Patent Application
20190172595
This invention relates to field of nuclear radiation contamination cleanup.
A recent nuclear power plant accident has brought to light significant challenges relating to the cleanup and waste management of radioactive materials at accident sites. These issues include, but are not limited to the following: the processing of large volumes of contaminated water, debris, soil, secondary wastes, potentially damaged spent fuel within reactor spent fuel pools, and damaged fuel and fuel debris within reactors and primary containment structures.
After progress has been made in the cooling of the reactors at an accident site mid-term to long-term waste management issues will continue to be a major technical concern that must be addressed and overcome as any recovery actions continue toward an acceptable end state. As such, there are considerable waste management challenges associated with the treatment of contaminated water, the resulting filter and equipment waste storage, the disposal of secondary waste, contaminated soil, vegetation, and debris decontamination.
The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a neutron absorbing decontamination pellet that comprises an innermost core of a predetermined neutron absorbing material and an insoluble polymer coating that forms a continuous outer casing for the core of neutron absorbing material. Further, the outer casing decontamination pellet will become sticky, yet retain its integrity, upon exposure to water or upon exposure to a predetermined temperature range.
A further exemplary embodiment of the present invention comprises a method for the formation of neutron absorbing decontamination pellets. The method comprises the steps of; creating a slurry comprising a predetermined neutron absorber material and a binding agent; transporting the slurry through a feeder hose, the hose terminating at a deposit nozzle; employing the deposit nozzle to form the slurry into neutron cores of predetermined sizes; immersing the neutron cores formed by the deposit nozzle into a bath of a predetermined insoluble polymer solution to create an outer casing upon each immersed neutron core in order to construct a neutron absorbing decontamination pellet; and exposing the neutron absorbing decontamination pellets to air to dry, and thereafter transferring the dry decontamination pellets to storage.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features, refer to the description and to the drawings.
The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
One or more exemplary embodiments of the invention are described below in detail. The disclosed embodiments are intended to be illustrative only since numerous modifications and variations therein will be apparent to those of ordinary skill in the art. In reference to the drawings, like numbers will indicate like parts continuously throughout the views. Herein, the use of the terms first, second, etc., do not denote any order or importance, but rather the terms first, second, etc., are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc., do not denote a limitation of quantity, but rather denote the presence of at least one of a referenced item.
Exemplary embodiments of the present invention comprise pellets fabricated from neutron moderating/absorbing materials that are coated with a water insoluble polymer. As shown in
As presented above, the pellets 100 within the exemplary embodiments of the present invention have a core 102 comprising a predetermined neutron moderating material and an outer shell coating 104 that is comprised of a predetermined polymer material. The polymer chosen to comprise the outer shell 104 must have the intrinsic property of being insoluble in water and being semi-rigid to rigid in structure when exposed to air. The semi-rigid to rigid hard coating of the outer shell 104 is necessitated to facilitate the storage and transportation of the neutron core moderator pellets 100.
The polymer coating employed within the exemplary embodiments of the present invention can have slowly degradable water insoluble, poor water soluble, or partial water soluble characteristics depending upon the area of usage in which the pellets 100 will be deployed and the ambient temperature range within the area of usage. Thus pellets configured with a degradable poor or partial water soluble polymer coating 104 can be configured to become tacky or sticky when introduced to water yet still retain their structural integrity. Further, pellets 100 compromising a water insoluble polymer coating can be constructed to retain their hard shell structural integrity in water until introduced to high temperatures ranges (any temperatures approximately above 60° C.) and thereafter become tactilely tacky or sticky.
The pellet 100 forming nozzle 206 deposits the formed neutron moderator cores 102 into a bath of a predetermined pellet 100 outer coating polymer 208. The characteristics necessitated by the polymer to be utilized will depend on the type of pellet 100 that is to be produced. For pellets 100 that are to be utilized in high temperature settings the pellets 100 can comprise a hard thermoplastic polymer shell at ambient temperatures-thus making the storage and transport of said pellets 100 relatively easy—wherein upon exposure to high temperatures the hard thermoplastic polymer shell will soften and become tacky, thus making it easier for the pellet 100 to adhere to whatever surface it is being applied to whether in an aqueous or dry environment. Also, since the pellets 100 will start to harden again when the temperature of the pellets 100 lowers, the ease of cleaning up the pellets 100 will be greatly enhanced.
Alternately, for pellets 100 that are to be applied to surfaces at or around ambient temperatures, the polymer 104 selected to coat the core 102 will have the characteristic of remaining solid yet pliably tacky or sticky at ambient temperatures while allowing the core 102 of the pellet 100 to completely dry and cure. In this instance the pellets 100 can be stored in a liquid stasis for the convenient storage and transportation of the pellets 100.
Within the hopper 200 the liquid neutron moderator pellet 100 and the polymer 208 are not miscible, thus within the polymer coating 208 solution of the hopper 200 the denser neutron moderating material does not mix with the less dense polymer material. As the neutron modulating pellets 100 are pulled by gravity to the lowermost portion of the polymer outer coating 208 solution each pellet is subsequently bathed in the polymer solution 208. As the pellets 100 exit the formation segment 210 of the hopper 200 they are deposited into a collector (not seen). The coating of the pellets 100 dry once they are exposed to air upon exiting the formation container and the coating solidifies around their neutron moderator cores 102 prior to the pellets 100 landing in the remotely situated collection container.
In either form, the pellets 100 are or would become tacky/sticky upon being introduced to the water 314 and fuel elements 312 and as such will easily adhere to the surface of the melted fuel elements 312 when deposited at the site and slow any reactions that may be occurring with the damaged fuel elements 312 (
The gel-solution is formulated to congeal upon coming into contact with air. Thus, as the gel-solution 504 containing the neutron modulating pellet strands 100 is sprayed onto a patch of contaminated wall the sprayed material will coagulate and form a thin cover over the sprayed patch of contaminated structural area. The congealing gel 504 serves to entrap and absorb the resulting radiation from the contaminated particles beneath it on the wall whereon the gel has been sprayed. The congealed gel covering can be removed from the wall and disposed of in a safe manner at a later period of time.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.
| Number | Date | Country | |
|---|---|---|---|
| 62593298 | Dec 2017 | US |
