Oxidation of cesium as a method for removing cesium vapor from cover gas in a nuclear reactor

Abstract

A method for removing cesium vapor from the cover gas flow in a nuclear reactor includes oxidizing the cesium vapor in the cover gas flow to obtain cesium oxide particles and removing the cesium oxide particles using a particle filter. By this method, a filtered cover gas having a cesium vapor content of 0% to about 2% of the initial cover gas flow is obtained, which corresponds to at least about 98% reduction.

Description

Detailed Description of the Invention

[0001] [Cross - Reference to Related Applications] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 388,981, entitled "OXIDATION OF CESIUM AS METHOD FOR REMOVING CESIUM VAPOR FROM COVER GAS IN NUCLEAR REACTORS", filed on July 13, 2022. The entire content of the said application is incorporated herein by reference.

[0002] [Government Licensing Rights] This invention was made with government support under DOE Cooperative Agreement No. DE - NE0009054 awarded by the U.S. Department of Energy. The government has certain rights in this invention.

[0003] [Field of the Disclosure] This disclosure relates to an improved process for removing radioactive cesium from an inert cover gas in a nuclear reactor. The process includes oxidizing cesium vapor in the cover gas to produce cesium oxide particles and removing the cesium oxide particles by mechanical filtration.

[0004] [Background] Radioactive cesium - 134 and cesium - 137 can be present in the coolant of a sodium - cooled fast reactor. Due to the high vapor pressure of elemental cesium, radioactive cesium - 134 and cesium - 137 can move into the cover gas (usually argon). Cesium has a relatively high vapor pressure at expected cover gas temperatures of 20°C to 550°C, and cesium vapor is carried by the cover gas through the vapor condenser and aerosol filters and can accumulate on or within the equipment in the downstream piping, valves, and radioactive gas treatment systems. An amount of cesium sufficient to raise concerns about the radiation dose to maintenance workers can be transported.

[0005] Many reactors include a sodium coolant treatment system that includes a filter. The filter is disposed within the flow of the cooling fluid to remove cesium and other radioactive fission by-products. However, an amount of cesium sufficient to raise concerns about the dose to workers can still evaporate into the cover gas system. For example, near downstream processing equipment (e.g., piping, service valves, and compressor cells), dose rates of up to 320 millirem per hour for cesium-134 and up to 13 rem per hour for cesium-137 have been detected. Such downstream processing equipment requires periodic maintenance, in part due to cesium accumulation. High levels of caution are required to perform such maintenance so that maintenance workers are not exposed to unacceptable radiation doses.

[0006] U.S. Publication No. 2017 / 0263339 to Eichel et al., published on September 14, 2017, describes an example of a known reactor filter. U.S. Publication No. 2017 / 0263339 discloses embodiments of getter elements for removing one or more fission products from a gaseous and / or liquid coolant flow within a reactor. The getter element includes one or more internal passages that facilitate continuous throughput of the cooling fluid and a getter material that chemically reacts with the target fission products to remove the fission products from the flow. The disclosed fission products include cesium and cesium-based compounds, rubidium and rubidium-based compounds, strontium and strontium-based compounds, and iodine and iodine-based compounds. The disclosed getter materials include zirconium oxide, titanium oxide, niobium oxide, and tantalum oxide. However, as described above, known filters disposed within the cooling fluid flow are not sufficient to prevent the migration of cesium vapor into the cover gas flow, and a significant amount of uncaught cesium vapor can migrate into the cover gas flow and subsequently accumulate on or within downstream equipment, resulting in concerns about the dose to maintenance workers.

[0007] 〔Summary〕 Embodiments of the present disclosure relate to a method for removing cesium vapor from the flow of cover gas in a nuclear reactor using an oxidation and filtration device disposed within the cover gas flow. According to some embodiments, the method may not be intended to replace any filtration device or filtration method conventionally employed in the flow of the cooling fluid, and relates to removing cesium that still leaks out before it can pass from the cooling fluid into the downstream processing facility within the cover gas flow.

