EP0278256A1 - Method and apparatus for removing oxide layers - Google Patents

Method and apparatus for removing oxide layers Download PDF

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Publication number
EP0278256A1
EP0278256A1 EP88100615A EP88100615A EP0278256A1 EP 0278256 A1 EP0278256 A1 EP 0278256A1 EP 88100615 A EP88100615 A EP 88100615A EP 88100615 A EP88100615 A EP 88100615A EP 0278256 A1 EP0278256 A1 EP 0278256A1
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Prior art keywords
branch
oxalic acid
destroyer
container
ozone
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EP88100615A
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German (de)
French (fr)
Inventor
Wilfred Dr. Morell
Rainer Dr. Gassen
Klaus Dipl.-Ing. Zeuch (Fh)
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Siemens AG
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Siemens 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
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/088—Iron or steel solutions containing organic acids

Definitions

  • the invention relates to a method for removing oxide layers from a container, in particular from components and pipes of a boiling water reactor.
  • oxide-containing corrosion layers that contain radioactive components form in the water cycle.
  • a removal of these corrosion layers is sought before an upcoming repair measure.
  • a known cleaning process which is used in components and pipelines of a boiling water reactor, provides a vanadium II compound as a reducing agent.
  • Picolinic acid is used as the solvent.
  • This process is technically very complex since the vanadium II compound is unstable in air. This chemical is therefore not commercially available. It has to be manufactured using an electrochemical process shortly before it is used on site. When performing the decontamination, work must be carried out in a protective gas atmosphere.
  • the invention has for its object to develop a method for removing oxide layers, which is particularly well suited for components and pipes of a boiling water reactor and can be carried out inexpensively and nevertheless quickly and reliably with commercially available chemicals.
  • the object is achieved in that the container is supplied as a reducing agent and as a decontaminating agent oxalic acid.
  • the process according to the invention for removing oxide layers is a simple one-step process. Only one chemical, namely oxalic acid, is required. This is advantageous compared to known multi-stage processes with short cleaning times.
  • the oxalic acid used according to the invention is insensitive to air and oxygen. A protective gas atmosphere is therefore not necessary.
  • the cleaning method according to the invention can be carried out in a closed, but also in an open system.
  • a further advantage is achieved through the use of oxalic acid according to the invention. Destruction of oxalic acid that is no longer required is in fact possible in a simple manner. Water and carbon dioxide are produced when ozone is added. This leads to a reduction in the amount of secondary waste.
  • Particularly suitable concentrations of oxalic acid when removing oxide layers from boiling water components Reactor are between 50 ppm and 5000 ppm at a pH of 3 to 1.
  • the advantage of the invention is that components and pipelines of a boiling water reactor can be freed from oxide layers in a technically simple manner, inexpensively and with little secondary waste.
  • the oxalic acid is destroyed in a closed circuit after the activity has been separated off by adding ozone. There are no residues that require special treatment.
  • a device for carrying out the method according to the invention provides that a supply line and a discharge line for oxalic acid containing a pump are connected to the container to be cleaned, which are connected to one another via a first branch which contains a first shut-off device. Parallel to the first branch, ion exchangers flanked by two shut-off devices are arranged in a second branch. In a third branch, an oxalic acid destroyer is arranged parallel to the first and second branches, flanked by two shut-off devices.
  • the first branch is open during cleaning. Then the first branch is closed and only the second branch, which contains the ion exchanger, is opened. In this way, the oxalic acid present in the system is freed from radioactive ions by the ion exchanger.
  • the second branch may already be open during cleaning. As a result, a partial stream of oxalic acid is passed through the ion exchanger during the cleaning process.
  • the third branch is opened. The oxalic acid in the oxalic acid destroyer is removed without residue.
  • the oxalic acid destroyer has connections for feeding in and discharging ozone.
  • the oxalic acid reacts with the ozone, producing water and carbon dioxide. In this way, oxalic acid that is no longer required is eliminated.
  • the discharge connection of the oxalic acid destroyer is connected to an ozone destroyer which has a blow-off opening for exhaust air. Excess ozone is destroyed there.
  • the advantage is achieved that components and pipelines of a boiling water reactor are quickly and reliably freed of contaminated oxide layers that would hinder maintenance work. Only inexpensive, commercially available chemicals are required. In addition, safe disposal of the secondary waste is guaranteed.
  • the drawing shows a container to be decontaminated, which is connected to a device for removing oxide layers.
  • the container 1 to be cleaned stands, for example, for components and pipelines of a boiling water reactor which, after a long period of operation, are coated on the inside with contaminated, oxide-containing corrosion layers 11.
  • a feed line 2 and a drain line 3 for oxalic acid are connected to the container 1.
  • a pump 4 is located in the discharge line 3.
  • the discharge line 3 and the feed line 2 are connected to one another by three branches 5, 6 and 7 connected in parallel. Branches 5, 6 and 7 can be individually closed. The procedure is such that as a rule only one of the branches 5, 6 and 7 is permeable, while the other branches 5, 6 and 7 are closed.
  • the first branch 5 contains only one shut-off device 8.
  • this shut-off device 8 and thus the first branch 5 is open, the oxalic acid is pumped through the container 1. As a result, the oxide layer 11 is dissolved in the container 1.
  • the second branch 6 there is an ion exchanger 9, flanked by two shut-off devices 10 and 12. While the oxide layer in the container 1 is still being dissolved via the first branch 5, a partial stream can already be passed through the ion exchanger 9 of the second branch 6 at the same time.
  • the shut-off device 8 in the first branch 5 is closed and only the shut-off devices 10 and 12 in the second branch 6 are opened.
  • the radioactive ions are separated from the decontamination solution in the ion exchanger 9.
  • the second branch 6 is also closed by the shut-off devices 10 and 12 and the third branch 7 is opened.
  • the decontamination solution previously treated in the ion exchanger 9 is then further treated in the oxalic acid destroyer 13.
  • the oxalic acid destroyer 13 is equipped with a connection 16 for feeding in and a connection 17 for discharging a substance, for example ozone, in addition to the lines of the third branch 7.
  • the oxalic acid in the oxalic acid destroyer 13 is split into water and carbon dioxide with ozone.
  • the connection 17 to the lead Ten of the gases from the oxalic acid destroyer 13 is connected to an ozone destroyer 18, which has a blow-off opening 19 for decontaminated exhaust air freed from oxalic acid and ozone.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Metallurgy (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Food Science & Technology (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)

