Inorganic compositions and fibers and sheets thereof

Abstract

Provided is an inorganic fiber or inorganic flake having excellent neutron shielding properties. A formulation composed of a base component in which SiO2 and Al2O3 are the main components (in which the total mass ratio of SiO2 and Al2O3 in the base component is 0.60 or more) and a neutron shielding component composed of at least one of gadolinium, gadolinium oxide, samarium, samarium oxide, cadmium, or cadmium oxide is prepared in a ratio of 50 to 90 parts by mass of the base component and 10 to 50 parts by mass of the neutron shielding component, and then melted, thereby obtaining a good amorphous inorganic fiber and inorganic flake.

Description

Technical Field

[0001] This invention relates to an inorganic composition and its fibers and sheets. More specifically, it relates to an inorganic composition and its fibers and sheets possessing neutron shielding and radiation degradation resistance. Background Technology

[0002] The necessity of neutron shielding materials in nuclear reactor facilities and radiation-based medical equipment is increasing. For example, in equipment for neutron capture therapy, which has received increasing attention in recent years, materials are needed to protect medical workers from neutron radiation. Furthermore, neutron shielding materials are also required for research equipment utilizing neutron beams for the same reasons.

[0003] Against this backdrop, efforts have been made to create neutron-shielding materials that incorporate neutron-shielding elements, such as gadolinium (Gd) or boron (B), into the materials.

[0004] For example, Japanese Patent Application Publication No. 7-138044 (Patent Document 1) and Japanese Patent Application Publication No. 8-119667 (Patent Document 2) disclose neutron shielding glasses with SiO2, Al2O3, B2O3, and Li2O as essential components, while Japanese Patent Application Publication No. 10-226533 (Patent Document 3) discloses radiation shielding glasses with B2O3, La2O3, and Gd2O3 as essential components. The glasses in Patent Documents 1-3 are all made by casting raw materials into a mold and slowly cooling them to obtain a plate-like glass material. Since these glass materials are intended for use in radiation shielding windows and observation windows, although they have excellent light transmittance, the glass materials themselves have weak impact resistance. Therefore, their use in structures that require both neutron shielding and impact strength is limited.

[0005] Therefore, methods for adding neutron-shielding components to impact-resistant resin materials have been proposed. For example, Japanese Patent Application Publication No. 6-180388 (Patent Document 4) discloses a heat-resistant neutron-shielding material formulated in phenolic resin using inorganic boron compounds, gadolinium oxide, etc., as thermal neutron-absorbing materials. Furthermore, Japanese Patent Application Publication No. 2006-145421 (Patent Document 5) discloses a heat-resistant neutron shielding body formulated in phenolic resin using powdered boron carbide powder and then cured. Similarly, Japanese Patent Application Publication No. 2020-30088 (Patent Document 6) discloses a resin composition formulated in a curable resin using boron carbide, boric acid, gadolinium, or mixtures thereof with a specific particle size range. The inventions described in Patent Documents 4-6 all involve adding neutron-shielding powdered raw materials to resin materials that already possess strength.

[0006] Previous technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 7-138044

[0009] Patent Document 2: Japanese Patent Application Publication No. 8-119667

[0010] Patent Document 3: Japanese Patent Application Publication No. 10-226533

[0011] Patent Document 4: Japanese Patent Application Publication No. 6-180388

[0012] Patent Document 5: Japanese Patent Application Publication No. 2006-145421

[0013] Patent Document 6: Japanese Patent Application Publication No. 2020-30088 Summary of the Invention

[0014] The technical problem to be solved by the invention

[0015] However, as can be seen from the aforementioned patent documents 4-6, if the neutron shielding component added to the resin is a powder, there is a problem that the strength of the resin decreases as the amount of powder added increases. Therefore, the amount of powdered neutron shielding component that can be added is limited.

[0016] However, glass fibers or glass sheets are known as reinforcing materials for resins. Glass fibers are effective in improving the strength (especially rigidity) of curable and thermoplastic resins. Furthermore, glass sheets have the advantage of improving the rigidity of thermoplastic resins in the same way as glass fibers, while also exhibiting less molding anisotropy in the strength seen in glass fiber-reinforced thermoplastic resins.

[0017] Therefore, if glass fibers or glass sheets with neutron shielding properties are created, the applicability of neutron shielding structures can be expected to be greatly expanded.

[0018] Therefore, the inventors conducted in-depth research on the development of novel inorganic compositions with neutron shielding properties, as well as their fibers and sheets.

[0019] means for solving technical problems

[0020] As a result, the inventors discovered that by preparing a matrix composition with SiO2 and Al2O3 as the main components and monomers or oxides of neutron-shielding elements (hereinafter referred to as "neutron-shielding components") in appropriate proportions, a novel inorganic composition with neutron shielding properties can be obtained. In addition, the allowable range of addition of neutron-shielding elements that can be melt-processed into inorganic fibers or inorganic sheets is smaller than that in the case of cast glass, thereby completing the present invention.

[0021] The inventors also discovered that fly ash can be effectively used as a matrix component, and that when fly ash is used, the upper limit of the amount of neutron shielding elements added can be increased by suppressing the content of specific impurities contained in the fly ash.

[0022] Surprisingly, the inorganic composition of the present invention not only possesses neutron shielding properties but also resistance to radiation degradation. To the best of the inventors' knowledge, no material has yet been found that combines both neutron shielding and radiation degradation resistance.

[0023] That is, the present invention is an inorganic composition and its fibers and sheets, characterized in that,

[0024] i) Composed of 10-50% by weight of at least one of gadolinium, gadolinium oxide, samarium, samarium oxide, cadmium, or cadmium oxide, and 50-90% by weight of residual components.

[0025] ii) The total proportion of SiO2 and Al2O3 in the residual components, by mass ratio, is 0.60 or more.

[0026] iii) It is amorphous.

[0027] The present invention will now be described in more detail.

[0028] The inorganic composition of the present invention, its fibers, and sheets (hereinafter, the inorganic fibers or sheets are sometimes referred to as "products") consist of 10 to 50% by mass of a "neutron shielding component" and 90 to 50% by mass of a residual component mainly composed of SiO2 and Al2O3. As described later, the aforementioned residual component is a component that contributes to the formation of the amorphous structure of the inorganic composition of the present invention, its fibers, and sheets. Therefore, hereinafter, the residual component is sometimes referred to functionally as a glass-forming component.

[0029] The inorganic composition, fibers, and sheets of the present invention are prepared by using "glass-forming components" with SiO2 and Al2O3 as main components and monomers or oxides of neutron-shielding elements as raw materials, and then melting and processing the raw material preparation. Furthermore, in the present invention, no substantial difference was found between the component ratio of the raw material preparation and the component ratio of the inorganic composition, fibers, and sheets obtained from the melt. Therefore, the component ratio of the raw material preparation can be used as the component ratio of the inorganic composition, fibers, and sheets.

[0030] "Neutron shielding components" are those containing elements such as gadolinium, samarium, and cadmium. Hereinafter, gadolinium, samarium, and cadmium will be referred to simply as "neutron shielding elements." The neutron shielding performance of "neutron shielding elements" differs significantly from other elements; therefore, the neutron shielding performance of a product is essentially determined by the content of these "neutron shielding elements." Furthermore, since neutrons are captured by the atomic nuclei of elements, the neutron shielding performance of a product depends almost entirely on the net content of "neutron shielding elements" in the product. Therefore, either monomers or oxides of neutron shielding elements can be used as raw materials.

