Removal of radioactive noble gases from gas volume

Abstract

In a first aspect, the present invention relates to a method for removing a radioactive noble gas from a gas volume, the method comprising: (a) providing the gas volume such that the dew point of the gas volume at a gas temperature of 20° C. is −20° C. or less, preferably −30° C. or less, more preferably −45° C. or less; and (b) passing the gas volume over a bed (33) of microporous molecular sieve comprising a transition metal disposed on and / or within the microporous molecular sieve, thereby adsorbing the radioactive noble gas onto the bed (33).

Description

Technical Field

[0001] The present invention relates to the removal of radioactive noble gases from a gas volume, and more particularly to such removal based on the adsorption of radioactive noble gases onto a microporous molecular sieve bed containing transition metals.

Background Art

[0002] For example, in the production of 226 , - , 226 , 225 , <​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​This is due to the Ac reaction. However, such a production process presents significant technical challenges. 226 Based on Ra precursor 225 One of the main problems with Ac production is target radioactivity and radon (more specifically) 222 This is a continuous release of Rn). Therefore, capturing radon is important for safe operation, for example, to minimize uncontrolled releases from ventilation systems. Furthermore, for example, at the gram level. 226 Having a radon capture system that can be performed in a hot cell environment where operation a can be carried out would be industrially important. However, noble gases are nonpolar monatomic molecules with their outermost electron shells filled with eight valence electrons. Therefore, they do not usually chemically interact with other substances. As a result, noble gases are known to be difficult to capture or otherwise remove.

[0004] One known method is based on the adsorption of noble gases onto an activated carbon bed. Generally, adsorption is the process by which atoms, molecules, or ions of a gas, liquid, or (dissolved) solid—i.e., adsorbents—diffuse onto the surface of an adsorbent—usually a solid—where they either form bonds (chemiadsorption) or are held by intermolecular forces (physicoadsorption). Thus, adsorption is a surface phenomenon. Because they are chemically inert, noble gases experience physicoadsorption rather than chemiadsorption. While physicoadsorption relies on relatively weak forces (e.g., van der Waals forces), its efficiency can usually be improved by lowering the temperature of the adsorbent. Consequently, the adsorption of noble gases such as Kr, Xe, and Rn is typically carried out in conventional techniques on activated carbon beds cooled to cryogenic temperatures. Based on literature from 1908 to 2002, a summary of radon adsorption results reported on activated carbon and under various conditions was prepared by Gaul (GAUL, Wayne C. The application of moment analysis to the dynamic adsorption of radon by activated carbon. University of South Carolina, 2004. PhD thesis).

[0005] However, this method has several challenges. For example, the activated carbon adsorption bed needs to be kept cool at extremely low temperatures (e.g., below 0°C, -50, -65, or -75°C), otherwise the adsorption coefficient k- of noble gases, and thus the retention time t-, will decrease significantly. Furthermore, even at extremely low temperatures, the adsorption coefficient k is such that the activated carbon bed must be large enough to capture a meaningful amount of noble gases, especially when the bed is operated in continuous mode. In addition, cooling systems operating at extremely low temperatures are susceptible to condensation and freezing in the pipes. Even if moisture traps are in place to protect the pipes, this can lead to gas flow being blocked by frozen water. Finally, large quantities of charcoal itself pose a high fire hazard.

[0006] Therefore, in this field, there is still a need for better approaches to capture or remove noble gases. [Overview of the Initiative]

[0007] An object of the present invention is to provide a good method for removing noble gases from a gas volume. A further object of the present invention is to provide an excellent device related thereto. This object is achieved by the method, apparatus and system according to the present invention.

[0008] An advantage of the embodiments of the present invention is that effective adsorption of noble gases can be achieved.

[0009] An advantage of the embodiments of the present invention is that the amount of water adsorbed onto the noble gas adsorption bed can be reduced. A further advantage of the embodiments of the present invention is that the effective adsorption of noble gases can be maintained for a long period of time.

[0010] An advantage of the embodiments of the present invention is that it enables the realization of a particularly compact apparatus for removing noble gases from a gas volume.

[0011] An advantage of the embodiments of the present invention is that, for example, in contrast to carbon-based materials, the noble gas adsorption bed does not pose a fire hazard.

[0012] An advantage of the embodiments of the present invention is that they can be implemented or installed in a nuclear environment, for example, near a source of radioactive noble gases. A further advantage of the embodiments of the present invention is that there is no need to transport the gas volume over long distances.

[0013] An advantage of the embodiments of the present invention is that they do not rely on cooling for their usefulness and can be very effective, for example, at room temperature (or above).

[0014] An advantage of the embodiments of the present invention is that the noble gas can be retained within the apparatus (for example, on a noble gas adsorption bed) until it is effectively decayed.

[0015] An advantage of the embodiments of the present invention is that redundancy can be incorporated into the device, thereby improving efficiency and safety.

[0016] An advantage of the embodiments of the present invention is that the adsorption bed can be directly regenerated.

[0017] An advantage of the embodiments of the present invention is that substances that may be toxic to the adsorption bed can be removed before the gas volume passes over them.

[0018] An advantage of the embodiments of the present invention is that they can be used to remove short-lived and / or long-lived radioactive noble gases from a gas volume.

[0019] An advantage of the embodiments of the present invention is that they can be implemented in a relatively simple and economical manner.

[0020] In a first aspect, the present invention provides a method for removing a radioactive noble gas from a gas volume, comprising: (a) providing a gas volume such that the dew point of the gas volume at a gas temperature of 20°C is -20°C or lower, preferably -30°C or lower, and more preferably -45°C or lower; and (b) passing the gas volume over a bed of a microporous molecular sieve containing a transition metal, which is placed on and / or in a microporous molecular sieve, thereby adsorbing the radioactive noble gas onto the bed.

[0021] In a second aspect, the present invention relates to an apparatus for removing radioactive noble gases from a gas volume, comprising (i) one or more moisture adsorption beds, and (ii) one or more noble gas adsorption beds of a microporous molecular sieve containing a transition metal, disposed on and / or within a microporous molecular sieve, wherein the noble gas adsorption bed has an input connected to the output of the moisture adsorption bed.

[0022] In a third aspect, the present invention relates to a multilayer system for removing radioactive noble gases from a gas volume, wherein one or more layers comprise an apparatus according to any embodiment of the second aspect.

[0023] Specific preferred embodiments of the present invention are described in the attached independent and dependent claims. Features from the dependent claims may be combined as necessary with features of the independent claims and other dependent claims, and may not be as explicitly stated in the claims.

[0024] While devices in this field have constantly been improved, modified, and evolved, this concept is considered to represent a substantially new and novel improvement, including a departure from conventional practices, resulting in a more efficient, stable, and reliable device of this nature.

[0025] The above-mentioned and other features, functions and advantages of the present invention will become apparent from the following detailed description, in conjunction with the accompanying drawings illustrating the principles of the present invention. This description is provided for illustrative purposes only and does not limit the scope of the present invention. The reference figures cited below refer to the accompanying drawings. [Brief explanation of the drawing]

[0026] [Figure 1] A schematic diagram illustrates an exemplary apparatus with built-in redundancy for removing radioactive noble gases according to the present invention. [Figure 2] A schematic diagram of the experimental setup used in the proof-of-concept radon adsorption experiment according to the first embodiment described herein is shown. [Figure 3] This is a flowchart of the process steps used during breakthrough experiments according to the first and second embodiments. [Figure 4] This is a graph of the 222Rn breakthrough curves for NuclearCarb207C, Ag-13X, and 1.5 mm Ag-ETS-10 pellets according to the first example. [Figure 5] This is a graph of the 222Rn breakthrough curve of Ag-ZSM-5 according to the first embodiment. [Figure 6] This is a graph of the 222Rn breakthrough curve for 16-30 mesh Ag-ETS-10 granules according to the first embodiment. [Figure 7] This graph shows the 222Rn breakthrough curve of a 1.5 mm Ag-ETS-10 pellet, illustrating the effect of removing moisture traps according to the first embodiment. [Figure 8] This graph shows a close-up of the curve in Figure 7, along with the relative humidity measured by the Rn monitor according to the first embodiment. [Figure 9] This graph shows the moisture absorption (weight %) of 16-30 mesh Ag-ETS-10 granules in relation to the function of regeneration temperature according to the first and second embodiments. [Figure 10] This is a graph of the 222Rn breakthrough curve for 16-30 mesh Ag-ETS-10 granules exposed to H2 and NOx vapor according to the first example. [Figure 11] This is a scanning electron microscope image of silver nanoparticles on an Ag-ETS-10 crystal according to the second example. [Figure 12] A schematic diagram of the experimental apparatus used in the radon adsorption experiment according to the second embodiment is shown. [Figure 13]This is a graph of the room-temperature breakthrough curve of 222Rn measured on NuclearCarb207C, CarboAct, Ag-13X, Ag-ZSM-5, and Ag-ETS-10 according to the second example described herein. [Figure 14] This is a graph of the measured emission of 222Rn from Ag-ETS-10 when in contact with laboratory air at 50% relative humidity, according to the second example. [Figure 15] This is a graph of the measured breakthrough curves of 222Rn from Ag-ETS-10 for different (dry) carrier gases (N2, air, and Ar) according to the third example described herein. [Modes for carrying out the invention]

[0027] In different drawings, the same reference numeral refers to the same or similar element.

