JP6077366B2 - Waste disposal method - Google Patents

Description

  The present invention relates to a method for treating waste when vitrifying waste such as radioactive waste and harmful compounds.

  In Patent Document 1 below, a solidified body made of glass or ceramics containing radioactive waste is covered with an intermediate layer made of glass or ceramics containing no radioactive waste, and the intermediate layer is covered with a metal coating. An invention relating to a method for solidifying a covered radioactive waste is disclosed. Patent Document 1 discloses that radioactive waste and phosphate glass or the like are mixed and melted to solidify the glass, and phosphate glass is also used for the intermediate layer. However, nothing is described about the characteristics of phosphate glass.

  Patent Document 2 discloses an invention relating to a method for producing a glass solidified body that prevents contamination when glass mixed with a radioactive substance is stored in a canister container and simplifies the decontamination process of the canister container. .

  Patent Document 3 discloses an invention relating to a solidified body in which magnesium or the like is added to a glass base material of a dry body of a low-level radioactive concentrated waste substance, including sodium nitrate and other sodium compounds.

  Patent Document 4 discloses an invention relating to a method for treating radioactive waste in which radioactive waste is mixed with a low-melting glass and melted, and then crystallized and solidified.

  In the invention described in Patent Document 1 and Patent Document 5 described above, a structure in which the surface of a glass solidified body containing radioactive waste is covered with an intermediate layer is disclosed, and the glass used for the glass solidified body and the intermediate layer is disclosed. For example, it is disclosed to use phosphate glass.

  In addition, in the invention relating to the method for treating radioactive waste of Patent Document 6, there is a description that pellets excellent in water resistance can be obtained by using phosphoric acid-based glass for the inorganic binder mixed with the radioactive waste.

Japanese Patent Publication No. 4-20159 Japanese Patent Laid-Open No. 5-126997 JP 2001-27694 A JP 11-295487 A JP 60-22700 A JP-A-63-115099

  However, in the glass solidified body in which the glass surrounding the radioactive waste is doubled as in Patent Document 1, etc., the characteristics of the inner glass and the outer glass are shown, and the radioactive waste is scattered in the molding process of the glass solidified body. There is no description on how to adjust and how to adjust the glass vitrified body after molding from the viewpoint of stable storage for a long period of time while preventing scattering of radioactive waste.

  The inner glass is a layer located inside the vitrified body and in contact with radioactive waste. On the other hand, the outer glass is a layer that does not contact the radioactive waste but constitutes the surface of the vitrified body. In forming each glass in this way, the environment in which each glass is exposed is different, so the inner glass and the outer glass do not have the same characteristics, but use glass materials with different characteristics, effectively and radioactively. Although it is necessary to prevent the scattering of waste and to ensure stable storage for a long period of time, conventionally, the properties of the doubled glass have not been changed between the inside and the outside.

  Therefore, the present invention is to solve the above-described conventional problems, and in particular, to prevent the scattering of harmful wastes such as radioactive wastes and to ensure stable storage for a long period of time compared to the conventional ones. The purpose is to provide a waste disposal method.

The waste processing method in the present invention is:
Covering the surface of the waste with the first glass;
Covering the surface of the first glass with a second glass,
The first is the glass melting point and a low glass transition point than the boiling point of the waste, and the use of a material having a lower glass transition point than the second glass, said the second glass the first A vitrified body is formed using a material having better corrosion resistance than glass. Thus, in the present invention, first, the surface of the waste is covered with the first glass having a glass transition point lower than that of the second glass. As a result, the first glass can be softened or melted at a low temperature, and diffusion due to evaporation of waste can be prevented. And the surface of the 1st glass was covered with the 2nd glass excellent in corrosion resistance rather than the 1st glass. Since the second glass that covers the surface of the first glass does not touch the waste, even if the softening temperature or the melting temperature of the second glass having a high glass transition point is high, the prevention of scattering of the waste can be maintained. And since the corrosion resistance of the 2nd glass used as the surface of a glass solidification body is superior to the 1st glass, even if it is stored for a long period of time, internal waste does not melt and scatter.

  As described above, according to the present invention, it is possible to effectively prevent waste from being scattered and stably ensure long-term storage as compared with the conventional case.

  In the present invention, the waste is preferably radioactive waste. Even if it is a radioactive waste, the processing method of this invention can prevent scattering appropriately.

