EP0406098A1 - Verfahren zur Auflösung von auf einem Substrat deponierten Oxiden und Verwendung zur Dekontaminierung - Google Patents

Verfahren zur Auflösung von auf einem Substrat deponierten Oxiden und Verwendung zur Dekontaminierung Download PDF

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Publication number
EP0406098A1
EP0406098A1 EP90401826A EP90401826A EP0406098A1 EP 0406098 A1 EP0406098 A1 EP 0406098A1 EP 90401826 A EP90401826 A EP 90401826A EP 90401826 A EP90401826 A EP 90401826A EP 0406098 A1 EP0406098 A1 EP 0406098A1
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EP
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Prior art keywords
solution
attack
reducing
oxidizing
decontamination
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Granted
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EP90401826A
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English (en)
French (fr)
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EP0406098B1 (de
Inventor
Didier Noel
Jacques Gregoire
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Electricite de France SA
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Electricite de France SA
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    • 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
    • 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 dissolving oxide deposited on a metal substrate.
  • It relates more particularly to a dissolution method of the above type, which is capable of being used for the decontamination of metal parts contaminated during their exposure in a hot zone.
  • Radioactivity in the primary circuit is due to corrosion products which are activated in the core and then are precipitated and incorporated into the oxide which forms on the walls of the circuit.
  • the contamination process being cumulative, it can lead in a few years in the primary circuit to a very high radioactivity.
  • the problem is particularly acute at the level of the water box of the steam generator, part of the primary circuit in which the interventions are the longest. It is therefore very important to have a process for rapidly decontaminating components or parts of the primary circuit during cold shutdowns on which personnel must intervene.
  • the main part of decontamination consists in eliminating the deposits formed on the walls of the circuit during use.
  • This deposit is mainly formed by an oxide layer which incorporates activated or radioactive corrosion products.
  • This oxide which may optionally include an external layer which is not very adherent, has an internal layer which is very compact and adherent. To decontaminate, it is necessary to remove this internal oxide, preferably down to the metal.
  • the principle of the chemical decontamination process consists in dissolving the adherent oxide layer, then in processing the solutions formed from small volume releases and easily storable in protected discharge systems.
  • the oxides formed in pressurized water reactors are generally very rich in chromium, the oxide and especially the spinels are known to be difficult to dissolve.
  • To dissolve these oxides rich in chromium it is usually proposed to oxidize chromium from degree 3 to degree 6 in an oxidizing medium and then to dissolve the residual oxide depleted in chromium in a reducing phase.
  • the reagents used must not contain elements which are liable to affect the mechanical properties of the steels to be etched. This is particularly the case for sulfur, the presence of which can cause stress corrosion if this element is in too high a concentration in the reagent.
  • the reagents used must be either easily separable from the radioactive elements or degradable to give products which are easily separable from the radioactive elements.
  • the reagents must be such that, after treatment, the effluents to be stored in a protected landfill are as small as possible in volume, or can enter standard containers.
  • one of the aims of the present invention is to provide a method which makes it possible to reduce the duration of attack or to improve the efficiency of attack compared to existing techniques.
  • Another object of the present invention is to provide a process of the above type which avoids the use of sulfur compounds in too large a concentration.
  • Another object of the present invention is to provide a process in which the reagents are easily reprocessable to give products either pure or storable in easily protected landfills.
  • the decontamination factor curves as a function of the duration of the oxidizing phase have the appearance of the conventional S curve.
  • the determination of the durations necessary to obtain the so-called exponential phase and the duration necessary to obtain the plateau value can easily be determined in each particular case.
  • a value for the duration of the oxidizing phase is set, such that there is at least 80, advantageously at least 90, preferably at least 99% of the decontamination factor obtained for the value of the plateau.
  • This value generally ranges from 5 to 20 hours. It is a value of this order which is generally chosen in the case of industrial use (one day).
  • the sulfate ion plays a catalytic role during this stage.
  • a sulfate ion concentration of between 10 ⁇ 2 and 10 ⁇ 5, preferably from 10 ⁇ 3 to 10 ⁇ 4 M.
  • the pH is preferably adjusted to a value between 2.5 and 3.5. The most acidic values are those which correspond to a better attack of the oxides without significant attack of the substrate.
  • the supplement can be supplied by nitric acid.
  • the permanganate anions are preferably at a concentration of less than 10 g / l and preferably advantageously between 2 and 1/4 of g / l. It should be noted that the total amount of permanganate anions is calculated so as to neutralize, as far as possible, the reducing nature of the attack solution from step b). This neutralization takes into account both strong reducing agents such as ascorbic acid and weak reducing agents such as complexing acids which will be discussed below.
