Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof

Definitions

• This invention relates to a method of decontaminating radioactive metal surfaces.
• the invention relates to a method of decontaminating difficulty accessible surfaces such as the walls and ceiling of a reactor vessel.
• the invention relates to a method of decontaminating radioactive surfaces wherein the decontaminating agent will be directed into a waste system containing aluminum ions.
• radioactive conlamination During the operation of a nuclear reactor, radioactive conlamination accumulates on the walls and contents of the main reactor vessel of the reactor above the reactor core. The consequent health hazard to maintenance men severely limits the length of time they may safely spend in this portion of the reactor during a shutdown. Similarly, other surfaces exposed to an atmosphere containing radioactive particles, such as those of a hot cell, may become contaminated and require decontaminating treatment.
• Such surfaces could, of course, be decontaminated by scrubbing them with a solution containing a chemical reagent which will remove the radioactive contamination from the surfaces. Scrubbing the surfaces is, however, not possible due to the difficulty of access to the surfaces and the radioactivity of the surfaces. The surfaces could be sprayed with the solution without undue hazard to personnel, but experience has shown that adequate decontamination cannot be obtained in this manner.
• Oxalic acid does not require an excessive amount of foaming agent even at fairly high concentration and alkaline permanganate requires even. less.
• incorporation of the foaming agent in alkaline permanganate results in rapid reduction of the deep purple permanganate to the green manganate ion and then to a precipitate of brown manganese dioxide.
• the volume of radioactive waste solution generated by chemical reagent-in-foam decontamination is signifi: cantly less than for any other aqueous decontamination system presently available.
• reagents may be arranged in order of their effectiveness in foam decontamination of stainless steel.
• reagents are effective in the order oxalic 452l ammonium citrate.
• the improvement is not sufficient to outweigh the disadvantage of having to prepare and use two different foams.
• oxalic acid foams alone are preferred for reactor use since it is not desirable to permit manganese ions to enter the reactor coolant system since an additional radioactive species would be added to the coolant. Since the foam condenses to the surface of the coolant water above the reactor core in reactor vessel decontamination, at least some of the foam components will diffuse into the body of the coolant system. Thus oxalic acid alone is preferred for reactor use.
• a specific product found acceptable contains as the active ingredient a condensation product of a hydrocarbon-substituted phenol with formaldehyde into which a hydrophyllic group is introduced. Such products form the subject matter of U.S. Pat. No. 2,454,541.
• the product is a proprietary product of Turco Products, identified as Turco 4527. it was first determined that Turco 4527 has suitable foaming characteristics. From the standpoint of decontamination, the stability factors of greatest interest are the rate of drainage of liquid from the foam and the expansion (volume of foam/volume of liquid in the foam).
• Turco 4527 is compatible with the decontaminating reagents to be used. Both oxalic acid and Turco 4521 had practically no effect on the foaming properties of Turco 4527. On the other hand, oxalic acid has a moderate inhibitory effect and Turco 4521 has a very pronounced inhibitory effect on Fome-Add.
• the extent of contamination removal was estimated by taking radiation readings before and after each treatment. From the two measurements a decontamination factor (D.F.) was calculated. The readings were taken with a .luno survey meter placed three-fourth inch from the surface of the specimen which was enclosed in one layer of polyethylene. The tubing was not uniformly contaminated and initial radiation readings varied by as much as 30 percent per sample as it was rotated under the metering device. Therefore, high and low readings were taken each time and, correspondingly, two decontamination factors calculated. The samples were placed in 400 ml. glass beakers so that they leaned at approximately a 60 angle. The beaker was then filled with foam. When the foam had completely broken out, the samples were rinsed with water and acetone and dried prior to taking a final reading.
• D.F. decontamination factor
• a method of decontaminating the radioactive surfaces of the reactor vessel of a nuclear reactor consisting of the steps of producing an aqueous foam from a solution of oxalic acid containing a nonionic foaming agent, carrying the oxalic acid to the surfaces to be decontaminated in the form of said aqueous foam, and contacting said surfaces with said foam whereby the oxalic acid attacks the radioactive contamina' tion.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Food Science & Technology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Detergent Compositions (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25168541

Family Applications (1)

Country Status (5)

Cited By (18)

• 1969
  • 1969-02-04 US US796579A patent/US3615817A/en not_active Expired - Lifetime
• 1970
  • 1970-01-20 AU AU10454/70A patent/AU1045470A/en not_active Expired
  • 1970-01-29 BE BE745126D patent/BE745126A/xx unknown
  • 1970-02-02 DE DE19702004600 patent/DE2004600A1/de active Pending
  • 1970-02-03 FR FR7003748A patent/FR2030290A7/fr not_active Expired

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