metallhydroxide aussedimentiert und in an sich bekannter Weise verfestigt werden, worauf die radioaktiv unbelastete, wässerige Lösung nach Zugabe von Ameisensäure für ein weiteres Dekontaminationsbad verwendbar ist.Method for decontamination of radioactive metal surfaces by means of an aqueous solution containing formic acid, characterized in that the radioactively contaminated metal objects are placed in a first bath with radioactive, contaminated, 0.05-5.0% by volume aqueous solution containing formic acid, in which the metal objects remain until the Formic acid is at least almost completely stoichiometrically consumed, whereupon the metal objects are added to the second same bath, which in turn is at least approximately completely stoichiometrically consumed and that this step is repeated until the metal objects have a residual radiocativity below the permissible free limit, and from that 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 radioactive, unpolluted, aqueous solution after the addition of Am iron acid can be used for another decontamination bath. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die zur weiteren Dekontamination verwendbare wässerige Lösung vollständig mittels einem Harzionentauscher zu deionisiertem Wasser gereinigt wird.A method according to claim 1, characterized in that the aqueous solution which can be used for further decontamination is completely purified to deionized water by means of a resin ion exchanger. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die wässerige Lösung des letzten Bades einer Elektrolyse unterzogen wird.A method according to claim 1, characterized in that the aqueous solution of the last bath is subjected to electrolysis. Verfahren nach Anspruch 1, wobei die radioaktiv kontaminierten Metallobjekte aus Blei oder Nickel sind oder Blei oder Nickel enthalten, dadurch gekennzeichnet, dass man der ameisensäurenhaltigen wässerigen Lösung ein Oxidationsmittel beigibt, insbesondere Wasserstoffhydroxid.A method according to claim 1, wherein the radioactive contaminated metal objects are made of lead or nickel or contain lead or nickel, characterized in that an oxidizing agent, in particular hydrogen hydroxide, is added to the aqueous solution containing formic acids. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Bäder auf einer Temperatur zwischen Raumtemperatur und 80°C gehalten werden.A method according to claim 1, characterized in that the baths are kept at a temperature between room temperature and 80 ° C. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Konzentration der Ameisensäure in der wässerigen Lösung von 0,1 bis 1,0 Mol/l beträgt und die Abtragungsgeschwindigkeit durch die Temperatur des Bades gesteuert wird.A method according to claim 1, characterized in that the concentration of formic acid in the aqueous solution is from 0.1 to 1.0 mol / l and the rate of removal is controlled by the temperature of the bath. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass man zur mindestens annähernd vollständig stöchiometrisch verbrauchten Lösung mit den darin gelösten Metallen und den radioaktiven Nukleiden ein Oxidationsmittel beigibt und der wasserunlösliche Schlamm entfernt wird.A method according to claim 1, characterized in that an oxidizing agent is added to the at least approximately completely stoichiometrically used solution with the metals dissolved therein and the radioactive nucleids and the water-insoluble sludge is removed. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass man nach Abschluss der Arbeit, nach der letzmaligen stöchiometrisch mindestens annähernd vollständigen Nutzung der wässerigen Lösung mit den darin gelösten Metallen mit den radioaktiven Nukleiden erst ein Oxidationsmittel und nachher eine Lauge beigibt, worauf der ausgefällte Schlamm entweder durch Filtration und/oder Dekantation und/oder Sedimentation ausgeschieden und zur Entsorgung verfestigt wird, während die verbleibende wässerige Lösung der Kanalisation zugeführt wird.A method according to claim 1, characterized in that after completion of the work, after the final stoichiometric at least approximately complete use of the aqueous solution with the metals dissolved therein with the radioactive nucleides, first an oxidizing agent and then an alkali are added, whereupon the precipitated sludge either through Filtration and / or decantation and / or sedimentation is excreted and solidified for disposal, while the remaining aqueous solution is fed to the sewage system. Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass als Oxidationsmittel vorzugsweise H₂0₂ verwendet wird.A method according to claim 7, characterized in that H₂0₂ is preferably used as the oxidizing agent. Verfahren nach Anspruch 8, dadurch gekennzeichnet, dass als Oxidationsmittel H₂0₂ verwendet wird und als Lauge NaOH und/oder Ca(OH)₂ benutzt wird.A method according to claim 8, characterized in that H₂0₂ is used as the oxidizing agent and NaOH and / or Ca (OH) ₂ is used as the alkali. Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass die regenerierte wässerige Lösung unter Beigabe von Ameisensäure auf die ursprüngliche Konzentration gebracht wird und das nächste Bad eingeleitet wird.A method according to claim 7, characterized in that the regenerated aqueous solution is brought to the original concentration with the addition of formic acid and the next bath is initiated. Verfahren nach Anspruch 11, dadurch gekennzeichnet, dass alle Dekontaminationsschritte im selben Bad erfolgen.A method according to claim 11, characterized in that all decontamination steps take place in the same bath.
EP94810037A 1993-02-01 1994-01-20 Process for decontaminating radioactive contaminated metallic surfaces Expired - Lifetime EP0610153B1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0610153B1 (en) 1993-02-01 1996-09-25 Deco-Hanulik Ag Process for decontaminating radioactive contaminated metallic surfaces
US5545795A (en) * 1993-02-01 1996-08-13 Deco-Hanulik Ag Method for decontaminating radioactive metal surfaces
GB9325323D0 (en) * 1993-12-10 1994-02-16 British Nuclear Fuels Plc Decontamination of metals
US5564105A (en) * 1995-05-22 1996-10-08 Westinghouse Electric Corporation Method of treating a contaminated aqueous solution
JPH09101397A (en) * 1995-10-02 1997-04-15 Morikawa Sangyo Kk Method and device for decomposing organic treatment liquid containing radioactive metal ion and method and device for extracting radioactive metal using the decomposition method and device
GB9610647D0 (en) 1996-05-21 1996-07-31 British Nuclear Fuels Plc Decontamination of metal
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 (en) * 2001-04-03 2006-08-16 株式会社日立製作所 Radioactive substance decontamination method and radioactive substance decontamination apparatus
FR2826355B1 (en) * 2001-06-22 2003-08-15 Commissariat Energie Atomique PROCESS FOR TREATING AN EFFLUENT, IN PARTICULAR RADIOACTIVE, CONTAINING ORGANIC MATTER
KR100724710B1 (en) * 2002-11-21 2007-06-04 가부시끼가이샤 도시바 System and method for chemical decontamination of radioactive material
JP2010101762A (en) * 2008-10-24 2010-05-06 Chubu Electric Power Co Inc Method for decontaminating radioactive metal waste