  • Potassium permanganate is the preferred source of permanganate anions.
  • the solution of attack b) preferably comprises, in addition to the reducing agent, a complexing agent.
  • the preferred complexing agents are di or polycarboxylic acids containing at least 3 carbon atoms and at most 10 carbon atoms.
  • the complexing agents preferably have groups which allow their destruction by permanganate.
  • groups which allow their destruction by permanganate.
  • alcohol groups in particular when the latter are vicinal to each other or vicinal to other functions such as the ketone or carboxylic function.
  • ketone and aldehyde functions are examples of ketone and aldehyde functions.
  • these acids form a ring with five, six or seven atoms with the cation which they are supposed to complex.
  • acids comprising amino functions such as ethylene diamine tetraacetic acid (EDTA) which are to be avoided as far as possible, because of the difficulties which they cause during reprocessing, bring little advantages. in the process according to the invention and their use can be avoided because of this.
  • EDTA ethylene diamine tetraacetic acid
  • oxalic acid although it is a good complexing agent, is preferably to be avoided during attack, since it facilitates attack on the substrate itself.
  • citric acid Although other hydroxylated di or polyacids give good results, one of the preferred acids is citric acid.
  • the reducing agent is preferably chosen so that it is completely degraded by a permanganate or ozone attack. This reducer must also be active vis-à-vis the oxidized elements during the first step, or before. Ascorbic acid and dehydroascorbic acid are reducing agents which give good results. As reducing agents which also give good results, mention may be made of sugars having aldehyde bonds.
  • the concentration of these elements is of the order of 0.1 to 10 g / l of ascorbic acid. Preferably, around 1 to 2 g / l of ascorbic acid.
  • concentration of these elements is of the order of 0.1 to 10 g / l of ascorbic acid.
  • the two etching solutions are mixed in a step e).
  • This step is preferably carried out in such a way that the organic compounds of the reducing attack are destroyed by the oxidation reagents of the oxidizing attack, the permanganate preferably being almost completely transformed into manganous ions (Mn ++).
  • the reaction of this mutual destruction of the oxidizing and reducing solutions is preferably carried out at a temperature of 50 ° C to 100 ° C, preferably between 60 and 80 ° C.
  • Step e) is advantageously followed by a step f) of elimination of the cations present in the solution.
  • This step is advantageously carried out using an anion exchange resin.
  • it can also be carried out by a simple cation exchanger, either in the liquid phase or on a solid support.
  • the active groups of the most effective resins are complexing resins, such as, for example, hydroxydiphosphonic, amino-phosphonic, iminodiacetic, malonic resins, etc. However, if it is desired that these resins can be burnt, it is desirable that these resins contain only groups containing carbon, oxygen as well as hydrogen.
  • These resins have a polystyrene skeleton with crosslinking by means of divinylbenzene.
  • the solutions resulting from stages a) and b) can be subjected to an exchange of cations before their mixing during stage c) for the attack solution resulting from a) and stage d) for the attack solution from b).
  • the solution from step d) can be partially or intermittently recycled to the reducing attack step b) envisaged.
  • This recycling can be replaced by a reducing attack in which the resin is kept in suspension.
  • FIG. 1 represents a block diagram of the whole of a decontamination system in a particular implementation for a primary pump of a pressurized water reactor.
  • This figure shows a decontamination tank 1, an intermediate storage tank for the oxidizing solution 2, an intermediate storage tank for reducing solution 3, a storage tank for rinsing water and destruction of reagents 4, a filter. 5, the loop of which is advantageously around 3 ⁇ m.
  • a cationic resin that is to say cation exchanger 6, and a system of circuit valves and pumps which makes it possible to circulate the different solutions from a tank to a device, from devices to a tank and from tank with tray.
  • this system includes the following different operations: - heating of deionized water to 80 ° C in tank 1; - injection of oxidizing reagents into tank 1, mixing with deionized water and reaction with part to be decontaminated to constitute the first oxidizing phase; simultaneously with this operation, the deionized water for the reducing phase is also heated to 80 ° C.
  • the oxidizing intermediate solution is transferred to the intermediate storage tank while being maintained at 80 ° C;
  • the hot water for the reducing phase is transferred from tank 3 to tank 1, while the reducing reagents are also injected into tank 1 and the reactant is left to react with the parts to be decontaminated; once the reaction has been carried out, the reducing solution is transferred to its temporary storage tank 3 or the solution is maintained at 80 ° C.
  • the residual radioactivity is then measured to determine whether a second cycle should take place; in the affirmative, the oxidizing solution already used is transferred after having checked its pH and its KMnO4 concentration from the intermediate storage tank 2 to the decontamination tank 1 in order to carry out the second oxidation phase; - once this is completed, the oxidizing solution is transferred from the decontamination tank 1 to the temporary storage tank 2 with maintenance at 80 ° C; - Then the transfer of the reducing solution already used is carried out after possible verification of the state of the reagents from the intermediate storage tank 3 to the decontamination tank 1 to carry out the second reduction phase once this has been completed, the reducing solution to the temporary storage tank 3 while maintaining at 80 ° C; - the parts are rinsed with hot water at 80 ° C in the decontamination tank using rinse water sotkcée in tank 4 and heated in the latter; - then a second rinse with cold water is carried out.