[0028] The present invention is described with reference to specific drawings for certain embodiments, but the present invention is not limited thereto and is limited only by the claims. The drawings provided are merely schematic and non-limiting. In the drawings, the sizes of some elements may be exaggerated and not depicted to a certain ratio for illustrative purposes. Dimensions and relative dimensions do not correspond to the actual implementation of the present invention.

[0029] Furthermore, terms such as “first,” “second,” and “third” in the description and claims are used to distinguish similar elements and are not necessarily intended to rank or describe them temporally or spatially in any other way. Naturally, such terms are interchangeable under appropriate circumstances, and embodiments of the invention described herein may operate in an order other than those described or illustrated herein.

[0030] Furthermore, terms such as "above," "below," "above," and "below" in the description and claims are used for convenience and are not necessarily intended to describe relative positions. Naturally, such terms are interchangeable with their antonyms under appropriate circumstances, and embodiments of the present invention described herein may operate in orientations other than those described or illustrated herein.

[0031] Furthermore, the term "including" used in the claims should not be construed as limiting the means listed thereafter. It does not exclude other elements or steps. Therefore, it should be interpreted as identifying the presence of the described features, integers, steps, or components as mentioned, but not as excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Accordingly, the term "including" encompasses situations in which only the described functions exist, and situations in which these functions and one or more other functions exist. Therefore, the scope of the expression "device including means A and B" should not be construed as limiting the device to a device consisting only of components A and B. What is meant is that, with respect to the present invention, A and B are the only relevant components of the device.

[0032] Similarly, it should be noted that the term “combined” as used in patent claims should not be interpreted as being limited only to direct connections. The terms “combined” and “connected” may be used together with their derivatives. It should be understood that these terms are not considered synonymous with each other. Therefore, the expression “device A coupled to device B” should not be limited to a device or system in which the output of device A is directly connected to the input of device B. There may be a path between the output of A and the input of B that may involve other devices or means. “Combined” means that two or more elements are in direct physical or electrical contact with each other, or that two or more elements are not in direct contact with each other but still cooperate or interact with each other.

[0033] Wherever the “one embodiment” or “embodiment” is used throughout this specification, it means that any particular feature, structure, or characteristic described in relation to an embodiment is included in at least one embodiment of the present invention. Therefore, wherever the phrase “in one embodiment” or “in one embodiment” appears throughout this specification, it does not necessarily refer to the same embodiment, but it does refer to at least one of them. Furthermore, it will be apparent to those skilled in the art from this disclosure that in one or more embodiments, particular features, structures, or characteristics may be combined in any preferred manner.

[0034] Similarly, naturally, in the description of typical embodiments of the present invention, various features of the invention may be grouped together in a single embodiment, figure, or description, for the purpose of streamlining this disclosure and helping to understand one or more of the various aspects of the invention. However, this method of disclosure should not be interpreted as reflecting the idea that the features necessary for the claimed invention are more numerous than those explicitly enumerated in each claim. Rather, as reflected in the following claims, aspects of the invention consist of fewer features than all the features of the single embodiment disclosed earlier. Accordingly, the claims following the detailed description are explicitly incorporated into this detailed description by this specification, and each claim stands alone as a distinct embodiment of the invention.

[0035] Furthermore, some embodiments described herein include some features included in other embodiments but not others, while combinations of features from various embodiments are intended to fall within the scope of the present invention and constitute various embodiments. This will be apparent to those skilled in the art. For example, in the following claims, any combination of the claimed embodiments may be used.

[0036] The description herein includes many specific details. However, embodiments of the present invention may, of course, be carried out without these specific details. In other cases, well-known methods, structures, and techniques are not described in detail. This is to avoid ambiguity in understanding this description.

[0037] The following terms are provided solely to aid in understanding the present invention.

[0038] As used herein, unless otherwise specified, zeolites are naturally or synthetically derived microporous aluminosilicate and / or titanosilicate molecular sieves. They can be used as adsorbents because they have a complex three-dimensional structure containing cavities that can accommodate various cations. Many types of zeolites exist, each with its own unique properties, for example, with respect to crystal structure, pore shape, and / or pore size.

[0039] As used herein, unless otherwise specified, a transition metal-exchanged microporous molecular sieve is a microporous molecular sieve that has undergone an exchange process in which some of its atoms (usually ions) are replaced with transition metals. For example, Na in a microporous molecular sieve + and / or K + In ion exchange reactions, transition metal cations (e.g., Ag) are involved. + ) can be (partially) replaced by.

[0040] In a first aspect, the present invention relates to a method for removing a radioactive noble gas from a gas volume, comprising: (a) providing a gas volume such that the dew point of the gas volume at a gas temperature of 20°C (293.15K) is -20°C or lower, preferably -30°C (243.15K) or lower, more preferably -45°C (228.15K) or lower, for example, -60°C (213.15K) to -100°C (173.15K); and (b) passing the gas volume over (e.g., through) the floor of a transition metal exchange microporous molecular sieve containing a transition metal disposed on and / or within a microporous molecular sieve, thereby adsorbing the radioactive noble gas onto the floor (this may also be referred to as a "noble gas trap").

[0041] Although not bound by theory, in adsorption processes, an equilibrium is established between the amount of adsorbent in the mobile (gas or liquid) phase and the amount of adsorbent on the adsorbent. This process is usually described by isotherms, which are expressed as the amount of adsorbent relative to the partial pressure of the adsorbent in the fluid (in the case of a gas). Various isotherm models exist to describe this equilibrium (e.g., linear, Freundlich, Langmuir, etc.). For example, the linear isotherm, a type of Henry's Law, can be used when the amount (partial pressure) of adsorbent is low. q = K·p In the equation, q is the amount of adsorption per unit mass of the adsorbent, K is a temperature-dependent empirical constant, and p is the partial pressure of the adsorbent in the gas flow. Furthermore, when the adsorbent—in this case, a noble gas (e.g., Rn)—moves through a packed column of an adsorbent material having a specific affinity for the adsorbent, the adsorption process causes a delay in the adsorbent compared to a carrier gas with weaker adsorption (e.g., nitrogen, oxygen, etc.). Depending on the type of system, there are various models that explain the dynamics of the packed adsorption column. A simple way to explain the average delay / retention time t (seconds), which is often seen in literature on noble gas adsorption, is: t = (k·m) / F And in the formula, k(cm 3 / g) is the adsorption coefficient, m(g) is the mass of the adsorbent, F(cm) 3The value of the adsorption coefficient k is the volumetric flow rate ( / s). This relationship provides a simple way to determine the value of the adsorption coefficient k from the measured retention time t in experiments where concentration pulses of a noble gas are injected into an adsorption column at a known mass and flow rate. The average retention time t is defined as the time at which the measured breakthrough noble gas concentration is 5% of the observed maximum noble gas concentration (see Examples). The adsorption coefficient is important for evaluating the capacity of the (noble gas) adsorption bed. For a given adsorbent, the coefficient can be influenced by the type of adsorbent, temperature, the carrier gas used, and its contaminants. The obtained adsorption coefficients can be compared. A higher coefficient indicates a higher affinity of the adsorbent to the adsorbent and a longer delay.

[0042] In the present invention, a noble gas adsorption bed based on a microporous molecular sieve containing a transition metal can adsorb a considerable amount of water (about 10-20% by weight), thereby impairing its further effectiveness in adsorbing noble gases (see Examples). Thus, without further precautions, the noble gas adsorption bed would need to be regenerated frequently or a larger bed would need to be used. However, by lowering the dew point of the noble gas adsorption bed before passing the gas through it, water adsorption is significantly reduced, and the bed can adsorb noble gases more efficiently for a longer period of time. This further enables a particularly compact design of the radioactive noble gas removal device—because the size of the noble gas adsorption bed can be significantly reduced while maintaining its effectiveness, thus allowing the device to be easily placed near the radioactive noble gas source (see below).