Abstract

Oxide layers are removed from a vessel (1), in particular components and piping of a boiling-water reactor, by feeding oxalic acid as a reducing agent and decontaminating agent to the vessel (1). The oxalic acid is first passed in a closed circulation by a first branch (5) through the vessel (1) which is to be cleaned. Radioactive constituents are separated off by means of at least one ion exchanger (9) which is located in a second branch (6) parallel to the first branch (5). Finally, the oxalic acid is destroyed by adding ozone in an oxalic acid destroyer (13) which is arranged parallel to the first branch (5) and to the second branch (6) in a third branch (7). The excess ozone is passed, for example, to an ozone destroyer (18). <IMAGE>

Description

Die Erfindung betrifft ein Verfahren zum Entfernen von Oxid­schichten aus einem Behälter, insbesondere aus Komponenten und Rohrleitungen eines Siedewasser-Reaktors.The invention relates to a method for removing oxide layers from a container, in particular from components and pipes of a boiling water reactor.

Im Laufe des Betriebes eines Kernkraftwerkes bilden sich im Wasserkreislauf oxidhaltige Korrosionsschichten, die radio­aktive Bestandteile enthalten. Um die Ortsdosisleistung gering zu halten, wird vor einer anstehenden Reparaturmaßnahme eine Entfernung dieser Korrosionsschichten angestrebt.During the operation of a nuclear power plant, oxide-containing corrosion layers that contain radioactive components form in the water cycle. In order to keep the local dose rate low, a removal of these corrosion layers is sought before an upcoming repair measure.

