WO2022025036A1 - 放射線遮蔽体、放射線遮蔽体の製造方法、及び放射線遮蔽構造体 - Google Patents
放射線遮蔽体、放射線遮蔽体の製造方法、及び放射線遮蔽構造体 Download PDFInfo
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- WO2022025036A1 WO2022025036A1 PCT/JP2021/027681 JP2021027681W WO2022025036A1 WO 2022025036 A1 WO2022025036 A1 WO 2022025036A1 JP 2021027681 W JP2021027681 W JP 2021027681W WO 2022025036 A1 WO2022025036 A1 WO 2022025036A1
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- WIPO (PCT)
- Prior art keywords
- gadolinium
- rays
- radiation
- radiation shield
- aggregate
- Prior art date
Links
- 230000005855 radiation Effects 0.000 title claims abstract description 93
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 238000000034 method Methods 0.000 title claims description 13
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims abstract description 48
- 229910052688 Gadolinium Inorganic materials 0.000 claims abstract description 47
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 37
- 239000004568 cement Substances 0.000 claims description 35
- 150000002251 gadolinium compounds Chemical class 0.000 claims description 29
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 28
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- CMIHHWBVHJVIGI-UHFFFAOYSA-N gadolinium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Gd+3].[Gd+3] CMIHHWBVHJVIGI-UHFFFAOYSA-N 0.000 claims description 14
- 229910001938 gadolinium oxide Inorganic materials 0.000 claims description 13
- 229940075613 gadolinium oxide Drugs 0.000 claims description 13
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- 239000000843 powder Substances 0.000 claims description 10
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- 239000002253 acid Substances 0.000 claims description 8
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 5
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- 239000010937 tungsten Substances 0.000 claims description 5
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- 239000012190 activator Substances 0.000 claims description 4
- ZPDRQAVGXHVGTB-UHFFFAOYSA-N gallium;gadolinium(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Gd+3] ZPDRQAVGXHVGTB-UHFFFAOYSA-N 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 3
- 229910052797 bismuth Inorganic materials 0.000 claims description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims description 3
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Images
Classifications
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- G21F1/047—Concretes combined with other materials dispersed in the carrier with metals
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/04—Silica-rich materials; Silicates
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
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- C04B14/02—Granular materials, e.g. microballoons
- C04B14/34—Metals, e.g. ferro-silicon
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
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- C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
- C04B22/08—Acids or salts thereof
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- G21F3/00—Shielding characterised by its physical form, e.g. granules, or shape of the material
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- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/0004—Compounds chosen for the nature of their cations
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- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/0004—Compounds chosen for the nature of their cations
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- G21F3/00—Shielding characterised by its physical form, e.g. granules, or shape of the material
- G21F3/04—Bricks; Shields made up therefrom
Definitions
- the embodiment of the present invention relates to a radiation shield, a method for manufacturing the radiation shield, and a radiation shield structure.
- the material used for the radiation shield is a substance that scatters or absorbs the radiation when it hits the shield material and attenuates the transmission of the radiation amount.
- Radiation is a general term for ⁇ rays, ⁇ rays, ⁇ rays, X-rays, neutron rays, and the like. Among them, neutron rays react with substances and emit ⁇ rays, ⁇ rays, ⁇ rays, and X-rays directly or secondarily. Therefore, in order to shield neutron rays, it is necessary to consider not only the shielding of neutrons alone but also the shielding of ⁇ -rays, ⁇ -rays, ⁇ -rays, and X-rays.
- One of the problems that the invention is trying to solve is to efficiently shield neutrons, X-rays, and ⁇ -rays.
- the radiation shield of the embodiment comprises 10% by volume or more and 90% by volume or less of gadolinium.
- One of the embodiments relates to a radiation shield that shields radiation and a method for manufacturing the same, and more particularly, radiation generated from a reactor or an accelerator, a radioisotope source, or radioactive waste, which reacts with neutrons or neutrons in particular.
