Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B37/00—Component parts or details of steam boilers
  • F22B37/002—Component parts or details of steam boilers specially adapted for nuclear steam generators, e.g. maintenance, repairing or inspecting equipment not otherwise provided for
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0433—Nickel- or cobalt-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B37/00—Component parts or details of steam boilers
  • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
  • F22B37/04—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler and characterised by material, e.g. use of special steel alloy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
  • B22F2003/241—Chemical after-treatment on the surface
  • B22F2003/244—Leaching
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2207/00—Aspects of the compositions, gradients
  • B22F2207/01—Composition gradients

Definitions

• the invention generally relates to elements of a nickel-based metal alloy, including nuclear reactor steam generator tubes.
• the invention relates in a first aspect to a steam generator for a pressurized water nuclear reactor, the steam generator being of the type comprising:
• an outer envelope in which is delimited a water box divided into an upstream compartment and a downstream compartment, the upstream compartment being designed to communicate fluidly with an outlet of a tank of the nuclear reactor, the downstream compartment being designed to communicate fluidly with an inlet of the reactor vessel,
• each element being a tube opening through an upstream end in the upstream compartment and a downstream end opposite the upstream end in the downstream compartment or being a plate, each element being made of a nickel-based alloy the alloy having the following mass contents:
• the primary liquid circulates inside the tubes and gives up its heat to the secondary liquid. It then passes inside the heart of the nuclear reactor, where it heats up before being redirected to the steam generator.
• the plates are in contact with the primary liquid.
• the inner surface of the tubes constitutes about 75% of the internal surface of the primary circuit in some nuclear reactors.
• nickel comes largely from steam generator tubes. It is released into the primary fluid and drawn to the heart by the primary fluid.
• the primary liquid also called primary medium
• the primary medium is a solution whose main components are water, boric acid and lithium to obtain a pH close to temperature neutrality.
• the temperature of the primary medium is close to 300 ° C (usually between 280 and 345 ° C).
• the primary medium contains dissolved hydrogen.
• the primary liquid is purified cold in a chemistry circuit of the plants in order to limit its concentration of metal cations and colloids resulting from the corrosion of the circuit materials.
• the metal cation concentrations in the primary media of power plants in operation are not known precisely but are close to the lowest published solubility limit concentrations.
• the primary medium is the purest possible water containing traces of hydrogen and dissolved oxygen, and the temperature is around 290 ° C.
• primary medium means any primary medium of a pressurized water reactor during the energy production phases, respecting the specifications of the main reactor operators or the main research and safety organizations in the field.
• solubility of most compounds in a primary medium has been studied and is published in particular in the form of commercial databases such as those proposed by the company OLI Systems.
• the invention aims to provide a steam generator for limiting the radioactive contamination of the primary circuit.
• the invention relates to a steam generator of the aforementioned type, characterized in that:
• the element has, on an internal side intended to be exposed to a liquid, a surface metal layer having an internal surface covered with an oxide layer, the superficial metallic layer having, at a depth p from the internal surface, a mass content of chromium w Cr (p), a carbon content w c (p), and a chromium content available w Cr _dispo (p), with w Cr (p) - 16.61 w c (p);
• the tubes of the state of the art have in particular a mass content of chromium available w Cr d is P o (p) less than 0 over the first 200 nanometers of the surface metal layer.
• the steam generator may also have one or more of the following characteristics, considered individually or in any technically feasible combination:
• the available chromium content w Cr d is P o (p) , taken on average over a thickness of 200 nm from the inner surface, is greater than 0;
• the chromium content available Cr 2d is P o (p), taken on average over a thickness of 10 nm, preferably over a thickness of 1 nm, from the inner surface, is greater than 0;
• the available chromium content w Cr P o (p) is constantly greater than 0 throughout the thickness of the surface metal layer from the inner surface;
• the alloy is an alloy 690 according to the standard UNS N06690 / W Nr 2.4642;
• the chromium content Cr (p), taken on average over the entire thickness of the surface metal layer from the inner surface, is less than 45%;
• the chromium content Cr (p) is increasing from the internal surface over the entire thickness of the surface metal layer;
• the surface metal layer is covered with an oxide layer that does not contain particles whose solubility is greater than that of the nickel oxide compounds in a primary medium and in particular no aluminum-rich oxide particles;
• the oxide layer has a thickness of less than 10 nm, when the element is new.
