Classifications

• • 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
  • G21F9/02—Treating gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
  • B08B3/04—Cleaning involving contact with liquid
  • B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
  • B08B3/102—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration with means for agitating the liquid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B7/00—Cleaning by methods not provided for in a single other subclass or a single group in this subclass
  • B08B7/0035—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like
  • B08B7/0042—Cleaning by methods not provided for in a single other subclass or a single group in this subclass by radiant energy, e.g. UV, laser, light beam or the like by laser
• • 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
  • G21F9/005—Decontamination of the surface of objects by ablation
• • 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
  • G21F9/28—Treating solids
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/10—Nuclear fusion reactors

Definitions

• the present invention relates to the laser decontamination of a metal part containing a gas, in particular in the nuclear field.
• the present invention relates to a method for decontaminating a metal part containing a gas which may be radioactive, by laser irradiation in a liquid medium, as well as to a device for implementing this decontamination method.
• the metal parts present in nuclear installations and in particular in contact with the heat transfer fluid comprising radioactive compounds can be found contaminated by radioactive substances. This contamination can be on the surface or internally. To avoid contamination of the environment during the dismantling of nuclear installations or to limit human exposure to the radioactivity emitted by these parts during maintenance or dismantling activities of these installations, it is often necessary to decontaminate the metal parts. present in these facilities.
• radioactive gases such as tritium ( 3 H) which is the radioactive isotope of hydrogen and which is capable of diffusing into the material to end up in the base metal of the metal part.
• ITER international thermonuclear experimental reactor which is a nuclear fusion reactor project, using deuterium and tritium as fuel. Because of the ability of tritium to diffuse in the material, the management of tritiated waste by confinement is difficult and the techniques for surface decontamination of waste, in particular metallic waste, are not appropriate.
• the present application aims to propose a solution making it possible to effectively decontaminate a metal part containing a gas which may be radioactive, that is to say whose base metal has adsorbed this gas, by reducing the risks of dispersion of the gas. gas in the air and the new contamination of the part by the redeposition of gas particles on the surface of the part and its diffusion in the material.
• the present invention provides a method for decontaminating a metal part containing a gas by laser irradiation in a liquid medium and a device for implementing this method.
• a first object of the invention relates to a method for decontaminating a metal part containing a gas by laser irradiation in a liquid medium, in which
• a glass interface capable of allowing the wavelength of a pulsed laser beam to pass, the interface being arranged between the metal part and said beam, at a distance of between 10 mm and 250 mm of said part
• liquid medium circulation system capable of directing the liquid medium located between the interface and the metal part, along said part
• a second object of the invention relates to a device for decontaminating a metal part containing a gas by laser in a liquid medium, comprising:
• a pulsed laser capable of emitting a pulsed laser beam at a wavelength between 1000 and 1080 nm, with a fluence between 30 and 200 J / cm 2 and a power peak between 1.2 and 7.5 kW, said laser comprising an irradiation head
• a glass interface capable of allowing the wavelength of the pulsed laser beam to pass, intended to be placed between the metal part and said beam and to be immersed in the liquid medium a system for circulating the liquid medium, all or part of which is intended to be placed between said part and the glass interface, capable of directing the liquid medium located between the interface and the metal part, along said part.
• FIG. 1 represents a diagram of the device according to the present invention implemented according to a mode not immersed in the liquid medium.
• the metal part (1) the liquid medium (2)
• the compartment comprising the liquid medium (3) the head of the pulsed laser (4)
• the glass interface (5) the nozzle (6 )
• the engine (7) the circulation system (8)
• FIG. 2 represents a diagram of the device according to the present invention implemented according to a mode immersed in the liquid medium.
• the metal part (1) the liquid medium (2)
• the compartment comprising the liquid medium (3) the head of the pulsed laser (4)
• the glass interface (5) the nozzle (6 )
• the engine (7) the circulation system (8)
• the hooking support (9) the waterproof compartment (10).
• the method for decontaminating a metal part containing a radioactive gas by laser irradiation in a liquid medium and the device for implementing this method proposed by the inventors advantageously make it possible to effectively decontaminate a metal part having adsorbed into the material a gas which may be radioactive. , while reducing the risks of dispersing gas which may be radioactive in the air, therefore environmental and human contamination, but also new contamination of the part by the redeposition of gas particles on the surface of the part and its diffusion into the room. matter.
• the objects of the present application make it possible in particular to avoid or reduce the difficulties of using a pulsed laser in a liquid medium, such as the reduction in the efficiency of decontamination and the generation of fumes at the surface of the liquid. .