[0008] The boiling temperature of cesium is 670 °C. However, due to its high vapor pressure, cesium evaporates at much lower temperatures and enters the cover gas flow. The much lower temperatures include temperatures in the range of about 20 °C to about 550 °C. The temperatures in the range of about 20 °C to about 550 °C are temperatures that can be found at various locations within the cover gas flow of any of many nuclear reactors. As a result, a cover gas flow containing an inert gas (usually argon) and carrying a small but radiologically significant amount of cesium-134 (half-life 2.1 years) and cesium-137 (half-life 30 years) is produced. In a representative example, at a high cover gas temperature of about 550 °C, the mole fraction of cesium vapor in the cover gas can be up to about 2.2X10 -10 It can be. As a result, the partial pressure in the cover gas flow of a nuclear reactor operating at atmospheric pressure correspondingly reaches up to about 2.2X10 -10 Atmospheric pressure. Over time, even a small concentration of cesium vapor can condense (solidify) and accumulate significantly in the downstream processing facility, thus requiring removal.

[0009] According to the disclosed method, a cover gas flow containing an inert cover gas and cesium vapor is provided (prepared) within the nuclear reactor. The cover gas flow contains a first mole fraction of cesium vapor. The first mole fraction of cesium vapor is up to about 2.2X10, as in a representative example. -10It can be, or can be at any mole fraction typically encountered in the reactors of various embodiments. The method further includes oxidizing cesium vapor in the cover gas stream to obtain cesium oxide (Cs2O) particles having a very low vapor pressure, and removing the cesium oxide particles from the cover gas stream using a particle filter disposed within the cover gas stream to obtain a filtered cover gas. The filtered cover gas stream can have a second mole fraction of cesium vapor that is 0% to about 2%, or 0% to about 0.2%, or 0% to about 0.02%, or 0% to about 0.002%, or 0% to about 0.0002% of the first mole fraction of cesium vapor.

[0010] In some embodiments, the step of oxidizing cesium vapor in the cover gas stream includes reacting the cesium vapor with a metal oxide to form cesium oxide particles. The metal oxide can have a first Gibbs free energy, and the cesium oxide particles can have a second Gibbs free energy. The difference in the Gibbs free energies of the two solid metal oxides corresponds to the difference in the Gibbs free energy of formation (ΔG f ). This is known and published for various metal oxides using reference conditions of 298 K (25 °C) and 1 atmosphere. The metal oxide can be selected such that the first Gibbs free energy is higher than the second Gibbs free energy. In other words, the metal oxide can be selected such that the first Gibbs free energy of formation is higher than the second Gibbs free energy of formation. Selecting the metal oxide in this way helps to enable the spontaneous progression of the chemical reaction in a temperature environment of about 20 °C to about 400 °C. The temperature environment of about 20 °C to about 400 °C is a temperature environment typically present in the cover gas treatment stream of a nuclear reactor.

[0011] Suitable metal oxides having a Gibbs free energy of formation higher than that of cesium oxide (Cs2O) include selected oxides of copper, bismuth, antimony, lead, nickel, selenium, tellurium, cobalt, and combinations thereof. However, it is not limited thereto. Regarding the "selected oxides", it should be understood that not all but some of the oxides of these metals can be selected so as to have a Gibbs free energy of formation higher than that of cesium oxide. The selected metal oxides will preferably be stable in a low-oxygen or oxygen-free environment at the use temperature. Suitable copper oxides that are "selected oxides" include cuprous oxide (Cu2O), cupric oxide (CuO), and combinations thereof.

[0012] Oxides of bismuth include bismuth oxide (Bi2O3) and bismuth oxide (Bi3O4). These can be "selected oxides". Oxides of antimony include antimony tetroxide (Sb2O4) and antimony pentoxide (Sb2O5). These can be eligible as selected oxides. Also, oxides of antimony include antimony trioxide (Sb2O3) and antimony hexatridecoxide (Sb6O 13) are included. These are not eligible as the selected oxides. Lead oxides include lead monoxide (PbO) and lead dioxide (PbO2). Both of these are the selected oxides. Also, lead oxides include lead (III, IV) oxide (Pb3O4). This is not the selected oxide. Nickel oxides may include nickel (II) oxide (NiO) (the selected oxide), nickel (III) oxide (Ni2O3). Selenium oxides may include selenium dioxide (SeO2), selenium trioxide (SeO3), diselenium pentoxide (Se2O5), and combinations thereof. Tellurium oxides may include tellurium dioxide (TeO2). This is barely the selected oxide. Cobalt oxides include cobaltous oxide (CoO). This is the selected oxide. Also, cobalt oxides include cobaltic oxide (Co2O3) and cobalt (II, III) oxide (Co3O4). These are not the selected oxides. To the extent that the reaction is promoted thermodynamically, determined from the relative Gibbs free energy of formation of the metal oxide with respect to cesium oxide, the metal oxide reacts with a stoichiometric amount of cesium vapor, resulting in cesium oxide (Cs2O) and a metal element (Cu, Ag, Bi, Sb, Pb, Ni, Se, Te, and / or Co) or a partially reduced metal oxide thereof. For example, CuO can be partially reduced to Cu2O.