Bei Druckwasser-Reaktoren führen bekannte chemische Dekontami­nationsverfahren, die eine oxidative Vorbehandlung und eine an­schließende Nachbehandlung mit Säure vorsehen, zum Erfolg. Diese Verfahren sind bei Siedewasser-Reaktoren nur bedingt ein­setzbar. Wegen der dort vorliegenden unterschiedlichen Zusam­mensetzung der Oxidschichten muß mit reduzierend wirkenden De­kontaminationsmitteln gearbeitet werden.In the case of pressurized water reactors, known chemical decontamination processes which provide an oxidative pretreatment and a subsequent aftertreatment with acid lead to success. These processes can only be used to a limited extent in boiling water reactors. Because of the different composition of the oxide layers there, it is necessary to work with reducing decontamination agents.

Ein bekanntes Reinigungsverfahren, das in Komponenten und Rohr­leitungen eines Siedewasser-Reaktors eingesetzt wird, sieht als Reduktionsmittel eine Vanadium II-Verbindung vor. Als Lösungs­mittel wird Picolinsäure verwendet. Dieses Verfahren ist tech­nisch sehr aufwendig, da die Vanadium II-Verbindung an Luft in­stabil ist. Diese Chemikalie ist daher nicht käuflich. Sie muß kurz vor ihrer Verwendung am Einsatzort mit einem elektroche­mischen Verfahren erst hergestellt werden. Bei der Durchführung der Dekontamination muß unter einer Schutzgasatmosphäre gear­beitet werden.A known cleaning process, which is used in components and pipelines of a boiling water reactor, provides a vanadium II compound as a reducing agent. Picolinic acid is used as the solvent. This process is technically very complex since the vanadium II compound is unstable in air. This chemical is therefore not commercially available. It has to be manufactured using an electrochemical process shortly before it is used on site. When performing the decontamination, work must be carried out in a protective gas atmosphere.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum Entfernen von Oxidschichten zu entwickeln, das für Komponenten und Rohrleitungen eines Siedewasser-Reaktors besonders gut ge­eignet ist und mit käuflichen Chemikalien kostengünstig und trotzdem schnell und zuverlässig durchzuführen ist.The invention has for its object to develop a method for removing oxide layers, which is particularly well suited for components and pipes of a boiling water reactor and can be carried out inexpensively and nevertheless quickly and reliably with commercially available chemicals.

Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß dem Be­hälter als Reduktionsmittel und als Dekontaminationsmittel Oxalsäure zugeführt wird.The object is achieved in that the container is supplied as a reducing agent and as a decontaminating agent oxalic acid.

Aufgrund chemischer Versuche zeigte sich für Fachleute völlig überraschend, daß allein käufliche Oxalsäure ohne vorherge­hende Oxidation sowohl reduzierend als auch lösend auf die Oxidschichten in einem Siedewasser-Reaktor wirkt.On the basis of chemical experiments, it was completely surprising for experts that only oxalic acid which can be bought without previous oxidation has both a reducing and a solvent effect on the oxide layers in a boiling water reactor.

Das erfindungsgemäße Verfahren zum Entfernen von Oxidschichten ist ein einfaches Einstufenverfahren. Es wird nur eine Chemi­kalie, nämlich Oxalsäure, benötigt. Dadurch kommt man vorteil­haft gegenüber bekannten Mehrstufenverfahren mit kurzen Reini­gungszeiten aus.The process according to the invention for removing oxide layers is a simple one-step process. Only one chemical, namely oxalic acid, is required. This is advantageous compared to known multi-stage processes with short cleaning times.