[0043] In a preferred embodiment, step (a) may include removing water from the gas volume ("drying") such that the dew point of the gas volume at a gas temperature of 20°C is -20°C or lower, preferably -30°C or lower, more preferably -45°C or lower, for example -60°C to -100°C. In such embodiments, step (a) may include passing the gas volume over (e.g., through) a moisture adsorption bed (which may also be referred to as a "moisture trap"). In some embodiments, the moisture adsorption bed may include further microporous molecular sieves such as zeolites (e.g., 4A, 13X, ZSM-5, or ETS-10). In contrast to noble gas adsorption beds, moisture adsorption beds may not typically contain transition metals. Preferably, drying the gas volume may be performed while the radioactive noble gas is present in it, for example, immediately before step (b) (e.g., as schematically shown in Figure 1). This is advantageous because it makes it more certain that the gas volume will have the desired low dew point as it passes over the noble gas adsorption bed in step (b), even if, for example, the radioactive noble gas source is also a water source for the gas volume. Alternatively, the drying of the gas volume may be carried out before the radioactive noble gas is present in it (for example, as described in the examples and schematically shown in Figure 2). This is advantageous because it is possible to dry the gas volume before contact with the radioactive noble gas, at which point the gas volume may not yet be radioactive. Therefore, the drying process does not yet involve a significant risk of radiation exposure, and the components used in the drying process (e.g., the water adsorption bed) are not usually contaminated with radioactivity. Thus, the safety measures required for the drying process can be relaxed, for example, and the handling and disposal of the components used can be made easier. It should be noted that by combining both methods, the gas volume can be easily dried before exposure to radioactive gas, while at the same time ensuring a dew point after such exposure—for example, immediately before step (b).

[0044] In alternative or supplemental embodiments, step (a) may include adding a radioactive noble gas to a dry gas volume (e.g., a dry carrier gas) (e.g., exposing it to the radioactive noble gas). Here, the dry gas volume is a gas volume having a dew point of -20°C or less, preferably -30°C or less, more preferably -45°C or less, for example, -60°C to -100°C at a gas temperature of 20°C (see above). In various embodiments, the dry gas volume may be a gas volume that has already undergone a drying step (see above), or a gas volume that is essentially dry (e.g., a dry inert gas such as N2). The advantages of this method are similar to those described above for drying the gas volume before the radioactive noble gas is present in it. Furthermore, the composition of such a dry gas volume is usually advantageous, as it does not contain substances that may be toxic to the adsorption bed(s) (e.g., NO x The process can be chosen to avoid (for example, at least partially, preferably completely) oxidizing agents such as CO2 and / or O2 (see below), thereby reducing—or even eliminating—the need for the step of removing the toxic substances.

[0045] The gas volume can typically include (i) one or more radioactive noble gases to be removed and (ii) a nonpolar carrier gas. For example—particularly when entering step (b)—the gas volume may substantially consist of (i) one or more radioactive noble gases to be removed and (ii) a nonpolar carrier gas. In other words, any nonpolar gas that remains in the gas volume when entering step (b) (i.e., not removed before step (b), see below) and is not a radioactive noble gas to be adsorbed in step (b) can be considered part of the nonpolar carrier gas. The nonpolar carrier gas can generally be any suitable nonpolar gas such as (dry) N2 (it should be noted that moisture / water and substances toxic to the adsorption bed(s) can preferably be avoided—see above—but these are typically polar and therefore not part of the nonpolar carrier gas). Nevertheless, the nonpolar carrier gas is, in a preferred embodiment, 1.700 Å 3 Preferably, 1,600 Å 3 More preferably, 1,200 Å3 More preferably, 0.800 Å 3 Below, most preferably 0.400 Å 3 For example, 0.300 Å 3 The following polarizability (α) is possible. Although not bound by theory, the adsorption strength of a nonpolar gas depends on its polarizability in a first-order approximation; therefore, the higher the polarizability, the stronger the interaction with the noble gas adsorption bed (e.g., with the transition metal within it). Consequently, it is advantageous to use a nonpolar carrier gas with low polarizability in order to minimize the interaction between the nonpolar carrier gas and the noble gas adsorption bed and to free up the adsorption sites as much as possible to adsorb the radioactive noble gas. In this regard, it should be noted that even a small difference in polarizability between two nonpolar carrier gases can result in a large difference in the retention of the radioactive noble gas. In fact, surprisingly, when using dry air (consisting of approximately 78% N2, 21% O2, and 1% Ar), the retention time of the radioactive noble gas is higher than that of pure N2 (α = 1.710 Å). 3 Compared to ), an increase of up to approximately 30-40% was observed, while Ar(α=1.664Å) 3 Using ) increased the retention time by about 10 times compared to pure N2. Therefore, O2(α=1.562Å 3 ), F2(α=1.160Å) 3 ), H2(α=0.787Å 3 ), Ne(α=0.381Å) 3 ), He(α=0.208Å) 3Using these mixtures as light gases such as ) or nonpolar carrier gases can yield increasingly greater effects. However, even with low polarizability, some of the aforementioned nonpolar gases (e.g., O2, F2, or H2) can nevertheless chemically react with one or more absorption bed materials (e.g., noble gas absorption bed materials)—and thus be toxic to them—and therefore their overall effect can actually be negative in the long run. For this reason, Ar, Ne, He, and mixtures thereof may be preferred. A comprehensive list of experimental polarizability of various substances is provided by the National Institute of Standards and Technology (https: / / cccbdb.nist.gov / pollistx.asp), and these also originate from Olney et al. (OLNEY, Terry N., et al. Absolute scale determination for photoabsorption spectra and the calculation of molecular properties using dipole sum-rules. Chemical Physics, 1997, 223.1:59-98.), Landolt-Bornstein (LANDOLT-BORNSTEIN. Zahlenwerte und Funktionen. Springer, 1962, Vol.1, Pt.3, p.509.), (GRAFF, J.; DAGDIGIAN, PJ; WHARTON, L. Electric resonance spectrum of NaLi. The Journal of Chemical Physics, 1972, 57.2:710-714.), Miller and Bederson (MILLER, Thomas M.;BEDERSON,Benjamin.Atomic and molecular polarizabilities-a review of recent advances.Advances in atomic and molecular physics,1978,13:1-55.),Bray and Gubbins(BRAY,CG;GUBBINS,KETheory of Molecular Fluids.Volume1:Fundamentals.1984.),Miller(MILLER,Kenneth J.Additivity methods in molecular polarizability.Journal of the American Chemical Society,1990,112.23:8533-8542.),Gussoni et al.(GUSSONI,M.;RUI,M.;ZERBI,Giuseppe. Electronic and relaxation contribution to linear molecular polarizability. An analysis of the experimental values.Journal of molecular structure,1998,447.3:163-215.),Ballard et al.(BALLARD,A.;BONIN,K.;LOUDERBACK,J.Absolute measurement of the optical polarizability of C60.The Journal of Chemical Physics,2000,113.14:5732-5735.),Jacobson et al.(JACOBSON,P.L.,et al.Microwave spectroscopy of heliumlike Rydberg states of H2 and D2:Determinations of the dipole polarizabilities of H2+ and D2+ ground states.Physical Review A,2000,62.1:012509.),Thakkar and Wu(THAKKAR,Ajit J.;WU,Taozhe. How well do static electronic dipole polarizabilities from gas-phase experiments compare with density functional and MP2 computations?The Journal of Chemical Physics,2015,143.14:144302.) and Miller (MILLER, T.M. Handbook of Chemistry and Physics Online, http: / / hbcponline.com / faces / documents / 10_04 / 10_04_0001.xhtml). Of these, Olney et al. are particularly relevant to the substance under consideration. Therefore, to facilitate comparison, the experimental determination of the polarizability of a substance can preferably be carried out according to the aforementioned references. When the nonpolar carrier gas is a mixture of substances, the weighted average (weighted by partial pressure) of the polarizability of the individual substances can be used as the "polarizability of the nonpolar carrier gas".

[0046] In some embodiments, removing a noble gas from a gas volume may mean removing the noble gas at least partially from the gas volume. In preferred embodiments, removing a noble gas from a gas volume may mean removing the noble gas completely from the gas volume.

[0047] Transition metals disposed on and / or within a microporous molecular sieve can exist in different forms. In some embodiments, the microporous molecular sieve may contain transition metal nanoparticles (i.e., the transition metal may exist in the form of nanoparticles). In alternative or supplemental embodiments, the microporous molecular sieve may be a transition metal exchange microporous molecular sieve (i.e., the transition metal may exist in the form of exchange ions). In a preferred embodiment, the microporous molecular sieve may be a transition metal exchange microporous molecular sieve containing transition metal nanoparticles (i.e., the transition metal may exist in both the form of exchanged atoms / ions and nanoparticles). The latter may, for example, typically be the case where nanoparticles are formed from the exchanged transition metal. In some embodiments, the transition metal may be inherently metallic (e.g., typically in the case of transition metal nanoparticles) and / or ionic (e.g., typically in the case of exchange transition metals). Both the transition metal nanoparticles and the exchanged transition metal interact with the noble gas, causing them to adsorb to the bed. Despite the foregoing, in the case of a given transition metal, the noble gas may interact more strongly with the transition metal nanoparticles than with the atomic transition metal (e.g., experiencing higher van der Waals forces). Thus, when a microporous molecular sieve contains both transition metal nanoparticles and exchange transition metals, binding to the transition metal nanoparticles may initially be dominant (and may remain so at lower partial pressures), while binding to the exchange transition metal may become increasingly important as the transition metal nanoparticle sites are occupied (this may be particularly relevant at higher partial pressures, such as above 1 kPa).