  In the present invention, the radioactive waste is particularly suitable when cesium is contained as a radioactive element. Although cesium reacts and is considered to exist in the form of cesium oxide or cesium hydroxide cesium compound, cesium oxide has a melting point of about 490 ° C, cesium hydroxide has a melting point of about 272 ° C and a boiling point of about 990 ° C. Low compared to uranium and plutonium. Therefore, as in the present invention, the first glass having a low glass transition point is covered with a radioactive waste containing a cesium compound and solidified, so that the softening temperature or the melting temperature of the first glass can be changed to that of cesium oxide or cesium hydroxide. It can be made lower than the melting point or boiling point, thereby preventing diffusion due to evaporation of the radioactive waste in the step of covering the surface of the radioactive waste with the first glass. And since the corrosion resistance of the first glass having a low glass transition point is not so good, the surface of the first glass is covered with the second glass having excellent corrosion resistance, so that the radioactive waste is scattered even during long-term storage. It is possible to realize a processing method that can prevent the above.

  In the present invention, it is preferable that the first glass and the second glass are formed of phosphate glass. Thereby, the concentration gradient of phosphoric acid can be suppressed between the first glass and the second glass, and composition diffusion can be suppressed. Moreover, it is easy to match | combine the thermal expansion coefficient (alpha) of 1st glass and 2nd glass. Thereby, scattering of waste can be suppressed even during long-term storage, and a vitrified body suitable for long-term storage can be maintained.

In the present invention, the first glass includes P ₂ O ₅ as the first component or the second component, and includes any one of SnO, BaO, and ZnO as the second component or the first component, The total of the component and the second component is preferably 65 (mol%) or more.

The first glass preferably contains P ₂ O ₅ and SnO as the first component or the second component, and further contains BaO and B ₂ O ₃ .

The second glass has at least P ₂ O ₅ , CeO ₂ and Cr ₂ O ₃ , and includes P ₂ O ₅ and CeO ₂ in a range of 50 to 90 (mol%), Cr ₂ O ₃ is preferably contained in the range of 0.7 to 15 (mol%).

  By adjusting the composition of the first glass and the second glass within the above range, the glass transition point of the first glass can be effectively made lower than that of the second glass, and the second glass Corrosion resistance can be made better than that of the first glass.

  In the present invention, the surface of the waste is first covered with the first glass having a glass transition point lower than that of the second glass. As a result, the first glass can be softened or melted at a low temperature, and diffusion due to evaporation of waste can be prevented. And the surface of the 1st glass was covered with the 2nd glass excellent in corrosion resistance rather than the 1st glass. Since the second glass that covers the surface of the first glass does not touch the waste, even if the softening temperature or the melting temperature of the second glass having a high glass transition point is high, the prevention of scattering of the waste can be maintained. And since the corrosion resistance of the 2nd glass used as the surface of a glass solidification body is superior to the 1st glass, even if it is stored for a long period of time, internal waste does not melt and scatter.

  As described above, according to the present invention, it is possible to effectively prevent the radioactive waste from being scattered and stably ensure long-term storage as compared with the prior art.

FIG. 1 is a schematic diagram showing each step of the waste treatment method. FIG. 2 is a schematic diagram showing each step of a waste processing method partially different from FIG.

FIG. 1 is a schematic diagram showing each step of the method for treating radioactive waste 1.
In the process of FIG. 1A, the radioactive waste 1 is shown in a container 2.

  The radioactive waste 1 contains, for example, cesium (Cs) as a radioactive element. Cesium reacts easily and is considered to exist in the form of cesium compounds such as cesium oxide and cesium hydroxide. The melting point of cesium oxide is about 490 ° C., the melting point of cesium hydroxide is about 272 ° C., and the boiling point is about 990 ° C.

  The radioactive waste 1 exists in a state where, for example, a fission product (FP) is adsorbed by zeolite or other adsorbing material, and the radioactive waste 1 needs to be appropriately treated as a high-level radioactive waste.

  A container 2 for containing the radioactive waste 1 shown in FIG. 1A is an assembly container surrounded by a carbon plate, for example. In the container 2 made of a carbon plate, the vitrified body 4 can be easily taken out from the container 2 and can be reused.