Die erfindungsgemäß verwendete Oxalsäure ist unempfindlich ge­gen Luft und Sauerstoff. Es ist daher eine Schutzgasatmosphäre nicht erforderlich. Das erfindungsgemäße Reinigungsverfahren ist in einem geschlossenen, aber auch in einem offenen System durchführbar.The oxalic acid used according to the invention is insensitive to air and oxygen. A protective gas atmosphere is therefore not necessary. The cleaning method according to the invention can be carried out in a closed, but also in an open system.

Durch die erfindungsgemäße Verwendung von Oxalsäure wird noch ein weiterer Vorteil erzielt. Eine Zerstörung von nicht mehr benötigter Oxalsäure ist nämlich auf einfache Weise möglich. Bei Zugabe von Ozon entsteht Wasser und Kohlendioxid. Das führt zu einer Verkleinerung der Sekundärabfallmenge.A further advantage is achieved through the use of oxalic acid according to the invention. Destruction of oxalic acid that is no longer required is in fact possible in a simple manner. Water and carbon dioxide are produced when ozone is added. This leads to a reduction in the amount of secondary waste.

Besonders geeignete Konzentrationen der Oxalsäure beim Ent­fernen von Oxidschichten aus Komponenten eines Siedewasser­ Reaktors liegen zwischen 50 ppm und 5000 ppm bei einem pH-Wert von 3 bis 1.Particularly suitable concentrations of oxalic acid when removing oxide layers from boiling water components Reactor are between 50 ppm and 5000 ppm at a pH of 3 to 1.

Mit der Erfindung wird der Vorteil erzielt, daß Komponenten und Rohrleitungen eines Siedewasser-Reaktors auf technisch einfache Weise, kostengünstig und mit wenig Sekundärabfall gut von Oxid­schichten zu befreien sind.The advantage of the invention is that components and pipelines of a boiling water reactor can be freed from oxide layers in a technically simple manner, inexpensively and with little secondary waste.

Die Oxalsäure wird beispielsweise in einem geschlossenen Kreis­lauf nach Abtrennen der Akivität durch Zugabe von Ozon zerstört. Dabei bleiben keine Rückstände zurück, die einer besonderen Be­handlung bedürfen.For example, the oxalic acid is destroyed in a closed circuit after the activity has been separated off by adding ozone. There are no residues that require special treatment.

Eine Einrichtung zum Durchführen des erfindungsgemäßen Ver­fahrens sieht vor, daß mit dem zu reinigenden Behälter eine Zu­leitung und eine eine Pumpe enthaltende Ableitung für Oxalsäure verbunden sind, die über einen ersten Zweig, der eine erste Ab­sperreinrichtung enthält, miteinander verbunden sind. Parallel zum ersten Zweig sind in einem zweiten Zweig Ionenaustauscher, flankiert von zwei Absperreinrichtungen angeordnet. In einem dritten Zweig ist parallel zum ersten und zum zweiten Zweig ein Oxalsäurezerstörer, flankiert von zwei Absperreinrichtungen, angeordnet.A device for carrying out the method according to the invention provides that a supply line and a discharge line for oxalic acid containing a pump are connected to the container to be cleaned, which are connected to one another via a first branch which contains a first shut-off device. Parallel to the first branch, ion exchangers flanked by two shut-off devices are arranged in a second branch. In a third branch, an oxalic acid destroyer is arranged parallel to the first and second branches, flanked by two shut-off devices.

