EP0180826A1 - Process for chemically decontaminating the metallic main components and systems of nuclear reactors - Google Patents

Process for chemically decontaminating the metallic main components and systems of nuclear reactors Download PDF

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Publication number
EP0180826A1
EP0180826A1 EP85113144A EP85113144A EP0180826A1 EP 0180826 A1 EP0180826 A1 EP 0180826A1 EP 85113144 A EP85113144 A EP 85113144A EP 85113144 A EP85113144 A EP 85113144A EP 0180826 A1 EP0180826 A1 EP 0180826A1
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Prior art keywords
ozone
primary coolant
decontamination
carried out
chemicals
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EP85113144A
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German (de)
French (fr)
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EP0180826B1 (en
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Horst-Otto Bertholdt
Bernhard Dipl.-Ing. Kress (Fh)
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Siemens AG
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Kraftwerk Union AG
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
    • 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 invention relates to a process for the chemical decontamination of large components and systems made of metallic materials of nuclear reactors with a liquid primary coolant, the treatment being carried out by means of an aqueous solution of oxidizing chemicals which is moved by the large components and systems to be decontaminated.
  • the invention has the aim of an improvement in which, with one process step, the combination of chemicals increases the effectiveness of decontamination and, at the same time, the incidence of secondary waste is reduced.
  • the treatment temperature should be S 50 0 C.
  • nitrates, chromates or cerium IV salts are introduced as oxidizing chemicals into the primary coolant, which contains borate in particular, and that an addition of ozone is used.
  • the decontamination is carried out as a one-step treatment using an aqueous solution of oxidizing chemicals with the additional addition of ozone.
  • the chemicals with an oxidizing effect for example nitrates, chromates, cerium salts, are inexpensive and lead to ions which can be easily removed using ion exchange resins.
  • the pH value is lowered during decontamination by withdrawing the cations using an ion exchanger.
  • the concentration range of the oxidizing chemicals is preferably 100-1000 mg kg-1, of ozone 10-40 mg kg-1. The effectiveness of the solution is monitored by measuring the red-ox potential.
  • Table 1 shows results of the one-step treatment according to the invention using the example of original contaminated samples from a pressurized water nuclear power plant.
  • Fig. 1 shows the metal removal M using the N03 parameter study.
  • the ozone content is maintained according to the further invention by means of an external ozone enrichment path.
  • continuous degassing advantageously prevents gas cushions from forming in the system to be decontaminated.
  • the ozone fed in comes from an ozone generator 8, which is supplied with oxygen from the tank 9. This is partly converted into ozone by means of silent electrical discharge.
  • the gas containing ozone is sucked into the enrichment section 5 by the injector 6. The mass transfer between gas and liquid takes place in the injector 6 and in the subsequent liquid column.
  • Excess oxygen present in the decontamination circuit and the non-absorbed ozone from the enrichment section 5 are released from their upper end via an aerosol separator 10 and, after heating in a heating device 11, via a catalytic ozone destruction system 12.
  • the cations formed during the decontamination and the dissolved activity are withdrawn via ion exchangers 13 in a second bypass with a pump 14.
  • the ion exchangers 13 are then disposed of using known measures, for example dried and solidified with bitumen.

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  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Chemical & Material Sciences (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)
  • Treatment Of Water By Oxidation Or Reduction (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Apparatus For Disinfection Or Sterilisation (AREA)

Abstract

Über ein Gas-Eintrags-System wird die Wasserfüllung eines Systems oder einer Komponente von Kernreaktoren aus metallischen Werkstoffen mit Ozon angereichert, damit die Dekontamination durch eine mittels oxidativen Zusätzen gesteuerte Wasser/Ozon/Metall-Reaktion erfolgt. Während des Prozesses werden die gelösten aktiven Kationen mit Ionentauscherharzen entfernt.The water filling of a system or a component of nuclear reactors made of metallic materials is enriched with ozone via a gas entry system, so that the decontamination is carried out by a water / ozone / metal reaction controlled by means of oxidative additives. During the process, the dissolved active cations are removed with ion exchange resins.