[0048] In some embodiments, transition metal nanoparticles (e.g., nanoclusters or nanodots) may have a diameter (e.g., average diameter) of about 10 nm, preferably between 0.5 and 50 nm, more preferably between 1 and 30 nm, even more preferably between 2 and 20 nm, and most preferably between 5 and 15 nm. In some embodiments, the transition metal nanoparticles may be arranged on the surface of a microporous molecular sieve or within the pores of a microporous molecular sieve. In some embodiments, the transition metal nanoparticles may be formed (in situ) by thermally activating a transition metal-exchanged microporous molecular sieve. For example, a transition metal-exchanged microporous molecular sieve may be thermally activated at a temperature of 100 to 500°C, preferably 150 to 400°C, more preferably 200 to 300°C, for example, about 250°C. Thermal activation may be carried out for 1 to 24 hours, preferably 3 to 18 hours, more preferably 6 to 15 hours, and even more preferably 9 to 12 hours. In such embodiments, not all of the exchanged transition metals are typically converted into transition metal nanoparticles; therefore, the result in such cases is generally a transition metal-exchanged microporous molecular sieve containing transition metal nanoparticles. In alternative or supplemental embodiments, the nanoparticles may be formed ex situ and deposited on and / or within the microporous molecular sieve. This can be done, for example, using methods such as chemical vapor deposition (CVD).

[0049] In various embodiments, the transition metal can be selected from Group 10 (i.e., Nickel group, e.g., Ni, Pd, or Pt), Group 11 (i.e., Copper group, e.g., Cu, Ag, or Au), and Platinum group (e.g., Ru, Rh, Pd, Os, Ir, or Pt). In preferred embodiments, the transition metal may be Ag. For comparison, silver-exchanged zeolites are known to exhibit a higher affinity than sodium zeolites for the removal of xenon from air. Since the physical and chemical properties of noble gases are generally similar, this is expected to be the same for other noble gases (e.g., Rn). Indeed, at least for Rn, Ag-exchanged zeolites containing Ag nanoparticles have been found to result in a high noble gas adsorption coefficient (see Examples). Similarly, based on the assumed interaction mechanism between noble gases and Ag (in the form of exchanged and / or nanoparticles), similar effects are expected for all Group 10, Group 11, and Platinum group transition metal elements that share similar physical and chemical properties. That said, molecular sieves containing these latter may have potentially low commercial relevance and / or availability (e.g., due to the difficulties associated with their synthesis). In some embodiments, a microporous molecular sieve may contain two or more (forms of) transition metals. For example, a microporous molecular sieve may contain one or more types of transition metal nanoparticles and / or one or more types of exchange transition metals. In such cases, each of the transition metals may be independently selected from Group 10, Group 11, and platinum group transition metals.

[0050] In various embodiments, the microporous molecular sieve may have a pore size of 2 nm or less, preferably between 0.2 and 1.5 nm, more preferably between 0.4 and 1.2 nm, and most preferably between 0.5 and 1 nm. In various embodiments, the microporous molecular sieve may be an inorganic molecular sieve such as a zeolite. In various embodiments, the microporous molecular sieve may be an aluminosilicate zeolite (e.g., ZSM-5 or 13X) or a titanosilicate zeolite (e.g., ETS-10), preferably a titanosilicate zeolite. In particularly preferred embodiments, the microporous molecular sieve may be ETS-10 or ZSM-5. ETS-10 and ZSM-5 containing transition metal (Ag) nanoparticles (Ag exchange) have been found to have advantageously very high capture efficiency, particularly for Rn (see Examples).

[0051] In various embodiments, the radioactive noble gas is Ar (for example, 37 Ar, 39 Ar or 42 Ar), Kr (for example) 85 / 85m Kr), Xe (for example, 133 / 135 Xe) and Rn (for example, 210 Rn, 211 Rn, 219 Rn, 220 Rn, 221 Rn or 222 Rn), preferably selected from Kr, Xe, or Rn, most preferably Rn. Adsorption efficiency is usually low for lighter noble gases and increasingly high for heavier noble gases. Therefore, significant adsorption of Kr, Xe, and Rn can usually be achieved even at room temperature, which is usually not as much for Ar. Although mass number is not expected to have a significant effect on the interaction with the noble gas adsorption bed—and differences in half-lives can affect the lifetime of the noble gas (e.g., the noble gas adsorption bed), and therefore play a role in that—nevertheless, the present invention 222 It is particularly suitable for the removal of Rn, which has a special need (see Background Art), and the present invention works very well (see Examples).

[0052] In some embodiments, the adsorbed radioactive noble gas may be retained—for example, contained within the apparatus (see below)—until it is effectively decayed. For example, the adsorbed radioactive noble gas may be retained until the activity of the radioactive noble gas is reduced by at least 90%, preferably at least 95%, more preferably at least 99%, even more preferably at least 99.9%, most preferably at least 99.99%, for example, completely (i.e., 100%). It should be noted that retaining the adsorbed noble gas may also include, for example, passing the noble gas from one noble gas adsorption bed to another (or back to a moisture adsorption bed), for example, during the regeneration of a previous bed. Thus, in the case of radioactive noble gases with relatively short decay periods, this method can advantageously involve capturing the noble gas and allowing it to decay within the apparatus (e.g., in a noble gas adsorption bed). This is, for example, in the case of Rn, whose longest-lived isotope has a half-life of 3.8 days. 222 This refers to Rn. More specifically, for radioactive noble gases (isotopes) with short lifetimes (e.g., half-lives of less than 7 days), two main modes for carrying out this method can be distinguished: (1) passing the gas volume over the noble gas adsorption bed at a low flow rate so that the noble gas can decay effectively within the apparatus, or (2) passing the gas volume over the noble gas adsorption bed at a high flow rate to reduce the concentration of the noble gas in the gas volume—achieving a constant decontamination factor (DF) without completely decomposing the noble gas within the apparatus. The former may be preferred when capturing highly radioactive noble gas puffs and / or when dealing with continuously emitting radioactive noble gas sources. The latter may be suitable when large volumes of gas need to be processed.

[0053] In other embodiments, the adsorbed radioactive noble gas may be collected for further storage and / or utilization. In fact, long-lived radioactive noble gases (e.g., 85 Kr, 39 Ar and / or 42In the case of Ar (with half-lives of 11, 269, and 32.9 years, respectively), waiting for them to decay within the apparatus (e.g., on a noble gas adsorption bed) is usually impractical. Thus, this method may rather involve capturing the noble gas on a noble gas adsorption bed—thus concentrating it—and then removing the noble gas from the adsorption bed (e.g., during its regeneration). The noble gas can then be collected, stored, and / or used for other purposes.

[0054] In various embodiments, the method includes a further step (a') prior to step (b) (preferably prior to step (a)) of removing a gas volume from a substance that may be harmful to the noble gas adsorption layer (e.g., such as a microporous molecular sieve and / or transition metal) and / or the moisture adsorption layer—if present (e.g., NO x This may include removing oxidizing agents such as CO2 and / or O2. In this context, a substance “toxic” to the adsorption bed is a substance other than the adsorbate for which the use of the adsorption bed is particularly intended, which reversibly or irreversibly binds or reacts with the adsorption bed, thereby reducing the capture efficiency for the intended adsorbent. In some embodiments, step (a') may include passing a gas volume over (e.g., through) a scrubber. For example, using a NaOH scrubber to remove NO x This allows for the removal of such toxic substances. If such toxic substances are expected to be present in the gas volume, removing them before passing the gas volume through the noble gas adsorption bed (and / or moisture adsorption bed) is advantageously possible, as it allows for better maintenance of its efficiency. This is similar to how ensuring a low dew point improves the effectiveness of the gas adsorption bed.

[0055] In some embodiments, the method may include a further step (c) of regenerating the noble gas adsorption bed and / or the moisture adsorption bed, if present. In some embodiments, step (c) may include heating the noble gas adsorption bed and / or the moisture adsorption bed, and / or flushing the noble gas adsorption bed and / or the moisture adsorption bed, if present, with a regeneration gas (e.g., an inert gas such as N2 or Ar, or another gas such as air). In this regard, it has been found that radioactive noble gases can be advantageously removed rapidly and efficiently (with sharp pulses, see Example 2) from the noble gas absorption bed using a regeneration gas containing water (moisture). Although not bound by theory, it is thought that water molecules strongly compete with noble gases (e.g., Rn) for active adsorption sites on Ag nanoparticles, thereby effectively removing the noble gas from the bed. Therefore, in preferred embodiments, the regeneration gas may include competing absorbers (i.e., adsorbents that compete with noble gases, such as water). In some embodiments, heating the noble gas adsorption bed may include heating the noble gas adsorption bed from the outside (e.g., by enclosing it in a heating element or by placing it in a furnace or oven) and / or heating the noble gas adsorption bed from the inside (e.g., by using a high-temperature regenerating gas). In some embodiments, heating the noble gas adsorption bed may include heating the noble gas adsorption bed to a temperature of 100 to 500°C, preferably 150 to 400°C, and more preferably 200 to 350°C.