  As shown in FIG. 1 (a), a gap 2 a is provided between the inner wall of the container 2 and the radioactive waste 1. Thereby, the 1st glass (low melting glass) 3 shown to the next process can be poured appropriately from crevice 2a.

  In the process of FIG. 1B, the first glass 3 in a softened or molten state is poured around the radioactive waste 1, and the surface of the radioactive waste 1 is covered with the first glass 3 and solidified.

  When the first glass 3 is poured into the container 2 from the glass injection machine 9 shown in FIG. 1 (b), the container 2 is made of, for example, gold so that the first glass 3 reaches the entire surface of the radioactive waste 1. The surface of the radioactive waste 1 is made to have a first configuration by making the surface of the radioactive waste 1 appropriately covered with the first glass 3 or stirring the radioactive waste 1 in the container 2. It can also be made to be appropriately covered with the glass 4.

  The first glass 3 is a material having a glass transition point (Tg) lower than that of the second glass 5 used in the next FIG.

  The glass transition point (Tg) of the first glass 3 is about 250 ° C. to about 500 ° C., preferably about 250 ° C. to about 400 ° C.

  In order to allow at least the first glass 3 to flow into the gap 2a of the container 2, the first glass 3 is heated to a temperature higher than about 1.5 times the glass transition point (Tg (° C.)). It is necessary to increase the fluidity of the glass 3. In this embodiment, since the temperature at this time can be set to a temperature lower than the melting point or boiling point of cesium oxide or cesium hydroxide, the cesium compound in the process of covering the surface of the radioactive waste 1 with the heated first glass 3 Can be appropriately prevented from evaporating and scattering.

As the first glass 3 (low melting point glass) having a low glass transition point (Tg), a phosphate glass can be selected. The first glass 3 includes P ₂ O ₅ as the first component or the second component, and includes any one of SnO, BaO, and ZnO as the second component or the first component. In addition, the total amount of the first component and the second component is 65 (mol%) or more. Thereby, the glass transition point (Tg) of the 1st glass 3 can be set to about 250 degreeC to about 500 degreeC.

The first glass 3 comprises a _P 2 _{O 5} and SnO as a first component and a second component, preferably further comprising BaO and _B 2 _{O 3.} The glass transition point (Tg) of the first glass 3 can be about 250 ° C. to about 400 ° C. In addition, the melting temperature of the first glass 3 can be set to about 600 ° C. or lower, more specifically between 375 ° C. and 600 ° C.
The materials examined as the first glass 3 are shown in Tables 1 and 2 below.

  The glass transition point (Tg), yield temperature (At), and thermal expansion coefficient α shown in Tables 1 and 2 were measured using a thermomechanical analyzer (TMA8310 manufactured by Rigaku Corporation).

Sample No. shown in Table 2 Since Nos. 40 to 46 are crystallized, sample nos. It turned out that 40-46 is not suitable as the 1st glass 3. FIG. In addition, sample No. 1 in Table 1 that partially crystallizes. 1 and 2 may not be used as the first glass 3, but sample Nos. 1 and 2 for maintaining the glass state appropriately. It is preferable to select the first glass 3 among 3 to 39. Sample No. 3 to 30 and 34 to 39 have one of P ₂ O _{5 and} SnO as the first component and the other as the second component, and the first component and the second component are combined to be 65 (mol%) or more. ing. The first component is a component having the largest content (mol%) among the glass components, and the second component is a component having the second largest content (mol%) after the first component.

  As shown in Tables 1 and 2, the glass transition point (Tg) of each sample is between about 250 ° C. and about 500 ° C. Which sample is used as the first glass 3 is set based on the melting point and boiling point of the radioactive substance contained in the radioactive waste 1. That is, the heating temperature for the first glass 3 in the step of FIG. 1B needs to be at least lower than the boiling point of the radioactive substance contained in the radioactive waste 1, but decomposes in the vicinity of the melting point. When radioactive material is contained, the temperature must be lower than the melting point.

  For example, if the radioactive waste 1 contains no cesium and the melting point and boiling point of the radioactive material contained in the radioactive waste 1 are higher than those of cesium, the glass transition point (Tg) in Tables 1 and 2 is slightly higher. High glass can also be used as the first glass 3.

  However, considering that the radioactive waste 1 contains a cesium compound having a low melting point and boiling point, the glass transition point (Tg) of the first glass 3 is preferably as low as possible.