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2064852A (en) * 1979-12-10 1981-06-17 Ca Atomic Energy Ltd Decontaminating reagents for radioactive systems
EP0073366A2 (en) * 1981-09-01 1983-03-09 Gesellschaft zur Förderung der industrieorientierten Forschung an den Schweizerischen Hochschulen und weiteren Institutionen Process for decontaminating steel surfaces and disposing of nuclear wastes
JPS61231496A (en) * 1985-04-05 1986-10-15 日立プラント建設株式会社 Method of decontaminating radioactive metallic waste
US5386078A (en) 1993-02-01 1995-01-31 Deco-Hanulik Ag Process for decontaminating radioactive metal surfaces
GB2284702A (en) 1993-12-10 1995-06-14 British Nuclear Fuels Plc Decontamination of metals

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4587043A (en) * 1983-06-07 1986-05-06 Westinghouse Electric Corp. Decontamination of metal surfaces in nuclear power reactors
EP0224510B1 (en) * 1985-05-28 1991-01-16 Recytec S.A. Process for decontaminating radioactively contaminated metalic or cement-containing materials
US5024805A (en) * 1989-08-09 1991-06-18 Westinghouse Electric Corp. Method for decontaminating a pressurized water nuclear reactor system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2064852A (en) * 1979-12-10 1981-06-17 Ca Atomic Energy Ltd Decontaminating reagents for radioactive systems
EP0073366A2 (en) * 1981-09-01 1983-03-09 Gesellschaft zur Förderung der industrieorientierten Forschung an den Schweizerischen Hochschulen und weiteren Institutionen Process for decontaminating steel surfaces and disposing of nuclear wastes
JPS61231496A (en) * 1985-04-05 1986-10-15 日立プラント建設株式会社 Method of decontaminating radioactive metallic waste
US5386078A (en) 1993-02-01 1995-01-31 Deco-Hanulik Ag Process for decontaminating radioactive metal surfaces
GB2284702A (en) 1993-12-10 1995-06-14 British Nuclear Fuels Plc Decontamination of metals

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE INIS INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA), VIENNA, AT; MAJERSKY, D.: "Decontamination solution for chemical and physico-chemical decontamination of metallic surfaces. Dekontaminacny roztok na chemicku a fyzikalno-chemicku dekontaminaciu povrchov kovovych materialov." *
DATABASE WPI Week 8648, Derwent World Patents Index; AN 86-314479 *

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