[0056] In preferred embodiments, the method (for example, at least step (b) therein) can be carried out at a temperature of -150°C to 50°C, preferably -100°C to 40°C, more preferably -50°C to 35°C, even more preferably 0°C to 30°C, and most preferably at room temperature (e.g., 15°C to 25°C, e.g., 20°C). The present invention is advantageous in that it is possible to achieve good adsorption efficiency without requiring cooling, but operating at lower temperatures can further improve adsorption efficiency.

[0057] In various embodiments, the method can be carried out in a nuclear environment. For example, the gas volume may originate from a source of radioactive noble gas, and the method can be carried out in close proximity to the noble gas source (for example, within 15 m, preferably 10 m, more preferably 5 m, even more preferably 3 m, still more preferably 2 m, and most preferably 1 m from the noble gas source). In various embodiments, the source of radioactive noble gas may be located in a nuclear glove box, hot cell, target station, fuel storage, or irradiation rig. In various embodiments, the method can be carried out in close proximity to or within the nuclear glove box, hot cell, target station, fuel storage, or irradiation rig. By carrying out the method near the source of radioactive noble gas, the need to transport radioactive gas over long distances is advantageously avoided, and the associated risks can be prevented.

[0058] In various embodiments, any feature of any embodiment of the first aspect may independently be described in correspondence with any embodiment of any other aspect.

[0059] In a second aspect, the present invention relates to an apparatus for removing radioactive noble gases from a gas volume, comprising (i) one or more moisture adsorption beds, and (ii) one or more adsorption beds of microporous molecular sieves containing transition metals, disposed on and / or in microporous molecular sieves, wherein the noble gas adsorption bed has an input coupled to the output of the moisture adsorption bed.

[0060] In various embodiments, the apparatus may further comprise (iii) one or more regenerating gas sources coupled to a noble gas adsorption bed and optionally to a moisture adsorption bed. In various embodiments, one or more regenerating gas sources may be coupled to the output of the noble gas adsorption bed(s). This allows the radioactive gases remaining in the noble gas adsorption bed(s) within the apparatus to be retained (for example, on a parallel second noble gas adsorption bed or returned to a moisture adsorption bed), while the noble gas adsorption bed(s) can be easily regenerated (in the opposite direction to the normal gas volume flow).

[0061] In various embodiments, the apparatus may further comprise one or more scrubbers for removing substances toxic to the noble gas adsorption bed and / or moisture adsorption bed from the gas volume. In various embodiments, the scrubber(s) may have an output coupled to the input of the noble gas adsorption bed(s)—for example, via the moisture adsorption bed(s).

[0062] By using multiple noble gas adsorption beds, moisture adsorption beds, scrubbers, etc., it is advantageous that a certain degree of redundancy can be incorporated into the apparatus. For example, while one or more noble gas adsorption beds or moisture adsorption beds are being regenerated, another bed can be actively used, or—complementarily or alternatively—another bed can be on standby (e.g., as a backup). Such redundancy can improve the level of efficiency (e.g., enabling more continuous use) and the level of safety (e.g., by having one or more backups in case one of the elements fails). Radioactive noble gases (20, e.g. 222An example of such apparatus (10) representing an environment contaminated with Rn) is shown in Figure 1, which is connected in order to a scrubber (31) with two parallel columns, a moisture adsorption bed (32) with two parallel columns, and a noble gas adsorption bed (33) with two parallel columns. A ventilation device (40) draws in a gas volume containing the radioactive noble gas through the columns (31-33)—after (partially) removing the noble gas—and circulates it back to the original environment (20). The content of the radioactive noble gas in the reverse-circulating gas volume is confirmed using a noble gas monitor (51). The flow rate of the gas volume passing through the apparatus (10) is controlled by a flow control device (52) located between the noble gas adsorption bed (33) and the ventilation device (40). A dew point (or relative humidity) meter (53) is placed between the moisture adsorption bed (32) and the noble gas adsorption bed (33). If either the measured noble gas content or dew point is too high (e.g., exceeding a predetermined threshold), the flow rate may be reduced—which may increase the time for capturing the noble gas and / or water in each column (32, 33)—or the column may be regenerated. For this purpose, each of the columns (31-33) is coupled to a regeneration gas source (60). Note that while one column is being regenerated, a parallel redundant column can be used and the apparatus (10) can operate continuously. As shown in Figure 1, coupling to the regeneration gas source is achieved through the column output, pushing the adsorbed material desorbed by the regeneration process upstream. In the case of the scrubber (31) and water adsorption bed (32), the desorbed toxic compounds and water are normally discharged into an exhaust system (70). However, the amount of radioactive noble gas discharged through the exhaust system should normally be kept to a minimum (e.g., below a predetermined threshold). In other words, if the concentration of radioactive noble gas has not decreased sufficiently, it should not be discharged. In the case of noble gases that decay within the apparatus (10), the noble gases desorbed by regeneration can (1) be guided onto a parallel column and captured there, (2) be pushed back into an upstream moisture adsorption column (however this may jeopardize the continuous operation of the apparatus), or (3) be circulated back into the original environment (20) and pass through the entire apparatus again.For noble gases that do not decay on the column, the radioactive noble gases can be recovered after being concentrated in the noble gas adsorption bed using a final pathway—not the original environment as shown in Figure 1—combined with the storage unit.

[0063] In some embodiments, the gas adsorption bed, moisture adsorption bed, and / or scrubber may be in the form of a column through which the gas volume passes.

[0064] In various embodiments, any feature of any embodiment of the second aspect may independently be as described in correspondence with any embodiment of any other aspect.

[0065] In a third aspect, the present invention relates to a multilayer system for removing radioactive noble gases from a gas volume, wherein one or more layers comprise an apparatus according to any embodiment of the second aspect.

[0066] For example, the apparatus according to the present invention can be attached to a first vessel (e.g., a receptacle, glove box, or hot cell) to remove a radioactive noble gas from the gas volume of the first vessel, while a further apparatus (according to the present invention or based on different principles) can be attached to a further vessel—surrounding the first vessel—(e.g., a glove box or hot cell in which the receptacle is located, or a space or bunker in which the receptacle, glove box, or hot cell is located) to remove a radioactive noble gas (e.g., the same noble gas) from the gas volume of the further vessel. In this way, a highly effective multi-layer system can be realized in which the first apparatus can remove most of the radioactive noble gas, while any that slip through (e.g., into the exhaust system of the first apparatus) can be captured by the further apparatus surrounding the first apparatus. In various embodiments, the first apparatus may be operated using a low flow rate, and the further apparatus may be operated using a high flow rate (see above).

[0067] In various embodiments, any feature of any embodiment of the third aspect may independently be as described in correspondence with any embodiment of any other aspect.

[0068] Herein, the present invention will be described by a detailed description of some embodiments of the present invention. It will be apparent that other embodiments of the present invention can be constructed according to the knowledge of those skilled in the art without departing from the true technical teachings of the present invention, and the present invention is limited only by the appended claims. [Examples]

[0069] Example 1 To illustrate and support the proof of concept of the present invention, many different experiments were conducted using Rn as the noble gas and different types of noble gas adsorption beds. Nevertheless, it will be apparent that these experiments can be similarly carried out using different noble gases and / or further noble gas adsorption beds.

[0070] While these experiments certainly demonstrate relevant general trends, it should be noted that more systematic and rigorous experiments could be conducted to arrive at a more complete picture. Therefore, the specific values ​​obtained from the current experiments should be considered preliminary results. Furthermore, there appears to be room for further optimization of the achieved results. For example, even higher adsorption coefficients could be achieved by further fine-tuning the process and / or the adsorbent configuration.

[0071] 1. Adsorbent materials Four adsorbents were tested and compared: activated carbon and three types of silver-exchanged zeolites containing Ag nanoparticles. The latter were prepared by thermally activating the silver-exchanged zeolites to form Ag nanoparticles in and / or on them.

[0072] activated carbon Activated carbon is a highly porous material with a large surface area—essentially composed of carbon—making it suitable for adsorption applications. It is typically manufactured from carbonaceous materials such as wood or coconut shells. Activated carbon can be considered the current standard material for capturing noble gases. In this experiment, NuclearCarb207C activated carbon with a mesh size of 6×12 was selected because—based on a literature review—it showed promising potential for radon capture at room temperature. It is a highly activated granular carbon manufactured from coconut shells and supplied by Chemviron Carbon (UK).

[0073] Silver exchange zeolite In this experiment, we evaluated three different types of silver-exchange zeolite.

[0074] Ag-13X:13X is an aluminosilicate molecular sieve in which (part of) sodium cations are exchanged with silver ions (chemical formula: Ag 84 Na2[(AlO2)] 86 (SiO2) 106 In this experiment, the chemical formula Ag was used with a mesh size of 10-20. 84 Na2[(AlO2)] 86 (SiO2) 106 Granular silver-exchanged Ag-13X of ]·xH2O was supplied by Sigma-Aldrich (Belgium).