[0031] From the perspective of neutron shielding performance, gadolinium or samarium are preferred among "neutron shielding elements", with gadolinium being the most preferred.

[0032] Furthermore, as a "neutron-shielding element," isotopes or isotope concentrates with excellent neutron shielding properties can be used. Gadolinium-157 is one such isotope. 157 Gd), Samarium-149 ( 149 Sm), cadmium-113 ( 113 Cd).

[0033] In the inorganic composition and its fibers and sheets of the present invention, which should possess neutron shielding and radiation resistance properties, gadolinium, gadolinium oxide, samarium, samarium oxide, cadmium or cadmium oxide should contain at least 10% by mass, preferably at least 30% by mass, more preferably at least 35% by mass, further preferably at least 40% by mass, and most preferably at least 45% by mass.

[0034] However, if the raw material contains more than 50% by mass of gadolinium, gadolinium oxide, samarium, samarium oxide, cadmium, or cadmium oxide, the viscosity of the melt becomes too low, making it difficult to fiberize or sheet. Simultaneously, the solidified melt mixes with the crystalline phase within the amorphous phase, leading to a decrease in strength. Therefore, the content of the "neutron shielding element" in the inorganic composition of the present invention, as well as its fibers and sheets, is less than 50% by mass.

[0035] In this invention, the residual components other than the "neutron shielding component", namely the "glass forming component", are the matrix components of the inorganic composition and its fibers and sheets of this invention, which help to form the amorphous (glassy) structure of the inorganic composition and its fibers and sheets.

[0036] Therefore, the aforementioned "glass-forming component" must primarily consist of glass-forming SiO2 and Al2O3. More specifically, the total mass ratio of SiO2 and Al2O3 in the "glass-forming component" is 0.50 or more, preferably 0.60 or more, more preferably 0.65 or more, further preferably 0.70 or more, and most preferably 0.75 or more.

[0037] Furthermore, from the viewpoint of processability of the melt into fibers or sheets, the mass ratio of SiO2 to the total mass of SiO2 and Al2O3 in the residual composition is preferably in the range of 0.60 to 0.90, more preferably in the range of 0.65 to 0.90, and most preferably in the range of 0.70 to 0.90.

[0038] Furthermore, the inorganic compositions, fibers, and sheets of the present invention do not exclude the unavoidable contamination of impurities contained in the raw materials. Examples of such impurities include Fe2O3, CaO, MgO, Na2O, K2O, TiO2, and CrO2. However, as will be described later, when the "neutron shielding component" is set to a high content, the content of Fe2O3 must be carefully considered.

[0039] There are no particular restrictions on the aforementioned "glass-forming components" as long as they contain both SiO2 and Al2O3. Therefore, SiO2 and Al2O3 can also be mixed separately as "glass-forming components." However, in industrial applications, rocks or fly ash rich in both SiO2 and Al2O3 are inexpensive and are therefore preferred.

[0040] As examples of the aforementioned rocks, volcanic rocks, such as basalt, can be cited. The use of volcanic rocks, such as basalt, requires mining and crushing processes.

[0041] In contrast, fly ash is a waste product from coal-fired power generation and can be obtained in powder form, thus eliminating the need for a crushing process and being inexpensive, making it a preferred "glass-forming component." Clinker ash can also be preferred as a similar waste. Furthermore, the waste generated in integrated coal gasification combined cycle (IGCC) power generation is specifically called coal gasification slag (CGS), but since its chemical composition is largely the same as conventional fly ash, it can also be used as a "glass-forming component." Because coal gasification slag is granular, it offers superior operability compared to conventional fly ash. In this invention, the term "fly ash" is used to include coal gasification slag.

[0042] In addition, the composition of fly ash and clinker ash varies depending on the coal from which the raw material is produced and the location (power plant, country).

[0043] According to the Fly Ash Handbook (compiled by the Japan Fly Ash Association), the composition (mass %) of fly ash, in order of its content, is as follows: SiO2: 40.1–74.4, Al2O3: 15.7–35.2, Fe2O3: 1.4–17.5, CaO: 0.3–10.1, MgO: 0.2–7.4. Therefore, Fe2O3 shows the greatest variation.

[0044] Through a series of tests conducted by the inventors, the following facts were discovered.

[0045] That is, as the content of Fe2O3 as an impurity in the "glass-forming component" increases, the amount of "neutron shielding component" that can be melted and processed into inorganic fibers or inorganic sheets decreases. In other words, if the Fe2O3 content in the "glass-forming component" is suppressed, the final composition can contain more "neutron shielding component," thus enabling the manufacture of inorganic fibers or inorganic sheets with superior neutron shielding performance.

[0046] More specifically, the proportion (mass ratio) of Fe2O3 in the "glass-forming component" is preferably 0.30 or less.

[0047] When the proportion of the "neutron shielding component" in the composition is 20% by mass or more, the proportion (by mass) of Fe2O3 in the "glass forming component" is preferably 0.25 or less.

[0048] When the proportion of the "neutron shielding component" in the composition exceeds 35% by mass, the proportion (by mass) of Fe2O3 in the "glass forming component" is preferably less than 0.15.

[0049] Therefore, when fly ash or clinker ash is used as a "glass-forming component", it is necessary to ensure that the Fe2O3 content meets the above requirements.

[0050] Furthermore, the inorganic composition of the present invention, as well as its fibers and sheets, are amorphous. Because they are amorphous, the strength reduction caused by the exfoliation of the crystalline and amorphous phase interfaces disappears.

[0051] Whether something is amorphous can be determined by observing only amorphous halos without any peaks of crystalline phase in the X-ray diffraction spectrum.

[0052] The neutron shielding properties of the inorganic composition, its fibers, and sheets of the present invention can be estimated by calculating the mole fraction of the constituent elements of the inorganic composition, its fibers, and sheets, and multiplying it by the aforementioned mole fraction value of the sum of the neutron absorption cross-section of each element and the total scattering cross-section.

[0053] In this invention, the neutron shielding (N) calculated for inorganic compositions and their fibers and sheets is compared with the neutron shielding (N) of lead. Pb The value to be compared, i.e., N / N Pb The value of indicates its superiority (the larger the value, the better the neutron shielding).

[0054] N=Σfx×(σax+σsx)---The sum of all elements X in the inorganic fiber or inorganic sheet.

[0055] in,

[0056] σax: Neutron absorption cross-section of element X (unit: 10) -24 cm 2 )

[0057] σsx: Total neutron scattering cross-section of element X (unit: 10^- ... -24 cm 2 )

[0058] fx: Mole fraction of element X in inorganic fibers or inorganic sheets

[0059] N Pb The sum of the neutron absorption cross-section and the total neutron scattering cross-section of lead.

[0060] Regarding the neutron absorption cross-sectional area (σax), total neutron scattering cross-sectional area (σsx), and their total value (σax+σsx) of each element (X) constituting the inorganic fibers and inorganic sheets of the present invention, the following values ​​(all in units of 10) are used. -24 cm 2 Additionally, for reference, hydrogen, boron, and lead were noted.