  • ascorbic acid and citric acid or their degradation product remain in the solutions, they can be destroyed by injection of a strong oxidant such as for example sodium persulfate at a temperature of 80 ° C.
  • a strong oxidant such as for example sodium persulfate at a temperature of 80 ° C.
  • the effluent is then brought to a pH of 7, with, for example, ammonia, then directed to the reservoirs of the circuit for controlling and discharging the effluents from the nuclear island.
  • the process is particularly well suited to stainless steels and in particular to those collected in the following table: VS Cr Or Mo Co W stainless steels Z3 CN 18-10 0.03 18 10 - - - Z6 CN 18-10 0.06 18 10 - - - Z3 CND 17-12 0.03 17 12 2.5 - - Z6 CND 17-12 0.06 17 12 2.5 - - Z3 CND 17-12 0.03 20 10 2.5 - - base alloys nickel alloy 600 0.1-0.3 14-17 72 - - - cobalt base alloys like stellite 0.9-1.4 26-32 3 1 60 4
  • the tests were carried out for primary pump parts made of steel 18, 10.
  • the tests were carried out in glass reactors, generally under ultrasound by means of probes whose power has been adapted (25 watts / liter) so as to be transposable to industrial operations.
  • the procedure includes two phases at 80 ° C: an oxidation phase in a KMnO4 1 g / l solution acidified to pH 3 or 2.5 with H2SO4 and / or HNO3.
  • a reduction phase in a mixture of organic acids pH3 (ascorbic acid 0.5 to 1 g / l + citric acid 0.5 g / l + oxalic acid 0 to 0.5 g / l).
  • the main parameters studied were the oxidation and reduction time, the effect of the pH and the nature of the acid in the oxidizing solution, the influence of the number of cycles, the presence of ultrasound and the absence of oxalic acid in the reducing phase.
  • the contaminated samples come, in 2 separate batches, from a tap of Tihange power plant.
  • the two lots have substantially distinct activities. Heterogeneity has been attributed to a difference in the sampling area.
  • test 11 makes it possible to show that the sulfate ion is more effective than the nitrate ion.
  • Test 13 shows that it is possible to combine the advantages of the two by using a mixture of nitric acid and sulfuric acid, while avoiding to penalize the process by the excessively high sulfur contents which would be contrary to specifications for chemicals used in pressurized water reactors.
  • tests 10 and 16 on the one hand, and tests 12, 15, 17 and 18 on the other hand shows without ambiguity the very favorable effect of 2 cumulative cycles, even if the duration of these is short .
  • results in a single cycle are almost as good if not better than with two cycles (see example 7 with example 16 where similar results are obtained for same total duration).
  • FIG. 2 is made from the data of Examples 1 to 19. It shows the phenomenon of incubation during the oxidative stage of the process. In fact, for the two samples, the low activity sample and the high activity sample, the decontamination factor as a function of the time of phase a) of the oxidative attack is represented. The ordinate volumes are given on the left for the left curve and on the right for the right curve.
  • the solutions from the previous tests are filtered through two filters of 19 cartridges 475 mm long and 3 ⁇ m porosity at a flow rate of 0.5 m3 / hour. This operation is carried out both on oxidizing solutions and on reducing solutions.
  • these solutions are passed over 80 l of a cation exchange resin with sulfonic group 2.2 eq./l sold under the brand Duolite C 20 at the maximum volume flow rate of 7 volumes per volume per hour (i.e. 7 bed volumes per hour or according to the Anglo-Saxon notation 7 V / V / h) or a maximum flow of 0.5 m3 / hour.
  • This passage over resin eliminates all of the soluble activity of the oxidizing and reducing solutions (CO58, CO60, Mn54, etc.) as well as the soluble potassium of the oxidizing solution and the solubilized metals (iron, chromium, nickel) of the reducing solution.
  • a resin allows the elimination of 140 g of iron and about 1 Ci of activity.
  • the decationated oxidizing and reducing solutions are mixed and react with each other at a temperature between 60 and 80 ° C, which allows the residual oxidizing solution to be completely destroyed without precipitation of the manganese dioxide.
  • the mixture of the two solutions remains at a pH less than or equal to approximately 3.5.
  • the residual ascorbic acid and citric acid are destroyed after dosing by injection of a sufficient quantity of sodium persulfate at a temperature of 80 ° C.
  • a new passage on resin makes it possible to eliminate all of the manganese thus produced in the stage of destruction of the oxidizing and reducing solutions.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Food Science & Technology (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Electrochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Water By Oxidation Or Reduction (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Oxygen, Ozone, And Oxides In General (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)
EP90401826A 1989-06-27 1990-06-26 Verfahren zur Auflösung von auf einem Substrat deponierten Oxiden und Verwendung zur Dekontaminierung Expired - Lifetime EP0406098B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8908524 1989-06-27
FR8908524A FR2648946B1 (fr) 1989-06-27 1989-06-27 Procede de dissolution d'oxyde depose sur un substrat metallique et son application a la decontamination