[0075] Ag-ZSM-5:ZSM-5 is an aluminosilicate zeolite specially developed by "Commissariat a l'energie atomique et aux energies alternatives" (CEA) for the new generation SPALAX® system, aiming to replace existing activated carbon columns in the process purification / concentration stage, reducing the size and energy consumption of this stage. Ag-ZSM-5 is supplied by CEA (France) in the form of spherical particles ranging from 20 to 50 mesh.

[0076] Ag-ETS-10:ETS-10 is a microporous titanosilicate molecular sieve with a Si / Ti ratio of approximately 5 and two exchangeable cations per Ti. It has a pore size of approximately 1 nm. Ag-ETS-10 has the unusual ability to auto-shrink the exchanged silver into nanoparticles smaller than 10 nm in size when heated (see Figure 11). Two forms of Ag-ETS-10 were used in this invention: bound 1.5 mm pellets and unbound 16-30 mesh granules, supplied by Extraordinary Adsorbents Inc. (Edmonton, Alberta, Canada).

[0077] 2. Experimental apparatus Radon adsorption experiments at room temperature were conducted using the experimental apparatus schematically shown in Figure 2. The apparatus included a 120 ml radon trap column (33) filled with one of the aforementioned adsorbents. Column (33) was equipped with a quick connector to ensure easy and rapid removal and / or replacement.

[0078] Air is 222 The radon-containing air was supplied to the capture device (33) via an Rn source (20, see below) or via an additional branch capable of supplying "low radon" (e.g., naturally occurring levels) laboratory air. The branch was equipped with a moisture trap (32, Agilent MT1204) containing a mixture of 13X and 4A desiccants. Similarly, the radon-containing air was supplied to the capture device (33) via an Rn source (20, see below) or via an additional branch capable of supplying "low radon" (e.g., naturally occurring levels) laboratory air. 222 The Rn source (20) was dehumidified by a corresponding moisture trap (32) located in front of it. The humidity of the air was monitored using a dew point meter (not shown in Figure 2, Michell Easidew OnlineEA2-TX-100).

[0079] The radon used for this experiment had a radioactivity of 3.8 MBq. 226It was produced by a Pylon model RN-1025 flow through a gas source (20) containing Ra. This consisted of a dry powder surrounded by glass and plastic filters to avoid the release of non-gaseous substances. The total volume of the gas source was 244 mL. The maximum flow rate through the gas source (20) was approximately 10 l / min.

[0080] The radon adsorption column was connected to a vacuum pump (40, KNF LABOPORT N86) providing a nominal flow rate of 6 l / min. An additional loop allowed the pump (40) to be bypassed. The flow rate was measured and adjusted with a flow meter (52, Vogtlin Q-Flow FLQ-CESA-BD) operating in the range of 0.2–2.2 l / min.

[0081] A flow meter (52) was connected to a dedicated radon monitor (51, AlphaGUARD DF2000), and the radioactivity / concentration of radon emitting from the adsorption column (33) was measured. The monitor (51) was equipped with a flow control pump that was adjusted to 0.5-1 l / min for this experiment.

[0082] Typical experimental parameters are listed in the table below. [Table 1]

[0083] 3. Experimental Procedure Sample pretreatment Activated carbon and silver-exchanged zeolite were thermally activated in a resistance furnace—either a Nabertherm L3 / P (1993) or a Carbolite AAF11 / 7—before each experiment. Prior to the experiment, Ag-13X, Ag-ETS-10, and Ag-ZSM-5 were activated overnight (at least 12 hours) using a furnace set to approximately 250°C. Carbon samples were activated at a temperature of 150°C. After activation, each sample was immediately transferred to the experimental column under laboratory conditions.

[0084] The amount of moisture absorbed by each material was also evaluated by repeatedly measuring the mass of regenerated samples exposed to laboratory air using a balance over several days.

[0085] Breakthrough experiment The breakthrough experiment was conducted according to the flowchart shown in Figure 3.

[0086] In the first step, Pylon RN-1025 was degassed and accumulated in the source since the last use. 222 Remove Rn. Total amount injected into the test apparatus 222 A degassing process is necessary to reduce Rn radioactivity. A column containing 50g of NuclearCarb207C was installed to degas and capture the accumulated radon. Degassing was performed at 1 l / min for 1 hour. After completely degassing the RN-1025 chamber, the column was removed. Next, a new column containing the adsorbent under consideration was installed in the instrument.

[0087] After approximately 3.5 hours, the radon source was flushed again, accumulating approximately 100 kBq of radon in the adsorbent being tested. After capturing the radon in the column, the radon source was closed, and clean air was pumped into the column using the radon monitor's pump. The experiment was completed when all the injected radon had passed through the column. At the end of each experiment, the system was flushed with clean air.

[0088] 4. Results and Discussion Effects of using adsorbents The radon breakthrough curves for three different adsorbents—NuclearCarb207C (81), Ag-13X (82), and Ag-ETS-10 (bound 1.5 mm pellets; 83)—are shown in Figure 4. The breakthrough curves for Ag-ZMS-5 and Ag-ETS-10 (without binder, 16-30 mesh) are shown in Figures 5 and 6, respectively. The preliminary results are summarized in the table below. The obtained adsorption coefficients, in ascending order, were 2680 ml / g (Ag-13X), 2750 ml / g (NuclearCarb207C), 50960 ml / g (Ag-ZMS-5), 115000 ml / g (Ag-ETS-10, 1.5 mm pellets), and 320000 ml / g (Ag-ETS-10, 16-30 mesh granules). The Ag-ETS-10 adsorbent exhibited the highest adsorption coefficient, outperforming other adsorbents. Small 16-30 mesh Ag-ETS-10 granules, with only 4.69 g of material, achieved an average retention time t of 25 hours at 1 l / min and a dew point of -75°C, resulting in the highest adsorption coefficient among the test materials. To obtain the same retention time as 1 g of 16-30 mesh Ag-ETS-10 granules, at least 100 g of NuclearCarb207C was required. Therefore, Ag-ETS-10 is a particularly promising material for use in noble gas (Rn) capture systems with compact adsorption. [Table 2]

[0089] The effect of moisture Since (Ag-exchanged) zeolites such as Ag-ETS-10 also have an affinity for H2O, the effect of moisture adsorption on radon adsorption was investigated. In the experiment, a moisture adsorption column (Figure 2) was removed to allow moisture access to the adsorption column containing Ag-ETS-10. Before the moisture trap was removed, the experiment was run for more than 10 days without Rn breakthrough. After removal (91), Rn breakthrough (92) began just 6 hours later (Figure 7). Figure 8 shows a detailed diagram of the breakthrough curve, including humidity measurements from a radon monitor (93). These measurements do not represent the actual moisture content in the tube, but are indicative. This diagram clearly shows that radon breakthrough is related to an increase in humidity. Although not bound by theory, this could tentatively be due to Ag-ETS-10 retaining polar H2O, thereby occupying the adsorption site, or even displacing nonpolar Rn. Therefore, Ag-ETS-10 essentially functions as a moisture trap, and once sufficiently saturated with H2O, it ceases to retain noble gases. Consequently, by controlling the humidity level (dew point) of the gas volume before it passes over the noble gas adsorption bed, it becomes possible to maintain the efficiency of the noble gas adsorption bed substantially better.

[0090] thermal stability In another experiment, the thermal stability of 16-30 mesh Ag-ETS-10 granules was evaluated by their ability to absorb moisture. For this purpose, approximately 10 g of Ag-ETS-10 samples were dried in a resistance furnace (see above) for 2 hours at various temperatures ranging from 200 to 700°C. The moisture intake (H2O capacity) was then brought to equilibrium, followed by the mass increase, which was recorded on the same balance (see above). The results are shown in Figure 9. It was observed that Ag-ETS-10 began to degrade at approximately 400°C and completely lost its moisture adsorption capacity at approximately 500°C. Subsequently, when the radon retention of samples roasted at 500°C was tested, breakthrough was observed immediately, confirming that the adsorption properties were more generally lost.

[0091] Impact of gas pollutants To assess the impact of (toxic) contaminants in the gas stream, 16-30 mesh Ag-ETS-10 was used to analyze H2 and NO in the ppm range. x It was exposed to an airflow containing fumes (produced from a molten bottle containing metallic Cu in 4M HNO3). 222 The Rn breakthrough curve is shown in Figure 10. As a result, decomposition of the adsorbent material was observed. Visual observation showed that the appearance of Ag-ETS-10 changed from brown to white, and subsequent tests (see above) showed that the adsorption coefficient k significantly decreased to approximately 40,000 ml / g (i.e., from approximately 320,000 ml / g, see above). The material's regeneration cycle failed to restore its Rn adsorption capacity, which is due to NO x This shows irreversible damage to the material caused by [the process]. Although not bound by theory, this tentatively suggests, for example, that Ag is produced from metallic silver. + Thus, AgNO3 can be formed within the microporous molecular sieve and / or AgO2, which is particularly adsorbent of water by forming hydrogen bonds, x This may be due to the oxidation of Ag. Therefore, these effects may cause the noble gas adsorption bed to lose its affinity for it. If such toxic contaminants are expected to be present in the gas volume, it may be beneficial to remove the contaminants before passing the gas volume through the noble gas adsorption bed (and / or before passing it through the moisture adsorption bed) in order to maintain good efficiency.