[0061] <Element Name: Neutron Absorption Cross-Section (σax) / Total Neutron Scattering Cross-Section (σsx) / Total of σax and σsx>

[0062] Boron (B): 767 / 5 / 772

[0063] Iron (Fe): 2.6 / 11.8 / 14.4

[0064] Kr: 25 / 7.7 / 32.7

[0065] ·Cadmium (Cd): 2520 / 6 / 2526

[0066] • Samarium (Sm): 5670 / 52 / 5722

[0067] ·Gadolinium (Gd): 48890 / 192 / 49082

[0068] Lead (Pb): 0.2 / 11.1 / 11.3

[0069] Oxygen (O): 0.0 / 4.2 / 4.2

[0070] Silicon (Si): 0.2 / 2.2 / 2.4

[0071] Aluminum (Al): 0.2 / 1.5 / 1.7

[0072] Calcium (Ca): 0.4 / 3.0 / 3.4

[0073] • Hydrogen (H): 0.3 / 81.7 / 82.0

[0074] As detailed in the experimental examples, the inorganic fibers and inorganic sheets of the present invention have neutron shielding performance that is more than tens of times greater than that of conventional glass fibers and glass sheets, and in a more preferred embodiment, more than hundreds of times greater than that of conventional glass fibers and glass sheets.

[0075] In this invention, inorganic fibers can be bundled into inorganic fiber bundles by attaching a bundling agent to their surface and bundling them according to conventional methods. The bundling agent, which is important in the formation of inorganic fiber bundles, will be described below.

[0076] As a bridging agent, a common starch-based bridging agent can be used, but for the inorganic fibers of this invention, it is preferable to use an agent with a hydrogen content higher than that of starch (molecular formula: (C6H2O)). 10 05) n The neutron trapping agent is composed of a material with a high hydrogen content. The neutrons produced by the elastic scattering of hydrogen have extremely high deceleration energy. Therefore, if the neutron trapping agent is composed of a material with a high hydrogen content, the neutrons are decelerated by the neutron trapping agent on the fiber surface. As a result, the neutron capture efficiency is further improved by the "neutron shielding element" in the inorganic composition of the present invention.

[0077] Examples of high-hydrogen-content materials suitable as clustering agents include

[0078] i) Paraffin

[0079] ii) Microcrystalline wax

[0080] iii) Polyethylene or ethylene-based copolymers

[0081] iv) Polypropylene.

[0082] On an atomic percentage basis, starch contains 48% hydrogen, while the materials described in i) to iv) above contain approximately 60% or more hydrogen on an atomic percentage basis. In polyethylene and polypropylene, the hydrogen content reaches approximately 67% on an atomic percentage basis.

[0083] In iii) above, an ethylene-based ethylene copolymer refers to an ethylene copolymer in which at least 70% by weight of the polymeric units are ethylene units. Examples of comonomers other than ethylene constituting the ethylene copolymer include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene.

[0084] Furthermore, the polyethylene in ii) above contains low molecular weight polyethylene (polyethylene wax), and the polypropylene in iv) contains low molecular weight polypropylene (polypropylene wax).

[0085] As described below, the materials mentioned in i) to iv) above include modified products that have undergone additional polarity treatment to improve their polarity.

[0086] When inorganic fibers are used as fillers for resin reinforcement, the softening temperature, molecular weight, and polarity of the high-hydrogen-containing materials mentioned in i) to iv) above are important factors.

[0087] The softening temperatures of the aforementioned high-hydrogen-containing materials are: i) paraffin wax: 50–60°C, ii) microcrystalline wax: 65–95°C, iii) polyethylene: 115–145°C, and iv) polypropylene: 145–165°C. Therefore, for example, when the heat resistance temperature of the inorganic fiber-filled resin is important, microcrystalline wax, polyethylene, and polypropylene with softening temperatures higher than paraffin wax are preferred, with polypropylene being the most preferred.

[0088] Furthermore, the higher the molecular weight of the aforementioned high-hydrogen-containing materials, the higher the film strength of the bridging agent at the interface between the resin and inorganic fibers. Therefore, when film strength is important, low molecular weight polyethylene (molecular weight: 9,000-30,000) or low molecular weight polypropylene (molecular weight: 8,000-40,000) is preferred over paraffin (molecular weight: 300-600) or microcrystalline wax (molecular weight: 400-800), and even more preferred are polyethylene or polypropylene with higher molecular weights that are commonly used in molding processes.

[0089] Furthermore, since the surface of the inorganic fibers of the present invention is rich in polarity, the bonding strength between the inorganic fibers and the bundler is increased by imparting polarity to the aforementioned high-hydrogen-content material. In paraffin or microcrystalline wax, polarity can be imparted through oxidation treatment. On the other hand, in polyethylene (or ethylene-based copolymers) or polypropylene, polarity can be imparted through acid-modified copolymerization or acid-modified grafting reactions. Acid-modified copolymerization can be achieved by copolymerizing ethylene or propylene with comonomers having carboxyl or carbonyl groups, represented by maleic acid or maleic anhydride. Acid-modified grafting reactions can be achieved by reacting polyethylene or polypropylene with monomers having carboxyl or carbonyl groups, represented by maleic acid or maleic anhydride, in the presence of a peroxide.

[0090] Hereinafter, polyethylene, ethylene-based ethylene copolymers, and polypropylene, which are given polarity through acid-modified copolymerization or acid-modified grafting reaction, will be referred to as acid-modified polyethylene, acid-modified ethylene copolymers, and acid-modified polypropylene, respectively.

[0091] The bridging agent composed of the aforementioned high-hydrogen-content material is used in the form of an aqueous emulsion (hereinafter, the bridging agent as an aqueous emulsion is sometimes referred to as a "bridging agent emulsion"). The bridging agent emulsion is obtained by mixing the aforementioned high-hydrogen-content material with water and a surfactant at a temperature higher than the softening temperature of the high-hydrogen-content material, preferably at a temperature 10°C or higher than the softening temperature, and even more preferably at a temperature 20°C or higher than the softening temperature. Furthermore, when the softening temperature of the high-hydrogen-content material exceeds 100°C, mixing is performed under high pressure. During mixing, the higher the molecular weight of the high-hydrogen-content material, the higher its viscosity even above the softening temperature; therefore, mixing is carried out under high shear conditions.

[0092] The adhesion of the bubbling agent to the inorganic fibers is achieved by spraying a bubbling agent emulsion onto the inorganic fibers or by immersing the inorganic fibers in the bubbling agent emulsion. Subsequently, the inorganic fibers with the bubbling agent attached are heated to a temperature above the softening temperature of the high-hydrogen-containing material, preferably at a temperature 10°C or higher, and more preferably at a temperature 20°C or higher, to dry them, thereby obtaining an inorganic fiber bundle in which the high-hydrogen-containing material is firmly attached to the surface of the inorganic fibers.

[0093] The resulting inorganic fiber bundles are then processed into products such as chopped filaments, rovings, and fiber sheets.

[0094] In these products, regarding the raw materials for the bridging agent, materials using polyethylene or ethylene-based ethylene copolymers are suitable as fillers for ethylene resins, materials using polypropylene are suitable as fillers for propylene resins, and materials using acid-modified polyethylene, acid-modified ethylene copolymers, and acid-modified polypropylene are suitable as reinforcing materials for FRPs in addition to being fillers for polyamide resins.

[0095] Invention Effects

[0096] Fibers or sheets made from the inorganic composition of the present invention are added as fillers to materials such as resins and cement, thereby imparting neutron shielding properties to the materials. Furthermore, unlike conventional powdered additives, the fibers or sheets of the present invention, due to their shape, also function as reinforcing materials for resins or cements. In addition, the fibers or sheets made from the inorganic composition of the present invention exhibit excellent resistance to radiation degradation, thus maintaining their function as reinforcing agents for resins, cements, and coatings constituting radiation-exposed components over a long period.

