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
  • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D11/00—Solvent extraction
  • B01D11/02—Solvent extraction of solids
  • B01D11/0261—Solvent extraction of solids comprising vibrating mechanisms, e.g. mechanical, acoustical
• • 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
  • B08B3/12—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 by sonic or ultrasonic vibrations

Definitions

• This invention relates to methods of removing radioactive material adhering to articles, an operation usually termed decontamination, and is especially directed to a process utilizing ultrasonic waves for that purpose.
• An object of the invention is to provide a novel decontamination method that will remove substantially all adherent radioactive material, substantial removal being intended to mean that, if there should be any residue of such material, its effects will be negligible and inconsequential.
• a further objective is to provide such a method that will not involve scrubbing or other abrasive operations, and which will be basically mechanical and not manual.
• An object of the invention is to provide a method of preventing contamination of the container during ultrasonic decontamination of articles in liquid.
• a related purpose is to accomplish this object by a simple, inexpensive and readily operated procedure.
• a further purpose is to provide a novel and improved method of facilitating the disposal of liquid canrying radioactive material.
• Another purpose is to prevent the contamination of the indicated container and also facilitate disposal of contaminated liquid by a single method.
• the material of which the inner container is made, and the thickness of such material, must be selected so that the ultrasonic waves will pass through the inner container into the liquid therein with suflicient energy to produce adequate cavitation therein.
• Materials having relatively low impedance to ultrasonic waves and low reflectance at an interface with liquids are required, among them being glass, metals and synthetic resins, comprising metal foils, especially aluminum and copper, and synthetic resin sheet material, particularly polyethylene and polyvinyl resins.
• the thickness of the container material must also be selected between a maximum at which the transmittal of ultrasonic waves at normal ultrasonic cleaner energies is impeded to the point where cavitation within the inner container is insuflicient for adequate cleaning, and a minimum at which the material is ruptured by the waves and cavitation. These limits necessarily vary, not only with different types of material but with diflerent kinds of each .maten'al; but for any given species of material for use in a particular ultrasonic cleaner a suitable thickness can be selected.
• An important feature of the invention is the use of flexible material for the inner container, since the latter can be readily closed and sealed after the cleaned articles are removed, greatly facilitating safe disposal of the contaminated liquid.
• Inner containers of this type can be supported in the container or bowl of the cleaner in various ways, one simple arrangement being to use an inner container of about the same top circumference as the outer container top, and bend the margin of the inner container outwardly over the top of the outer container. This is especially effective when the inner container material is somewhat elastic.
• metal foil When metal foil is used, its thickness likewise should not be greater than one-sixteenth of an inch in order to avoid objectionable loss of energy. With foil there is more danger of rupture by cavitation; and when standard commercial aluminum foil is used, a thickness greater than five thousandths of an inch should be used.
• Other metal foils that may be employed include lead, copper and tin foils. The tin or copper foil should not be less than one-thousandth of an inch thick, and neither should be more than one-sixteenth of an inch thick. Ordinary commercial grades of these foils may be used. However, the foil thickness will of course be adequate to avoid rupture by the inserted articles or by handling during disposal.
• the liquid detergent will be selected in accordance with the character of the contaminants following established practicein ultrasonic cleaning in liquids. It maybe water, an-aqueous solution ofdetergent substancesgor a liquid of a different character, which may be basically.
• the inner container is 1nserted in the outer container. or bowl of the ultrasonic cleaner, filled with liquid and the articles to be decontaminated are submerged in the liquid.
• the space bea tween the containers will also be filled with liquid- The.
• An additional step which constitutes a-further feature of the invention greatly reduces, and in practice 'substantially eliminates, any material danger of objectionable effects from the radioactive particles in the cleaning liquid.
• This is accomplished by mixing with the liquid a material which adsorbs such particles.
• Such material is advantageously in finely divided form .-and is added after the cleaned articles areremoved from the. inner container.
• the liquid containing theadsorptivematerial may be agitated, asby shaking tbe container or stirring, to obtain uniform distribution and the consequent removal from the liquid of the greater part of the radioactive substance.
• iron oxides activated charcoal, halogen salts, manganese dioxide and clays, especially fullers earth. -These substances are of course most effective when introducedin very fine or pulverulent form.
• the adsorbent used should be selectedv on the basis of the particular radioactive substance or substances that produce the contamination, since each-radioactive substance'is adsorbedmore.
• Example I isinserted in the bowl with the upper edge of the con-- 4 Y tainer bent outwardly over the margin of the bowl.
• Detergent'liquid is poured into the foil container and liquid, which may be water or detergent liquid, is poured between the'foil container and the bowl. Articles to be. cleaned are placed in the liquid in the container and the cleaner is operated to produce cavitatignin such liquid 7' I
• Example 3 The procedure 'of Example 1 is followed toclean 'arti- .cles contaminated with radioactive cesium. After the,
• Example 4 A-container' formed of a flexible sheet of -'polyethylene, plastic, 0.01 inch thick, is placed in the bowl of' an ultra? 'sonic cleaner and the upper edge of the container is turned outwardly aroundthe bowl margin with the conof-the articles. When'cleaning iscompleted the'articles are removed, the upper. margin of the plasticcontainer;
• ultrasonic refers to V mechanical wave action and does not refer to a wave action limited to any frequency or frequency range within or above the range of audible frequencies.
• the method of removing radioactive material from a contaminated article by the action of ultrasonic waves in cleaning apparatus provided with a bowl which comprises inserting in the bowl an inner container, placing detergent liquid in such container, submerging the article in the liquid, transmitting ultrasonic waves from the bowl into the liquid to produce cavitation at the surface of the article, removing the article from the liquid after removal of such material therefrom, mixing with the liquid a finely divided adsorbent of the radioactive material, and sealing the liquid in the container in condition for disposal.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Food Science & Technology (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Cleaning By Liquid Or Steam (AREA)
• Water Treatment By Sorption (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

Family

ID=24458803

Family Applications (1)

Country Status (4)

Cited By (10)

Families Citing this family (3)

Citations (10)

• 0
  • NL NL221303D patent/NL221303A/xx unknown
  • NL NL103068D patent/NL103068C/xx active
• 1956
  • 1956-10-04 US US613819A patent/US3007814A/en not_active Expired - Lifetime
• 1957
  • 1957-10-01 GB GB30724/57A patent/GB839402A/en not_active Expired
  • 1957-10-04 FR FR1183942D patent/FR1183942A/fr not_active Expired

Patent Citations (10)

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