EP0091646B1 - Méthode de décontamination par laser - Google Patents

Méthode de décontamination par laser Download PDF

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Publication number
EP0091646B1
EP0091646B1 EP83103326A EP83103326A EP0091646B1 EP 0091646 B1 EP0091646 B1 EP 0091646B1 EP 83103326 A EP83103326 A EP 83103326A EP 83103326 A EP83103326 A EP 83103326A EP 0091646 B1 EP0091646 B1 EP 0091646B1
Authority
EP
European Patent Office
Prior art keywords
laser
steam generator
approximately
laser beam
manway
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP83103326A
Other languages
German (de)
English (en)
Other versions
EP0091646A1 (fr
Inventor
Thaddeus A. Wojcik
Herbert E. Ferree
William H. Kasner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CBS Corp
Original Assignee
Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Publication of EP0091646A1 publication Critical patent/EP0091646A1/fr
Application granted granted Critical
Publication of EP0091646B1 publication Critical patent/EP0091646B1/fr
Expired legal-status Critical Current

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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
    • F22B37/003—Maintenance, repairing or inspecting equipment positioned in or via the headers
    • 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
    • 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

Definitions

  • This invention relates to decontamination methods and more particularly to methods for decontaminating components of nuclear power plants with the aid of lasers.
  • a solution of this problem may be to reduce the radiation field associated with the component to allow the working personnel a longer working time.
  • One approach for reducing the radiation field associated with the nuclear component on which the repair operation is to be performed is to remove the deposited film of radioactive metal oxides from the exposed surfaces of the nuclear component.
  • an abrasive grit may be sprayed against the component to abrade the oxide film from the component thereby lowering the radiation field associated with the component.
  • chemical processes have been attempted to dissolve the oxide film from the component to thereby remove the oxide film and associated radiation field from the component.
  • the present invention resides in a method for decontaminating interior walls of a radioactive nuclear steam generator having a manway by removing a thin oxide layer of radioactively contaminated metal from the surface of said walls thus lowering the radiation level within said steam generator so as to permit human access, characterized in that a remotely movable reflective mechanism is removably placed into said steam generator through said manway, a Neodymium YAG pulsed laser beam generator is arranged outside said steam generator and operated so as to direct a laser beam onto said reflective mechanism and the reflective mechanism is remotely operated such that said walls are scanned by the laser beam, said laser beam having an energy density of 4.6 to 23 joules/cm 2 adapted to achieve a thermal penetration corresponding to the thickness of said oxide layer and that the contaminants released from said surface are sucked off through said manway and transported away from said steam generator.
  • a one-dimensional surface heating model of a laser beam interacting with a surface is generally known in the art. This model assumes that the laser beam is uniform with no transverse variation and that the surface film is approximately uniform. The model also assumes that the surface is plane and normal to the incident laser beam. These conditions are approximately true if:
  • the first condition is satisfied in most situations where the laser beams are 0.1 to 1 cm in diameter and the oxide films of interest are typically less than 10- 4 cm (approximately 40 microns). In the case of typical nuclear components, the transverse dimensions of the actual laser beam are much greater than the oxide film thicknesses of the nuclear reactor component which satisfied the first condition.
  • the second condition requires consideration of the thermal diffusivity for the material and the laser pulse length. For typical metals and metal oxides of nuclear reactor components, the thermal diffusivity is approximately 0.2 cm sq. per second.
  • the distance that the thermal wave will advance into such a material during a typical laser pulse length of approximately 1 microsecond is approximately 4.0 x 10- 4 cm which easily satisfies the second condition that the transverse dimensions of the actual laser beam be much greater than the thermal diffusion distance into the material.
  • the third condition should be satisfied over most of the area of the nuclear component, because the lateral scale size for changes in the surface contour and oxide thickness is much greater than the average oxide thickness itself. Therefore, it appears that a one-dimensional surface heating model of a laser beam interacting with an oxide covered surface will adequately predict the interaction of a suitable laser on the oxide layer of a nuclear component.
  • the oxide films encountered on nuclear components are typically less than approximately 10- 4 cm thick. It has been found that to achieve thermal penetration depths comparable to the film thicknesses on these components thereby avoiding extensive thermal damage to the base metal, the layer pulse length should be approximately one microsecond in duration. Q-switched YAG laser can be used to satisfy this pulse length criteria.
  • the penetration depth of a pulse of the laser it is also important to be able to determine the oxide surface temperatures as a function of the incident laser pulse length so as to be able to ascertain the laser energy densities required.
  • high surface temperatures of approximately 2,000 ⁇ 3,000°K are generally required. Since short laser pulses of approximately 1 microsecond are required to limit the thermal penetration depth to avoid base metal damage and in order to achieve surface temperatures of approximately 2,000 ⁇ 3,000°K with a laser pulse length of approximately 1 microsecond, it is generally desirable to have laser energy densities of approximately 1.5 to 3 joules per square cm. Laser energydensities of approximately 1.5 to 3 joules per square cm. are easily produced by pulsed YAG lasers.
  • Steam generator 20 comprises an outer shell 22 with a divider plate 24 and tubesheet 26 disposed therein as is well known in the art.
  • Outer shell 22, divider plate 24, and tubesheet 26 define a plenum 28 through which the reactor coolant passes.