Description

Die Erfindung betrifft ein Verfahren zur chemischen Dekontamination von Großkomponenten und Systemen aus metallischen Werkstoffen von Kernreaktoren mit einem flüssigen Primärkühlmittel, wobei die Behandlung mittels einer wäßrigen Lösung oxidierender Chemikalien durchgeführt wird, die durch die zu dekontaminierenden GroBkomponenten und Systeme bewegt wird.The invention relates to a process for the chemical decontamination of large components and systems made of metallic materials of nuclear reactors with a liquid primary coolant, the treatment being carried out by means of an aqueous solution of oxidizing chemicals which is moved by the large components and systems to be decontaminated.

Das aus der DE-OS 26 13 351 bekannte Verfahren der oben genannten Art ist ein Mehrstufenverfahren, bei dem im Wechsel oxidative Behandlungen und Säurebehandlungen bei Temperaturen von > 90°C durchgeführt werden. Dieser laufende Chemikalienwechsel erfordert einen relativ hohen Aufwand an Zeit und Chemikalien sowie an Energie.The process of the type mentioned above, which is known from DE-OS 26 13 351, is a multi-stage process in which oxidative treatments and acid treatments are carried out alternately at temperatures of> 90.degree. This ongoing chemical change requires a relatively large amount of time, chemicals and energy.

Die Erfindung hat demgegenüber das Ziel einer Verbesserung, bei der mit einem Verfahrensschritt durch die Kombination von Chemikalien die Dekontaminationswirksamkeit erhöht und gleichzeitig der Anfall von Sekundärwaste vermindert wird. Die Behandlungstemperatur soll bei S 500C liegen.In contrast, the invention has the aim of an improvement in which, with one process step, the combination of chemicals increases the effectiveness of decontamination and, at the same time, the incidence of secondary waste is reduced. The treatment temperature should be S 50 0 C.

Erfindungsgemäß ist vorgesehen, daß als oxidierende Chemikalien Nitrate, Chromate oder Cer-IV-Salze in das insbesondere borathaltige Primärkühlmittel eingegeben werden und daß ein Zusatz von Ozon verwendet wird.It is provided according to the invention that nitrates, chromates or cerium IV salts are introduced as oxidizing chemicals into the primary coolant, which contains borate in particular, and that an addition of ozone is used.

Damit wird die Dekontamination als Einstufenbehandlung mittels einer wäßrigen Lösung oxidierender Chemikalien unter zusätzlicher Zugabe von Ozon durchgeführt. Die oxidierend wirkenden Chemikalien, zum Beispiel Nitrate, Chromate, Cer-Salze sind preiswert und führen zu Ionen, die mit Ionentauscherharzen gut entfernbar sind. Dabei wird während der Dekontamination durch Entzug der Kationen mittels Ionentauscher der pH-Wert abgesenkt. Der Konzentrationsbereich der oxidierenden Chemikalien liegt vorzugsweise bei 100 - 1000 mg kg-1, von Ozon bei 10-40 mg kg-1. Die Wirksamkeit der Lösung wird hierbei über die Messung des Red-Ox-Potentials verfolgt.The decontamination is carried out as a one-step treatment using an aqueous solution of oxidizing chemicals with the additional addition of ozone. The chemicals with an oxidizing effect, for example nitrates, chromates, cerium salts, are inexpensive and lead to ions which can be easily removed using ion exchange resins. The pH value is lowered during decontamination by withdrawing the cations using an ion exchanger. The concentration range of the oxidizing chemicals is preferably 100-1000 mg kg-1, of ozone 10-40 mg kg-1. The effectiveness of the solution is monitored by measuring the red-ox potential.

Tabelle 1 zeigt Ergebnisse der erfindungsgemäßen Einstufenbehandlung am Beispiel von original kontaminierten Proben aus einem Druckwasser-Kernkraftwerk.

Figure imgb0001
Table 1 shows results of the one-step treatment according to the invention using the example of original contaminated samples from a pressurized water nuclear power plant.
Figure imgb0001

Werkstoff: 1.4024Material: 1.4024

Mit zunehmender Betriebsdauer nimmt die Säurelöslichkeit bei aktiven Oxid-Schutzschichten des Primärkreislaufs eines Druckwasserreaktors ab. Durch Variieren der Kombination von oxidativen Chemikalien und Ozon und durch selektiven Entzug von Kationen kann das Verfahren auf die jeweils vorliegende Oxidschutzschicht eingestellt werden. Das in der beiliegenden Zeichnung als Fig. 1 dargestellte Diagramm zeigt an Hand der N03-Parameter-Studie den Metallabtrag M.With increasing operating time, the acid solubility decreases with active oxide protective layers of the primary circuit of a pressurized water reactor. By varying the combination of oxidative chemicals and ozone and by selectively removing cations, the process can be adjusted to the respective oxide protective layer. The diagram shown in the accompanying drawing as Fig. 1 shows the metal removal M using the N03 parameter study.