- the present invention relates to a method for producing secondary ⁇ -rays and X-ray radiation-shielding concrete and radiation-shielding concrete.
- X-rays and ⁇ -rays have different names depending on how they are generated (hereinafter, X-rays and ⁇ -rays are collectively referred to as ⁇ -rays), but the reaction with substances depends on the size of atomic number Z and has the same energy.
- ⁇ -rays the larger the atomic number Z and the density, the larger the reaction cross section and the higher the shielding ability. Therefore, tungsten, bismuth, lead and molybdenum are used as ⁇ -ray shielding materials rather than the light elements carbon and aluminum.
- the transmittance shielding effect
- X-rays have different absorption ends depending on the orbits of electron shells such as K shells and L shells of atoms, and the amount of transmission differs depending on the energy, but there is no distinction between isotopes. Further, the higher the energy of X-rays and ⁇ -rays, the higher the transmittance (the shielding efficiency deteriorates).
- the neutron beam is not particularly related to the atomic number Z, and the reaction ratio differs depending on the specific element isotope. Therefore, even for the same element, the ratio of reaction and absorption changes depending on the difference in isotopes and the difference in neutron energy, and the ratio of neutron transmittance (shielding effect) differs.
- the value defined by multiplying the neutron cross section by the atomic number density ⁇ is called the macroscopic cross section ⁇ (cm -1 ) and corresponds to the X-ray ray attenuation coefficient.
- the above elements are, for example, hydrogen, lithium, boron, etc., which have a low reaction ratio with ⁇ -rays.
- lithium lithium 6 (Li-6), which is an isotope with a natural abundance ratio of 7.6%, reacts
- boron 10 boron 10 (B-10), which is an isotope with a natural abundance ratio of 20%, reacts.
- lithium-7 Li-7
- B-11 which has a natural abundance ratio of 80%, hardly react with neutrons.
- Lithium and boron compounds are mainly used as shielding materials for neutrons.
- the isotope B-10 may be concentrated by 90% or more from natural boron and used, or the ratio of the reacting isotopes may be concentrated and used.
- Concrete is composed of cement, water, coarse aggregate, fine aggregate, and admixture.
- Coarse aggregate is the largest in volume, followed by fine aggregate, with cement, water and admixtures entering these gaps.
- coarse and fine aggregates are gravel and sand, but the chemical composition differs depending on the place where they are collected, and oxides such as aluminum and calcium, silicates, and rocks such as carbonates. It is a mineral.
- Sand is also divided into river sand and sea sand, and although the salt content is different, it is basically formed by the smaller particles due to the weathering of rocks.
- As the cement, Portland cement, alumina cement and the like are known. These cements have the property that they are cured by a chemical reaction with water and their strength does not decrease even in water after curing.
- Heavy concrete is used for radiation shielding.
- the larger the atomic number Z and the higher the density the higher the effect of shielding ⁇ -rays. Therefore, for coarse aggregate and fine aggregate, the iron composition ratio is high and the density is 3 to 4 g / cm 3 .
- Brown iron steel (2Fe 2 O 3.3H 2 O), magnetic iron ore with a density of 4.6 to 5.1 g / cm 3 (Fe 3 O 4 ), and heavy crystal stone with a density of 4.2 to 4.4 g / cm 3 .
- BaSO 4 a higher density 7.5 g / cm 3 square lead ore (PbS) is used, and iron ingots, iron pieces, steel balls, etc.
- the aggregates using these materials are lightweight aggregates, and if they are used alone, the ⁇ -ray shielding efficiency will deteriorate, so they will be mixed with heavy aggregates. As a result, the proportion of isotopes that are present in the entire volume and react with neutrons is further reduced, and the shield must be thickened.
- Radiation shielding concrete is required to be able to shield not only ⁇ rays, ⁇ rays, ⁇ rays, and X-rays but also neutron rays.