[0013] In some embodiments, the metal oxide can be a copper oxide selected from cuprous oxide (Cu2O), cupric oxide (CuO), and combinations thereof. According to the following exemplary reaction equations, cuprous oxide and cupric oxide react with cesium vapor, resulting in cesium oxide particles and copper metal and / or a partially reduced oxide:

[0014]

Chemical formula

[0015]

Chemical formula

[0016] [Chemical formula]

[0017] According to known data, cerium oxide has a Gibbs free energy of formation (ΔG f ) of -308.36 kJ / mole. For comparison, cuprous oxide and cupric oxide have ΔG f values of -146.03 kJ / mole and -129.56 kJ / mole, respectively, at 25°C and 1 atmosphere. See "Thermodynamic Properties of Minerals and Related Substances at 298.15 K and 1 Bar (10 5 Pascals) Pressure and at Higher Temperatures" by Robie et al., U.S. Geological Survey Bulletin 1452, U.S. Department of the Interior (1984). Cerium oxide has a much lower Gibbs free energy of formation than copper oxides. Therefore, forming cerium oxide from copper oxides is thermodynamically very favorable.

[0018] Some of the oxides of the listed metallic elements do not have a higher Gibbs free energy of formation than cerium oxide and are not included in the selected group. The following table shows the Gibbs free energies of formation for some of the selected oxides of these metallic elements, based on the aforementioned U.S. Geological Survey Bulletin 1452. Those not within the selected group are also shown. A higher Gibbs free energy of formation, or a "less negative" Gibbs free energy of formation, corresponds to a higher Gibbs free energy in the compound.

[0019] [Table 1]

[0020] In some embodiments, the metal oxide can be provided in the form of a porous material disposed within the cover gas stream, and the cesium vapor can react with the metal oxide as the cover gas stream passes through the porous material. For example, the porous material containing the metal oxide can be a packing material, wool, mesh, or screen material. Cesium vapor can react with the metal oxide in the porous material to form cesium oxide particles.

[0021] When cesium oxide particles are formed by reacting the metal oxide with cesium vapor, the cesium oxide particles can be removed from the cover gas stream using a particle filter, and as a result, a filtered cover gas stream can be obtained. In some embodiments, the porous material containing the metal oxide can act as a particle filter or the first stage of a two-stage particle filter. This not only reacts with cesium vapor to form cesium oxide particles but also retains at least some or all of the cesium oxide particles and removes them from the cover gas stream. For example, packing materials, wool, mesh, screens, powders, and / or granules, which can be formed from copper oxide or other suitable metal oxides, can act as particle filters that retain at least some of the cesium oxide particles while forming them.

[0022] In some embodiments, the particle filter can include a particle filter or the second stage of a two-stage particle filter. This is separate from the porous material used to react cesium vapor with the metal oxide to form cesium oxide particles. When a separate particle filter is used, the separate particle filter can include physical constraints designed to capture small particles of cesium oxide. For example, the separate particle filter can include a mesh screen or a series of screens having pores less than about 20 microns, or less than about 15 microns, or less than about 10 microns, or between about 5 microns and about 10 microns. The separate particle filter can also be disposed within the cover gas stream, and as a result, the cover gas exits the particle filter as a filtered cover gas stream.

[0023] In some embodiments, the separate particle filter may also include a suitable metal oxide. The suitable metal oxide may react with residual cesium vapor that remains entrained in the cover gas stream even after passing through the reactive porous material. For example, the separate particle filter may include copper oxide, or other suitable metal oxides, as a constituent material for a mesh screen or series of screens, or in addition to (one or more) screens.