Während der Reinigung ist in der Regel nur der erste Zweig geöffnet. Anschließend wird der erste Zweig geschlossen und nur der zweite Zweig, der den Ionenaustauscher enthält, geöffnet. Die im System vorhandene Oxalsäure wird auf diese Weise durch den Ionenaustauscher von radioaktiven Ionen befreit. Während der Reinigung kann neben dem ersten Zweig auch bereits der zwei­te Zweig geöffnet sein. Dadurch wird ein Teilstrom der Oxalsäure schon während des Reinigungsprozesses durch den Ionenaustauscher geleitet. Abschließend wird bei geschlossenem ersten und zweiten Zweig der dritte Zweig geöffnet. Dabei wird die Oxalsäure im Oxalsäurezerstörer rückstandsfrei beseitigt.As a rule, only the first branch is open during cleaning. Then the first branch is closed and only the second branch, which contains the ion exchanger, is opened. In this way, the oxalic acid present in the system is freed from radioactive ions by the ion exchanger. In addition to the first branch, the second branch may already be open during cleaning. As a result, a partial stream of oxalic acid is passed through the ion exchanger during the cleaning process. Finally, with the first and second branches closed, the third branch is opened. The oxalic acid in the oxalic acid destroyer is removed without residue.

Mit der erfindungsgemäßen Einrichtung ist vorteilhaft eine kostengünstige, schnelle und zuverlässige Reinigung und an­schließend eine rückstandsfreie Beseitigung der verwendeten Chemikalie durchführbar.With the device according to the invention, an inexpensive, fast and reliable cleaning and subsequently a residue-free removal of the chemical used can advantageously be carried out.

Der Oxalsäurezerstörer weist außer den Anschlüssen für die Lei­tungen des dritten Zweiges Anschlüsse zur Einspeisung und zum Ableiten von Ozon auf. Im Oxalsäurezerstörer reagiert die Oxal­säure mit dem Ozon, wobei Wasser und Kohlendioxid entsteht. Auf diese Weise wird nicht mehr benötigte Oxalsäure beseitigt.In addition to the connections for the lines of the third branch, the oxalic acid destroyer has connections for feeding in and discharging ozone. In the oxalic acid destroyer, the oxalic acid reacts with the ozone, producing water and carbon dioxide. In this way, oxalic acid that is no longer required is eliminated.

Beispielsweise ist der Ableitungsanschluß des Oxalsäurezer­störers mit einem Ozonvernichter, der eine Abblaseöffnung für Abluft aufweist, verbunden. Dort wird überschüssiges Ozon ver­nichtet.For example, the discharge connection of the oxalic acid destroyer is connected to an ozone destroyer which has a blow-off opening for exhaust air. Excess ozone is destroyed there.

Aus der erfindungsgemäßen Einrichtung gelangen keine Schad­stoffe in die Atmosphäre.No pollutants get into the atmosphere from the device according to the invention.

Mit der Erfindung wird der Vorteil erzielt, daß Komponenten und Rohrleitungen eines Siedewasser-Reaktors schnell und zuverläs­sig von kontaminierten Oxidschichten befreit werden, die War­tungsarbeiten behindern würden. Dabei werden nur kosten­günstige, handelsübliche Chemikalien benötigt. Darüber hinaus ist eine sichere Beseitigung des Sekundärabfalles gewähr­leistet.With the invention, the advantage is achieved that components and pipelines of a boiling water reactor are quickly and reliably freed of contaminated oxide layers that would hinder maintenance work. Only inexpensive, commercially available chemicals are required. In addition, safe disposal of the secondary waste is guaranteed.

Die Erfindung wird anhand der Zeichnung näher erläutert:The invention is explained in more detail with reference to the drawing:

Die Zeichnung zeigt einen zu dekontaminierenden Behälter, der mit einer Einrichtung zum Entfernen von Oxidschichten verbunden ist.The drawing shows a container to be decontaminated, which is connected to a device for removing oxide layers.