• a first object of the invention relates to a method for decontaminating a metal part containing a gas by laser irradiation in a liquid medium, in which
• a glass interface capable of allowing the wavelength of a pulsed laser beam to pass, the interface being arranged between the metal part and said beam, at a distance of between 10 mm and 250 mm of said part
• liquid medium circulation system capable of directing the liquid medium located between the interface and the metal part along said part
• the pulsed laser includes an irradiation head.
• laser irradiation head or “laser head” is understood to mean a coherent light source generating a pulsed laser beam and an optical module for focusing this beam and directing it along at least one axis on the surface of the part. to be decontaminated.
• metal part containing a gas is understood to mean a metal part of which the base metal, that is to say the metallic material of which the part is made, and not only the surface, contains a gas such as hydrogen or again tritium which is a radioactive gas.
• the present invention is particularly advantageous for the decontamination of a metal part containing a radioactive gas, because the radioactive gases and in particular tritium have the capacity to diffuse in the metallic material, to a depth which can go up to 35 ⁇ m or even 50. pm.
• tritium is able to contaminate a metal part to a depth of about 10 ⁇ m.
• the metal part implemented in the context of the present invention is a metal part containing a radioactive gas and more preferably said gas is tritium.
• the ability of the process to effectively decontaminate a metal part containing a gas in a liquid medium is determined as a function of the ability of the process to pickle, to abrade the metal part and in particular as a function of the depth of abrasion of the part which must be sufficient to release all or part of the gas present in the material.
• the process according to the present invention is considered to be effective when it allows to abrade at least 10 ⁇ m of the base metal of the part.
• base metal is understood to mean the metallic material in which the metallic part is made.
• the metal part can be in direct or indirect contact with a nuclear installation and this part can be subjected to the process according to the invention in cut or whole form.
• the base metal in which the part is made can for example be stainless steel, black steel or a metal alloy such as those comprising high proportions of nickel, chromium, iron such as INOCONEL® 600, 625 , 718.
• the liquid medium can be contained in a compartment, the dimensions and composition of which are suited to the metal part, to the liquid medium considered and to the process according to the invention.
• the liquid medium can be water, demineralized water, a concentrated chemical solution with cerium or a nitrifying solution.
• the liquid medium considered in the context of the present invention is water, preferably demineralized.
• the metal part, the glass interface and the system for circulating the liquid medium can, independently of one another, be totally or partially immersed in the liquid medium. However, care will be taken to ensure that the part of the part to be subjected to the decontamination process is completely immersed in said medium.
• the glass interface can for example be completely immersed in the liquid medium or else be placed on the surface of this medium.
• the glass interface implemented in the method according to the invention can for example be produced from fused silica and comprises an anti-reflective coating whose refractive index is between 1.20 and 1.45.
• the thickness of this interface can vary depending on the part to be decontaminated, the liquid medium in which the part is located, the gas contaminating said part or even the parameters of the process.
• the thickness of the glass interface can be between 5 and 100 mm, preferably between 10 and 50 mm.
• the glass interface is permanently or removably connected to the irradiation head of the pulsed laser by a fastening system or integrated into the irradiation head of the laser, preferably on the front face of said head.
• the fluence corresponds to the energy density of the laser per unit area, and according to a preferred aspect of the method according to the invention, the fluence can be between 50 and 150 J / cm 2 .
• the power peak in watts corresponds to the ratio of the energy per pulse in joules over the duration of the pulse in seconds, according to a preferred aspect of the method according to the invention, the power peak may be between 1.2 and 7, 5 kW.
• the width of the pulsed laser beam is able to be modulated to adapt to the dimensions of the metal part to be decontaminated.
• the pulsed laser implemented in the method according to the invention is an Nd: YAG laser emitting at a wavelength of 1064 nm.
• the wavelength is 1064 nm
• the fluence is between 50 and 150 J / cm 2
• the power peak is between 2 and 4 kW
• the speed of displacement is between 3000 and 20,000 mm / seconds.
• the speed of movement or scanning speed refers to the speed at which the pulsed laser beam is applied to the metal part, according to a preferred aspect of the method according to the invention, the speed of movement is between 5000 and 10 000 mm / seconds.
• the pulsed laser beam is applied to the metal part enough times and for a sufficient time for the gas to be released from the material, that is to say to abrade the base metal. the room to a depth at which all or part of the gas is found.
• the number of passes depends on the parameters of the laser, the dimensions of the metal part considered, the type and depth of contamination by the gas.
• the laser beam in the method according to the invention is applied to the workpiece between 10 and 150 times at the same location, preferably between 30 and 100 times.
• each pass is made at the same place as the previous one.
• the pulsed laser beam is applied to the metal part in the same direction on each pass.