[0097] Inorganic fibers are processed into chopped filaments, rovings, and fiber sheets according to their intended purpose. Rovings and fiber sheets can be used to create composite materials that can be combined with resins. This increases the freedom of shape design for target items (final products) that require both neutron shielding and strength. The shape freedom offered by inorganic fibers is something that sheet-like cast glass cannot achieve.

[0098] On the other hand, by adding inorganic flakes to resins or coatings, and through the shear force applied during the molding process in the resin or the coating process in the coating, the inorganic flakes easily achieve a layered orientation along the surface of the resin molded article or the coating film. As a result, the neutron shielding effect will be more effectively achieved. Attached Figure Description

[0099] Figure 1 This is a diagram that roughly represents a fibrosis test.

[0100] Figure 2 This is a diagram that roughly represents the thin-film experiment.

[0101] Figure 3 These are the XRD spectra of Example 10 and Comparative Example 2.

[0102] Figure 4 This is a schematic diagram of an apparatus used for positron lifetime determination.

[0103] Figure 5 This is a comparison graph of the positron lifetime spectra of the inorganic composition of Test Example 19 before and after radiation irradiation.

[0104] Figure 6 This is a comparison graph of the positron lifetime spectra of the inorganic composition of Comparative Example 6 before and after radiation irradiation.

[0105] Figure 7 This is a graph showing the relationship between the content of neutron shielding elements in the composition and its resistance to radiation degradation.

[0106] Figure 8 These are comparison photographs of the inorganic fibers of this invention and inorganic fibers of conventional technologies, taken with neutron radiation. Detailed Implementation

[0107] The present invention will now be described in detail through experimental examples.

[0108] In addition, the following reagents and raw materials were used in the following test examples (examples and comparative examples).

[0109] <Raw materials for glass forming components>

[0110] • Fly ash: FA1, FA2, FA4, FA5 (obtained from domestic and international sources. Composition (mass %) is listed in Table 1.)

[0111] Copper Slag: CS (obtained domestically. Composition (wt%) is listed in Table 1.)

[0112] Volcanic rock: BA (obtained from Japan. Composition (wt%) is listed in Table 1.)

[0113] • Silicon dioxide: SiO2 (reagent, powder)

[0114] • Aluminum oxide: Al2O3 (reagent, powder)

[0115] Calcium oxide: CaO (reagent, powder)

[0116] Calcium carbonate: CaCO3 (reagent, powder)

[0117] Iron oxide (III): Fe2O3 (reagent, powder)

[0118] Magnesium oxide: MgO (reagent, powder)

[0119] Titanium oxide: TiO2 (reagent, powder)

[0120] Potassium carbonate: K₂CO₃ (reagent, powder)

[0121] Boric acid: H3BO3 (reagent, powder)

[0122] <Reagents for Neutron Shielding>

[0123] Gadolinium (monomer): Gd (reagent, powder)

[0124] Gadolinium oxide: Gd₂O₃ (reagent, powder)

[0125] • Samarium (monomer): Sm (reagent, powder)

[0126] • Samarium oxide: Sm₂O₃ (reagent, powder)

[0127] Cadmium (monomer): Cd (reagent, powder)

[0128] [Table 1]

[0129]

[0130] In addition, the compositional analysis of FA1, FA2, FA4, FA5, CS, and BA was based on fluorescence X-ray analysis.

[0131] <Adjustment of Raw Material Formulation>

[0132] Weigh the glass-forming component raw materials and the neutron-shielding component reagents in a specified ratio, mix them in a mortar, and prepare a powdered raw material formulation.

[0133] <Evaluation of fiberization test and melt spinning properties>

[0134] Regarding the raw material formulations, their melt spinning properties were evaluated in the following order. A summary of the tests is shown below. Figure 1 .exist Figure 1In the electric furnace (11), the height (H) is 60cm, the outer diameter (D) is 50cm, and it has an opening (14) with a diameter (d) of 10cm in the center. On the other hand, in the inner diameter 30g of the preparation was placed in a carbon granule heating tube (12) that was 2.1cm in diameter and 10cm in length. Additionally, a 2mm diameter hole was made in the center of the bottom of the carbon granule heating tube (12). During the melting test, the carbon granule heating tube (12) was held in a predetermined position within the opening (14) of the electric furnace by a rod (13).

[0135] The electric furnace heats up according to a prescribed heating program, with the maximum temperature inside the furnace set at 1450°C. At this point, it is pre-confirmed that the temperature inside the carbon granule heating tube (molten material) will follow the furnace temperature at approximately 50°C lower. As the raw material mixture melts upon heating, it flows down from the bottom of the carbon granule heating tube due to its own weight, solidifying upon contact with the outside air.

[0136] In this invention, the evaluation index for melt spinning properties is defined as follows: the raw material formulation melts before the furnace temperature reaches 1450°C, and the melt flows down to form yarn; that is, the melting temperature of the raw material formulation is below 1400°C, and it has appropriate melt viscosity when the melt forms yarn. The melting behavior of the raw material formulations used as samples is generally divided into groups A to C as shown below.

[0137] <Melt spinning performance rating>

[0138] A: It becomes yarn.

[0139] B: The sample does not melt, or the viscosity of the melt is too high, so it will not fall down by its own weight and will not become yarn.

[0140] C: The sample melts, but the viscosity of the melt is too low, so it drips down as droplets and does not form yarn.

[0141] <Thinning Experiment>

[0142] The raw material formulations were provided for the sheeting test (evaluation of sheet processability) in the following order. A summary of the test is shown below. Figure 2 .

[0143] Following steps 1 to 4, melt the raw material formulation to attempt to sheet the melt.

[0144] Step 1: Place approximately 60 grams of the raw material preparation (fp) into a crucible (21) with a diameter (D1) of 20 mm. Additionally, prepare a carbon granule heating tube (22) with a diameter (D2) of 10 mm. The carbon granule heating tube (22) has an opening (21) with a diameter (Φ) of 2 mm at the bottom. Figure 2 (the upper part).

[0145] Step 2: Heat the crucible (21) containing the preparation (fp) using an electric furnace (23). Figure 2 (The middle left side). The electric furnace is heated through a prescribed heating program. The maximum temperature to be reached inside the furnace is set at 1450°C. It is confirmed in advance that the temperature inside the crucible (21) and the molten material (fm) will follow at a temperature approximately 50°C lower than the furnace temperature.

[0146] Step 3: Immediately remove the heated crucible (21) from the electric furnace (3), and press the carbon particle heating tube (22) downwards from the top of the crucible (21). The inorganic composition melt (fm) inside the crucible (21) enters the interior of the carbon particle heating tube (22) through the opening (21). Figure 2 (Right side of the middle section).

[0147] Step 4: Next, remove the carbon particle heating tube (22) containing the molten material (fm) from the crucible (22), and immediately blow air into it through its opening (222) at a pressure of approximately 10 MPa. Figure 2 (Lower left side). When the melt (fm) has appropriate viscosity, the melt expands and forms a hollow film air pocket (fb). Figure 2 (Lower right side). The airbag is crushed to obtain a thin sheet.

[0148] Based on the results of the sheeting tests in the above order, the sheet processability is classified into the following categories: a, b, and c.

[0149] <Evaluation Grades for Thin Sheet Processability>

[0150] a: Proceed through steps 1 to 4 to form an airbag.

