Patent Application
20240371536
The invention relates to a method and system for the recovery of radioactive Carbon-14 (14C) isotopes, or other radioactive isotopes from spent resin material of nuclear power plants and other facilities. This invention more particularly relates to the use of alkaline chemicals in methods and systems for extracting, solidification and degassing of carbon-14 isotopes (14C) from spent ion exchange resins.
Carbon-14 (14C) or radiocarbon is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Carbon-14 (14C) is produced in nuclear reactors by neutron activation of Oxygen-17, nitrogen-14, and to a lesser extent carbon-13. Carbon-14 (14C) a contaminant with an extremely long (5730 years) half-life. It can cause dosage to inhabitants by contact, inhalation or through the food cycle via photosynthesis. Therefore, it is generally accepted that release of Carbon-14 (14C) to the environment must be minimized. However, Carbon-14 (14C) has also shown to have a valuable commercial product for medical, pharmaceutical, agricultural and traceability of fertilizers and pesticides, as well as, in scientific research.
The CANDU (CANadian Deuterium Uranium) nuclear reactor as the particularity of generating a significant amount of radioactive carbon-14 (14C) isotope during the reactor operation. The 14C and other radioactive isotopes produced by the CANDU reactor are retrieved from the reactor through a purification media, that is composed of ion exchange resins.
In CANDU nuclear reactors, Carbon-14 (14C) is produced mainly in the Moderator and Primary Heat Transport (PHT) systems. Control of Carbon-14 (14C) emission from CANDU reactors is very effective. Over 90-95% of the C-14 produced is removed by the ion exchangers in the respective purification systems. The actual Carbon-14 (14C) emission from the generating stations are minimal.
The 14C isotopes are mostly present in a molecular form in the carbonate family, including but not limited to carbonate, bicarbonate, carbonic acid and carbon dioxide. The molecular form of 14C isotopes, when kept under the proper pH conditions, are present in aqueous solution under ionic form. Therefore, the carbonate family ions containing 14C isotopes are adsorbed by the ion exchange resins during the purification process of the CANDU reactor.
The ion exchange resins remove and contain the Carbon-14 (14C) contaminant, but produce large volumes of spent resin waste, which create a waste disposal problem. Most spent resin waste is treated by pyrolysis for volume reduction before disposal. However, pyrolysis before removal of Carbon-14 (14C) causes release of Carbon-14 (14C) as a gaseous species. Such gaseous release of radioactive species is to be avoided. Consequently, removal of Carbon-14 (14C) prior to pyrolysis is required. Because of the large volumes of spent resins waste generated and the long half-life of Carbon-14 (14C), the long-term storage of these resins without pyrolysis and volume reduction tends to be uneconomical. Once the 14C has been removed, the residual resins can be treated by pyrolysis and disposed of as conventional low-level waste. Furthermore, there is an interest in recovering the Carbon-14 (14C) from these spent resins and to purify the recovered Carbon-14 (14C) for commercial purposes.
Recovering Carbon-14 (14C) contaminant from spent ion exchange resins waste and its enrichment is not new. For Example, the Ontario Hydro process is a known process, wherein Carbon-14 (14C) is recovered from spent resins, then it is enriched and further converted into barium carbonate as a final product. The Ontario Hydro process consists in the extraction of 14C from resins in an acidic environment, by using Hydrochloric acid (HCl), a strong acid, for stripping the 14C and produce carbon dioxide (CO2) with a low concentration of 14C from the wash solution of the resins. The use of a strong acid is known to remove other gamma emitting radionuclides. The process then followed by a conversion of CO2 into carbon monoxide (CO), then an isotopic enrichment process by thermal diffusion column. Essentially pure 14C monoxide (14CO) is obtained and oxidized to produce 14C dioxide (14CO2), a gas that is then converted into barium carbonate. Reconversion of CO to C14-enriched CO2, then formation of a C14-enriched barium carbonate solid.
Other methods are also known. For example, the Atomic Energy of Canada Limited (AECL) method uses a CO2 gas over wet resin, resulting in a H2CO3 (carbonic acid) stripping process followed by a gas phase washing. The use of a weak acid is known for not removing other gamma emitting radionuclides.