- radiation is applied, so soundness must be considered for radiation deterioration.
- the energy of the radiation is absorbed and heat is generated.
- the aggregate and cement paste repeatedly expand and contract, causing brittleness and cracking.
- radiolysis occurs, and especially in resins containing water and hydrogen, chemical bonds are broken and hydrogen gas is generated, which is liberated and embrittlement occurs.
- ionizing action occurs due to radiation, it causes a chemical reaction with another substance at the molecular level, leading to deterioration.
- neutrons it may change to another nuclide.
- boron which is often used as a neutron absorber, emits ⁇ rays when the isotope B-10 reacts with neutrons to become the lithium isotope Li-7, and emits 478 keV prompt gamma rays from Li-7. Will be done.
- the level of energy handling is from thermal neutrons (around 0.025 eV) that use the reactor as the neutron source, accelerator neutron sources, radioisotope (RI) neutron sources, and high-energy neutrons from the sun in the space environment. different.
- Neutron scattering can be broadly divided into two characteristics: coherent scattering and non-coherent scattering.
- Coherent scattering is dominant in many elements. Elements with a large coherent cross-sectional area are mainly scattered by diffraction, and Bragg edges appear due to the difference in neutron energy.
- Non-coherent scattering is scattering with atomic motion, and the cross-sectional area increases in inverse proportion to the neutron velocity v equivalent to the energy of neutrons. This is called the "1 / v law".
- elements such as B-10 and Li-6 correspond to the 1 / v law, and when the energy is high (the speed v is high), it becomes difficult to react and the shielding efficiency is high. become worse.
- there is an absorption cross section due to resonance capture that appears in different neutron energy regions depending on the element isotope.
- neutron rays output from a neutron source contain neutrons of various energies, and at neutrons smaller than 1 MeV, reactions in the resonance region such as the 1 / v law and resonance absorption (mainly ⁇ by reacting with neutrons).
- a reaction in which a line is emitted hereinafter referred to as a (n, ⁇ ) reaction), but at 1 MeV or higher, a threshold reaction different from these reactions (reacts with one neutron and emits two neutrons).
- boron may become lithium
- sulfur may become phosphorus
- the elements may change, and elements that were not originally radioactive substances may become radioactive substances.
- the half-life is used to display the time index until the rate of radiation as a radioactive substance is halved due to decay. If the half-life is in milliseconds or nanoseconds, it will not be a radioactive substance almost instantly, so there is no particular problem. And does not satisfy the role as a shield.
- cormanite also known as cholemanite
- tambri stone B 2 O 3
- Pyrex® registered trademark
- B 2 O 3 boron carbide
- B 4 C boron carbide
- the neutron reactant is boron.
- isotopes of boron-10 B-10
- boron-11 B-11
- nuclear data JENDL-4.0 showing the reaction ratio with neutron energy is the homepage (https://wwwndc.jaea.go) of each data research group of Japan Atomic Energy Agency.
- the reaction cross section of B-10 is about 6 orders of magnitude larger than the reaction cross section of B-11. However, in the region where the energy exceeding 1 MeV is high, the reaction cross section of B-10 is substantially the same as the reaction cross section of B-11.
- B-10 reacts with neutrons and emits ⁇ rays to become Li-7. This reaction is more accurately described as a 10 B (n, ⁇ ) 7 * Li reaction. 7 * Li is given an initial recoil energy of 840 keV by the (n, ⁇ ) reaction, and emits 478 keV prompt ⁇ -rays while exercising with a short lifetime of 0.105 ps to become Li-7 in the ground state.
- the number of boron atoms present in them, the isotope ratio of B-10, which has a high reaction ratio with neutrons, and the cross-sectional area depending on neutron energy these The shielding efficiency is determined by the product of.