Da in Wasser gelöstes Ozon in Kontakt mit oxidischen Oberflächenschichten nur eine begrenzte Halbwertszeit hat, wird gemäß der weiteren Erfindung mittels einer externen Ozonanreicherungsstrecke der Ozon-Gehalt aufrechterhalten. Gleichzeitig wird durch eine laufende Entgasung vorteilhafterweise verhindert, daß sich im zu dekontaminierenden System Gaspolster ausbilden.Since ozone dissolved in water has only a limited half-life in contact with oxidic surface layers, the ozone content is maintained according to the further invention by means of an external ozone enrichment path. At the same time, continuous degassing advantageously prevents gas cushions from forming in the system to be decontaminated.

Die Fig. 2 der beiliegenden Zeichnung zeigt in vereinfachter Form ein kontaminiertes System mit den dazugehörigen Hilfseinrichtungen zur Dekontamination nach dem erfindungsgemäßen Verfahren. Anhand dieses Ausführungsbeispiels wird das Verfahren näher erläutert:

  • Die Dekontaminationschemikalien werden aus dem Ansetzbehälter 1 mit einer Dosierpumpe 2 dem zu dekontaminierenden System 3, nämlich dem mit borathaltigem Primärkühlwasser gefüllten Primärkreis eines Druckwasserreaktors, auf der Saugseite einer Pumpe 4 zugeführt. Mit der Pumpe 4 wird ein aus dem zu dekontaminierendem System 3 abgezweigter Teilstrom über eine Ozon-Anreicherungsstrecke 5 mit einem Injektor 6 gefördert. Dieser Teilstrom über die Anreicherungsstrecke 5 beträgt >10% des während der Dekontamination umgewälzten Kühlwasser-Volumens. Zur Verbesserung der Stoffaustauschleistung in der Anreicherungsstrecke wird der Injektor 6 mit einer Druckerhöhungspumpe 7 betrieben.
2 of the accompanying drawing shows in simplified form a contaminated system with the associated auxiliary devices for decontamination using the method according to the invention. The method is explained in more detail using this exemplary embodiment:
  • The decontamination chemicals are fed from the preparation tank 1 with a metering pump 2 to the system 3 to be decontaminated, namely the primary circuit of a pressurized water reactor filled with borate-containing primary cooling water, on the suction side of a pump 4. With the pump 4, a partial flow branched off from the system 3 to be decontaminated is conveyed via an ozone enrichment path 5 with an injector 6. This partial flow over the enrichment section 5 is > 10% of the cooling water volume circulated during decontamination. To improve the mass transfer performance in the enrichment section, the injector 6 is operated with a booster pump 7.

Das eingespeiste Ozon stammt aus einem Ozongenerator 8, der aus dem Tank 9 mit Sauerstoff versorgt wird. Dieser wird mittels stiller elektrischer Entladung zum Teil in Ozon umgewandelt. Das ozonhaltige Gas wird vom Injektor 6 in die Anreicherungsstrecke 5 gesaugt. Im Injektor 6 und in der anschließenden Flüssigkeitssäule erfolgt der Stoffaustausch zwischen Gas und Flüssigkeit.The ozone fed in comes from an ozone generator 8, which is supplied with oxygen from the tank 9. This is partly converted into ozone by means of silent electrical discharge. The gas containing ozone is sucked into the enrichment section 5 by the injector 6. The mass transfer between gas and liquid takes place in the injector 6 and in the subsequent liquid column.

In dem Dekontaminationskreislauf vorhandener überschüssiger Sauerstoff und das nicht absorbierte Ozon aus der Anreicherungsstrecke 5 gelangt aus deren oberem Ende über einen Aerosolabscheider 10 und nach Erwärmung in einer Heizeinrichtung 11 über eine katalytische Ozonvernichtungsanlage 12 ins Freie.Excess oxygen present in the decontamination circuit and the non-absorbed ozone from the enrichment section 5 are released from their upper end via an aerosol separator 10 and, after heating in a heating device 11, via a catalytic ozone destruction system 12.