  • a manway 30 is provided in outer shell 22 for allowing access to plenum 28 by working personnel.
  • a reactor coolant flows through plenum 28 and through tubes 32 which are disposed through tubesheet 26. Since the reactor coolant flowing through steam generator 20 is radioactive, various surfaces of steam generator 20 become deposited with an oxide film that is radioactive.
  • the inner surface of shell 22, divider plate 24 and the lower surface of tubesheet 26 develop an oxide coating thereon that is radioactive.
  • working personnel may enter plenum 28 through manway 30 to perform maintenance on tubes 32.
  • the invention described herein provides a laser decontamination means for removing the oxide film on the surfaces of steam generator 20 to thereby reduce the radiation field associated with those surfaces.
  • an optical mechanism 34 may be placed in plenum 28 and suspended from tubesheet 26 by attachment to the open ends of tubes 32.
  • Optical mechanism 34 may comprise an electrically controlled movable reflective mechanism 36 for reflecting radiation, such as light, to various surfaces of the steam generator.
  • reflective mechanism 36 may comprise a plurality of mirrors or prisms attached to the bottom of optical mechanism 34 for reflecting radiation that is directed to those reflective surfaces.
  • Optical mechanism 34 is connected electrically by electrical line 38 to an optical mechanism power supply 40 which may be located remote from steam generator 20 and separated from steam generator 20 by a biological shield 42. In this manner, optical mechanism 34 may be remotely controlled and manipulated so that the operator is not exposed to the radiation field associated with steam generator 20.
  • Optical mechanism power supply 40 provides a means by which optical mechanism 34 may be adjusted so as to change the reflective angles of the mirrors or prisms of reflective mechanism 36 which thereby redirects the radiation that is reflected from the mirrors or prisms to the desired surface to be decontaminated.
  • a power laser 46 as previously described herein may be arranged near the opening of manway 30 so that the radiation emitted from power laser 46 may be directed toward optical mechanism 34 as shown in the drawing.
  • Power laser 46 may be mounted on a support fixture 48 that is capable of moving power laser 46 relative to manway 30 and relative to optical mechanism 34 for properly aligning the radiation beam emitted from power laser 46.
  • Support fixture 48 may be mounted on a generator platform 50 arranged near the opening of manway 30.
  • Power laser 46 is connected electrically by electrical line 52 to laser power supply 54 located remote from steam generator 20 and behind a biological shield 42.
  • Power laser 46 may be a laser capable of emitting pulses of radiation with pulse lengths of less than 100 microseconds and preferably less than approximately 1 microseconds in duration. Power laser 46 may also be capable of emitting pulses having a wavelength of less than approximately 12 micrometers and preferably between approximately 0.30 to 1.5 micrometers for typical decontamination applications. In addition, power laser 46 may be capable of producing pulses with energy densities of between 0.5 to 1.5 x 10 3 joules/ cm 2 and preferably of approximately 4.5-23 joules/cm 2 at the surface to be decontaminated. Of course, typical optical instruments such as lenses and mirrors may be employed in conjunction with power laser 46 to achieve the desired energy densities at the surface.
  • power laser 46 is a Neodymium YAG pulsed laser capable of emitting pulses of radiation with a wavelength of approximately 1.06 micrometers, an energy output of approximately 0.3 joules/ pulse, a pulse length of approximately 30-40 nanoseconds and an energy density of approximately 8-9 joules/cm 2 .
  • a shield plate 56 having an aperture 58 may be bolted to the outside of manway 30 for isolating plenum 28 from the outside of steam generator 20 for containing the contaminants removed from the surfaces of plenum 28.
  • Aperture 58 is provided for allowing the radiation beam from power laser 46 to pass therethrough and at optical mechanism 34.
  • a suction mechanism 60 is attached to shield plate 56 and extends therethrough into plenum 28 and may extend at the other end to a radioactive waste filtering system 62.
  • Suction mechanism 60 provides a means by which the contamination removed from plenum 28 is suctioned out of plenum 28 and into a radioactive waste filtering system 62 for disposal of the waste.
  • steam generator 20 is deactivated and the reactor coolant is drained therefrom.
  • the manway cover is removed from manway 30 and optical mechanism 34 is suspended from tube sheet 26 either manually or remotely.
  • Shield plate 56 is then attached to manway 30 and power laser 46 is arranged near aperture 58 as shown in the drawing.
  • power laser 46 is activated by laser power supply 54 so that a beam of radiation is emitted from power laser 46 and directed toward the reflective surfaces of optical mechanism 34. From the reflective mechanism 36 of optical mechanism 34, the radiation emitted from power laser 46 is reflected toward the selected surface of the interior of steam generator 20.
  • Power laser 46 may be pulsed with a pulse length of approximately 30-40 nanoseconds and at an energy level of approximately 0.3 joules/pulse so as to impinge the surface to be decontaminated with an energy density of approximately 8-9 joules/ cm 2 (50-60 joules/in 2 ).
  • the laser radiation is such that it removes an oxide layer of approximately 0.0005 mm. from the surfaces of plenum 28 and thereby reduces the radiation field associated with the oxide film without damaging the base metal.
  • the oxide layer removed is exhausted from plenum 28 by means of suction mechanism 60.
  • optical mechanism 34 is controlled so as to allow the laser beam from power laser 46 to scan all of the surfaces of the interior of plenum 28. In this manner, the entire interior of plenum 28 may be decontaminated.
  • the invention provides a decontamination method that reduces the radiation field in components of nuclear reactor power plants without damaging the component.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Optics & Photonics (AREA)
  • Food Science & Technology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Cleaning In General (AREA)
  • Laser Beam Processing (AREA)
  • Apparatus For Disinfection Or Sterilisation (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)