[0151] b: Proceeding to step 2, but the melting of the preparation (fp) has not yet begun, or due to the high viscosity of the melt, the melt does not enter the interior of the carbon particle heating tube (22) from the opening (221) in step 3.

[0152] c: Steps 1 to 3 are performed, but due to the low viscosity of the melt, in step 4, the melt (fm) contained in the carbon particle heating tube (22) drips from the opening (222) and does not form a spherical capsule.

[0153] [Example 1]

[0154] As glass-forming components, 30 parts by mass of FA1, 10 parts by mass of FA4, 20 parts by mass of CS, and 30 parts by mass of BA were weighed, and as neutron shielding components, 10 parts by mass of gadolinium (monomer) was weighed to prepare the raw material formulation.

[0155] The raw material formulation contains the following components: Gadolinium: 10% by mass, SiO2: 44% by mass, Al2O3: 11% by mass, CaO: 8% by mass, Fe2O3: 22% by mass, and others: 5% by mass. The mass of SiO2, Al2O3, CaO, Fe2O3, and other components in the glass-forming composition, calculated from the proportions of each raw material, the total mass ratio of SiO2 and Al2O3 in the glass-forming composition, the mass ratio of SiO2 relative to the total mass of SiO2 and Al2O3 in the glass-forming composition, the mass ratio of Fe2O3 in the glass-forming composition, and the total mass ratio of SiO2 and Al2O3 in the final composition (inorganic fibers, inorganic sheets) are all shown in Table 2. Furthermore, in the following tables, the abbreviations [S], [A], [C], and [F] are used for SiO2, Al2O3, CaO, and Fe2O3, respectively.

[0156] A fiberization test was conducted on the raw material formulation, resulting in yarn with a diameter of approximately 10 μm. The obtained yarn possesses strength that makes it difficult to break even when pulled by hand. Furthermore, although the term "fiber" is sometimes used instead of "yarn" in the following description, the meaning is the same.

[0157] Furthermore, a thin-film processing experiment was conducted on the raw material formulation, resulting in an airbag with a film thickness of approximately 800 nm. The airbag was then pulverized to obtain a thin film.

[0158] No crystal peaks were found in the X-ray diffraction (XRD) spectra of the fibers and sheets, indicating amorphous properties. These results are shown in Table 2. Furthermore, in the evaluation of amorphous states in the following tables, "○" indicates amorphousness, and "×" indicates the presence of crystal peaks.

[0159] Furthermore, based on the component ratio (mass%) of the final composition, the elemental ratio (molar%) was determined, and the relative neutron shielding efficiency (N / N) relative to lead was calculated. Pb (Table 2, bottom row).

[0160] [Example 2]

[0161] Except for the use of samarium (monomer) as the neutron shielding component in Example 1, the raw material formulation was prepared in the same manner, and melt spinning and sheet processing tests were conducted. The results are shown in Table 2. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous. The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 2, bottom row).

[0162] [Example 3]

[0163] Except for the use of cadmium (monomer) as the neutron shielding component in Example 1, the raw material formulation was prepared in the same manner, and melt spinning and sheet processing tests were conducted. The results are shown in Table 2. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous. The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 2, bottom row).

[0164] [Comparative Example 1]

[0165] As glass-forming components, a raw material formulation was prepared by weighing 14 parts by mass of FA2, 44 parts by mass of FA5, 22 parts by mass of CS, and 20 parts by mass of BA.

[0166] The ingredients in this raw material formulation are as follows: SiO2: 51% by mass, Al2O3: 13% by mass, CaO: 8% by mass, Fe2O3: 22% by mass, and others: 7% by mass.

[0167] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 2. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0168] Furthermore, the resulting fibers and sheets do not contain neutron-shielding components, resulting in an extremely low relative neutron shielding efficiency of 3 (N / N) relative to lead. Pb (Table 2, bottom row).

[0169] [Table 2]

[0170]

[0171] [Example 4]

[0172] As glass-forming components, 33 parts by mass of FA1, 11 parts by mass of FA2, 6 parts by mass of FA4, 22 parts by mass of CS, and 11 parts by mass of BA were weighed, and as neutron shielding components, 17 parts by mass of gadolinium (monomer) were weighed to prepare the raw material formulation.

[0173] The ingredients in this raw material formulation are as follows: Gadolinium: 17% by mass, SiO2: 41% by mass, Al2O3: 10% by mass, CaO: 6% by mass, Fe2O3: 20% by mass, and others: 6% by mass.

[0174] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 3. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0175] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 3, bottom row).

[0176] [Example 5]

[0177] As a glass-forming component, 70 parts by mass of FA5 were weighed, and as a neutron-shielding component, 30 parts by mass of gadolinium (monomer) were weighed to prepare the raw material formulation.

[0178] The ingredients in this raw material formulation are as follows: Gadolinium: 30% by mass, SiO2: 42% by mass, Al2O3: 13% by mass, CaO: 3% by mass, Fe2O3: 8% by mass, and others: 6% by mass.

[0179] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 3. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0180] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 3, bottom row).

[0181] [Example 6]

[0182] The raw material formulation was prepared by weighing 65 parts by mass of FA5 as a glass-forming component and 35 parts by mass of gadolinium (monomer) as a neutron-shielding component.

[0183] The ingredients in this raw material formulation are as follows: Gadolinium: 35% by mass, SiO2: 39% by mass, Al2O3: 12% by mass, CaO: 2% by mass, Fe2O3: 7% by mass, and others: 5% by mass.

[0184] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 3. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0185] [Example 7]

[0186] As glass-forming components, 30 parts by mass of FA1, 10 parts by mass of FA2, 5 parts by mass of FA4, 20 parts by mass of CS, and 10 parts by mass of BA were weighed, and as neutron shielding components, 25 parts by mass of gadolinium oxide (Gd2O3) were weighed to prepare the raw material formulation.

[0187] The ingredients in this raw material formulation are as follows: gadolinium oxide: 25% by mass, SiO2: 37% by mass, Al2O3: 9% by mass, CaO: 6% by mass, Fe2O3: 18% by mass, and others: 4% by mass.

[0188] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 3. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0189] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 3, bottom row).

[0190] [Example 8]

[0191] The raw material formulation was prepared in the same manner, except that CS was set to 15 parts by mass and gadolinium oxide (Gd2O3) was set to 30 parts by mass in Example 7.

[0192] The ingredients in this raw material formulation are as follows: gadolinium oxide: 30% by mass, SiO2: 36% by mass, Al2O3: 9% by mass, CaO: 6% by mass, Fe2O3: 16% by mass, and others: 5% by mass.

[0193] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 3. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0194] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 3, bottom row).

[0195] [Example 9]

[0196] The raw material formulation was prepared by weighing 35 parts by mass of FA1, 5 parts by mass of FA2, 20 parts by mass of CS, and 5 parts by mass of BA as glass-forming components, and 35 parts by mass of gadolinium oxide as a neutron shielding component.

[0197] The ingredients in this raw material formulation are as follows: gadolinium oxide: 35% by mass, SiO2: 32% by mass, Al2O3: 8% by mass, CaO: 4% by mass, Fe2O3: 17% by mass, and others: 4% by mass.

[0198] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 3. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0199] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 3, bottom row).

[0200] [Table 3]

[0201]

[0202] [Example 10]

[0203] A raw material formulation was prepared by weighing 60 parts by mass of FA5 as a glass-forming component and 40 parts by mass of gadolinium (monomer) as a neutron-shielding component.

