Cleaning and liquid contact with solids – Processes – Including regeneration – purification – recovery or separation...
Reexamination Certificate
2001-10-12
2002-12-24
Carrillo, Sharidan (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including regeneration, purification, recovery or separation...
C134S002000, C134S003000, C134S026000, C134S028000, C134S022190, C134S041000, C134S042000, C510S110000, C376S308000, C376S309000, C376S310000, C423S002000, C423S003000, C423S020000, C588S001000, C588S020000, C210S682000, C210S688000, C976SDIG003, C976SDIG003
Reexamination Certificate
active
06497769
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a method for decontamination of surfaces. More particularly, the present invention relates to using an acidic solution to remove radioactive contaminants from a given area, location or surface.
Contamination of various areas or surfaces from radioactive or other unwanted materials is a common problem. The contamination of an area or surface may occur as a result of contact with a radioactive isotope during transport, storage, use in a nuclear reactor, mining operations, or a variety of other industrial or military processes. In recent years, methods have been explored to reduce or remove such contaminants from various areas or surfaces and equipment so that such items or areas may be put back into use and the contaminants be disposed of safely. These methods have met with varying success and often present trade-offs between decontamination of the surface or area and the toxicity of the waste product containing the radioactive contaminant.
One method of removing radioactive materials is to physically wash the contaminated area or surface with water and an optional surface-active agent. However, such methods are generally limited to physical separation of contaminants that are not physically or chemically adhered to surfaces or areas. Thus, this method does not work well where the contaminants are chemically bound to a solid surface or structure.
For example, a number of methods have been developed to remove radioactive contaminated scale or rust deposits from metal surfaces. The radioactive substances are removed in a solution that is transported at safe levels for disposal. However the concentrated radioactivity found in scale or rust adhering to surfaces presents increased danger and cost in removal and disposal. Depending on the type of scale or rust deposit either acidic or basic treatments may be appropriate. U.S. Pat. Nos. 5,200,117, 5,049,297 and 5,824,159 illustrate typical approaches to removing radioactive substances in these situations.
Another method for removing contaminants from surfaces or areas, which are not necessarily limited to deposited scales, is known generally as acid leaching. In acid leaching methods, a strong acid is used to dissolve radioactive contaminants from the surface into solution. The resulting solution is removed and disposed of leaving a clean, or at least a reduced amount of radioactive contaminants, on the surface. Such acid leaching processes may or may not use chelating agents.
Chelating agents have been the subject of much research in this area and include ligand or binding agents such as oxalate, citrate, gluconate, picolinate, EDTA, hydrazines with a carboxylic acid, and hydroxamic acids. Acidic and basic solutions containing a chelating agent are used to dissolve and bind contaminants depending on the characteristics of the surface and the contaminants. When used to remove radioactive substances from contaminated areas, the chelating agent is thought to have the effect of stabilizing certain dissolved radioactive contaminants to keep them in solution. Several of these methods use concentrated carbonate solutions to recover uranium, thorium, radium, technetium, and other actinides.
With several of these methods, a separate ion-exchange process is used to purify the resulting solution to make disposal of the radioactive contaminants easier.
In addition n to these challenges, other considerations include providing a decontaminating agent and method which is not excessively corrosive and is easy to prepare and use. Further, the solution containing removed contaminants should preferably be easily disposed of in compliance with state and federal regulations. It would therefore be a significant advancement and contribution to the art to provide a method which is a simple, economic, and an effective way of removing substantially all of radioactive contaminants from various surfaces or areas.
SUMMARY OF THE INVENTION
While many methods for removing radioactive or other unwanted contaminants have been developed there remains the need for improved decontamination methods which speed up the decontamination process and remove substantially all of the radioactive contaminants.
The present invention relates to the removal of radioactive contaminants from a surface or area using a highly acidic solution which includes a complex substituted keto-amine
The present invention provides a method for removing radioactive contaminants from a surface or area comprising the steps of: forming a solution containing a complex substituted keto-amine, a mixture of saturated and unsaturated lower alkanols, e.g. isopropyl alcohol and propargyl alcohol, and a concentrated acid or acid mixture to form an acidic solution; applying the keto-amine, lower alkanol mixture and acidic solution in such a manner as to contact the contaminants on the surface or in the area such that at least a portion of such radioactive or other contaminants migrate into the acidic solution; collecting the contaminant rich acidic solution for further treatment or disposal.
In accordance with a more detailed aspect of the present invention, the concentrated acid is selected from strong acids consisting of the group hydrochloric acid, hydrofluoric acid, sulfuric acid, phosphoric acid, sulfurous acid, bromic acid, iodic acid, nitric acid, perchloric acid, oxalic acid, aqua regia (nitrohydrochloric acid) and mixtures thereof. In a more detailed aspect, the resulting acidic solution using one of the above acids has a pH of less than 1.5.
In accordance with yet another more detailed aspect of the present invention, the method is used to remove radioactive contaminants, and particularly those found in the actinide and lanthanide series such as thorium, uranium, and plutonium. Exemplary of radioactive contaminants, some of which are in the actinide and lanthanide series, are Actinium-227, Americium-241, Americium-243, Antimony-124, Antimony-125, Barium-133, Beryllium-7, Bismuth-207, Cadmium-109, Calcium-45, Carbon-14, Cerium-139, Cerium-141, Cerium-144, Cesium-134, Cesium-135, Cesium-137, Chromium-51, Cobalt-56, Cobalt-57, Cobalt-58, Cobalt-60, Copper-67, Curium-242, Curium-243, Curium-244, Curium-247, Europium-152, Europium-154, Europium-155, Gadolinium-153, Germanium-68, Gold-195, Hafnium-181, Hydrogen-3(Tritium), Iodine-125, Iodine-126, Iodine-129, Iodine-131, Iodine-133, Iridium-192, Iron-55, Iron-59, Lead-210, Manganese-54, Mercury-203, Neptunium-237, Nickel-59, Nickel-63, Niobium-94, Plutonium-236, Plutonium-238, Plutonium-239, Plutonium-240, Plutonium-241, Plutonium-242, Plutonium-243, Plutonium-244, Polonium-210, Potassium-40, Promethium-147, Protactinium-23 1, Radium-223, Radium-224, Radium-226, Radium-228, Ruthenium-106, Samarium-151, Scandium-46, Selenium-75, Silver-108 m, Silver-110 m, Sodium-22, Strontium-85, Strontium-89, Strontium-90, Sulfur-35, Tanalum-182, Technetium-99, Thallium-204, Thorium-natural, Thorium-228, Thorium-230, Thorium-232, Tin-i13, Uranium-232, Uranium-233, Uranium-234, Uranium-235, Uranium-236, Uranium-238, Uranium-natural, Uranium-depleted, Yttrium-88, Yttrium-91, Zinc-65, Zirconium-95 and associated decay products thereof.
By “surface” or “area” is meant the presence of a contaminant on or about a surface or area that may include solid structures, such as trucks, equipment, and the like, particulate, compressible or linear solids such as soils, wires, gauzes, steel wool and the like. “Area” may also be used to define a location which may be inclusive of liquids such found in ponds, tanks, open or enclosed containers and is inclusive of such containers. In most instances, all contaminants will be associated in, on, attached to, embedded in or associated with a solid having a surface area.
In accordance with another aspect of the present invention, the method is applied to a solid surface or area as defined above which comprises metal, plastic, glass, concrete, wood, soil, or any other material.
In general, the method comprises applying the acid solution, as hereinafter defined, in such a manner
Bobolink, Inc.
Carrillo Sharidan
Thorpe North and Western
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