Other technologies also use the concept of acid stripping carbonate containing 14C from waste resin and capturing the CO2 laden gas into molecular sieves. Releasing radionuclides (such as 14C) into the gaseous phase and the risk of spreading these gases environment is a known problem in the art, in particular during the upgrade from immobilization methods to volume reduction methods, namely high-temperature processing and oxidation of spent resins.
Alkaline conditions for 14C desorption are also known. For example, Park, S-C., et al. “A Study On Adsorption and Desorption Behaviours of 14C from a mixed Bed Resin”, Nuclear Engineering and Technology, Vol 46 No. 6 Dec. 2014 pgs. 847-856. This article suggests that a NH4H2PO4 solution is preferable for the stripping of 14C from the spent resin.
Other alkaline conditions for 14C desorption are also known. For example, C Bucur et al., “14C Content In Candu Spent Ion Exchange Resins And Its Release Under Alkaline Conditions”, Radiocarbon, Vol. 60, Nr 6, 2018 pgs 1797-1808. This article suggests that under alkaline conditions and in the presence of sodium hydroxide (NaOH), 14C could be released both as gaseous (7%) and as soluble species (79%) for unconditioned spent ion exchange resins (SIERs). The article suggests that SIERs may be immobilized in a suitable matrix for disposal, and the presence of Calcium (Ca) ions dissolved in cement pore water favour precipitation of 14C and consequently the amount of 14C released from disposal area should be lower.
Thus, despite recent advancements and desired progress in this area, there remains a need for a novel and improved methods and systems for the extraction, solidification and degasification of carbon-14 isotopes (14C) from spent ion exchange resins in alkaline conditions.
The present invention addresses these needs and other needs as it will be apparent from the review of the disclosure and description of the features of the invention hereinafter.
In a general sense, the present technology provides a system and method system and method for the extraction, solidification and degasification of carbon-14 isotopes (14C) and other radioactive isotopes from spent ion exchange resins in alkaline conditions.
In embodiments, there is provided a system extraction, solidification and degasification of carbon-14 isotopes (14C) and other radioactive isotopes from spent ion exchange resins, the system comprising: a washing vessel for washing the spent resins; a reaction vessel for treating the washed spent resins with alkaline chemicals of a given concentration for a given time and at a given temperature to obtain a process solution, wherein the process solution is recirculated through the resin washing vessel and the reaction vessel by a recirculating a means, thereby allowing the extraction of carbonate and/or bicarbonate ions containing the radioactive isotope, and whereby the extracted carbonate and/or bicarbonate ions containing the radioactive isotope is reacted with a chemical of a given concentration in the reaction vessel to form a reacted solution, wherein the reacted solution is recirculated by a recirculating means within the reaction vessel to form a suspended precipitate; and a decantation vessel for receiving the reacted solution and the suspended precipitate, thereby allowing for the removal of a supernatant from the remaining solution to form a solid form of carbonate and/or bicarbonate ions product, or salts thereof, comprising the radioactive isotope.
In embodiments, there is also provided a method for the extraction of a radioactive isotope from spent resins of a nuclear plant, the method comprising the steps of: providing a first volume of spent resins; washing the spent resins in a washing vessel in a recirculating liquid of a second volume; and treating the washed spent resins with alkaline chemicals of a given concentration in a reaction vessel for a given time and at a given temperature to obtain a process solution, wherein the process solution is recirculated through the resin washing vessel and the reaction vessel by a recirculating a means, thereby allowing the extraction of carbonate and bicarbonate ions containing the radioactive isotope.
In embodiments, there is also provided a method for solidification of a radioactive isotope from spent resins of a nuclear plant, the method comprising the steps of: providing a carbonate and/or bicarbonate ions extraction solution from the spent resins containing the radioactive isotope; contacting the carbonate and/or bicarbonate ions extraction solution with a chemical of a given concentration in a reaction vessel to form a reacted solution, wherein the reacted solution is recirculated by a recirculating means within the reaction vessel to form a suspended precipitate; and transferring the reacted solution and the suspended precipitate to a decantation vessel, wherein a supernatant is removed from the remaining solution to form a solid form of carbonate and/or bicarbonate ions product, or salts thereof, comprising the radioactive isotope.