Der zu reinigende Behälter 1 steht beispielsweise für Kompo­nenten und Rohrleitungen eines Siedewasser-Reaktors, die nach langer Betriebszeit mit kontaminierten, oxidhaltigen Korro­sionsschichten 11 innen beschichtet sind. Zum Entfernen dieser Korrosionsschichten 11 sind mit dem Behälter 1 eine Zuleitung 2 und eine Ableitung 3 für Oxalsäure verbunden. In der Ablei­tung 3 befindet sich eine Pumpe 4. Die Ableitung 3 und die Zu­leitung 2 sind durch drei parallelgeschaltete Zweige 5, 6 und 7 miteinander verbunden. Die Zweige 5, 6 und 7 sind einzelnen verschließbar. Es wird so verfahren, daß in der Regel nur einer der Zweige 5, 6 und 7 durchlässig ist, während die übrigen Zweige 5, 6 und 7 verschlossen sind. Der erste Zweig 5 enthält lediglich eine Absperreinrichtung 8. Wenn diese Absperreinrich­tung 8 und damit der erste Zweig 5 offen ist, wird die Oxalsäure durch den Behälter 1 gepumpt. Dadurch wird die Oxidschicht 11 im Behälter 1 aufgelöst. Im zweiten Zweig 6 befindet sich ein Ionen­austauscher 9, flankiert von zwei Absperreinrichtungen 10 und 12. Während noch die Oxidschicht im Behälter 1 über den ersten Zweig 5 aufgelöst wird, kann auch bereits gleichzeitig ein Teilstrom durch den Ionenaustauscher 9 des zweiten Zweiges 6 geleitet werden. Wenn die Oxidschicht 11 im Behälter 1 aufgelöst ist, wird die Absperreinrichtung 8 im ersten Zweig 5 geschlossen und nur die Absperreinrichtungen 10 und 12 im zweiten Zweig 6 werden geöffnet. Im Ionenaustauscher 9 werden die radioaktiven Ionen aus der Dekontaminationslösung abgetrennt. Wenn dieser Schritt vollzogen ist, wird auch der zweite Zweig 6 durch die Absperreinrichtungen 10 und 12 verschlossen und es wird der dritte Zweig 7 geöffnet. Dort ist ein Oxalsäurezerstörer 13, flankiert von zwei Absperreinrichtungen 14 und 15, angeordnet. Die zuvor im Ionenaustauscher 9 behandelte Dekontaminationslö­sung wird dann im Oxalsäurezerstörer 13 weiterbehandelt. Dazu ist der Oxalsäurezerstörer 13 außer mit den Leitungen des dritten Zweiges 7 mit einem Anschluß 16 zum Einspeisen und einem Anschluß 17 zum Ableiten einer Substanz, beispielsweise von Ozon, ausge­stattet. Mit Ozon wird die Oxalsäure im Oxalsäurezerstörer 13 in Wasser und Kohlendioxid aufgespaltet. Der Anschluß 17 zum Ablei­ ten der Gase aus dem Oxalsäurezerstörer 13 ist mit einem Ozon­vernichter 18 verbunden, der eine Abblaseöffnung 19 für dekonta­minierte, von Oxalsäure und Ozon befreite Abluft, aufweist.The container 1 to be cleaned stands, for example, for components and pipelines of a boiling water reactor which, after a long period of operation, are coated on the inside with contaminated, oxide-containing corrosion layers 11. To remove these corrosion layers 11, a feed line 2 and a drain line 3 for oxalic acid are connected to the container 1. A pump 4 is located in the discharge line 3. The discharge line 3 and the feed line 2 are connected to one another by three branches 5, 6 and 7 connected in parallel. Branches 5, 6 and 7 can be individually closed. The procedure is such that as a rule only one of the branches 5, 6 and 7 is permeable, while the other branches 5, 6 and 7 are closed. The first branch 5 contains only one shut-off device 8. When this shut-off device 8 and thus the first branch 5 is open, the oxalic acid is pumped through the container 1. As a result, the oxide layer 11 is dissolved in the container 1. In the second branch 6 there is an ion exchanger 9, flanked by two shut-off devices 10 and 12. While the oxide layer in the container 1 is still being dissolved via the first branch 5, a partial stream can already be passed through the ion exchanger 9 of the second branch 6 at the same time. When the oxide layer 11 is dissolved in the container 1, the shut-off device 8 in the first branch 5 is closed and only the shut-off devices 10 and 12 in the second branch 6 are opened. The radioactive ions are separated from the decontamination solution in the ion exchanger 9. When this step has been completed, the second branch 6 is also closed by the shut-off devices 10 and 12 and the third branch 7 is opened. There is an oxalic acid destroyer 13, flanked by two shut-off devices 14 and 15, arranged. The decontamination solution previously treated in the ion exchanger 9 is then further treated in the oxalic acid destroyer 13. For this purpose, the oxalic acid destroyer 13 is equipped with a connection 16 for feeding in and a connection 17 for discharging a substance, for example ozone, in addition to the lines of the third branch 7. The oxalic acid in the oxalic acid destroyer 13 is split into water and carbon dioxide with ozone. The connection 17 to the lead Ten of the gases from the oxalic acid destroyer 13 is connected to an ozone destroyer 18, which has a blow-off opening 19 for decontaminated exhaust air freed from oxalic acid and ozone.