[0024] In some embodiments, the cover gas stream includes an inert gas (e.g., argon) and cesium vapor at a first molar concentration. The filtered cover gas stream includes an inert gas and cesium vapor at a second molar concentration. Depending on the temperature of the cover gas stream and other conditions under which the reaction occurs, the second molar concentration of cesium vapor can be from 0% to about 2% of the first molar concentration of cesium vapor, or from 0% to about 0.2% of the first molar concentration of cesium vapor, or from 0% to about 0.02% of the first molar concentration of cesium vapor, or from 0% to about 0.002% of the first molar concentration of cesium vapor, or from 0% to about 0.0002% of the first molar concentration of cesium vapor.

[0025] The target concentration of cesium vapor described above was verified using FactSage R thermochemical software with an initial molar concentration of cesium vapor of 1.0X10 6 in an argon cover gas at a pressure of 1 atmosphere. At a pressure of 1 atmosphere, the molar concentration of cesium vapor will correspond to its partial pressure in the atmosphere. In this example, the molar concentration can be estimated to be 1X10 -6 atmospheres. Using FactSage R thermochemical software, the following partial pressures can be expected to be obtained at equilibrium following the reaction of cesium vapor with cupric oxide (CuO):

[0026] [Table 2]

[0027] Using the same conditions and assumptions, the aforementioned modeling was repeated for the reaction of cesium vapor with cuprous oxide (Cu2O). FactSage R Using thermochemical software, the following partial pressures can be expected to occur in the equilibrium state regarding the reaction of cesium vapor with cuprous oxide (Cu2O):

[0028] [Table 3]

[0029] From Tables 2 and 3 above, it can be understood that the amount of cesium vapor in the cover gas stream can be reduced to a negligible level using the oxidation process, and in some cases, can be reduced to an undetectable level. Using experimental work, the optimal temperature of the cover vapor stream used to achieve an equilibrium reaction state, or a reaction state as close to equilibrium as possible, can be determined. As shown in the table, the partial pressure of residual Cs at equilibrium is expected to be very low at relatively low temperatures. However, at relatively low temperatures, the reaction rate will also be slow, and the time required to reach the equilibrium reaction state will be long. The optimal placement of the reaction and filtration device within the cover gas stream requires consideration of both the temperature and time required to complete the reaction in that location.

[0030] In some embodiments, the oxidation can be carried out by directly injecting oxygen gas into the cover gas stream. At this time, the oxygen gas easily reacts with cesium vapor to form cesium oxide particles. The amount of oxygen gas required to complete the following reaction can be very small. This reaction is highly exothermic and can proceed spontaneously:

[0031] [Chemical formula]

[0032] In the direct injection of oxygen gas, the use of a particle filter disposed within the vapor stream is required to remove the cerium oxide particles from the cover vapor stream. The particle filter can include any of the filter assemblies described above. The particle filter can include a mesh sieve, a series of sieves, or other porous material having pores of less than about 20 microns, or less than about 15 microns, or less than about 10 microns, or from about 5 microns to about 10 microns. In some embodiments, the particle filter can be formed using a suitable reactive metal oxide so as to facilitate the capture of cerium oxide particles and residual cerium vapor entrained in the cover gas stream.

[0033] The foregoing and other features of the present disclosure will become more apparent from the following detailed description when read in conjunction with the drawings.

[0034] 〔Brief Description of the Drawings〕 FIG. 1 schematically shows one embodiment of a reaction and filtration device that can be disposed within a cover gas stream to carry out an exemplary embodiment of the disclosed method.

[0035] 〔Detailed Description〕 Referring to FIG. 1. The exemplary reaction and filtration device 10 can be disposed within the cover gas stream 12 of a nuclear reactor and can be used to implement an exemplary embodiment of the disclosed method. The cover gas stream 12 includes an inert cover gas (which may be argon in some cases). The cover gas stream 12 can contain a small but radiologically significant amount of cesium-134 and cesium-137 (collectively referred to as cesium) in the form of vapor. Depending on the type and condition of the nuclear reactor, the cover gas stream 12 can contain up to about 2.2×10 -10 moles of cesium vapor at a first concentration per mole of cover gas, but is not limited to these concentrations for the purpose of implementing the disclosed method. Assuming ideal gas behavior and a pressure of 1 atmosphere, the cesium present at these concentrations is up to about 2.2X10 -10It will indicate the corresponding partial pressure of the atmospheric pressure. The method of the present disclosure is not limited to these partial pressures, nor is it limited to the total pressure of 1 atmosphere, and can be implemented under various pressures.