- the cross-sectional area becomes smaller when the energy of neutrons is high, it is important to reduce the energy of high-energy neutrons by the number of collisions with neutrons with moderators such as hydrogen and carbon to efficiently react.
- moderators such as hydrogen and carbon
- the mass attenuation coefficient ⁇ / ⁇ ( ⁇ : line absorption coefficient, ⁇ : density of substance), which is important in action, is generally said to be proportional to Z to the 3rd to 4th power. Therefore, the shielding effect against ⁇ -rays is low.
- Gadolinium is a rare earth element and a rare metal.
- the naturally occurring isotopes are gadolinium 154 (Gd-154) having a natural abundance ratio of 2.18%, gadolinium 155 (Gd-155) having a natural abundance ratio of 14.80%, and a natural abundance ratio of 20.
- Gadolinium 156 (Gd-156) with 47%, Gadolinium 157 (Gd-157) with a natural abundance ratio of 15.65%, Gadolinium 158 (Gd-158) with a natural abundance ratio of 24.84%, naturally present It is an isotope of 6 kinds of gadolinium (Gd-160) having a ratio of 21.86%.
- the reaction cross section of Gd-157 is 66 times larger than the reaction cross section of B-10
- the reaction cross section of Gd-155 is the reaction cross section of B-10. 15.8 times larger than.
- Gd-157 and Gd-155 also have a plurality of resonance absorption peaks of other Gd isotopes, and the reaction cross section is larger than that of B-10.
- the main reaction of gadolinium is a (n, ⁇ ) reaction that reacts with neutrons and emits ⁇ -rays (data indicated as capture in the figure showing the cross-sectional area).
- boron 7 * Li was generated by the (n, ⁇ ) reaction, and 478 keV prompt ⁇ -rays were emitted in the process of becoming Li-7, but in the case of Gd, 154 Gd (n, ⁇ ) 155 Gd reaction.
- Gd-158 is a stable isotope and does not emit ⁇ -rays or ⁇ -rays with decay.
- 158 Gd (n, ⁇ ) 159 Gadolinium 159 (Gd-159) produced by the Gd reaction becomes a stable isotope terbium (Tb-159) with ⁇ decay.
- This ⁇ -ray emission mode is roughly divided into (1) continuous spectrum (93.8%) and (2) discrete spectrum (6.2%). Most are continuous spectra of (1), with high emission rates from high to low energies rather than a single energy of 8 MeV from unstable complex nuclei to stable basal levels.
- (2) Discrete spectra are 5.62 MeV + 2.25 MeV (1.3%), 5.88 MeV + 1.99 MeV (1.6%), 6.74 MeV + 1.11 MeV (3.2%), 7.87 MeV (0.02%). ). The energy of the discrete spectrum is high, but the proportion is low.
- the purpose of shielding is to prevent people and equipment such as detection equipment from being damaged by radiation.
- High-energy ⁇ -rays that pass through a substance with a large atomic number Z pass through a human tissue composed of light elements or a thin-film detector element. That is, if the amount of linear energy transfer (LET: Linear Energy Transfer) in the substance to be protected is small, the permeating substance is less likely to be given energy and does not cause damage.
- LET represents how much energy is given to a substance as it travels through the substance. On the contrary, the larger the LET, the larger the energy given to the substance, which inevitably leads to the larger damage to human cells and tissues. This is expressed as an increase in the biological effect ratio (RBE: Relative Biological Effectiveness), and the larger the LET, the larger the RBE.
- RBE Relative Biological Effectiveness
- the purpose of shielding can be achieved even if the ⁇ -ray shielding material is transmitted.
- the ⁇ -rays of 2MeV and 500keV have monochromatic energy (strictly speaking, they have a range of energy) at the time of generation, the energy is attenuated by the photoelectric effect or Compton scattering due to the interaction between the ⁇ -rays and the substance. Extends to the low energy range.