  Sample No. shown in Table 1 As for the glass of 3-11, a glass transition point (Tg) is 400 degrees C or less, and can ensure a low glass transition point. In addition, each sample No. shown in Table 1 and Table 2. Although the glass of 3-39 can be made into a liquid state with extremely high fluidity by applying a high vitrification temperature of 900 ° C. or higher, the glass transition point (Tg: ° C.) without applying a high temperature so far. By applying a temperature (700 ° C. to 900 ° C.) that is about 1.5 times higher than that of the glass, the fluidity of the glass can be increased, and the glass can be poured into the gap 2 a of the container 2.

Sample No. shown in Table 1 Glass 3-11 _includes P ₂ O 5, SnO, BaO and _B 2 _{O 3.} Sample No. _P 2 _{O 5} contained in the glass of 3 to 11 is less than 40 45 (mol%) with (mol%) or more, SnO is, 30 (mol%) or more 52 (mol%) or _{less, P} 2 O _{One of 5} and SnO is the first component and the other is the second component. Here, the phosphate glass refers to a glass containing P ₂ O ₅ as a first component or a second component and containing 30 (mol%) or more.

Sample No. Glass 3-11 _is, B comprises 2 _{O 3} of 3 (mol%) or more 9 (mol%) or less, include a BaO 5 20 (mol%) with (mol%) or more or _less, B 2 _{O 3} and BaO of One is the third component and the other is the fourth component.

Sample No. The glass of No. 9 contains Al ₂ O ₃ , Li ₂ O, and CeO ₂ in respective minimum amounts. The 8, 11 glass contains Al ₂ O ₃ and CeO ₂ respectively in a minimum amount.

  Next, in the process of FIG. 1C, the vitrified body (intermediate body) 4 in which the surface of the radioactive waste 1 is covered with the first glass (low melting point glass) 3 is taken out from the container 2 and another container 6 is removed. The surface of the glass solidified body 4 is covered with the second glass 5. As shown in FIG. 1 (c), by providing a gap 6a between the glass solidified body (intermediate body) 4 and the container 6, the second glass 5 in the softened or molten state is poured into the gap 6a. Thus, the surface of the first glass 3 can be covered with the second glass 5.

  The container 6 shown in FIG. 1C is preferably a container made of metal (such as stainless steel) or concrete having good corrosion resistance so that it can withstand long-term storage. However, when it is assumed that the vitrified body 7 is finally transferred from the container 6 to a container (canister) for long-term storage, the container 6 is the same as the container 2 shown in FIG. A carbon container etc. may be sufficient.

  In addition, in order to cover the whole surface of the glass solidified body (intermediate body) 4 obtained in FIG. 1B with the second glass 5 (high corrosion resistance glass), the container 6 is configured as a mold or the glass solidified body. It is preferable to appropriately cover the entire surface of the glass solidified body (intermediate body) 4 with the second glass 5 by holding the (intermediate body) 4 in a state of being floated in the container 6.

  The second glass 5 is a material superior in corrosion resistance to the first glass 3. The second glass 5 has a glass transition point (Tg) higher than that of the first glass 3. Accordingly, the second glass 5 has to be softened or melted by applying heat at a temperature higher than that in the step of FIG. 1B, but the radioactive waste 1 is wrapped in the first glass 3. Since it is stored, even if the second glass 5 having a temperature higher than the melting point or boiling point of the radioactive waste 1 is poured into the container 6 in the process of FIG. 1C, the radioactive waste 1 is appropriately prevented from scattering. it can.

As the second glass 5 (high corrosion resistance glass) excellent in corrosion resistance, a phosphate glass can be selected. In particular, it is preferable to use cerium phosphate glass. Cerium phosphate glass is a composition excellent in water resistance because it is produced in large quantities on the coast as monaz sand.
The materials studied as the second glass are shown in Table 3 below.

The glass transition point (Tg), yield temperature (At), and thermal expansion coefficient α shown in Table 3 were measured using a thermomechanical analyzer (TMA8310 manufactured by Rigaku Corporation).
Since the comparative example shown in Table 3 has poor corrosion resistance, it was used as a comparative example.

The glasses of the examples shown in Table 3 have at least P ₂ O ₅ , CeO ₂ and Cr ₂ O ₃ . In addition, it is preferable that P ₂ O ₅ and CeO ₂ are combined in a range of 50 to 90 (mol%) and Cr ₂ O ₃ is included in a range of 0.7 to 15 (mol%).