Claims (4)

1. Procédé pour décontaminer les parois intérieures d'un générateur de vapeur d'eau nucléaire radioactif comportant un trou d'homme en éliminant de la surface desdites parois une mince couche d'oxydes d'un métal contaminé de façon radioactive en diminuant ainsi le niveau de radiation à l'intérieur dudit générateur de vapeur d'eau de manière à permettre un accès aux personnes, caractérisé en ce que l'on place dans ledit générateur de vapeur d'eau en l'introduisant par ledit trou d'homme un mécanisme réflecteur pouvant être déplacé à distance, on dispose un générateur de faisceaux laser pulsé YAG au néodyme à l'extérieur dudit générateur de vapeur d'eau et on le fait fonctionner de manière à diriger un faisceau laser sur ledit mécanisme réflecteur et on commande à distance le mécanisme réflecteur de manière que lesdites parois soient balayées par le faisceau laser, ledit faisceau laser présentant une densité d'énergie de 4,6 à 23 joules/cm2 adaptée pour que l'on obtienne une pénétration thermique correspondant à l'épaisseur de ladite couche d'oxydes et en ce que l'on aspire à travers ledit trou d'homme les contaminants libérés de ladite surface et qu'on les évacue dudit générateur de vapeur d'eau.
2. Procédé selon la revendication 1, caractérisé en ce que l'on filtre le courant d'aspiration pour recueillir lesdits contaminants en vue de les mettre au rebut.
3. Procédé selon la revendication 1 ou 2, caractérisé en ce que ledit laser adapté pour fournir, à l'endroit de ladite surface, une densité d'énergie d'environ 8,5 joules/cm2.
4. Procédé selon la revendication 1, 2 ou 3, caractérisé en ce que l'on utilise un laser qui émet des impulsions d'environ 0,3 joules/impulsion présentant une durée d'impulsion de 30-40 na- nosecondes et une longueur d'onde d'environ 1,06 micromètres.
EP83103326A 1982-04-14 1983-04-06 Méthode de décontamination par laser Expired EP0091646B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US36807582A 1982-04-14 1982-04-14
US368075 1982-04-14