[0036] The reaction and filtration device 10 can be arranged at any location within the cover gas flow. The reaction and filtration device 10 can be arranged at a selected location, for example, based on the cover gas temperature at that location. The range of the cover gas temperature can typically be from about 20 °C to about 550 °C at various locations and in the cover gas treatment systems of various nuclear reactors. The disclosed method is not limited to implementation within this temperature range. The reaction rate of the (one or more) chemical reactions from cesium vapor to cesium solid particles generally increases with an increase in temperature. Therefore, according to this factor, it may be advantageous to arrange the device 10 at a location with a relatively high temperature in the cover gas flow. As used herein, the term "location with a relatively high temperature" refers to a location where the cover gas flow is at a temperature above 250 °C. On the other hand, the chemical reaction can proceed to a higher degree of equilibrium of completion at relatively low temperatures. According to this, it may be advantageous to arrange the device 10 at a location with a relatively low temperature within the cover gas flow. The optimal arrangement of the device 10 within the cover gas flow will depend on multiple factors. For example, the multiple factors may include the amount or concentration of cesium vapor to be removed, the flow rate and residence time of the cover gas flow within the device 10, the specific type of reaction used to convert cesium vapor to cerium oxide particles (by contact with a metal oxide or by direct injection of oxygen, and if a metal oxide is used, its specific type), etc. In some exemplary embodiments, two or more devices 10 can be arranged at selected locations within the cover gas flow. In some embodiments, the first device can be arranged at a first position within the cover gas flow, and the second device can be arranged at a second position within the cover gas flow. In some cases, the first position may have a higher cover gas flow temperature than the second position.

[0037] In some embodiments, the reaction and filtration apparatus 10 can be heated or cooled so that a desired reaction temperature and / or filtration temperature is achieved. In some embodiments, a selected portion of the reaction and filtration apparatus 10 can be heated or cooled so that a desired reaction temperature and / or filtration temperature is achieved at the selected portion of the apparatus. Similarly, the first and second apparatuses can be heated or cooled to various temperatures so that a desired reaction temperature and / or filtration temperature is achieved in the first and second apparatuses 10.

[0038] A cover gas stream 12 containing cesium vapor at a first concentration can enter the apparatus 10 at an inlet location 14 and pass through a narrower constriction 16 into the reaction chamber 18. In some embodiments, the reaction chamber 18 can be filled with a metal oxide material having a first Gibbs free energy of formation higher than a second Gibbs free energy of formation of solid cerium oxide. The metal oxide can be in the form of any porous material. The metal oxide can include, for example, at least one of packing materials, wool, mesh, sieves, powders, and / or granules, among various designs. The porous material may be formed of a metal oxide or may be formed of other materials (e.g., stainless steel). The porous material may have metal oxide particles dispersed therein.

[0039] In some embodiments, the metal oxide material may be an oxide of copper, bismuth, antimony, lead, nickel, selenium, tellurium, and / or cobalt, or may be a combination of one or more oxides. In some embodiments, the metal oxide material may include copper oxides selected from cupric oxide, cuprous oxide, and combinations thereof. In some embodiments, the metal oxide material can be cupric oxide. In some embodiments, the metal oxide material can be cuprous oxide. In some embodiments, the metal oxide material can be a mixture or other combination of cupric oxide and cuprous oxide. In some embodiments, two or more metal oxides can be provided within the apparatus 10. In some cases, a first metal oxide, or a first combination of a plurality of metal oxides, can be provided within a first apparatus 10, and a second metal oxide, or a second combination of a plurality of metal oxides, can be provided within a second apparatus 10.