Claims (5)

1. Verfahren zum Entfernen von Oxidschichten (11) aus einem Be­hälter (1), insbesondere aus Komponenten und Rohrleitungen eines Siedewasser-Reaktors, dadurch gekenn­zeichnet, daß dem Behälter (1) als Reduktionsmittel und als Dekontaminationsmittel Oxalsäure zugeführt wird.1. A method for removing oxide layers (11) from a container (1), in particular from components and pipes of a boiling water reactor, characterized in that the container (1) is supplied as a reducing agent and as a decontaminating agent oxalic acid. 2. Verfahren nach Anspruch 1, dadurch gekenn­zeichnet, daß in einem geschlossenen Kreislauf zuerst die Oxalsäure durch den zu reinigenden Behälter (1) geleitet wird, daß dann radioaktive Bestandteile abgetrennt werden und daß abschließend die Oxalsäure durch Zugabe von Ozon zerstört wird.2. The method according to claim 1, characterized in that the oxalic acid is first passed through the container to be cleaned (1) in a closed circuit, that radioactive components are then separated and that the oxalic acid is finally destroyed by the addition of ozone. 3. Einrichtung zur Durchführung des Verfahrens nach den An­sprüchen 1 und 2, dadurch gekennzeichnet, daß mit dem Behälter (1) eine Zuleitung (2) und eine eine Pumpe (4) enthaltende Ableitung (3) für Oxalsäure verbunden sind, die über einen ersten Zweig (5), der eine Absperreinrichtung (8) enthält, miteinander verbunden sind, daß parallel zum ersten Zweig (5) in einem zweiten Zweig (6) mindestens ein Ionenaus­tauscher (9), flankiert von zwei Absperreinrichtungen (10 und 12) angeordnet ist, und daß parallel zum ersten Zweig (5) und zum zweiten Zweig (6) in einem dritten Zweig (7) ein Oxalsäure­zerstörer (13), flankiert von zwei Absperreinrichtungen (14 und 15), angeordnet ist.3. Device for performing the method according to claims 1 and 2, characterized in that with the container (1) a feed line (2) and a pump (4) containing discharge line (3) for oxalic acid are connected via a first Branch (5), which contains a shut-off device (8), are connected to one another such that at least one ion exchanger (9), flanked by two shut-off devices (10 and 12), is arranged parallel to the first branch (5) in a second branch (6) , and that parallel to the first branch (5) and the second branch (6) in a third branch (7) an oxalic acid destroyer (13), flanked by two shut-off devices (14 and 15), is arranged. 4. Einrichtung nach Anspruch 3, dadurch gekenn­zeichnet, daß der Oxalsäurezerstörer (13) außer den Anschlüssen der Leitungen des dritten Zweiges (7) einen An­schluß (16) zum Einspeisen und einen Anschluß (17) zum Ableiten einer Oxalsäure zerstörenden Substanz aufweist.4. Device according to claim 3, characterized in that the oxalic acid destroyer (13) in addition to the connections of the lines of the third branch (7) has a connection (16) for feeding and a connection (17) for discharging an oxalic acid-destroying substance. 5. Einrichtung nach Anspruch 4, dadurch gekenn­zeichnet, daß der Ableitungsanschluß (17) des Oxal­säurezerstörers (13) mit einem Ozonvernichter (18), der eine Abblaseöffnung (19) für Abluft aufweist, verbunden ist.5. Device according to claim 4, characterized in that the discharge connection (17) of the oxalic acid destroyer (13) with an ozone destroyer (18) having a blow-off opening (19) for exhaust air is connected.
EP88100615A 1987-01-28 1988-01-18 Method and apparatus for removing oxide layers Withdrawn EP0278256A1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2689298A1 (en) * 1992-03-24 1993-10-01 Framatome Sa Copper@ elimination in corrosion deposits from pressurised water reactor steam generator - by bubbling ozone through acid soln. in sec. part of steam generator, for tube sheet upper face, support plates and tube bundle deposit removal
WO2000028112A1 (en) * 1998-11-10 2000-05-18 Framatome Anf Gmbh Method for decontaminating the surface of a component
US6635232B1 (en) * 1999-05-13 2003-10-21 Kabushiki Kaisha Toshiba Method of chemically decontaminating components of radioactive material handling facility and system for carrying out the same
CN102262909B (en) * 2006-02-09 2014-06-25 株式会社东芝 Chemical decontamination apparatus and decontamination method therein