[0204] The raw material formulation contains the following components: Gadolinium: 40% by mass, SiO2: 36% by mass, Al2O3: 11% by mass, CaO: 2% by mass, Fe2O3: 6% by mass, and others: 5% by mass. In addition, the proportion (by mass) of Fe2O3 in the glass-forming components is 0.11.

[0205] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 4. Good yarns and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous. The XRD spectra are shown in Table 4. Figure 3 .

[0206] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 4, bottom row).

[0207] [Comparative Example 2]

[0208] The raw material formulation was prepared in the same manner, except that instead of FA5:60 parts by mass, which replaced the glass-forming components of Example 10, FA1:30 parts by mass, FA4:10 parts by mass, and BA:20 parts by mass.

[0209] The raw material formulation contains the following components: Gadolinium: 40% by mass, SiO2: 33% by mass, Al2O3: 9% by mass, CaO: 5% by mass, Fe2O3: 9% by mass, and others: 4% by mass. Additionally, the proportion (by mass) of Fe2O3 in the glass-forming components is 0.15.

[0210] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 4. Due to the low melt viscosity of the raw material formulation, yarn could not be formed in the melt spinning test. Similarly, in the sheet processing test, the melt viscosity was also too low to form air pockets. In addition, no peaks originating from the crystalline phase were found in the XRD spectrum of the melt-cured product. Figure 3 ).

[0211] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 4, bottom row).

[0212] [Example 11]

[0213] The raw material formulation was prepared in the same manner, except that the gadolinium monomer (40 parts by mass) used instead of the neutron shielding component in Example 10 was set as gadolinium oxide (40 parts by mass).

[0214] The raw material formulation contains the following components: gadolinium oxide: 40% by mass, SiO2: 36% by mass, Al2O3: 11% by mass, CaO: 2% by mass, Fe2O3: 6% by mass, and others: 5% by mass. In addition, the proportion (by mass) of Fe2O3 in the glass-forming components is 0.11.

[0215] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 4. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0216] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 4, bottom row).

[0217] [Comparative Example 3]

[0218] The raw material formulation was prepared in the same manner, except that instead of FA5:60 parts by mass, which replaced the glass-forming components in Example 10, FA1:35 parts by mass, FA2:5 parts by mass, CS:13 parts by mass, and BA:8 parts by mass.

[0219] The raw material formulation contains the following components: gadolinium oxide: 40% by mass, SiO2: 31% by mass, Al2O3: 8% by mass, CaO: 4% by mass, Fe2O3: 14% by mass, and others: 3% by mass. In addition, the proportion (by mass) of Fe2O3 in the glass-forming components is 0.23.

[0220] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 4. Due to the low melt viscosity of the raw material formulation, yarn could not be formed in the melt spinning test. Similarly, in the sheet processing test, the melt viscosity was also too low to form air pockets. In addition, XRD analysis showed that the melt contained crystalline components.

[0221] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 4, bottom row).

[0222] [Example 12]

[0223] A raw material formulation was prepared by weighing 55 parts by mass of FA5 as a glass-forming component and 45 parts by mass of gadolinium oxide as a neutron-shielding component.

[0224] The raw material formulation contains the following components: gadolinium oxide: 40% by mass, SiO2: 33% by mass, Al2O3: 10% by mass, CaO: 2% by mass, Fe2O3: 6% by mass, and others: 5% by mass. In addition, the proportion (by mass) of Fe2O3 in the glass-forming components is 0.11.

[0225] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 4. Good fibers and sheets were obtained from the raw material formulation. Furthermore, both the fibers and sheets were amorphous.

[0226] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 4, bottom row).

[0227] [Comparative Example 4]

[0228] A raw material formulation was prepared by weighing 40 parts by mass of FA5 as a glass-forming component and 60 parts by mass of gadolinium oxide as a neutron-shielding component.

[0229] The raw material formulation contains the following components: gadolinium oxide: 60% by mass, SiO2: 24% by mass, Al2O3: 7% by mass, CaO: 1% by mass, Fe2O3: 4% by mass, and others: 3% by mass. In addition, the proportion (by mass) of Fe2O3 in the glass-forming components is 0.11.

[0230] Melt spinning and sheet processing tests were conducted on the raw material formulation. The results are shown in Table 4. Due to the low melt viscosity of the raw material formulation, yarn could not be formed in the melt spinning test. Similarly, in the sheet processing test, the melt viscosity was also too low to form air pockets. In addition, XRD analysis showed that the melt contained crystalline components.

[0231] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 4, bottom row).

[0232] [Table 4]

[0233]

[0234] As can be seen from the comparison between Example 10 and Comparative Example 2, and between Example 11 and Comparative Example 3, when the neutron shielding component exceeds 35% by mass, if the mass ratio of Fe2O3 in the glass-forming component is 0.15 or higher, fibers and sheets cannot be obtained from the inorganic composition. Furthermore, when the content of the neutron shielding component in the composition exceeds 50% by mass, even if the mass ratio of Fe2O3 in the glass-forming component is less than 0.15, it is clearly evident that fibers and sheets cannot be obtained.

[0235] [Examples 13-17, Comparative Example 5]

[0236] As a neutron shielding component, samarium monomer and samarium oxide (Sm2O3) were used in the same experiments. The results are shown together with the formulation of the raw materials and the composition of the final composition (Table 5).

[0237] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 5, bottom column). Similar to the use of gadolinium monomer and gadolinium oxide, good fibers and sheets can be obtained even when using samarium monomer and samarium oxide (Examples 13-17). However, as observed in Comparative Example 4, no fibers or sheets were obtained from the composition of Comparative Example 5, in which the content of the neutron shielding component (samarium oxide) in the composition exceeded 50% by mass.

[0238] [Table 5]

[0239]

[0240] In Examples 18, 19, and Comparative Examples 6-9 shown below, in addition to evaluating their spinnability, the radiation resistance to degradation was also evaluated for each composition. The evaluation of radiation resistance to degradation was based on positron annihilation lifetime spectroscopy (PALS).

[0241] [Test Example 19]

[0242] As glass-forming components, 40 parts by mass of FA1, 10 parts by mass of FA2, 15 parts by mass of BA, and 20 parts by mass of CaCO3 (reagent) were weighed; as neutron-shielding components, 15 parts by mass of gadolinium oxide were weighed to prepare the raw material formulation.

[0243] The ingredients in this raw material formulation are as follows: gadolinium oxide: 15% by mass, SiO2: 35% by mass, Al2O3: 9% by mass, CaO: 18% by mass, Fe2O3: 9% by mass, and others: 14% by mass.

[0244] Melt spinning experiments were conducted on the raw material formulation. The results are shown in Table 6. Good fibers were obtained from the raw material formulation. Furthermore, the fibers were amorphous.

[0245] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 6).

[0246] Next, the molten solidified material of the raw material formulation is micronized, and the micronized material is divided into a sample for radiation irradiation and a sample not irradiated.

[0247] Using electron beams as a radiation source, a sample was irradiated with approximately 1.45 gigagray (GGy) of radiation to obtain an irradiated sample.

[0248] For the irradiated and unirradiated samples obtained in this way, respectively, use... Figure 4 The apparatus shown is used for positron lifetime determination. As the positron radiation source, a portion of sodium isotopes were used. 22 Sodium chloride with sodium substitution.

[0249] exist Figure 4 In the middle, the positron emission tomography source (31) is set as a 10 mm square plate, wrapped with titanium foil (not shown). Below the positron emission tomography source (31) is a first scintillator for gamma ray measurement.