- 500 keV ⁇ -rays react more and attenuate than 2 MeV ⁇ -rays. The lower the energy of ⁇ -rays of several hundred keV or less, the larger the LET and RBE for devices such as the human body and sensors.
- the attenuation rate is specifically calculated.
- ⁇ -rays with energies of 50 keV, 100 keV, 500 keV, and 2 MeV each contain iron, lead, boron carbide, and gadolinium oxide, and are shielded with a shielding material having a thickness of 5 cm and a uniform density
- boron carbide is used at 2 MeV. Attenuates up to 60%, 20% with iron and gadolinium oxide, and less than 10% with lead.
- boron carbide is about 30% and 5 minutes, while other iron, lead and gadolinium oxide are less than 0.5% (1/20).
- boron carbide is not attenuated to 10% or less, but the others are 4 ⁇ 10 ⁇ 7 (4 ⁇ 10-7 ) or less for iron and 1 ⁇ 10 ⁇ 42 for gadolinium oxide (1 ⁇ 10 ⁇ 42). It is 1 ⁇ 10 -42 ) or less, and for lead, it is 2 ⁇ 10 to the 137th power (2 ⁇ 10 -137 ) or less.
- the lower the energy the more it attenuates. Since the actual concrete shield is composed of cement, water, coarse aggregate, fine aggregate, and admixture, it is difficult to construct it with a uniform density. Even if a lump of iron is used for the coarse aggregate, the density becomes low in the cement paste portion of the fine aggregate, cement, water, and admixture.
- concrete is used as a radiation shield, and a gadolinium compound is used as the aggregate (coarse aggregate and fine aggregate) constituting the concrete.
- a gadolinium compound is used as the aggregate (coarse aggregate and fine aggregate) constituting the concrete.
- the aggregate coarse aggregate or a fine aggregate having a large particle size
- the general composition of concrete is 1: 2 to 3: 4 to 6 when the volume ratio of cement, fine aggregate (sand), and coarse aggregate (gravel) is 1.
- the volume ratio of the fine aggregate to the cement is preferably 2 or more and 3 or less.
- the volume ratio of the coarse aggregate to the cement is preferably 4 or more and 6 or less.
- the radiation shield of the embodiment may be a so-called mortar.
- the volume ratio of water to cement is preferably 0.5 or more and 0.6 or less.
- the amount of water is 50 to 60% as a ratio to cement. That is, assuming that the volume of the concrete product is 100%, the ratio of the aggregate including the fine aggregate and the coarse aggregate is 85 to 90%, and the water content is about 5%. Therefore, the high-density aggregate becomes a material that shields neutrons and ⁇ -rays, and the neutrons with higher energy are scattered by water, decelerated, and absorbed by the aggregate.
- this aggregate is a scintillator that has already been HIP-treated from powdered raw materials such as shavings and shavings during the production of scintillators used as detectors for X-rays and ⁇ -rays. Since it is possible to manufacture using defective products or materials that are discarded when the product has reached the end of its life, it is not only cheaper than manufacturing from raw material powder, but also effective for treating environmental waste. be.
- the concrete which is the radiation shield of the embodiment contains 10% by volume or more and 90% by volume or less of gadolinium element with respect to concrete. If the content is less than 10% by volume, the effect of shielding radiation is not sufficient, and even if the thickness of the concrete is increased, it becomes too thick to be effective and is not practical. Further, when the content exceeds 90% by volume, the strength as concrete decreases.
- the desirable content is 30% by volume or more and 70% by volume or less.
- the content of gadolinium element contained in concrete is measured as follows.
- the method of analyzing the composition that constitutes a radiation shield in a non-destructive manner and the method of measuring the contained gadolinium element are fluorescent X-ray analysis that detects fluorescent X-rays peculiar to gadolinium generated by irradiating an object with X-rays. Can be mentioned.
- the composition and elements can be obtained accurately and easily by X-ray fluorescence analysis.