• the invention relates to a method of manufacturing a steam generator having the above characteristics, the method comprising the following steps:
• a surface treatment to the internal surface of the untreated element being chosen from: electropolishing, mechanical or chemical-mechanical polishing, chemical cleaning, the untreated element after treatment of surface constituting said element.
• the surface treatment being effected by circulating in the primary circuit a solution of a given chemical composition, such that the inner surface of the untreated element is brought into contact with said solution.
• the invention relates to another method of manufacturing a steam generator having the above characteristics, which is an alternative to the above method, the method comprising a step of manufacturing the element by rolling an ingot with a non-carbonaceous lubricant, or by continuous casting then rolling with a non-carbonaceous lubricant.
• the invention relates to the use of a surface treatment on the element of a steam generator having the above characteristics; the surface treatment etching the inner surface until the available chromium mass content w Cr d ispo, taken on average over the entire thickness of the surface metal layer from the inner surface, is greater than 0;
• the invention relates to the use of a steam generator having the above characteristics in a pressurized water nuclear reactor, in order to limit the oxidation likely to cause formation on the surface. of the filament element whose mass composition is rich in nickel, and / or the direct release into a primary liquid of ions or colloids from the zone where these filaments are likely to form, when the internal surface is exposed to the primary liquid during the nominal operation of the pressurized water nuclear reactor.
• FIG. 1 is a schematic sectional representation of the inner side of the tube of a steam generator according to the invention
• FIG. 2 is a graph showing the chromium mass content, and the normalized chromium content available, as a function of depth, measured on a tube sample;
• FIG. 3 is a graph showing the normalized mass content of available chromium, as a function of depth, measured on other samples.
• FIG. 4 is a simplified schematic representation of a nuclear reactor primary circuit comprising the steam generator according to the invention.
• the invention will be described below by detailing the constitution of an element 1 which is a steam generator tube.
• the element may alternatively be a plate of the steam generator, an inner side of which has an internal surface exposed to contact with the primary fluid.
• the element 1 partially shown in Figure 1 is made of a nickel-based alloy.
• the alloy exhibits on the macroscopic scale the following mass contents: - not more than 50%;
• the alloy preferably has on the macroscopic scale the following mass contents:
• the alloy preferably still has the following mass contents:
• the alloy is a 690 alloy according to the UNS standard N06690 / W Nr 2.4642 also known under the name INCONEL® alloy 690.
• the mass contents of the chemical elements composing this alloy are as follows:
• Such an element is used in pressurized water nuclear reactor steam generators.
• the primary liquid from the heart flows inside the tube or in contact with the plate.
• the element 1 has, on an internal side intended to be exposed to the primary liquid, a surface metal layer 7, having an internal surface 5 covered by an oxide layer 3.
• the oxide layer 3 typically has a thickness of less than 10 mm, because of the method of manufacture of the element 1 described below.
• This oxide layer typically comprises an oxide layer called an outer layer composed of iron, chromium and nickel spinel type oxides, which covers another oxide layer called an inner oxide layer that is generally rich in chromium.
• the thickness of the oxide layer 3 is defined as the thickness measured by glow discharge spectroscopy (calibrated according to the state of the art) from the free external surface 4 until the mass content of oxygen less than 50% of the mass content of oxygen at the free external surface 4.
• the oxide layers can have a total thickness of up to a few micrometers.
• the surface metal layer 7 has a composition which deviates from, but remains close to, the composition of the nickel-based alloy. Beneath the surface metal layer 7 is the base metal 9 of the tube. Typically, the layer 7 has a thickness of approximately 1 ⁇ (see FIG. 2).
• internal surface 5 of element 1 is understood to mean the surface formed by the metal interface / internal oxide layer, delimiting the internal passage in which the primary liquid flows in the case of a tube.
• the base metal 9 has substantially the mass contents of the alloy used to make the tube.
• the metallic surface layer 7 is predominantly of metal, and not of metal oxide, although it contains nonmetallic inclusions - inclusions that can be up to several hundred nanometers along their larger dimensions. It has mass contents that are a little different from those of the base metal, resulting from the treatments applied during the manufacture of the tube.