  Here, the second glass 5 not only has a structure in which the whole is in a glass state, but may be partially crystallized, but the whole is in a solid state (glass) in a glass state. From the viewpoints of heat resistance and weather resistance.

To include in the range of 50 to 90 (mol%) combined _P 2 _{O 5} and CeO ₂ as an essential component, it is possible to suppress crystallization, can facilitate the glassy state.

In the glass shown in Table 3, Cr ₂ O ₃ is an essential component in addition to P ₂ O ₅ and CeO ₂ . As described above, the content of Cr ₂ O ₃ is in the range of 0.7 to 15 (mol%). When the content of Cr ₂ O ₃ is less than 0.7 (mol%), chemical resistance cannot be improved appropriately. Further, when more than the content of 15 _{Cr 2 O 3 (mol%)} , likely glassy state is unstable crystallization is promoted. Therefore, in the present embodiment, the content of Cr ₂ O ₃ is set to 15 (mol%) or less.

  The glass transition point (Tg) of the glass shown in Table 3 is about 550 to 700 ° C., which is higher than the glass transition point (Tg) of the glass shown in Tables 1 and 2.

  As shown in Table 4 below, it was found that the glass (second glass 5) shown in Table 3 was superior in water resistance to the glass shown in Table 1 (first glass 3).

  In the experiment of Table 4, each sample which grind | pulverized glass and sifted to 250-425 mesh was immersed in the pure water of 98 degreeC for 1 hour, the mass before and after immersion (after a test) of immersion. The change (decrease rate) was measured. The quality change rate shown in the table was determined by {(mass before test (g) −mass after test (g)) / mass before test (g)} × 100 (%).

  As shown in Table 4, it was found that the second glass had a lower reduction rate than the first glass and was excellent in water resistance.

The chemical resistance of the second glass was also examined. In the experiment, each glass of Comparative Examples listed in Table 3 and Examples 16, 28, 42, 45, and 47 was contained in an aqueous solution, an aqueous hydrofluoric acid solution (50% HF) containing 50% HF by mass, and 60 by mass. % aqueous solution of nitric acid (60% _HNO 3) containing HNO ₃ in the mass with an aqueous solution of sulfuric acid _(98% H 2 _SO 4) containing 98% _H 2 SO _4, HCl aqueous solution containing 36% HCl by mass (36% HCl). Then, the mass of each glass was measured before immersion in each aqueous solution, after 6 hours of immersion, and after 27 hours of immersion, and the change in mass was determined.

  As a conventional example, quartz glass was immersed in each of the above aqueous solutions, and the change in mass was determined. The results are shown in Tables 5 to 8 below.

Table 5 shows experimental results when each glass is immersed in 50% HF, Table 6 shows experimental results when each glass is immersed in 60% HNO ₃ , and Table 7 shows 98% of each glass. Experimental results when immersed in H ₂ SO ₄ , Table 8 shows experimental results when each glass was immersed in 36% HCl.

  The rate of change shown in each table was determined by {(mass before test (g) -6 hours or mass after 27 hours (g)) / mass before test (g)} × 100 (%). The smaller the change rate, the better the etching resistance (chemical resistance) without melting.

Incidentally, as shown in the Table, when gradually increasing the content of Cr ₂ O ₃ contained in the glass, it was found that the rate of change becomes smaller.

  From the above experiment, it can be seen that the second glass (glass shown in Table 3) is superior in water resistance and chemical resistance to the first glass (glass shown in Table 1 and Table 2). It was.

  For this reason, as shown in FIG.1 (c), the glass solidified body 7 suitable for a long-term storage is formed by covering the surface of the 1st glass 3 with the 2nd glass 5 excellent in corrosion resistance. Can do.

  FIG. 1 (d) shows an example of a method for storing the vitrified body 7. As shown in FIG. 1 (d), it is desirable to store the vitrified body 7 for a long period of time in a canister with a lid 8 on the upper surface of the vitrified body 7. In FIG. 1 (d), the vitrified body 7 may be stored for a long time using the container 6 used in FIG. 1 (c) as it is, or the vitrified body 7 formed in FIG. The container 6 may be transferred to another container (canister) and stored for a long time.