- the gadolinium atom number density that reacts in the radiation shield is measured from the ratio of the neutron intensity irradiating the object to the thickness of the object and the transmitted neutron intensity, and the content of the gadolinium isotope is contained. It is possible to find the ratio.
- the gadolinium compound is formed of, for example, a ceramic having a density of 6.5 g / cm 3 or more and insoluble in water, or heavy concrete using a sintered body as a coarse aggregate and a fine aggregate.
- gadolinium oxide with a density of 7.4 g / cm 3 (Gd 2 O 3 : hereinafter abbreviated as GO)
- gadolinium gallium garnet with a density of 7.09 g / cm 3 Gd 3 Ga 5 O 12 : hereinafter abbreviated as GGG
- density 7 examples thereof include gadolinium acid sulfide (Gd 2 O 2 S: hereinafter abbreviated as GOS) having a density of 3 g / cm 3 and gadolinium silicate (Gd 2 SiO 5 : hereinafter abbreviated as GSO) having a density of 6.7 g / cm 3 .
- a fluorescent material obtained by mixing these as a base material with praseodymium, terbium, europium, cerium and the like is also included. It should be noted that an embodiment in which any combination of the above components or components or expressions of the embodiments are replaced with each other among methods, devices, systems and the like is also effective as an aspect of the present invention.
- the radiation shield of the embodiment may further contain at least one selected from the group consisting of tungsten (W), bismuth (Bi), lead (Pb), molybdenum (Mo), and heavy alloy.
- W tungsten
- Bi bismuth
- Pb lead
- Mo molybdenum
- Heavy Roy is a sintered body of a tungsten-based alloy containing tungsten as a main component and elements such as nickel, copper, and iron, and has a high density and high radiation shielding property. Since these elements or materials shield ⁇ -rays, it is possible to enhance the shielding effect of radiation including ⁇ -rays and neutrons by containing them in a radiation shield together with gadolinium that shields neutrons.
- the powdered aggregate having an average particle size, an average length, or an average thickness of less than 5 mm is used as it is as a fine aggregate, and the average particle size and the average are used.
- a ceramic or sintered body having a length or an average thickness of 5 mm or more is used as it is as a coarse aggregate, or crushed to less than 5 mm and used as a fine aggregate.
- HIP treatment is performed to produce a ceramic or sintered body, which is then crushed or cut to obtain an average particle size, average length, and so on.
- a coarse aggregate having an average thickness of 5 mm or more can be produced and used.
- the gadolinium compound used here is used as a product such as a phosphor for X-rays and ⁇ -rays, a sensor for a detector, or a sensitizing paper.
- the gadolinium compound may be replaced due to waste such as cutting chips and defective products generated during manufacturing, because the product used does not obtain the specified amount of light emission, or because it is scratched or damaged.
- Materials that are discarded due to the disposal of equipment are collected and used.
- a sensor that bundles multiple thin columnar GOS scintillators as a scintillator for X-rays can be used as it is or crushed because it has a size of 5 mm or more.
- the gadolinium compounds contained in the fine aggregate and the coarse aggregate may be the same or different from each other.
- the gadolinium compound may contain an activator.
- activators include rare earth elements and the like.
- rare earth elements praseodymium (Pr), terbium (Tb), europium (Eu), cerium (Ce) and the like are particularly preferable.
- a radiation shield that can absorb energy and reduce energy by using a high-density gadolinium compound for the aggregate and scattering high-energy neutron rays with water mixed with cement.
- the radiation shield of the embodiment it is possible to provide a radiation-shielding concrete containing a neutron beam in an environment-friendly manner at low cost. Therefore, it is possible to provide a radiation shield that can efficiently shield with the same or thinner concrete thickness as the conventional ⁇ -ray shielding concrete, including not only ⁇ -ray shielding but also neutron shielding, at the lowest possible cost. ..