[0040] When the cover gas vapor passes through the reaction chamber 18, cesium vapor can react with the metal oxide to obtain cesium oxide particles and elemental metal and / or the reduced metal oxide. For example, when the metal oxide is cuprous oxide, the reaction proceeds as follows:

[0041]

Chemical formula

[0042] In another example, when the metal oxide is cupric oxide, the reaction proceeds as follows:

[0043]

Chemical formula

[0044]

Chemical formula

[0045] The resulting cerium oxide particles are then filtered from the cover gas stream using a particle filter disposed within the cover gas stream. This results in a filtered cover gas stream 20. In some embodiments, the porous metal oxide material disposed within the reaction chamber 18 can serve as, or as a component of, the particle filter. Thus, the metal oxide particles can remain incorporated within the porous material. In some embodiments, the apparatus 10 may further include a separate particle filter 22 designed to remove small particles. The particle filter 22 can be disposed downstream of the reaction chamber 18, between the reaction chamber 18 and the outlet opening 24 of the apparatus 10. The particle filter 22 can act as a primary filter (if the reaction chamber 18 performs little or no filtration) or as a secondary filter (if the porous material within the reaction chamber 18 performs substantial filtration of the metal oxide particles). The reaction chamber 18 can include an end cap 19, or other mechanism for directing the cover gas stream towards the particle filter 22.

[0046] In some embodiments, the particle filter 22 can include a sieve, a series of sieves, or other porous material having pores of less than about 20 microns, or less than about 15 microns, or less than about 10 microns, or between about 5 microns and about 10 microns. The particle filter can be formed using a durable sieve material (e.g., stainless steel).

[0047] Alternatively, in some embodiments, the particle filter may be formed using a suitable reactive metal oxide so as to facilitate the capture of cerium oxide particles and residual cerium vapor entrained in the cover gas stream.

[0048] In some embodiments, the reaction and filtration device 10 may include an oxygen supply system 28 and a flow meter disposed within the auxiliary inlet conduit 26. The oxygen supply system 28 may be isolated and controlled using a check valve 30. If the reaction chamber 18 is filled with a porous material containing a reactive metal oxide, a separate source of oxygen may not be required and the device 10 may operate with the check valve 30 and the inlet conduit 26 closed. In an alternative embodiment, the reaction chamber 18 may not contain a metal oxide material and the oxygen supply system 28 may be used to convert cesium vapor to cesium oxide particles according to the following exothermic reaction:

[0049]

Chemical formula

[0050] The check valve 30 may be a three-way check valve to selectively open and close and regulate the inflow stream 32 of air mixed with an inert gas (e.g., argon) and the inflow stream 34 of pure inert gas (e.g., argon) so that the supply of highly reactive oxygen is regulated. The reaction between cesium and oxygen can occur spontaneously. If too much oxygen or heat is added to the reaction chamber 18, the reaction can proceed violently. By carefully controlling the oxygen supply using additional argon as a diluent, the reaction can be controlled at a manageable level while successfully converting cesium vapor to cesium oxide particles.

[0051] In embodiments where cesium is reacted with oxygen gas within the reaction chamber 18, the reaction chamber 18 may not perform a filtration function. In these embodiments, the particle filter 22 may serve as a primary filter and / or the only filter for removing cesium oxide particles from the cover gas stream, thereby obtaining a filtered cover gas stream 20 that exits through the outlet 24.

[0052] The disclosed method provides a highly effective method for removing cesium vapor from the cover gas flow of a nuclear reactor. The incoming cover gas flow includes an inert cover gas and cesium vapor at a first molar concentration. The filtered cover gas flow includes an inert cover gas and cesium vapor at a second molar concentration. The range of the second molar concentration of cesium vapor can be from 0% to about 2% of the first molar concentration of cesium vapor. In some embodiments, the range of the second molar concentration of cesium vapor can be from 0% to about 0.2%, or 0% to about 0.02%, or 0% to about 0.002%, or 0% to about 0.0002% of the first molar concentration of cesium vapor.

[0053] The general nature of the embodiments of the present disclosure will be apparent from the foregoing description of the specific embodiments to such an extent that others may readily modify and / or adapt the specific embodiments for various applications without undue experimentation by applying the knowledge of those skilled in the art without departing from the general concepts of the embodiments of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and scope of the equivalents of the disclosed embodiments based on the teachings and guidance presented herein. The syntax or terminology herein is for the purpose of explaining the terms or syntax of the present specification as would be interpreted by those skilled in the art in light of the teachings and guidance presented herein, and is not for the purpose of limitation.