[0250] (32a) Furthermore, the first scintillator (32a) is connected to a first photomultiplier tube (33a). The first photomultiplier tube (33a) is connected to a first wave height classifier (34a). The signal captured by the first scintillator (32a) passes through the first photomultiplier tube (33a), the first wave height classifier (34a), and is input to the data processing unit (35) via the first channel (36a). The data processing unit (35) includes a digital oscilloscope (37). Here, the first wave height classifier (34a) detects... 22 When Na undergoes β+ decay, it emits 1.28 MeV gamma rays, which are then sent to the data processing unit (35). By setting the digital oscilloscope (37), when a signal is input from the first channel (36a), the data processing unit (35) records the time (t0) and starts measuring the time.

[0251] The sample (S) used for determining the positron lifetime is housed in a sample support container (not shown) that holds a specified amount of powder sample. A second scintillator (32b) is placed above the positron radiation source (31) on which the sample (S) is placed. The second scintillator (32b) is connected to a second photomultiplier tube (33b). The second photomultiplier tube (33b) is connected to a second wavelength classifier (34b). The signal captured by the second scintillator (32b) passes through the second photomultiplier tube (33b), the second wavelength classifier (34b), and is transmitted to the data processing unit (35) via the second channel (36b). Here, the second wavelength classifier (34b) sends a signal to the data processing unit (35) when it detects a 0.511 MeV gamma ray generated during electron-pair annihilation. The data processing unit (35) records the time input from the second channel (36b).

[0252] The above measurements lasted approximately 24 hours. The count of 0.511 MeV gamma rays was accumulated over time to obtain the positron lifetime spectrum (PALS spectrum). Figure 5 The annihilation time expands due to the varying distances traveled by the positrons, thus forming a time spectrum with a peak at the start of the measurement (t0), and the count gradually decreases over time. Here, the scintillator count relative to the peak time (t0) (normalized value: 1) is taken as 10. -3 The time of the count is taken as the representative value (t1) of the annihilation time of the sample (hereinafter, the expression of the "representative value of annihilation time" is simply referred to as "annihilation time").

[0253] The same measurements were also performed on the irradiated samples to obtain PALS spectra. The normalized PALS spectra almost overlapped with those of the unirradiated samples. Therefore, the ratio (t1' / t1) of the annihilation time (t1') of the irradiated samples to the annihilation time (t1) of the unirradiated samples was 1.0.

[0254] Even after irradiation, the PALS spectra largely overlap, and the experimental results with a t1' / t1 value of 1.0 show that the fine structure of this inorganic composition remains almost unchanged before and after irradiation, indicating excellent resistance to radiation degradation.

[0255] [Example 18]

[0256] As a glass-forming component, 75 parts by mass of FA5 and 15 parts by mass of CaCO3 (a reagent) were weighed, and as a neutron-shielding component, 10 parts by mass of gadolinium oxide were weighed to prepare the raw material formulation.

[0257] The ingredients in this raw material formulation are as follows: Gadolinium oxide: 10% by mass, SiO2: 44% by mass, Al2O3: 14% by mass, CaO: 11% by mass, Fe2O3: 8% by mass, and others: 7% by mass.

[0258] Melt spinning experiments were conducted on the raw material formulation. The results are shown in Table 6. Good fibers were obtained from the raw material formulation. Furthermore, the fibers were amorphous.

[0259] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 6).

[0260] In the same manner as in Test Example 19, the PALS spectra of the unirradiated and irradiated samples were determined using the PALS method for the molten solidified material. The results showed that the PALS spectra of the unirradiated sample (sample before irradiation) and the irradiated sample (sample after irradiation) largely overlapped. Therefore, the ratio (t1' / t1) of the annihilation time (t1') of the irradiated sample to the annihilation time (t1) of the unirradiated sample was 1.0.

[0261] [Comparative Example 6]

[0262] The raw material formulation was prepared by weighing 16 parts by mass of SiO2 (reagent), 4 parts by mass of Al2O3 (reagent), 2 parts by mass of Fe2O3 (reagent), 8 parts by mass of CaO (reagent), 1 part by mass of MgO (reagent), 1 part by mass of TiO2 (reagent), and 1 part by mass of K2CO3 (reagent).

[0263] The ingredients in this raw material formulation are as follows: SiO2: 50% by mass, Al2O3: 12% by mass, CaO: 26% by mass, Fe2O3: 5% by mass, and others: 6% by mass.

[0264] Melt spinning was attempted on this raw material formulation, and yarn was obtained (Table 6). Furthermore, the melt was amorphous.

[0265] In the same manner as in Example 18, the PALS spectra of the unirradiated and irradiated samples were determined for the molten solidified material. The results showed that the PALS spectra of the unirradiated and irradiated samples changed (…). Figure 6 That is, the annihilation time (t1') of the irradiated sample is less than the annihilation time (t1) of the unirradiated sample. Specifically, the value of t1' / t1 becomes 0.6.

[0266] Since the PALS spectra of the unirradiated sample and the irradiated sample changed, it is speculated that some changes occurred in the microstructure of the sample through radiation irradiation.

[0267] [Comparative Example 7]

[0268] The raw material formulation was prepared by weighing 75 parts by mass of FA5 and 18 parts by mass of CaCO3 (reagent) as glass-forming components, and 7 parts by mass of gadolinium oxide as neutron-shielding components.

[0269] The ingredients in this raw material formulation are as follows: Gadolinium oxide: 7% by mass, SiO2: 44% by mass, Al2O3: 14% by mass, CaO: 13% by mass, Fe2O3: 8% by mass, and others: 14% by mass.

[0270] Melt spinning was attempted on this raw material formulation, and good yarn was obtained. The resulting fibers were amorphous.

[0271] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 6).

[0272] In the same manner as in Example 18, the PALS spectra of the unirradiated and irradiated samples were determined using the PALS method for the molten solidified material. The results showed that, as observed in Comparative Example 6, the PALS spectra of the unirradiated and irradiated samples changed. However, the degree of change was less than that shown in Comparative Example 6. The value of t1' / t1 was 0.7.

[0273] [Comparative Example 8]

[0274] Except that in Comparative Example 7, the CaCO3 (reagent) was set to 17 parts by mass and the gadolinium oxide to 8 parts by mass, the experiment was conducted in the same manner. The results are shown in Table 6.

[0275] In the same manner as in Example 18, the PALS spectra of the unirradiated and irradiated samples were determined using the PALS method for the molten solidified material. The results showed that, as observed in Comparative Example 6, the PALS spectra of the unirradiated and irradiated samples changed. The degree of change was smaller than that shown in Comparative Example 7. The value of t1' / t1 was 0.8.

[0276] [Comparative Example 9]

[0277] As a glass-forming component, 35 parts by mass of FA5 and 5 parts by mass of H3BO3 (a reagent) were weighed, and as a neutron-shielding component, 60 parts by mass of gadolinium oxide were weighed to prepare the raw material formulation.

[0278] Melt spinning was attempted on this raw material formulation, but yarn could not be obtained by simply dripping the melt (Table 6).

[0279] In addition, XRD analysis showed that the melt contained crystalline components.

[0280] The relative neutron shielding efficiency (N / N) relative to lead was calculated in the same manner as in Example 1. Pb (Table 6).

[0281] Even after radiation exposure, no change was observed in the PALS spectrum of the composition. The value of t1' / t1 was 1.0.