• the filaments 11 are torn from the oxide layer or dissolved during their growth and are entrained in the primary circuit. They thus constitute one of the sources of Co-58 and Co-60. On the other hand, there is no published mechanism explaining the formation of these filaments.
• a significant proportion of the oxidation rate of the tube material can be characterized by the formation rate of the filaments 11, which are formed especially when the speed of the primary medium is low, and when the primary medium tends to be saturated with nickel in ionic form.
• the applicant has discovered that, surprisingly, it was possible to limit or even prevent the formation of the filaments 11 in a primary medium, and consequently to slow down or eliminate one of the oxidation forms of the metallic material, while maintaining the surface metal layer 7 has a mass content of significant available chromium. Maintaining a low carbon content also helps to prevent the formation of the filaments 1 1 when this can take place.
• the particles of oxides or carbides whose solubility is greater than that of the nickel oxides in a primary medium - in particular the particles of aluminum oxide, when they are substituted for the native oxide layer - contribute also to the formation of the filaments 1 1 in a primary environment when it can take place.
• the oxide layer 3 does not contain a particle whose solubility is greater than that of the nickel oxide compounds in a primary medium, and in particular no aluminum-rich particles.
• the filaments are not always observable. It is preferable to use specific conditions in a primary environment with low convection and low levels of nickel iron, oxygen and dissolved chromium to obtain them. In a hydrogenated primary medium when the dissolved iron content is less than 1 kg, the oxidation of the alloy is always at the origin of the formation of filaments. The rate of oxidation in the filament formation zone controls the rate of filament formation, if formed.
• the filaments can be dissolved faster than they are formed and / or are torn off.
• the Applicant has indeed discovered that the formation of the filaments 11, results from the fact that, in the surface layer 7, the carbon content present in the carbides or out of the carbides, contributes to the formation of filaments. Moreover, in this layer, a large part of the chromium is present in the form of carbides. Chromium embedded in carbides does not contribute, or contributes little, to preventing the formation of filaments 1 1. On the contrary, the available chromium, that is to say not integrated in the carbides, helps to prevent the formation of the filaments.
• the zones where the filaments are formed are the most favorable zones for oxidation of the alloy and relaxation, regardless of its shape (ions or colloids). These Areas are characterized by low chromium availability and / or the presence of soluble oxides in the oxide layer.
• the mass content of available chromium is evaluated as follows.
• w Cr (p) the mass content of chromium of the surface metal layer at a depth p from the inner surface 5 of the tube
• w c (p) the carbon content of the superficial metal layer at the depth p
• w Cr carbure (p) the chromium content potentially integrated into the carbides in the hypothesis where the carbides have Cr 23 C 6 stoichiometry of the superficial metallic layer at the depth p
• w Cr d is P o (p) the available chromium content of the surface metal layer at depth p.
• the depth p as illustrated in FIG. 1, is taken radially, from the inner surface 5, towards the base metal 9.
• the mass content is defined here as the mass of the chromium or carbon atoms divided by the mass of the surface metal layer, for a unit volume of the given surface metal layer.
• thermodynamically stable chromium carbide is considered in the alloy type considered for element 1, having the formula C 6 Cr 23 . It should be noted that this is an overriding hypothesis. There are other forms of carbides, consuming less chromium.
• the molar masses of carbon and chromium are respectively 12 and 52.
• the mass content of chromium available w Cr dis P o (p) at a depth p can have a negative value.
• a negative value has no physical meaning, but expresses the magnitude of the non-carburizable chromium deficit or the magnitude of the excess carbon.
• the mass content of available chromium taken on average over the entire thickness of the surface metal layer 7 from the inner surface 5, is greater than 0.
• This free chromium content throughout the thickness of the superficial metal layer will form during its oxidation a layer of oxide rich in chromium which will thus constitute a barrier effectively preventing the formation of nickel-rich filaments 1 1 and the relaxation of nickel-rich colloidal or ionic compounds when element 1 is used in a pressurized-water nuclear reactor.
• the available chromium content is less than zero when:
• the superficial metal layer 7 is depleted of chromium.