[0054] The breadth and scope of the embodiments of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0055] Unless otherwise specified or understood differently within the context in which it is used, terms related to conditions, such as in particular "can", "could", "might" or "may", generally intend to convey that while a particular implementation form can include certain features, elements and / or operations, other implementation forms do not include such features, elements and / or operations. Thus, such terms related to conditions generally do not intend that a feature, element and / or operation is required in any way in one or more implementation forms, or that the logic for determining whether these features, elements and / or operations are included in any particular implementation form, or whether these features, elements and / or operations are to be performed in any particular implementation form, is necessarily included in one or more implementation forms regardless of the presence or absence of user input or prompt.

[0056] One of ordinary skill in the art will recognize that any process or method disclosed herein can be modified in many ways. The process parameters and order of steps illustrated and / or exemplified herein are provided by way of example only and can be varied as desired. For example, the steps illustrated and / or exemplified herein may be shown or discussed in a particular order, but these steps need not necessarily be performed in the order illustrated or discussed.

[0057] Also, in the various exemplary methods described and / or illustrated herein, one or more of the steps described or illustrated herein may be omitted, or additional steps may be included in addition to the disclosed steps. Further, the steps of any method disclosed herein can be combined with any one or more of the steps of any other method disclosed herein.

[0058] Also, in the various exemplary methods described and / or illustrated herein, one or more of the steps described or illustrated herein may be omitted, or additional steps may be included in addition to the disclosed steps. Further, the steps of any method disclosed herein can be combined with any one or more steps of any other method disclosed herein.

[0059] Of course, for the purpose of describing the various features of the present disclosure, it is impossible to describe all possible combinations of elements and / or methods. However, those skilled in the art will recognize that numerous additional combinations and permutations of the disclosed features are possible. Accordingly, various changes can be made to the present disclosure without departing from the scope or spirit of the present disclosure. Further, by considering the specification and the attached drawings, and by practicing the disclosed embodiments presented herein, other embodiments of the present disclosure may become apparent. The examples presented in the specification and the attached drawings should be considered in all respects to be illustrative and not restrictive. Specific terms are used herein, but they are used only in a general and descriptive sense and not for purposes of limitation.

[0060] Unless otherwise specified, the term "a" or "an" as used herein is to be construed to mean "at least one of". Finally, for ease of use, the terms "including" and "having" (and their derivatives) as used herein are interchangeable with the term "comprising" and have the same meaning.

[0061] From the foregoing description and the accompanying drawings, while specific implementations are described herein for illustrative purposes, it will be understood that various modifications can be made without departing from the spirit and scope of the appended claims and the elements recited in the claims. Additionally, while specific aspects are presented below in specific claim forms, the inventors contemplate various aspects in any available claim form. For example, while only some aspects may presently be described as being embodied in a specific configuration, other aspects may likewise be so embodied. Various modifications and changes can be made that will be apparent to those skilled in the art who obtain the benefits of this disclosure. All such modifications and changes are intended to be included, and thus the foregoing description should be considered in an illustrative rather than a limiting sense.

Brief Description of the Drawings

[0062]

Figure 1

Claims

1. A method for removing cesium from a cover gas flow in a nuclear reactor, comprising: providing a cover gas flow containing an inert cover gas and cesium vapor in the nuclear reactor; oxidizing the cesium vapor in the cover gas flow to form cesium oxide particles; removing the cesium oxide particles from the cover gas flow using a particle filter disposed within the cover gas flow to obtain a filtered cover gas flow. A method comprising the above steps.

2. The step of oxidizing the cesium vapor in the cover gas flow includes reacting the cesium vapor with a metal oxide, wherein the metal oxide has a first Gibbs free energy of formation, and cesium oxide has a second Gibbs free energy of formation lower than the first Gibbs free energy of formation. The method according to claim 1.

3. The method according to claim 2, wherein the metal oxide includes an oxide of at least one of copper, bismuth, antimony, lead, nickel, selenium, tellurium, and cobalt.

4. The method according to claim 2, wherein the step of oxidizing the cesium vapor includes passing the cover gas flow through a porous material containing the metal oxide.