Der Entzug der bei der Dekontamination gebildeten Kationen und der gelösten Aktivität erfolgt über Ionentauscher 13 in einem zweiten Bypass mit einer Pumpe 14. Die Ionentauscher 13 werden dann mit bekannten Maßnahmen entsorgt, zum Beispiel getrocknet und mit Bitumen verfestigt.The cations formed during the decontamination and the dissolved activity are withdrawn via ion exchangers 13 in a second bypass with a pump 14. The ion exchangers 13 are then disposed of using known measures, for example dried and solidified with bitumen.

Claims (13)

1. Verfahren zur chemischen Dekontamination von Großkomponenten und Systemen aus metallischen Werkstoffen von Kernreaktoren mit einem flüssigen Primärkühlmittel, wobei die Behandlung mittels einer wäßrigen Lösung oxidierender Chemikalien durchgeführt wird, die durch die zu dekontaminierenden Großkomponenten und Systeme bewegt wird, dadurch gekennzeichnet,, daß als oxidierende Chemikalien Nitrate, Chromate oder Cer-IV-Salze in das insbesondere borathaltige Primärkühlmittel eingegeben werden und daß ein Zusatz von Ozon verwendet wird.1. A process for the chemical decontamination of large components and systems made of metallic materials from nuclear reactors with a liquid primary coolant, the treatment being carried out by means of an aqueous solution of oxidizing chemicals which is moved by the large components and systems to be decontaminated, characterized in that as oxidizing agents Chemicals nitrates, chromates or cerium IV salts in which borate-containing primary coolant in particular and that an addition of ozone is used. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß Ozon in einem Konzentrationsbereich von 10-40 mg kg-1 verwendet wird.2. The method according to claim 1, characterized in that ozone is used in a concentration range of 10-40 mg kg- 1 . 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß Ozon kontinuierlich über eine Ozon-Anreicherungsstrecke in das Primärkühlmittel nachgespeist wird.3. The method according to claim 1 or 2, characterized in that ozone is continuously replenished via an ozone enrichment path in the primary coolant. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß die Ozon-Anreicherung über einen Injektor, eine Blasensäule oder einen Blasensäule-Abstromreaktor stattfindet.4. The method according to claim 3, characterized in that the ozone enrichment takes place via an injector, a bubble column or a bubble column outflow reactor. 5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß in Strömungsrichtung vor der Stelle der Ozonanreicherung kontinuierlich eine Sauerstoff- und Ozonentgasung mit anschließender Ozonvernichtung erfolgt.5. The method according to claim 4, characterized in that an oxygen and ozone degassing with subsequent ozone destruction takes place continuously in the flow direction before the location of the ozone enrichment. 6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß die Ozonvernichtung katalytisch erfolgt.6. The method according to claim 5, characterized in that the ozone destruction is carried out catalytically. 7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß die Wirksamkeit der Dekontlösung durch Erfassung des Red-Ox-Potentials kontrolliert wird.7. The method according to any one of claims 1 to 6, characterized in that the effectiveness of the decontamination solution is checked by detecting the Red-Ox potential. 8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß die Konzentration des gelösten Ozons kontinuierlich analytisch überwacht wird.8. The method according to any one of claims 1 to 7, characterized in that the concentration of the dissolved ozone is continuously monitored analytically. 9. Verfahren nach Anspruch 8, dadurch gekennzeichnet, daß die kontinuierliche Überwachung aus einem mit Luft ausgestrippten Teilstrom photometrisch erfolgt.9. The method according to claim 8, characterized in that the continuous monitoring is carried out photometrically from a partial stream stripped with air. 10. Verfahren nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß die gelöste Aktivität dem Primärkühlmittel laufend mittels Ionenaustausch entzogen wird.10. The method according to any one of claims 1 to 9, characterized in that the dissolved activity is continuously withdrawn from the primary coolant by means of ion exchange. 11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß den oxidierenden Chemikalien während der Dekontamination die Kationen entzogen werden.11. The method according to claim 10, characterized in that the cations are removed from the oxidizing chemicals during decontamination. 12. Verfahren nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, daß die oxidierenden Chemikalien in einem Konzentrationsbereich von 100-1000 mg kg-1 verwendet werden.12. The method according to any one of claims 1 to 11, characterized in that the oxidizing chemicals are used in a concentration range of 100-1000 mg kg- 1 . 13. Verfahren nach einem der Ansprüche 1 bis 12, dadurch gekennzeichnet, daß das Primärkühlmittel bei der Behandlung auf Temperaturen von 20 bis 600C gehalten wird.13. The method according to any one of claims 1 to 12, characterized in that the primary coolant is kept in the treatment at temperatures of 20 to 600C.
EP85113144A 1984-10-31 1985-10-16 Process for chemically decontaminating the metallic main components and systems of nuclear reactors Expired - Lifetime EP0180826B1 (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0278256A1 (en) * 1987-01-28 1988-08-17 Siemens Aktiengesellschaft Method and apparatus for removing oxide layers
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
FR2701155A1 (en) * 1993-02-02 1994-08-05 Framatome Sa Method and installation for decontaminating worn vessel heads of light-water nuclear reactors
WO1999043006A1 (en) * 1998-02-20 1999-08-26 Centre D'etudes De L'energie Nucleaire Method and installation for decontaminating metallic surfaces