Publications (2)

Publication Number Publication Date
EP0091646A1 EP0091646A1 (fr) 1983-10-19
EP0091646B1 true EP0091646B1 (fr) 1986-12-30

Family

ID=23449771

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83103326A Expired EP0091646B1 (fr) 1982-04-14 1983-04-06 Méthode de décontamination par laser

Country Status (7)

Country Link
EP (1) EP0091646B1 (fr)
JP (1) JPS58187898A (fr)
KR (1) KR840004610A (fr)
CA (1) CA1198482A (fr)
DE (1) DE3368800D1 (fr)
ES (1) ES8703050A1 (fr)
FR (1) FR2525380A1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005009324A1 (de) * 2005-02-24 2006-09-07 Technische Universität Dresden Verfahren und Vorrichtung zur Dekontamination von Oberflächen
EP3706140A1 (fr) 2019-03-06 2020-09-09 Evekinger Rohr- und Profilwerke GmbH Dispositif et procédé de décontamination d'une surface de paroi d'un corps creux, en particulier tubulaire
DE102021110458A1 (de) 2021-04-23 2022-10-27 Evekinger Rohr- Und Profilwerke Gmbh Vorrichtung zur Behandlung einer Innenwandfläche eines Hohlkörpers

Families Citing this family (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2169496B (en) * 1985-01-16 1987-12-23 Stc Plc Cleaning metal surfaces
US5643472A (en) * 1988-07-08 1997-07-01 Cauldron Limited Partnership Selective removal of material by irradiation
US5821175A (en) * 1988-07-08 1998-10-13 Cauldron Limited Partnership Removal of surface contaminants by irradiation using various methods to achieve desired inert gas flow over treated surface
US5531857A (en) * 1988-07-08 1996-07-02 Cauldron Limited Partnership Removal of surface contaminants by irradiation from a high energy source
US6048588A (en) * 1988-07-08 2000-04-11 Cauldron Limited Partnership Method for enhancing chemisorption of material
FR2674983B1 (fr) * 1991-04-05 1994-08-05 Framatome Sa Procede et equipement de travail au laser dans une zone contaminee d'une installation nucleaire.
FR2678418B1 (fr) * 1991-06-26 1994-08-05 Framatome Sa Procede de travail au laser dans une zone contaminee d'une installation nucleaire, et equipement pour sa mise en óoeuvre.
EP0574564B1 (fr) * 1992-01-04 1997-04-16 British Nuclear Fuels PLC Procede de traitement d'une surface contaminee par des radionucleides
FR2700882B1 (fr) * 1993-01-26 1995-03-03 Commissariat Energie Atomique Procédé et installation de décontamination d'une surface radioactive au moyen d'un faisceau de lumière cohérente.
GB9322845D0 (en) * 1993-11-05 1993-12-22 British Nuclear Fuels Plc A method of treating a surface
GB9323052D0 (en) * 1993-11-09 1994-01-05 British Nuclear Fuels Plc Radioactive decontamination
JP2615362B2 (ja) * 1994-02-10 1997-05-28 理化学研究所 レーザによる表面付着物の除去方法及び装置
CA2162573A1 (fr) * 1994-03-10 1995-09-14 Tsutomu Fukuda Appareil servant a l'enlevement d'un revetement
GB9407058D0 (en) * 1994-04-09 1994-06-01 British Nuclear Fuels Plc Material removal by laser ablation
GB9412238D0 (en) * 1994-06-17 1994-08-10 British Nuclear Fuels Plc Removing contamination