5. The method according to claim 4, wherein the porous material containing the metal oxide includes at least one of a packing material, wool, mesh, sieve material, powder, or granules.

6. The method according to claim 1, wherein the step of oxidizing the cesium vapor in the cover gas flow includes reacting the cesium vapor with a copper oxide to obtain the cesium oxide particles and copper metal or reduced copper oxide.

7. The method according to claim 6, wherein the step of oxidizing the cesium vapor includes passing the cover gas flow through a porous material containing the copper oxide.

8. The method according to claim 7, wherein the porous material containing the copper oxide includes at least one of a packing material, wool, mesh, sieve material, powder, or granules.

9. The method according to claim 1, wherein the step of oxidizing the cesium vapor in the cover gas flow includes reacting the cesium vapor with oxygen gas to obtain the cesium oxide particles.

10. The cover gas flow includes the inert gas and the cesium vapor at a first molar concentration. The filtered cover gas flow contains the inert gas and the cesium vapor at a second molar concentration. The method according to claim 1, wherein the cesium vapor at the second molar concentration is from 0% to about 2% of the cesium vapor at the first molar concentration. **Claim 11** The method according to claim 10, wherein the cesium vapor at the second molar concentration is from 0% to about 0.2% of the cesium vapor at the first molar concentration. **Claim 12** The method according to claim 10, wherein the cesium vapor at the second molar concentration is from 0% to about 0.02% of the cesium vapor at the first molar concentration. **Claim 13** The method according to claim 10, wherein the cesium vapor at the second molar concentration is from 0% to about 0.002% of the cesium vapor at the first molar concentration. **Claim 14** A method for removing cesium from a cover gas flow in a nuclear reactor, comprising: providing a cover gas flow containing an inert cover gas and cesium vapor in the nuclear reactor; oxidizing the cesium vapor in the cover gas flow by reacting the cesium gas with at least one of a metal oxide and oxygen gas to form cesium oxide particles; removing the cesium oxide particles from the cover gas flow using a particle filter disposed within the cover gas flow to obtain a filtered cover gas flow; The method comprising. **Claim 15** The step of oxidizing the cesium vapor in the cover gas flow comprises: passing the cesium vapor through a porous metal oxide material disposed within the cover gas flow; reacting the cesium vapor with the metal oxide material to form the cesium oxide particles; The method according to claim 14, comprising. **Claim 16** The method according to claim 15, wherein the metal oxide material comprises an oxide of copper. **Claim 17** The particle filter comprises the metal oxide material, The method according to claim 15, wherein the metal oxide material acts as a first filter for removing at least a portion of the cesium oxide particles from the cover gas flow. **Claim 18** The particle filter further comprises a second filter, The method according to claim 17, wherein the second filter removes residual cesium oxide particles from the cover gas flow. **Claim 19** The step of oxidizing the cesium vapor in the cover gas flow comprises adding oxygen gas to the cover gas flow. A step of reacting the cesium vapor with the oxygen gas to form the cesium oxide particles; The method according to claim 14, including this.

20. A method for removing cesium from the cover gas flow in a nuclear reactor, comprising: A step of providing a cover gas flow containing an inert cover gas and cesium vapor in the nuclear reactor; A step of providing a metal oxide having a first Gibbs free energy of formation in the cover gas flow; A step of oxidizing the cesium vapor in the cover gas flow by a chemical reaction with the metal oxide to form particles of cesium oxide having a second Gibbs free energy of formation smaller than the first Gibbs free energy of formation; A step of removing the cesium oxide particles from the cover gas flow using a filter disposed in the cover gas flow to obtain a filtered cover gas flow; A method including this.

21. The method according to claim 20, wherein the metal oxide includes at least one of copper oxide, bismuth oxide, antimony oxide, lead oxide, nickel oxide, selenium oxide, tellurium oxide, and cobalt oxide.

22. The method according to claim 20, wherein the metal oxide includes a copper oxide selected from the group consisting of cupric oxide, cuprous oxide, and combinations thereof.

23. The cover gas flow includes the inert gas and the cesium vapor at a first molar concentration. The filtered cover gas flow includes the inert gas and the cesium vapor at a second molar concentration. The method according to claim 20, wherein the cesium vapor at the second molar concentration is 0% to about 0.002% of the cesium vapor at the first molar concentration.

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