Publications (2)

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EP0406098A1 true EP0406098A1 (de) 1991-01-02
EP0406098B1 EP0406098B1 (de) 1994-09-21

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EP90401826A Expired - Lifetime EP0406098B1 (de) 1989-06-27 1990-06-26 Verfahren zur Auflösung von auf einem Substrat deponierten Oxiden und Verwendung zur Dekontaminierung

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EP (1) EP0406098B1 (de)
AT (1) ATE112089T1 (de)
DE (1) DE69012677T2 (de)
ES (1) ES2064683T3 (de)
FR (1) FR2648946B1 (de)
ZA (1) ZA904913B (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2699936A1 (fr) * 1992-12-24 1994-07-01 Electricite De France Procédé de dissolution d'oxydes déposés sur un substrat métallique.
WO1999056286A2 (de) * 1998-04-27 1999-11-04 Siemens Aktiengesellschaft Verfahren zum abbau der radioaktivität eines metallteiles
US6549603B1 (en) 1999-09-09 2003-04-15 Hitachi, Ltd. Method of chemical decontamination
FR2850673A1 (fr) * 2003-02-04 2004-08-06 Electricite De France Procede de dissolution d'oxydes deposes sur un substrat metallique stellite
WO2013041595A1 (de) * 2011-09-20 2013-03-28 Nis Ingenieurgesellschaft Mbh Verfahren zum abbau einer oxidschicht
WO2017157668A1 (de) * 2016-03-16 2017-09-21 Areva Gmbh Verfahren zur behandlung von abwasser aus der dekontamination einer metalloberfläche, abwasserbehandlungsvorrichtung und verwendung der abwasserbehandlungsvorrichtung

