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
  • G21F9/04—Treating liquids
• • 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
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F3/00—Electrolytic etching or polishing
  • C25F3/16—Polishing

Definitions

• the invention relates to an electropolishing process for the purpose of decontamination of parts of plants in nuclear plants.
• dilute sulfuric acid or dilute phosphoric acid is used.
• the sponge electrode is used to wipe the surface to be decontaminated when the voltage is switched on. With this method, a very thin surface layer with the surface-attached impurities is removed and the removal is washed away with the electrolyte solution of deionized water and electrolyte.
• the radioactivity of contaminated surfaces can easily be reduced by more than a power of ten.
• the acid used in decontamination contains radioactive residues from the material removal after decontamination and must therefore be disposed of at great expense.
• the disposal effort is Considerable in terms of both costs and personal protection.
• the acidic solutions that remain after decontamination are collected in special containers and transported to processing plants. Special shielding is required in the factory and during transport in order to reduce the radioactive radiation into the environment to the permissible level.
• the object of the invention is to reduce the radiation exposure of the personnel during the decontamination of system parts on the one hand and the technical and financial outlay of such measures on the other.
• deionate is used for electropolishing, which is enriched to ensure electrical conductivity with an electrolyte which can be worked up by the factory water treatment system.
• the solution that remains after decontamination no longer needs to be transported in shielded containers, but can be transported through the company's own water purification or treatment system can be refurbished.
• the resulting salts can be filtered out.
• the component to be decontaminated leaks into other system parts, for example into a connected pipeline, it is possible to dispense with a special suction of the leaked liquid. From there, it gets to the factory water treatment plant without further measures, where it is treated. This significantly reduces the radiation exposure of the personnel.
• those electrolytes that are present in the primary coolant can be added to the deionate. This reliably prevents damage to materials due to electrolyte residues remaining in the adjacent system parts, because the electrolytes used are present in the primary coolant anyway and the materials used are designed for these electrolytes.
• the temperature of the deionate enriched with an electrolyte is increased above the ambient temperature. This increases its conductivity, which improves the result of the decontamination.
• a sponge electrode is inserted whose distance from the surface of a component to be treated is less than 10 mm. A largely complete decontamination is thus achieved.
• the inner wall of a pressure line in the primary circuit of a nuclear reactor is intended for the purpose of implementation be decontaminated from maintenance work, for example an electropolishing device can be used, as disclosed in German Offenlegungsschrift 33 45 278.
• an electropolishing device can be used, as disclosed in German Offenlegungsschrift 33 45 278.
• the electrolyte solution used there mostly dilute sulfuric acid - deionate is used, to which boric acid, for example, has previously been added. Since the electrical conductivity that can be achieved with boric acid is significantly lower than the conductivity that can be achieved with sulfuric acid, the current flow and thus the erosion per unit of time will also be lower.
• the deionate enriched with boric acid supplied to the sponge electrodes can be warmed up before being introduced into the sponge electrode.
• the limit temperature to be maintained is limited by the temperature resistance of the sponge and the other components of the sponge electrode and by the formation of steam. Temperatures of the deionate enriched with boric acid around 75 ° C are realistic when using temperature-resistant sponges.
• the thickness of the sponge used ie the distance of the metallic part of the sponge electrode from the surface to be decontaminated, can be reduced. Sponge thicknesses of 10 mm and below, preferably 5 mm, can be used well.
• the operation of the electropolishing device can be carried out in a conventional manner, as is known from DE-OS 33 45 278 or DE-OS 33 43 396.
• a heater for heating the electrolyte solution to the supply line to the sponge electrode.
• the boron acid-enriched deionate with the removed surface substances, including the radioactive material originally attached to the surface is located in a collecting container for the electrolyte solution.
• the interior of the tube or container treated in this way is left with small amounts of Electrolyte solution contaminated.
• the nuclear power plant can be put into operation again after the decontamination without cumbersome extraction of the remaining electrolyte solution quantity.
• the resulting slight increase in the boric acid content in the coolant can easily be worked up by the factory water treatment system. This saves the human effort that would otherwise be required with the extraction.
• the amount of electrolyte solution in the collecting container can also be gradually fed to the factory water treatment system after filtering off the removed material, processed there and fed to the primary coolant.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Physics & Mathematics (AREA)
• High Energy & Nuclear Physics (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Food Science & Technology (AREA)
• General Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Apparatus For Disinfection Or Sterilisation (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=6359787

Family Applications (1)

Country Status (8)

Cited By (1)

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Citations (3)

Family Cites Families (4)

• 1989
  • 1989-07-17 DE DE8989113091T patent/DE58904254D1/de not_active Expired - Fee Related
  • 1989-07-17 EP EP89113091A patent/EP0352594B1/fr not_active Expired - Lifetime
  • 1989-07-17 ES ES89113091T patent/ES2042895T3/es not_active Expired - Lifetime
  • 1989-07-24 JP JP1191216A patent/JP2750909B2/ja not_active Expired - Lifetime
  • 1989-07-27 RU SU894614625A patent/RU2009557C1/ru active
  • 1989-07-27 BR BR898903736A patent/BR8903736A/pt not_active Application Discontinuation
  • 1989-07-28 US US07/387,069 patent/US5019228A/en not_active Expired - Fee Related
  • 1989-07-28 KR KR1019890010704A patent/KR900002341A/ko not_active Application Discontinuation

Patent Citations (3)

Non-Patent Citations (1)

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