• a carbon or high carbide content generally results from the hot conversion of impurities at the time of manufacture of the element 1, including lubricant. It can also come from the fact that the alloy casting used for the manufacture of the tube itself had a high carbon content.
• the surface metal layer 7 is depleted of chromium by dilution when the contents of the alloying elements other than chromium, and the contents of the minority compounds are concentrated towards the surface of the metal during manufacture, handling or processing. oxidation of the material.
• the available chromium content taken on average over a thickness e from the inner surface 5, is called the average chromium content available on e below. This thickness e is typically taken less than or equal to the thickness E of the superficial metallic layer 7.
• the average chromium content available on e denoted by w Cr dist P o e , is evaluated in the following manner.
• the chromium mass content w Cr (p) and / or the carbon mass content w c (p) is measured at different depths p of the superficial metal layer 7, on a sample of the element 1.
• This sample has for example a diameter of 20 ⁇ 1 mm at the inner surface and a thickness of 1 mm.
• the surface metal layer is analyzed at 100 different depths, distributed between 0 and e.
• the retained mass contents w Cr (p) and / or w c (p) correspond, for example, to the average of the measurement results.
• the mass content of chromium and / or carbon is measured by glow discharge spectrometry (SDL, GDOES in English). This technique is known and will not be detailed here.
• the mass content of chromium and / or carbon is measured by Auger spectrometry or X-ray photoelectron spectrometry coupled with a method of abrasion of the inner surface of the tube (for example ionic abrasion).
• the mass content of chromium and / or carbon is measured by ray spectroscopy Energy dispersive X-ray spectroscopy (EDS) on a transverse section (or microscope obtained by focused ion probe) of the tube studied by scanning electron microscope (SEM) or transmission ( TEM).
• EDS ray spectroscopy Energy dispersive X-ray spectroscopy
• SEM scanning electron microscope
• TEM transmission
• Standardized weight contents of chromium available w N _ _dispo Cr (p) are then calculated, to exclude measurements made by mistake in the oxide layer and impurities 3 and not in the surface metal layer 7.
• the contents w N _ Cr _dispo (p) are determined for each of different depths, as follows:
• w N _cr_dispo (p) w Cr _dispo (p) x (w Cr (p) + w Fe (p) + w Ni (p)) / 100 Equation 2 where w Fe (p) and w Ni (p) are the mass contents of iron and nickel at the depth p of the surface metal layer 7 from the inner surface 5.
• w Fe (p) and w Ni (p) are measured using the same technique as w Cr (p) and w c (p) at the same points.
• the measurements carried out on carbonaceous impurities generally present on the metallographic preparations are thus assigned a weight of almost 0, and the measurements made in the surface metal layer are assigned a weight substantially equal to 1.
• the element 1 of the invention is such that the mass content of available chromium, taken on average over the entire thickness E of the surface metal layer 7, from the inner surface 5, is greater to 0.
• the element 1 of the invention is such that the chromium content available in the surface metal layer 7, taken on average 200 nm thick of the surface metal layer 7 from the inner surface 5, is greater than 0.
• w Cr _dispo 200nm 1/200 nm x
• the element 1 of the invention is such that the mass content of available chromium, taken on average on the thickness E of the surface layer 7 and / or on a thickness of 200 nm of the superficial metallic layer 7 from the inner surface 5, is greater than 0.
• the element 1 of the invention is such that the available chromium content in the surface metal layer 7, taken on average over a thickness of 10 nm of the surface metal layer 7 from the inner surface 5 is greater than 0.
• the element 1 the invention is such that the mass content available chromium, taken on average on the thickness E of the surface layer 7 and / or on a thickness of 200 nm and / or on a 10 nm thickness of the surface metal layer 7 from the inner surface 5, is greater than 0.
• the element 1 of the invention is such that the chromium content available in the surface metal layer 7, taken on average over a thickness of 1 nm of the surface metal layer 7 from the inner surface 5, is greater than 0.
• the average chromium contents available on the thickness E, and / or 200 nm, and / or 10 nm, and / or 1 nm are greater than 0.
• the average chromium contents available on E , and / or 200 nm, and / or 10 nm, and / or 1 nm are greater than 5%, more preferably greater than 15%.