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013102331B3 (de) 2013-03-08 2014-07-03 Horst-Otto Bertholdt Verfahren zum Abbau einer Oxidschicht
EP4269657A1 (de) * 2022-04-29 2023-11-01 Technochim SA Verfahren zum lösen von metalloxiden aus life-science-ausrüstung

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0071336A1 (de) * 1981-06-17 1983-02-09 Central Electricity Generating Board Verfahren zur chemischen Zersetzung von Oxydniederschlägen
WO1984003170A1 (en) * 1983-02-09 1984-08-16 Studsvik Energiteknik Ab Decontamination of pressurized water reactors
GB2191329A (en) * 1986-06-04 1987-12-09 British Nuclear Fuels Plc Decontamination of surfaces
FR2600203A1 (fr) * 1986-06-17 1987-12-18 Lemmens Godfried Procede pour la decontamination des materiaux a contamination radioactive

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0071336A1 (de) * 1981-06-17 1983-02-09 Central Electricity Generating Board Verfahren zur chemischen Zersetzung von Oxydniederschlägen
WO1984003170A1 (en) * 1983-02-09 1984-08-16 Studsvik Energiteknik Ab Decontamination of pressurized water reactors
GB2191329A (en) * 1986-06-04 1987-12-09 British Nuclear Fuels Plc Decontamination of surfaces
FR2600203A1 (fr) * 1986-06-17 1987-12-18 Lemmens Godfried Procede pour la decontamination des materiaux a contamination radioactive

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994015001A2 (fr) * 1992-12-24 1994-07-07 Electricite De France Procede de dissolution d'oxydes deposes sur un substrat metallique
WO1994015001A3 (fr) * 1992-12-24 1994-10-13 Electricite De France Procede de dissolution d'oxydes deposes sur un substrat metallique
CN1039037C (zh) * 1992-12-24 1998-07-08 法国国家电力企业 沉积在金属基体的氧化物的溶解方法
FR2699936A1 (fr) * 1992-12-24 1994-07-01 Electricite De France Procédé de dissolution d'oxydes déposés sur un substrat métallique.
US6613153B1 (en) 1998-04-27 2003-09-02 Framatome Anp Gmbh Method for reducing the radioactivity of metal part
WO1999056286A2 (de) * 1998-04-27 1999-11-04 Siemens Aktiengesellschaft Verfahren zum abbau der radioaktivität eines metallteiles
WO1999056286A3 (de) * 1998-04-27 1999-12-23 Siemens Ag Verfahren zum abbau der radioaktivität eines metallteiles
US6549603B1 (en) 1999-09-09 2003-04-15 Hitachi, Ltd. Method of chemical decontamination
FR2850673A1 (fr) * 2003-02-04 2004-08-06 Electricite De France Procede de dissolution d'oxydes deposes sur un substrat metallique stellite
WO2013041595A1 (de) * 2011-09-20 2013-03-28 Nis Ingenieurgesellschaft Mbh Verfahren zum abbau einer oxidschicht
US10056163B2 (en) 2011-09-20 2018-08-21 Siempelkamp NIS Ingenieurgesellschaft mbH Method for dissolving an oxide layer
WO2017157668A1 (de) * 2016-03-16 2017-09-21 Areva Gmbh Verfahren zur behandlung von abwasser aus der dekontamination einer metalloberfläche, abwasserbehandlungsvorrichtung und verwendung der abwasserbehandlungsvorrichtung
TWI714732B (zh) * 2016-03-16 2021-01-01 德商法瑪通股份有限公司 用於處理使金屬表面去汙所產生之廢水的方法、廢水處理裝置及廢水處理裝置之用途
US10950360B2 (en) 2016-03-16 2021-03-16 Framatome Gmbh Method for treating waste water from the decontamination of a metal surface, waste-water treatment device and use of the waste-water treatment device

Also Published As

Publication number Publication date
FR2648946B1 (fr) 1994-02-04
ES2064683T3 (es) 1995-02-01
DE69012677T2 (de) 1995-03-16
ATE112089T1 (de) 1994-10-15
DE69012677D1 (de) 1994-10-27
EP0406098B1 (de) 1994-09-21
ZA904913B (en) 1991-05-29
FR2648946A1 (fr) 1990-12-28

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