• the present invention relates to a method according to the first object in which, the liquid medium is water, the glass interface is placed in the water at a distance of between 10 and 50 mm from said part. , the wavelength is 1064 nm, the fluence is between 100 and 150 J / cm 2 , the power peak is between 2 and 4 kW and the laser beam is applied between 30 and 60 times on the metal part with a displacement speed between 5000 and 10 000 mm / second.
• the head of the pulsed laser is placed at a focal distance from the metal part sufficient for the laser use to be effective.
• This focal length corresponds to the distance between the focusing device of the irradiation head of the laser and the surface of the metal part to be decontaminated.
• the head of the pulsed laser is placed at a focal length whose value is increased by 25% compared to the value of the distance between the metal part and the surface of the liquid.
• the method according to the invention can be implemented according to an immersed mode, that is to say in which the irradiation head of the laser is totally or partially immersed in the liquid medium or according to a non-immersed mode, in which said head is not immersed in the liquid medium.
• the irradiation head of the laser to which the glass interface is connected via the attachment system is placed outside the liquid medium.
• the glass interface is arranged on the surface of the liquid medium.
• the irradiation head of the laser to which the glass interface is connected via the attachment system or integrated is totally or partially immersed in the liquid medium.
• the irradiation head is surrounded by a sealed compartment.
• the liquid circulation system implemented in the method according to the present invention comprises a motor and a nozzle, said nozzle being immersed in the liquid medium and located between the interface and the metal part, along an axis parallel to the metal part.
• the motor can also be immersed in the liquid medium, thanks to a sealed compartment surrounding it.
• the liquid medium circulation system advantageously makes it possible to direct the liquid medium situated between the glass interface and the metal part, precisely the surface of said part, along said part, that is to say - say according to the longitudinal axis of the part and according to a laminar flow.
• the nozzle of the circulation system is arranged at a sufficient distance between the interface and the part to ensure the direction of the liquid medium along the part, along the longitudinal axis of the part and with a laminar flow.
• the motor of the circulation system has sufficient power to ensure said direction of the liquid medium.
• the method according to the invention can comprise an additional step of collecting the liquid medium in which the gas is located after decontamination of the part, by means of a collection system which communicates with the liquid medium.
• the collection system comprises a conduit, one end of which communicates with the liquid medium and the other end communicates with a compartment for collecting the contaminated liquid, said system comprising a pump connected directly or indirectly to said conduit and capable of aspirate the liquid to direct it to the collection compartment.
• the step of collecting the liquid medium comprising the gas can be carried out during or after the implementation of the decontamination process, preferably during.
• the collected liquid medium is stored in tanks in order to reduce the radioactivity to tritium by simple radioactive decay.
• the liquid medium can be stored for a period equal to the radioactive decay period of tritium which is 12.3 years so as to reduce its activity by a factor of 2.
• the method according to the invention comprises an additional step of decontamination of the liquid medium comprising the gas collected, in particular the radioactive gas.
• This step can be carried out by any of the methods of decontaminating liquid effluents containing a radioactive gas such as tritium, known from the prior art.
• a liquid decontamination method reference can be made to vacuum distillation which is based on the difference in volatility between the isotopes of water or to the separation of tritium by direct electrolysis of water. which is based on the difference in voltage of electrolysis and diffusion of ions in the electrolyte and which results in the decomposition of tritium into dioxygen and hydrogen gas.
• chemical exchange processes which include two main steps, namely the transfer of the tritiated liquid, in particular water, to a flow of gaseous hydrogen gas circulating in countercurrent in the presence of a catalyst based on platinum, followed by a step of separating and concentrating the tritium and concentrating the gaseous tritium, in particular using cryogenic distillation.
• the present invention also relates to a device for implementing the method according to the first object.
• the device according to the invention comprises a compartment comprising a liquid medium (1), a pulsed laser, a glass interface (5) and a system for circulating the liquid medium (8).
• a second object of the invention relates to a device for decontaminating a metal part (1) containing a gas by laser in a liquid medium (2), comprising:
• compartment (3) comprising a liquid medium in which the metal part is intended to be immersed
• a pulsed laser capable of emitting a pulsed laser beam at a wavelength between 1000 and 1080 nm, with a fluence between 30 and 200 J / cm 2 and a power peak between 1.2 and 7.5 kW, said laser comprising an irradiation head (4)
• the dimensions of the compartment depend on the dimensions of the metal part to be decontaminated.
• the pulsed laser implemented in the context of the present invention is a laser, the amplifying medium of which is composed of a neodymium-doped yttrium-aluminum garnet commonly known as an Nd: YAG laser. More preferably, the pulsed laser is an Nd: YAG laser emitting at a wavelength of 1064 nm.