DE69612411T2 (de) * 1995-01-31 2001-12-06 Toshiba Kawasaki Kk Unterwasserbehandlungsverfahren und -system
JP3461948B2 (ja) * 1995-02-06 2003-10-27 株式会社東芝 水中レーザ加工方法
TW284907B (en) * 1995-06-07 1996-09-01 Cauldron Lp Removal of material by polarized irradiation and back side application for radiation
US5780806A (en) * 1995-07-25 1998-07-14 Lockheed Idaho Technologies Company Laser ablation system, and method of decontaminating surfaces
FR2887161B1 (fr) * 2005-06-20 2007-09-07 Commissariat Energie Atomique Procede et dispositif d'ablation laser d'une couche superficielle d'une paroi, telle q'un revetement de peinture dans une installation nucleaire
JP5500620B2 (ja) * 2009-04-28 2014-05-21 独立行政法人日本原子力研究開発機構 除染装置及び除染方法
US10112257B1 (en) 2010-07-09 2018-10-30 General Lasertronics Corporation Coating ablating apparatus with coating removal detection
US9895771B2 (en) 2012-02-28 2018-02-20 General Lasertronics Corporation Laser ablation for the environmentally beneficial removal of surface coatings
KR101437384B1 (ko) * 2013-01-31 2014-09-15 대한민국 Nd:YAG 레이저를 이용한 칠박도금 표면의 오염물 및 칠 층 제거방법
FR3100002B1 (fr) 2019-08-21 2021-11-19 Onet Tech Cn Procédé pour décontaminer par laser pulsé une pièce métallique comprenant à sa surface une couche d’oxydes de métaux
FR3101558B1 (fr) 2019-10-03 2021-10-22 Onet Tech Cn Procédé pour décontaminer une pièce métallique contenant un gaz par irradiation laser dans un milieu liquide

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1382915A (en) * 1972-04-25 1975-02-05 British Nuclear Fuels Ltd Decontamination of fuel element sheaths
LU71852A1 (fr) * 1975-02-14 1977-01-05

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005009324A1 (de) * 2005-02-24 2006-09-07 Technische Universität Dresden Verfahren und Vorrichtung zur Dekontamination von Oberflächen
DE102005009324B4 (de) * 2005-02-24 2007-11-22 Technische Universität Dresden Verfahren und Vorrichtung zur Dekontamination von Oberflächen
DE102005009324B9 (de) * 2005-02-24 2008-05-21 Technische Universität Dresden Verfahren und Vorrichtung zur Dekontamination von Oberflächen
EP3706140A1 (fr) 2019-03-06 2020-09-09 Evekinger Rohr- und Profilwerke GmbH Dispositif et procédé de décontamination d'une surface de paroi d'un corps creux, en particulier tubulaire
DE102021110458A1 (de) 2021-04-23 2022-10-27 Evekinger Rohr- Und Profilwerke Gmbh Vorrichtung zur Behandlung einer Innenwandfläche eines Hohlkörpers
DE102021110458B4 (de) 2021-04-23 2022-12-29 Evekinger Rohr- Und Profilwerke Gmbh Vorrichtung zur Behandlung einer Innenwandfläche eines Hohlkörpers

Also Published As

Publication number Publication date
FR2525380A1 (fr) 1983-10-21
JPS58187898A (ja) 1983-11-02
KR840004610A (ko) 1984-10-22
DE3368800D1 (en) 1987-02-05
CA1198482A (fr) 1985-12-24
JPH0145039B2 (fr) 1989-10-02
ES8703050A1 (es) 1987-01-16
ES521391A0 (es) 1987-01-16
FR2525380B1 (fr) 1985-04-19
EP0091646A1 (fr) 1983-10-19

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