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EP0134664A1 (en) * 1983-07-12 1985-03-20 Westinghouse Electric Corporation Improvements in or relating to the ozone oxidation of deposits in cooling systems of nuclear reactors
DE3439864A1 (en) * 1984-10-31 1986-04-30 Kraftwerk Union AG, 4330 Mülheim Process for the chemical decontamination of heat exchangers having vertical U-tubes made of metallic materials by means of an aqueous solution
EP0180826A1 (en) * 1984-10-31 1986-05-14 Siemens Aktiengesellschaft Process for chemically decontaminating the metallic main components and systems of nuclear reactors

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0134664A1 (en) * 1983-07-12 1985-03-20 Westinghouse Electric Corporation Improvements in or relating to the ozone oxidation of deposits in cooling systems of nuclear reactors
DE3439864A1 (en) * 1984-10-31 1986-04-30 Kraftwerk Union AG, 4330 Mülheim Process for the chemical decontamination of heat exchangers having vertical U-tubes made of metallic materials by means of an aqueous solution
EP0180826A1 (en) * 1984-10-31 1986-05-14 Siemens Aktiengesellschaft Process for chemically decontaminating the metallic main components and systems of nuclear reactors

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2689298A1 (en) * 1992-03-24 1993-10-01 Framatome Sa Copper@ elimination in corrosion deposits from pressurised water reactor steam generator - by bubbling ozone through acid soln. in sec. part of steam generator, for tube sheet upper face, support plates and tube bundle deposit removal
US6875323B2 (en) 1998-06-23 2005-04-05 Kabushiki Kaisha Toshiba Method of chemically decontaminating components of radioactive material handling facility and system for carrying out the same
WO2000028112A1 (en) * 1998-11-10 2000-05-18 Framatome Anf Gmbh Method for decontaminating the surface of a component
US6444276B2 (en) 1998-11-10 2002-09-03 Framatome Anp Gmbh Method for decontaminating a surface of a component
KR100637950B1 (en) * 1998-11-10 2006-10-23 프라마톰 아엔페 게엠베하 Method for decontaminating the surface of a component
US6635232B1 (en) * 1999-05-13 2003-10-21 Kabushiki Kaisha Toshiba Method of chemically decontaminating components of radioactive material handling facility and system for carrying out the same
CN102262909B (en) * 2006-02-09 2014-06-25 株式会社东芝 Chemical decontamination apparatus and decontamination method therein

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