[0092] Example 2 As mentioned above, the purpose of the experiment described in Example 1 was rather to demonstrate and support the proof of concept of the present invention. In contrast, a general method was used, and the same trend was observed, but the apparatus was modified for Example 2 to better control the experimental conditions and obtain more reliable results.

[0093] 1.Results Breakthrough curves experimentally measured at room temperature for NuclearCarb207C(101), CarboAct(102), Ag-13X(103), Ag-ZSM-5(104), and Ag-ETS-10(105) - flow rate 2 L / min, adsorption bed volume 17 cm³. 3 Figure 13 shows the use of a nitrogen carrier gas with a dew point between -70 and -90°C.

[0094] Rn breakthrough occurred within minutes of injection in both activated carbon and Ag-13X, but the retention of Rn in Ag-ZSM-5 and Ag-ETS-10 was considerably longer. In the case of the last listed material, Rn release was observed to begin 7 days after injection, but due to decay by the adsorption bed, only 1 / 32 of its initial radioactivity was detectable. Mass of each adsorbent material, injected and discharged. 222 The following table summarizes the Rn radioactivity, Rn retention time, packing density, and measured adsorption coefficient k. [Table 3]

[0095] As can be seen in Figure 13, similar results were obtained with Ag-ZSM-5, but the carbon materials examined and Ag-13X showed much weaker radon interactions.

[0096] As described in the "Methods" section below, all experiments were performed using bottled 5N nitrogen as the carrier gas due to its low residual moisture content. After Rn adsorption occurred, laboratory air was passed over the Ag-ETS-10 adsorption bed, experimentally demonstrating a clear competitive effect of moisture on Rn adsorption. Figure 14 shows a graph of the Rn breakthrough curve (111) (using a flow rate of 2 L / min and a mass of 16.3 g of adsorbent), the dew point before the Rn adsorption bed (112), the dew point after the Rn adsorption bed (113), the temperature of the Rn adsorption bed (114), and the moment of ambient air introduction (115). As can be observed, the Rn breakthrough precisely coincides with the increase in the dew point of the exhausted airflow. The temperature rise of the adsorption bed is measured when moisture enters the column. It can also be seen that Rn leaves the adsorption bed as a sharp pulse, in contrast to the broad peak observed in the previous experiment shown in Figure 13. This behavior can be explained by the competition between water molecules and Rn for the active adsorption site of Ag nanoparticles. Similar observations were made with Ag-ZSM-5. The results confirmed the strong properties of both materials examined, Ag-ETS-10 and Ag-ZSM-5, as desiccants at low moisture pressures.

[0097] 2. Consideration Measurements taken with the materials under consideration 222 Based on the Rn breakthrough curve, both Ag-ETS-10 and Ag-ZSM-5 showed significant retention properties for radon at room temperature. For each of these two synthetic zeolite frameworks, in the effluent gas stream... 222 A substantial reduction in Rn can be achieved. 16.3g of Ag-ETS-10 222 The amount of Rn in MBq can be maintained for one week, in the exhaust system 222 Before a measurable increase in Rn concentration can be detected, 20m 3 (or 10 6 N2 exceeding the bed volume passed through the column. At maximum breakthrough, the release of Rn from the Ag-ETS-10 adsorbed bed was delayed by 17 days, which indicates that... 222This corresponds to approximately 4.5 half-lives of Rn. Along with Ag-ZSM-5, Ag-ETS-10 exhibits a radon adsorption coefficient at least two orders of magnitude larger than NuclearCarb207C, CarboActo, and Ag-13X. To the best of the inventor's knowledge, the radon adsorption coefficient at room temperature is 1000m 3 No scientific literature has yet reported measurement results showing adsorbents exceeding / kg.

[0098] To evaluate the obtained results, moisture control proved to be crucial. The Ag-ETS-10 material examined demonstrated to be a very strong desiccant, and caution is needed when interpreting Rn breakthrough experiments regarding the possibility of interference with co-adsorption of moisture. In fact, the initial experiments conducted with laboratory air (see, e.g., Example 1) revealed large fluctuations in the measured adsorption coefficient of Rn due to changes in the relative humidity in the laboratory. Careful in situ regeneration of the material to avoid exposure to ambient humidity has proven to be crucial for data reproducibility. Experiments using a similar experimental system with laboratory air dried on a 13X moisture-adsorbing bed confirmed that other air components such as Ar, Kr, Xe, CO2, and CO showed only slight competition with Rn (at least at concentrations normally encountered in the atmosphere), while a strong influence of relative humidity was observed. This is advantageous for designing efficient but simple Rn adsorption systems for air purification. This is because, in order to efficiently capture Rn, only dehumidification of the input airflow—or dehumidification combined with the removal of oxidizing species and / or acid vapors (see below)—is required. However, it has recently been shown that chlorine-containing organic species exhibit a measurable toxic effect on Ag-ZSM-5 with respect to Xe adsorption. It can be concluded that adequately protecting the adsorption bed from species that oxidize silver may be useful.

[0099] Nevertheless, the innovative properties of Ag-ETS-10 and Ag-ZSM-5 can be visualized by the following examples of Rn reduction systems proposed for laboratory air purification requiring a low background environment. 222 Rn radioactivity concentration is 20Bq / m 3Assuming that air is processed at 100 m 3 / h, in an adsorption bed with a diameter of 30 cm and a height of 100 cm (V = 70 L), the incoming Rn flow can be delayed for 650 hours or 4 weeks (k = 1000 m 3 / kg). This corresponds to a breakthrough of 0.15 Bq / m 3 in the outlet air flow of a single adsorption column operating continuously at room temperature. A similar adsorption system using activated carbon requires a bed volume of several cubic meters and cryogenic cooling. This clearly demonstrates the economic viability of silver-exchanged zeolite in Rn-related research and the air separation industry.

[0100] Using such a system, it can be easily shown that when the adsorption system reaches a steady state where the decay rate of adsorbed Rn approaches its inflow flux, significant accumulation of Rn occurs in the column. Furthermore, as the results in Figure 14 show, by allowing moisture to pass through the adsorption bed and thereby displacing Rn, Rn can be efficiently removed in a limited volume. In the above example, 100 kBq of 222 Rn can be obtained in a few m<​​​​​​​​​​​​​​​​​​​​The adsorbent materials Ag-ZSM-5, Ag-ETS-10 (granular, mesh 16-30), Ag-13X, and Nuclearcarb207C were as described in Example 1. Furthermore, CarboAct high-purity carbon (fragmented, 0.01-0.4 cm) was obtained from Carbo-act International (Netherlands). The hygroscopic agent 13X APG was obtained from UOP CH Sarl (Switzerland) as spherical 8×12 mesh beads.

[0103] Similar to Example 1, PYLON RN-1025 flow-through 3.8MBq provided by PYLON Electronics Inc. (Canada) 226 By degassing the Ra source, 222 Rn was generated and supplied before each experiment, before each experiment performed. 222 The source was degassed to increase the specific radioactivity of Rn.

[0104] 4. Method Rn adsorption device for experiments The Rn adsorption experiment was performed in a laboratory-scale apparatus (10) located inside a fume hood ("exhaust system" 70). This is schematically shown in Figure 12. The capture apparatus consists of two redundant moisture traps (32) and two Rn adsorption columns (33), a hygrometer (dew point meter, 53) to indicate the moisture content in the system, a flow control device (MFC and VA flow meters, 52), a vacuum pump (40), and a radon monitor (51). The system is constructed with stainless steel tubing (OD 1 / 4 inch, solid or long dashed lines), fittings, and valves to ensure leak-proofing and moisture control. Flexible PFA (perfluoroalkoxy) tubing (short dashed or dotted lines) is used where possible / prudence is appropriate. The solid lines (stainless steel) and short dashed lines (PFA) indicate forward loops, while the long dashed lines (stainless steel) and dotted lines (PFA) indicate regeneration loops.

[0105] Nitrogen supplied from the in-house LN2 supply tank (21) is depressurized (54) and supplied to the experimental system as a carrier gas. Nevertheless, the apparatus could also use / introduce ambient air (22). The carrier gas flow within the apparatus is controlled by a thermal mass flow control device (Red-y smart, Vogtlin Instruments GmbH (Switzerland), 52).

[0106] The apparatus is equipped with two redundant moisture traps (32) filled with molecular sieves 13X to reduce the moisture content of the incoming gas. The columns were designed and manufactured in-house. The volume of both columns is approximately 385 cm³. 3 The column (4.05 cm inner diameter and 30 cm length) is made of stainless steel (SS316). A Cu-sealed CF flange at the top of the column allows for opening and closing of the column, ensuring leak prevention. Redundancy is provided to ensure continuous operation in case one column becomes saturated (or is regenerated at some point). Several dew point transmitters (53, Easidew online, Michell Instruments (UK)) are mounted on the instrument to measure moisture content at various positions in the instrument.