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EP0355628B1 (en) * 1988-08-24 1993-11-10 Siemens Aktiengesellschaft Process for chemically decontaminating the surface of a metallic construction element of a nuclear power plant
DE3919885C2 (en) * 1989-06-19 1994-06-30 Wedeco Umwelttechnologien Wass Process and plant for the treatment of aqueous liquids contaminated with poorly degradable pollutants
US5205999A (en) * 1991-09-18 1993-04-27 British Nuclear Fuels Plc Actinide dissolution
US5244000A (en) * 1991-11-13 1993-09-14 Hughes Aircraft Company Method and system for removing contaminants
DE19818772C2 (en) * 1998-04-27 2000-05-31 Siemens Ag Process for reducing the radioactivity of a metal part
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
JP3977963B2 (en) * 1999-09-09 2007-09-19 株式会社日立製作所 Chemical decontamination method
US6466636B1 (en) * 2000-07-26 2002-10-15 Westinghouse Electric Company Llc Decontamination method
TW529041B (en) * 2000-12-21 2003-04-21 Toshiba Corp Chemical decontamination method and treatment method and apparatus of chemical decontamination solution
JP3849925B2 (en) * 2000-12-21 2006-11-22 株式会社東芝 Chemical decontamination method
KR100724710B1 (en) * 2002-11-21 2007-06-04 가부시끼가이샤 도시바 System and method for chemical decontamination of radioactive material
JP2004191259A (en) * 2002-12-12 2004-07-08 Toshiba Corp Chemical decontamination method
JP3945780B2 (en) * 2004-07-22 2007-07-18 株式会社日立製作所 Radionuclide adhesion suppression method and film forming apparatus for nuclear plant components
JP6901947B2 (en) * 2017-09-29 2021-07-14 三菱重工業株式会社 Chemical decontamination method

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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

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US4287002A (en) * 1979-04-09 1981-09-01 Atomic Energy Of Canada Ltd. Nuclear reactor decontamination
WO1984003170A1 (en) * 1983-02-09 1984-08-16 Studsvik Energiteknik Ab Decontamination of pressurized water reactors
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

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0278256A1 (en) * 1987-01-28 1988-08-17 Siemens Aktiengesellschaft Method and apparatus for removing oxide layers
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
FR2701155A1 (en) * 1993-02-02 1994-08-05 Framatome Sa Method and installation for decontaminating worn vessel heads of light-water nuclear reactors
WO1999043006A1 (en) * 1998-02-20 1999-08-26 Centre D'etudes De L'energie Nucleaire Method and installation for decontaminating metallic surfaces
BE1011754A3 (en) * 1998-02-20 1999-12-07 En Nucleaire Etabilissement D Method and metal surfaces decontamination installation.

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ES8700486A1 (en) 1986-10-16
ES548371A0 (en) 1986-10-16
JPS61110100A (en) 1986-05-28
DE3578635D1 (en) 1990-08-16
US4942594A (en) 1990-07-17
EP0180826B1 (en) 1990-07-11

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