• the average chromium contents available on E, and / or 200 nm, and / or 10 nm and / or 1 nm are calculated by averaging the available chromium mass contents w Cr d is P o (p), and not the standardized mass contents in available chromium W N Cr_dispo (p) -
• the element 1 of the invention preferably has an available chromium content w Cr di Spo (p) which is constantly greater than 0 throughout the thickness of the surface metal layer 7.
• the surface metal layer 7 always has an available chromium content w Cr di Spo (p) greater than 0.
• This chromium content available w Cr dis P0 (p) is preferably greater than 5%, more preferably greater than 15%, whatever the depth p.
• the chromium content available Cr di Spo (p) in the surface metal layer 7 is constantly greater than 0 in a thickness of 200 nm from the inner surface 5, and / or in a thickness of 10 nm to from the inner surface 5, and / or in a thickness of 1 nm from the inner surface 5.
• the available chromium content is constantly greater than 5%, more preferably still greater than 15%, in a thickness of 200 nm from the inner surface 5, and / or in a thickness of 10 nm from the inner surface 5, and / or in a thickness of 1 nm from the inner surface 5
• Figure 2 shows the mass content of chromium w Cr (p) (curve 1), and the normalized mass content of available chromium w N Cr _dis P o (p) (curve 2), as a function of the depth from the internal surface, for a piece of new steam generator tube. It is seen that there exists in this tube a high chromium deficit available between 0 and 10 nm. The available chromium mass content is negative up to 10 nm, and remains below 15% to a depth of about 50 nm. A negative value of the available chromium mass content has no physical meaning, a negative value expresses the magnitude of the non-carburizable chromium deficit or the magnitude of the excess carbon.
• Figure 3 shows the standardized chromium mass contents available w N cr_dis P o (p), as a function of the depth from the inner surface, for sections from different steam generator tubes. These tubes are new and have been manufactured by different suppliers. They are intended to equip steam generators of new nuclear reactors, or new steam generators installed in replacement on old reactors. As in Figure 2, we see that there is in these samples a high chromium deficit available between 0 and 10 nm. The available chromium mass content is negative for most samples at least up to 10 nm.
• the surface metal layer 7 has a composition which departs from the composition of the nickel-based alloy, while remaining close to it. It has mass contents which are a little different from those of the base metal, that is to say of the nickel-based alloy, resulting from the treatments applied during the manufacture of the element 1.
• This chromium content w Cr (p) is increasing, from the inner surface 5, over the entire thickness of the surface metal layer 7. It is typically between 0.1% and 20% at the inner surface 5. It grows constantly when the depth p increases. It is close to the content of the nickel-based alloy at a depth of 100 nm. Typically, the difference between the chromium content of the nickel-based alloy and the chromium content of the surface layer is less than 30%, preferably less than 5%, at a depth of 100 nm.
• the nickel content, taken on average over the entire thickness of the surface metal layer 7 from the inner surface 5, is greater than 1%. It is typically greater than 40%.
• the nickel content, taken on average over 100 nm from the inner surface 5, is greater than 40%, typically greater than 45%.
• the steam generators of the invention are capable of being manufactured according to various methods.
• the manufacturing method comprises the following steps:
• the surface treatment being selected from: electropolishing, mechanical or chemical mechanical polishing, chemical cleaning.
• the untreated element is in the nickel-based alloy defined above. It is manufactured by any suitable method. It is for example extruded, rolled from an ingot, rolled, welded etc.
• the inner surface 5 delimits the inner side of the tube, that is to say the internal passage of the tube.
• the surface treatment is intended to eliminate or replace a thin layer of the inner surface of the untreated element, which has an available chromium deficiency.
• the surface treatment aims to eliminate or replace a portion of the surface metal layer 7, which has a low chromium content available.
• the surface treatment is intended to eliminate or replace the entire surface metal layer 7.
• the surface treatment aims to eliminate or replace a portion of the surface metal layer 7 of thickness selected so that the average chromium content available over the entire thickness E of the surface metal layer 7 w Cr d is P o E is less than a predetermined limit, after application of the surface treatment.
• the predetermined limit is for example 0%, 5% or 15%. It is also possible to consider the average chromium content available at 200 nm, or at 10 nm, or at 1 nm instead of the average chromium content available over the entire thickness of the surface metal layer 7.
• Surface treatment also aims to remove unwanted compounds in the oxide layer, including alumina.