[0107] Radon adsorption is performed in one of the adsorption columns (33). These columns can be packed with a selected adsorbent. The columns were designed and manufactured in-house. The volume of both columns is approximately 17 cm³. 3 It has an inner diameter of 1.2 cm and a length of 15 cm, and is made of stainless steel (SS316). The CF flange with a Cu seal at the top of the column allows the column to be opened and closed, ensuring leak prevention.

[0108] This apparatus allows for the regeneration of different adsorbents in situ, that is, while retaining the adsorbent within the column. Heating of the stainless steel column is performed via a heating wire connected to a temperature controller that adjusts the temperature to a predetermined setpoint via a thermocouple (55). The thermocouple (55) is placed on the outer wall of the column. The column and heating wire are insulated with fiberglass tape.

[0109] The radon concentration of the emitted stream is monitored by sampling a portion of the emission flow with a radon monitor (51), namely, an AlphaGUARD professional radon monitor DF2000, Bertin GmbH (Germany). It is 2 Bq / m³. 3 ~2 MBq / m 3 The volumetric radon concentration can be continuously measured within the specified measurement range. The monitor is equipped with a flow control pump that can be adjusted from 0.05 L / min to 2 L / min, enabling sampling of the discharge flow.

[0110] The device is equipped with a (vacuum) pressure transmitter (pressure range 1-2.5 bar, 56) that allows monitoring of the pressure inside the device. Furthermore, this transmitter is used to verify leak prevention in the device and column, particularly after switching them on and off.

[0111] (Removable) adsorption column (120 cm) 3 34) can be inserted into the experimental loop via a quick connector (57) to allow degassing of the Rn source. When removed, the loop is closed via a stainless steel tube.

[0112] material recycling Each adsorbent tested underwent an activation process by heat treatment under inert gas conditions prior to each experiment. In all cases, dry nitrogen was used as the regeneration gas. Activation was carried out at 230°C for Ag-ETS-10 and at 250°C for Ag-13X and Ag-ZSM-5 for at least 15 hours, with 150°C being selected for both activated carbons. The moisture adsorbent 13X APG was regenerated at 280°C. Nitrogen was supplied from an in-house LN2 supply tank with a nominal pressure of 8 bar and a dew point between -70 and -90°C.

[0113] Breakthrough experiment The breakthrough experiment was conducted following the same general flowchart as in Example 1 (see Figure 3).

[0114] In the first step, the radon source (Pylon RN-1025) was degassed using a column containing activated carbon (NuclearCarb207C) and accumulated 222 Remove Rn and 3.8MBq 226 Bring Ra to equilibrium. Total amount injected into the test apparatus 222 A degassing process is necessary to reduce Rn radioactivity. A column packed with approximately 50g of NuclearCarb207C is installed. Degassing is performed at 0.5L / min for 1 hour. After the radon source is completely degassed, the column is removed.

[0115] After degassing, radon begins to accumulate again in the source until it reaches the desired radioactivity. In the next step, the accumulated radon is injected into a selected adsorbent column by flushing the radon source at the experimental flow rate for 5 minutes.

[0116] After capturing radon in the column, the radon source is closed, and N2 is supplied to the column until all the injected radon has passed through (complete breakthrough). At this point, the experiment is complete.

[0117] The adsorption coefficient k(m) of each adsorbent tested 3 The value ( / kg) is calculated using the following formula: k=(t*F) / m Here, t is the retention time (seconds), m is the mass of the adsorbent (kg), and F is the volumetric flow rate (m³).3 The average retention time t was defined as the time at which the measured breakthrough radon radioactivity concentration reached 5% of the observed maximum radon radioactivity concentration. For large datasets, the data is averaged across 250 points. Thus, the retention time is considered to be the time at which the average of 5% of the maximum mean was observed. The overall uncertainty associated with the measured adsorption coefficient is estimated to be around 20%.

[0118] Example 3 Repeat Example 1 and / or Example 2, but using a different low-polarity (see above) carrier gas such as Ar, O2, Ne, He, or a mixture thereof.

[0119] Figure 15 shows nitrogen, (dry) air, and Ar (485 kBq) injected per run at a flow rate of 3 L / min. 222 The graph shows the Rn breakthrough curves measured experimentally on Ag-ETS-10 using different carrier gases (Rn and 3g of adsorbent). Nitrogen is supplied from the company's LN2 supply tank. Air is supplied by the building's central compressed air supply and further dried with 13X molecular sieves. Finally, argon is supplied via a gas cylinder (Ar technical grade 4.8, X50S, Air Products). The dew points measured in various experiments were similar, averaging approximately -80°C.

[0120] Using dry air (approximately 78% N2, 21% O2, and 1% Ar, where both O2 and Ar are less polarizable than N2) resulted in an increase of approximately 30% to 40% in Rn retention time compared to pure N2. The use of Ar increased retention time, leading to the decision to terminate the experiment early. Comparing the obtained data, an approximately seven-fold increase in retention time can be expected. The increase in retention time indicates a weakening of the interaction between the carrier gas and the adsorbent, resulting in less competition with radon at the adsorption site. N2 interacts more strongly with Ag-ETS-10 than air, and air shows a stronger interaction than Ar. While not theoretically bound, the adsorption strength of nonpolar gases depends, by a first-order approximation, on their polarizability; therefore, the higher the polarizability, the stronger the interaction between the noble gas adsorption bed (and, for example, the transition metals within it).

[0121] Using gases such as O2, Ne, He, or mixtures thereof can achieve even lower polarizability and greater effects.

[0122] While these are preferred embodiments, it should be understood that certain structures, configurations, and materials are discussed herein in order to illustrate the present invention. It will be apparent to those skilled in the art that various modifications, changes, and variations can be made in form and detail without departing from the scope of the present invention as defined in the appended claims.

Claims

1. A method for removing radioactive noble gases from a gas volume, a. A step of providing the gas volume such that the dew point of the gas volume at a gas temperature of 20°C is -20°C or lower, b. A step of passing the gas volume over a microporous molecular sieve bed (33) containing a transition metal placed on and / or within a microporous molecular sieve, thereby adsorbing the radioactive noble gas onto the bed (33), Includes, The aforementioned radioactive noble gas is Rn, A method characterized in that the microporous molecular sieve is ETS-10 or ZSM-5.

2. The aforementioned microporous molecular sieve is containing transition metal nanoparticles and / or It is a transition metal exchange microporous molecular sieve. The method according to claim 1.

3. The method according to any one of claims 1 to 2, wherein the transition metal is selected from Group 10, Group 11 and Platinum Group.

4. The aforementioned gas volume is 1,700 Å. ３ The method according to any one of claims 1 to 3, comprising a nonpolar carrier gas having the following polarizability.

5. The method according to any one of claims 1 to 4, wherein the gas volume comprises a nonpolar carrier gas having a polarizability of 1.664 ų or less.

6. The method according to any one of claims 1 to 5, wherein step a includes passing the gas volume over a moisture adsorption bed (32).

7. Further step c c. A step of regenerating the noble gas adsorption bed (33) and / or, if present, the moisture adsorption bed (32). The method according to any one of claims 1 to 6, including the method described in any one of claims 1 to 6.

8. The aforementioned step c is, Heating the noble gas adsorption bed (33) and / or, if present, the moisture adsorption bed (32), and / or Flushing the aforementioned noble gas adsorption bed (33) and / or, if present, the moisture adsorption bed (32) with a regenerating gas. The method according to claim 7, including the method described in claim 7.

9. The preceding step a' is a step that precedes step b. a'. A step of removing substances toxic to the noble gas adsorption bed (33) and / or, if present, the moisture adsorption bed (32) from the gas volume. The method according to any one of claims 1 to 8, including

10. The adsorbed radioactive noble gas is It is held until it is effectively decayed, or Collected for further storage and / or use, The method according to any one of claims 1 to 9.

11. The method according to any one of claims 1 to 10, carried out at room temperature.

12. The method according to any one of claims 1 to 11, carried out in a nuclear environment.

13. A device (10) for removing radioactive noble gases from a gas volume, i. One or more moisture-absorbing beds (32), ii. One or more noble gas adsorption beds (33) of a microporous molecular sieve containing a transition metal, disposed on and / or within the microporous molecular sieve, Equipped with, The noble gas adsorption bed (33) has an input coupled to the output of the moisture adsorption bed (32), The aforementioned radioactive noble gas is Rn, The apparatus is characterized in that the microporous molecular sieve is ETS-10 or ZSM-5.

14. iii. One or more regenerative gas sources (60) optionally coupled to the noble gas adsorption bed (33) and the moisture adsorption bed (32); and / or iv. One or more scrubbers (31) for removing substances toxic to the noble gas adsorption bed (33) and / or the moisture adsorption bed (32) from the gas volume; Furthermore, The scrubber (31) has an output coupled to the input of the noble gas adsorption bed (32), The apparatus (10) according to claim 13.

15. A multilayer system for removing radioactive noble gases from a gas volume, wherein one or more layers comprise the apparatus (10) described in any one of claims 13 to 14.

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