[0282] [Table 6]

[0283]

[0284] Figure 7 Based on the results in Table 6, a graph was created showing the relationship between the gadolinium oxide content in the composition and the value of t1' / t1 (dimensionless), which should be referred to as an indicator of radiation resistance. In a series of tests in the preceding Comparative Examples 6, 7, and 8, signs of improved radiation resistance were observed as the gadolinium oxide content added to impart neutron shielding properties to the composition increased, and an unexpected effect of complete radiation resistance was observed at a critical state of 10% by mass or higher.

[0285] Inorganic fibers (Sample I) were manufactured using a mass production facility from the inorganic composition of Example 18 (gadolinium oxide content: 10% by mass). Similarly, inorganic fibers (Sample II) were manufactured from the inorganic composition of Comparative Example 6 (gadolinium oxide content: 0% by mass). In addition, commercially available basalt fibers (Sample III) and glass fibers (Sample IV) were prepared for comparison.

[0286] The fiber samples I to IV were arranged sequentially on the test bench for neutron-neutron radiation imaging. Figure 8 In the middle, from the top left, the samples are labeled as follows: Sample I (gadolinium oxide content: 10% by mass), Sample II (gadolinium oxide content: 0% by mass), Sample III (basalt fiber), and Sample IV (glass fiber). Figure 8 The lower part shows neutron beam images obtained by irradiating these samples without changing their positions. In the image, from left to right, (I), (II), (III), and (IV) correspond to fiber samples I through IV, respectively. This clearly shows that the fibers in sample I (gadolinium oxide content: 10% by mass) shield neutrons, while all other fibers allow neutrons to pass through.

[0287] Industrial availability

[0288] The inorganic composition of the present invention possesses neutron shielding properties, and is therefore useful as a raw material for neutron-irradiated components. Furthermore, the inorganic composition of the present invention can be easily processed into fibers or sheets. Therefore, when compounded with resins, rubbers, cement, or other materials, not only can they be endowed with neutron shielding properties, but due to the shape of the fibers or sheets, they can also function as reinforcing materials. The fibers are processed into chopped filaments, rovings, and fiber sheets using conventional methods.

[0289] As mentioned earlier, when flakes composed of the inorganic composition of the present invention are added to a thermoplastic resin, the flakes are arranged in a layered manner in the resin molded article due to the shear force generated during the injection molding process, resulting in an effective neutron shielding effect. Similarly, when flakes composed of the inorganic composition of the present invention are added to a coating (lining material), the flakes in the coating film are arranged in a layered manner along the coating surface due to the shear force applied to the coating film (lining material) during the coating stroke using a brush or roller. As a result, the neutron shielding effect per unit mass is superior compared to powder or granular additives.

[0290] The inorganic composition of the present invention also has excellent resistance to radiation degradation. Therefore, even if the neutron-irradiated part is irradiated by neutrons for a long time, the fibers or sheets contained in the neutron-irradiated part will not deteriorate. Thus, it has the advantage of maintaining its function as a reinforcing material for the part for a long time.

[0291] The inorganic composition of the present invention, or its fibers and sheets, exhibit excellent neutron shielding properties. Therefore, they are preferred as materials constituting neutron-irradiated portions. Representative examples of neutron-irradiated portions include equipment / machines / components in the fields of nuclear energy, aerospace, and medicine.

[0292] As equipment / machinery / components in the nuclear energy field, examples can be cited.

[0293] Equipment / machinery / components used for nuclear power generation

[0294] • Equipment / machinery / components used to prevent critical reactions during operations related to the removal and storage of debris (molten nuclear fuel).

[0295] Equipment / machinery / components used for mining and processing uranium ore;

[0296] • Equipment / machinery / components used for secondary processing of nuclear fuel (including conversion / enrichment / reconversion / forming / MOX manufacturing of the same fuel)

[0297] • Equipment / machinery / components used for storing / processing / reprocessing used nuclear fuel

[0298] • Equipment / machinery / components used for storing / processing / disposing of neutron radiation waste

[0299] • Transport machinery / components for uranium ore, secondary processed nuclear fuel, used nuclear fuel, or neutron radiation waste.

[0300] • Other nuclear-related equipment / machines / components.

[0301] More specific examples of equipment / machinery / components used in the aforementioned nuclear power generation include nuclear reactor buildings (including research and test reactors), nuclear reactor storage containers, internal piping of nuclear reactor equipment, and robots for handling deactivated nuclear reactors.

[0302] As equipment / machines / components in the aerospace field, examples can be cited.

[0303] • Space base buildings, space stations, artificial satellites, planetary exploration satellites, spacesuits, etc.

[0304] As for medical devices / machines / components, examples can be given.

[0305] • Medical devices that utilize particle beams.

[0306] The above examples are provided to demonstrate the effectiveness of the inorganic compositions of the present invention and do not limit the scope of the invention.

[0307] Symbol Explanation

[0308] 11-Electric furnace, 12-Carbon granule heating element, 13-Hanging rod, 14-Opening, 15-Fiber, D-Outer diameter of electric furnace, H-Height of electric furnace, d-Diameter of opening of electric furnace, 21-Crucible, 22-Carbon granule heating element, 221-Opening, 222-Mouth, 23-Electric furnace, D1-Diameter of crucible, H1-Height of crucible, D2-Diameter of carbon granule heating element, H2-Height of carbon granule heating element, Φ-Diameter of opening, fp-Raw material Preparation, inorganic oxide preparation, fm-melt, inorganic oxide melt, fb-airbag, P-load pressure, 31-positron radiation source, 32a-scintillator, 32b-scintillator, 33a-photomultiplier tube, 33b-photomultiplier tube, 34a-wave height classifier, 34b-wave height classifier, 35-data processing unit, 36a-channel 1, 36b-channel 2, 37-digital oscilloscope, S-sample.

Claims

1. A fibre or sheet of an amorphous inorganic composition, wherein, the inorganic composition is composed of i) 50 to 90 mass% of a glass forming component consisting of Si02 and Al203, and ii) 10 to 50 mass% of a neutron shielding component consisting of gadolinium in a simple substance, gadolinium oxide (Gd203), samarium in a simple substance, samarium oxide (Sm203), cadmium in a simple substance, cadmium oxide (CdO) or a mixture thereof, the total mass ratio of Si02 and Al203 in the glass forming component is 0.60 or more, and the mass ratio of Fe203 in the glass forming component is less than 0.

15.

2. The fibre or sheet according to claim 1, wherein, the neutron shielding component in the inorganic composition is more than 35 mass%.

3. The fibre or sheet according to claim 1 or 2, wherein, the glass forming component contains fly ash, clinker ash or basalt.

4. The fibre or sheet according to claim 3, wherein, the glass forming component is fly ash.

5. A material filled with the fibre or sheet according to any one of claims 1 to 4.

6. The material according to claim 5, which is a fibre reinforced resin.

7. The material according to claim 5, which is a fibre reinforced cement.

8. A paint containing the sheet according to any one of claims 1 to 4 as a mixing agent.

9. A neutron shielding member composed of the material according to claim 5.

10. A neutron shielding member coated with the paint according to claim 8.

11. An inorganic fiber bundle which is an inorganic fiber bundle in which a binder is attached to the fiber described in any one of claims 1 to 4, wherein the bundling agent is i) paraffin ii) microcrystalline wax iii) polyethylene or ethylene-based ethylene copolymer iv) any one of polypropylene.

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