In embodiments, there is also provided a method for the degassing of a radioactive isotope from spent resins of a nuclear plant, the method comprising the steps of: providing a solid form of carbonate and/or bicarbonate ions product, or salts thereof, extracted from the spent resins of a nuclear plant; reacting the solid form of carbonate and/or bicarbonate ions product, or salts thereof in an acidic solution of a given concentration in a temperature-controlled chemical reactor, thereby producing a gas stream and a residual product; and contacting the gas stream with molecular sieves and desiccant.
Additional aspects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments which are exemplary and should not be interpreted as limiting the scope of the invention.
In order for the invention to be readily understood, embodiments of the invention are illustrated by way of example in the accompanying figures.
Further details of the invention and its advantages will be apparent from the detailed description included below.
In the following description of the embodiments, references to the accompanying figures are illustrations of one or more examples by which the invention may be practised. It will be understood that other embodiments may be made without departing from the scope of the invention disclosed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs.
In a most general sense, the invention provides a system and method system and method for the extraction, solidification and degasification of carbon-14 isotopes (14C) and other radioactive isotopes from spent ion exchange resins in alkaline conditions.
In the context of the present specification, the word “about” when used in relation to numerical designations or ranges means the exact numbers plus or minus experimental measurement errors and plus or minus 10 percent of the exact numbers.
Moreover, all statements herein reciting principles, aspects, and implementations of the present technology, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof, whether they are currently known or developed in the future. Thus, for example, it will be appreciated by those skilled in the art that any block diagrams or illustrations represent conceptual views of the principles of the present technology. Similarly, it will be appreciated that any diagrams, flowcharts, and the like represent various processes which may be substantially represented in computer-readable media and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.
Implementations of the present technology each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.
Additional and/or alternative features, aspects and advantages of implementations of the present technology will become apparent from the following description, the accompanying drawings and the appended claims.
Referring now to
Referring to
In embodiments, as illustrated in
In embodiments, as illustrated in
Still referring to the system previously described and illustrated in
The alkaline chemicals may be selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), a monohydroxide base chemical, and any combination thereof.
The concentration of the alkaline chemical in the solution may range between about 1 to 10% (w/w).
The given temperature may range between about 0° C. to 100° C., preferably 5° C. to 70° C., most preferably 20° C. to 50° C.
The given time may range between about 30 to 180 min.
The ratio of the second volume of the recirculating liquid and the first volume of the spent resin may range from about 2:1 to 7:1.
In embodiments, the alkaline chemicals may be selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), a monohydroxide base chemical, and any combination thereof.
The concentration of the alkaline chemical in the solution may range between about 1 to 10% (w/w).
Referring now to
In embodiments, as illustrated in
In embodiments, the alkaline chemicals may be selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH4OH), a monohydroxide base chemical, and any combination thereof.
The concentration of the alkaline chemical in the solution may range between about 1 and 10% (w/w).
The given temperature may range between about 0° C. to 100° C., preferably 5° C. to 70° C., most preferably 20° C. to 50° C.
The given time may range between about 30 to 180 min.
In embodiments, as illustrated in
The resin may optionally be treated in a Pyrolysis Resins in Mobile Electric (PRIME) (120) installation to reduce its volume.
Referring now to
Still referring to the method previously described and represented in
The chemical may be barium hydroxide (Ba(OH)2).
Still referring to
The radioactive isotope may be C-14.
The solid form of carbonate and/or bicarbonate ions product, or salts thereof (500) may be stored (510) using storing means (530).
In embodiments, and now referring to
Still referring to the method previously described and represented in
In embodiments, the acidic solution may comprise inorganic and/or organic acids, or a combination thereof.
The acidic solution (600) may be selected from the group consisting of hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), acetic acid (C2H4O2), citric acid (C6H8O7).
The concentration of the acid in the acidic solution (600) may range from about 10% (w/w) to 90% (w/w), and it may be further adjusted depending on the acid used.
The radioactive isotope is C-14.
Those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific procedures, embodiments, claims, and examples described herein. Such equivalents are considered to be within the scope of this invention and covered by the claims appended hereto.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2023/050513 | 1/20/2023 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63267075 | Jan 2022 | US |