• Such a treatment can be obtained for example by a chemical cleaning in heated alkaline solution.
• the thickness of the pickled layer by surface treatment is chosen on a case by case basis, after analysis of the profile of the available chromium mass content as a function of the depth from the internal surface of the untreated element. .
• This profile depends on the alloy used to manufacture the untreated element, and the method of manufacture.
• this thickness is less than 1 ⁇ , preferably less than 200 nm, more preferably less than 100 nm.
• Electropolishing is an electrochemical surface treatment process by which the metal of the surface layer is removed by anodic dissolution. Some elements of the alloy that are partially insoluble in the electropolishing bath - particularly chromium oxide - remain on the surface of the workpiece and form a protective barrier.
• Mechanical polishing consists of stripping the piece by an abrasive means. Many means can be used: circulate in contact with the surface a liquid loaded with abrasive particles, moving in contact with the surface an abrasive member such as a disc, a brush, etc.
• Chemical cleaning is a technique of contacting the surface to be treated with a chemical solution of selected composition to dissolve the surface layer of the surface.
• the chemical solution comprises, for example, concentrated acids and complexing agents making it possible to increase the solubility of certain oxides.
• Chemical mechanical polishing combines mechanical polishing and chemical cleaning.
• a chemical solution loaded with abrasive particles is circulated in contact with the surface to be treated.
• Struers sells polishing suspensions suitable for such operations, for example the suspensions sold under the name OP-AA and OP-S which are solutions of acids or bases, complexing agents and colloidal suspensions of abrasive oxides. silicone or alumina.
• the untreated element becomes said element described above, having the available chromium content required by the invention.
• the surface treatment is carried out on the untreated element before final assembly in the steam generator.
• the method comprises the following steps:
• the chemical composition used is in this case compatible with all the requirements relating to the chemistry of the primary circuit.
• the solution comprises boric acid, and / or peroxides.
• the surface treatment is performed in the nuclear power plant, once the steam generator permanently connected to the primary circuit.
• the method comprises the following steps:
• the treatment in this case is mechanical or chemical-mechanical polishing, or chemical cleaning.
• the steam generator in this case is not yet connected to the primary circuit of the nuclear reactor.
• the treatment is for example carried out in the steam generator manufacturing workshop, which is not on the site of the nuclear power plant.
• the method comprises a step of manufacturing the element by rolling an ingot with a non-carbonaceous lubricant or by continuous casting then rolling with a non-carbonaceous lubricant.
• the ingot is in the nickel-based alloy described above. Before rolling, it has the shape of a hollow cylinder in the case where the element is a tube.
• non-carbonaceous liquids can be used as lubricants including certain molten salts, low melting metals or many aqueous solutions.
• the lubricant used is non-carbon
• the amount of carbon on the inner surface of the tube is reduced, and the amount of chromium carbides on the inner surface of the tube is reduced as well. As a result, the amount of chromium available is increased.
• the element having the available chromium content required by the invention is a tube, it is mounted in the steam generator as shown in FIG. 4.
• the steam generator 13 comprises an outer casing 15, and a tubular plate 17 dividing the internal volume of the casing into a water box 19 and an upper volume 21.
• the water box 17 is divided by an internal partition 22 into an upstream compartment 23 and a downstream compartment 25.
• the steam generator comprises a secondary liquid inlet 27 and a vapor outlet 29, both opening into the upper volume 21. They are connected respectively to a secondary pump and a steam turbine.
• the tubes 1 each open through an upstream end in the upstream compartment 23 of the water box, and by a downstream end opposite the upstream end in the downstream compartment 25.
• the tubes each have a U-shape and their ends are rigidly fixed to the tube plate 17.
• the upstream compartment 23 is fluidly connected to an outlet 31 of a tank
• the downstream compartment 25 is fluidly connected to an inlet 35 of the tank 33 of the nuclear reactor.
• the primary liquid is heated in the reactor vessel and then flows to the upstream compartment of the water box. he then flows from the upstream compartment to the downstream compartment, inside the tubes 1. It gives in passing some of its thermal energy to the secondary liquid. It then flows from the downstream compartment to the tank inlet.