  In the present embodiment, it is preferable that both the first glass 3 and the second glass 5 are formed of phosphate glass. For example, it is possible to use borosilicate glass as the second glass 5, but between the first glass 3 and the second glass 5 by using both glasses 3 and 5 as phosphate glass. The concentration gradient of phosphoric acid can be suppressed, and composition diffusion can be suppressed. Note that the phosphoric acid glass used as the second glass 5 shown in Table 3 is a material that has a resistance to hydrofluoric acid that is 6000 times or more higher than that of quartz glass and is extremely excellent in corrosion resistance. Moreover, it is easy to match | combine the thermal expansion coefficient (alpha) of the 1st glass 3 and the 2nd glass 5 by forming both the 1st glass 3 and the 2nd glass 5 with phosphoric acid type glass. As described above, by forming both the first glass 3 and the second glass 5 with phosphoric acid-based glass, it is possible to more effectively suppress the scattering of waste by long-term storage, and long-term storage. It is possible to maintain a state suitable for.

FIG. 2 shows a waste treatment method that is partially different from FIG.
In FIG. 2A, the generated first glass 10 is once crushed into a state in which a plurality of first glasses 10 (powder) are coated on the surface of the radioactive waste 1. The first glass 10 (powder) is softened or melted by applying heat at a temperature lower than the melting point or boiling point of the radioactive material contained, and the surface of the radioactive waste 1 is made to be the first glass as shown in FIG. 10 covered.

  Then, the surface of the glass solidified body 11 (intermediate body) obtained in FIG. 2B is covered with the second glass 12, and the radioactive waste 1 is surrounded by the first glass 10 and the second glass 12. A solidified body 13 is formed. In the step of FIG. 2C, similarly to FIG. 2A, the generated second glass 12 is once crushed into a plurality of second glasses (powder) on the surface of the first glass 10. The surface of the radioactive waste 1 is made soft as shown in FIG. 2C by softening or melting the second glass 12 (powder) by applying a temperature higher than that in FIG. It can be in the state covered with the second glass 12. Or about the 2nd glass 12, the 2nd glass 12 melt | dissolved using the glass injection machine 9 like FIG.1 (c) is poured in in the container 6, and the surface of the 1st glass 10 is made into 2nd glass. 12 can also be covered.

  1 and 2, the waste is the radioactive waste 1, but the waste may be a harmful compound other than the radioactive waste. However, the present embodiment is suitable for the method for treating the radioactive waste 1, and even the radioactive waste 1 containing the cesium compound can appropriately prevent the cesium compound from being dissolved and scattered, Can be stored stably.

DESCRIPTION OF SYMBOLS 1 Radioactive waste 2, 6 Container 3, 10 1st glass 4 Vitrified body (intermediate body)
5, 12 Second glass 7 Vitrified body

Claims (8)

Covering the surface of the waste with the first glass;
Covering the surface of the first glass with a second glass,
The first is the glass melting point and a low glass transition point than the boiling point of the waste, and the use of a material having a lower glass transition point than the second glass, said the second glass the first A method for treating waste, comprising forming a vitrified body using a material having better corrosion resistance than glass.   The waste treatment method according to claim 1, wherein the waste is a radioactive waste.   The waste disposal method according to claim 2, wherein the radioactive waste contains cesium as a radioactive element.   The waste glass treatment method according to claim 3, wherein the glass transition point of the first glass is lower than the melting point of cesium oxide and the boiling point of cesium hydroxide. The waste processing method according to any one of claims 1 to 4 , wherein the first glass and the second glass are formed of phosphate glass. The first glass includes P ₂ O ₅ as a first component or a second component, and includes any one of SnO, BaO, and ZnO as a second component or a first component. The waste processing method according to claim 5, wherein the components are combined to 65 (mol%) or more. Wherein the first glass comprises _P 2 _{O 5} and SnO as a first component and a second component, further processing method of waste of claim 6, further comprising BaO and _B 2 _{O 3.} The second glass has at least P ₂ O ₅ , CeO ₂ and Cr ₂ O ₃ , and contains P ₂ O ₅ and CeO ₂ in a range of 50 to 90 (mol%), Cr ₂ O ₃ method of processing waste according to any one of claims 5 to 7 comprising in the range of 0.7 to 15 of (mol%).

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