• the glass interface (5) is permanently or removably connected to the irradiation head of the pulsed laser (4) by a fastening system (9) or integrated into the irradiation head of the laser. laser, preferably on the front face of said head.
• the irradiation head of the laser (4) to which the glass interface (5) is connected via the attachment system (9) is intended to be placed outside the liquid medium ( Figure 1 ).
• the glass interface (5) is intended to be placed on the surface of the liquid medium (2).
• the irradiation head of the laser (4) to which the glass interface (5) is connected via the attachment system (9) or integrated is able to be totally or partially immersed. in the liquid medium (2).
• the irradiation head (4) is surrounded by a sealed compartment (10) (FIG. 2).
• the total or partial immersion of the irradiation head (4) in the liquid medium advantageously makes it possible to be able to implement the method according to the invention easily in various configurations.
• the system for circulating the liquid medium (8) comprises a motor (7) and a nozzle (6), said nozzle being intended to be immersed in the liquid medium (2) and arranged between the interface (5) and the metal part (1), along an axis parallel to the metal part.
• the device according to the invention comprises a system for collecting the liquid comprising a pipe, one end of which communicates with the liquid medium and the other end communicates with a compartment for collecting the liquid, and a connected pump. directly or indirectly to said conduit and capable of sucking the liquid.
• the present invention also relates to the use of a device according to the present invention for decontaminating a metal part containing a gas, preferably tritium, by laser in a liquid medium.
• a device according to the present invention for decontaminating a metal part containing a gas, preferably tritium, by laser in a liquid medium.
• the pulsed laser used emits at a wavelength of 1064 nm, has a power of 100 W, a frequency of 100 KHz and a focal length of 100 mm. Several distances between the metal part and the surface of the liquid were tested. Ten successive passes were carried out, with a total duration of about 80 seconds and an overlap of 10%.
• the method implemented does not allow the samples to be effectively and homogeneously stripped in the presence of water, regardless of the distance between the part and the surface of the liquid.
• the formation of bubbles of pickled material is observed, formed on the surface of the metal parts.
• the presence of fumes at the surface of the compartment comprising the liquid medium and in which the metal part is placed has also been observed.
• the process tested is not capable of abrading the base metal of the part.
• Example 2 Implementation of an optimized process for the decontamination of a metal part in a liquid medium by a pulsed laser with a liquid circulation system.
• Example 1 The same conditions relating to the material and method as for Example 1 were implemented.
• a liquid circulation system has been implemented in this process.
• This system comprises a motor and a rotating propeller submerged in the liquid compartment, located in the horizontal axis of the metal part.
• Example 3 Implementation of a method for decontaminating a metal part according to the invention.
• This study aims to determine the efficiency of a pulsed laser in the presence of a glass interface and a liquid circulation system, to decontaminate a metal part containing a gas in the base metal in a liquid medium. . Abrasion of the base metal of the part to a depth of at least 6 ⁇ m will be considered representative of the depth of contamination of a metal part with tritium.
• the metal part was immersed in a compartment comprising demineralized water as a liquid medium, with a glass interface transparent to the 1064 nm wavelength of the laser, with a thickness of 5 mm.
• the glass interface is placed on the surface of the liquid medium, between the pulsed laser beam and the metal part.
• the metal part is placed at a water height below the surface of 25 mm.
• the liquid circulation system comprises a motor and a nozzle, the nozzle being immersed in the compartment, arranged between the interface and the part, along an axis parallel to the metal part.
• the pulsed laser implemented in the present study emits at a wavelength of 1064 nm, has a power of 100 W, a frequency of 100 KHz, a focal length of 140.3 mm. Several passes of the laser beam over the same area of the part were tested.
• the capacity of the process to avoid the phenomena of material bubbles on the surface of the metal plate and to avoid the formation of fumes on the surface of the liquid was analyzed visually.
• Surface topography analyzes by optical 3D measurements were carried out, in the same direction as the laser treatment and with a profile width of 0.5 mm, to characterize the step height between the reference surface and the etched surface.
• the step height represents the difference in height between the surface of the part not treated by the laser and that treated.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
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• Optics & Photonics (AREA)
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• Food Science & Technology (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

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Citations (5)

• 2019
  • 2019-10-03 FR FR1910974A patent/FR3101558B1/fr active Active
• 2020
  • 2020-09-16 WO PCT/FR2020/051598 patent/WO2021064304A1/fr unknown
  • 2020-09-16 EP EP20786025.5A patent/EP4038642A1/de active Pending
  • 2020-09-16 JP JP2022519988A patent/JP2022550787A/ja active Pending

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