• the element having the available chromium content required by the invention is a plate mounted in the steam generator, an inner surface of which is in contact with the primary fluid.
• This plate is for example the plate 22 separating the upstream and downstream compartments from one another.
• Element 1 is made of a nickel-based alloy, the alloy having the following mass contents:
• the surface treatment is intended to etch the inner surface until the available chromium mass content w Cr dis P o (p), taken on average over the entire thickness of the surface metal layer 7 from the surface internal 5, greater than 0, in order to limit the oxidation likely to result in the formation of filaments rich in nickel 1 1, and / or the direct release into the primary liquid of the nuclear reactor ions or colloids from areas where these filaments are likely to form, when the inner surface 5 is exposed to the primary liquid of the pressurized water reactor during the energy production phases, that is to say during the nominal operation of the nuclear reactor.
• the primary fluid considered here meets the specifications of the major reactor operators or the main research and safety organizations in the field.
• it has a nickel content (ions) less than or equal to the lowest solubility limit, the flow being characterized by a number of
• filament rich in nickel is meant a filament comprising more than 50% of nickel by mass.
• the alloy is typically one of the alloys defined above.
• Surface treatment is one of the surface treatments defined above. Alternatively, the surface treatment is used until the available chromium mass content w Cr d is P o (p), taken on average over a thickness of 200 nm from the inner surface 5, and / or taken on average 10 nm thick from the inner surface 5, and / or taken on average to a thickness of 1 nm from the inner surface 5, greater than 0, always for the same purpose.
• the surface treatment is used until the mass content of available chromium Cr 0dis P o (p), taken on average over the entire thickness of the surface metal layer, and / or 200 nm, and or 10 nm, and / or 1 nm from the inner surface, is greater than 5%, more preferably 15%.
• the invention also relates to the use of a steam generator as described above in a pressurized-water nuclear reactor, in order to avoid the formation on the inner surface 5 of the filament element whose composition mass is rich in nickel and / or the direct release in a primary liquid of the nuclear reactor of colloids from these filaments January 1, when the inner surface 5 is exposed to the primary liquid during the nominal operation of the nuclear reactor.
• the element 1 is for example a tube 1 which serves for the circulation of the primary liquid of the nuclear reactor during normal operation of the reactor, the upstream compartment 23 of the water box 19 to the downstream compartment 25, or a plate.
• the primary liquid considered here is as described above.
• the manufacturing processes of the invention are particularly advantageous because they do not create a heating of the material constituting the untreated element. It retains its initial microstructure. This is particularly important for steam generator tubes, which are for example 690TT alloy.
• This alloy is subjected, prior to the surface treatment step described here, to a defined heat treatment, aimed in particular at forming intergranular chromium carbides while maintaining a grain size of the metal in a precise range. Excessive heating of the tube during the surface treatment, bringing the alloy to more than 800 ° C for example, would lose at least a portion of the benefit of heat treatment or would cause a change in grain size of the metal.
• most of the surface treatments considered in the invention are carried out by circulating a fluid in contact with the inner surface of the element to be treated.
• the fluid is propelled for example by a pump or a swab or a felt floss pushed by means of a compressed gas.
• the implementation of these circulating treatments is much simpler than that of plasma deposition treatment, or other similar treatment, for steam generator tubes. These tubes are of great length, more than 20 m, and small external diameters, less than 20 mm. he There is currently no enclosure for depositing by PVD (Physical Vapor Deposition) on the inner surface of this type of room.
• PVD Physical Vapor Deposition
• Treatments to remove a portion of the surface metal layer are particularly advantageous. They are simpler to implement than those involving a deposit on the surface metal layer. There is no risk that the deposited material has cracks, or that there are decohesions at the interface between the surface metal layer and the deposited material.

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• High Energy & Nuclear Physics (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
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• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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• 2015
  • 2015-11-24 CN CN201580085693.1A patent/CN108700285B/zh active Active
  • 2015-11-24 EP EP15845497.5A patent/EP3380787B1/fr active Active
  • 2015-11-24 ES ES15845497T patent/ES2930449T3/es active Active
  • 2015-11-24 WO PCT/FR2015/053193 patent/WO2017089658A1/fr active Application Filing
  • 2015-11-24 JP JP2018527810A patent/JP6850800B2/ja active Active

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