- Another embodiment is, for example, a nuclear reactor, an accelerator facility, an RI neutron source facility, a nuclear fuel facility, a nuclear fuel storage facility, a nuclear shelter, and the medical field as a facility involving the generation of neutrons or a facility for the purpose of shielding.
- BNCT neutron capture therapy
- a separate ⁇ -ray shielding material should be prepared for facilities related to neutrons. It is possible to design a facility with a high radiation shielding effect.
- FIG. 1 is a cross-sectional view schematically showing the configuration of the radiation shielding concrete 1.
- the radiation shielding concrete 1 includes cement 2, fine aggregate 3, and coarse aggregate 4.
- FIG. 2 is a specific radiation shielding ceramic coarse aggregate used for the coarse aggregate 4 shown in FIG. 1, and shows a large-sized coarse aggregate 5.
- the large-sized coarse aggregate 5 is a waste material formed by scraping a sintered body when a scintillator material for X-rays or ⁇ -rays is produced by HIP-treating gadolinium acid sulfide (Gd 2 O 2 S). be.
- FIG. 1 is a cross-sectional view schematically showing the configuration of the radiation shielding concrete 1.
- the radiation shielding concrete 1 includes cement 2, fine aggregate 3, and coarse aggregate 4.
- FIG. 2 is a specific radiation shielding ceramic coarse aggregate used for the coarse aggregate 4 shown in FIG. 1, and shows a large-sized coarse aggregate 5.
- the large-sized coarse aggregate 5 is a waste material formed by scraping a sintered body when a
- FIG. 3 shows a medium-sized coarse aggregate 6 which is a ceramic coarse aggregate for radiation shielding which is the same material as the large-sized coarse aggregate 5 but has a different size, and radiation which is smaller as a coarse aggregate and larger as a fine aggregate.
- the large-sized fine aggregate 7 which is a ceramic fine aggregate for shielding is shown.
- FIG. 4 shows a small size fine aggregate (powder) 8.
- the small-sized fine aggregate 8 is a powder obtained by pulverizing the coarse aggregate or fine aggregate of FIGS. 2 and 3 with a crusher such as a hammer, a roller mill, or a ball mill, or a powder of a raw material.
- Gadolinium acid sulfide is used as the coarse aggregate and the fine aggregate, but a phosphor containing praseodymium (Pr), terbium (Tb), or europium (Eu) may be used as an activator using this as a base material.
- Pr praseodymium
- Tb terbium
- Eu europium
- waste materials in the manufacturing process of intensifying screens that are uniformly coated on resin materials such as polyethylene terephthalate (PET) resin by mixing a binder with powder such as gadolinium oxide and waste materials that have passed the product life are also cut or crushed to make aggregates. be able to.
- PET polyethylene terephthalate
- the hydrogen component contained in the PET resin contributes to the scattering of neutrons.
- FIG. 6, FIG. 7, and FIG. 8 are diagrams showing the relationship between the neutron energy and the reaction cross section in the isotope of boron.
- natural boron B is composed of isotopes of B-11 having an abundance ratio of 80.1% and B-10 having an abundance ratio of 19.9%.
- the reaction with neutrons is B-10, which has a natural abundance ratio of 19.9%.
- FIG. 10, FIG. 11, FIG. 12, FIG. 13, and FIG. 14 are diagrams showing the relationship between the neutron energy and the reaction cross section in the isotope of gadolinium.
- Natural gadolinium Gd is mainly composed of 6 isotopes, as shown in FIGS. 9 to 14. Especially in the thermal neutron region where the neutron energy is low, the reaction cross-sectional area is 10 to 100 times larger than that of B-10.
- Gd-155 (natural existence ratio 14.8%) and Gd-157 (15.65%) are 30 in total.
- gadolinium acid sulfide Gad 2 O 2 S
- the atom of gadolinium is 2/5 and the reaction with neutrons is 13.3%, and the reaction ratio of neutrons is high.
- FIG. 15 shows the results of comparing the thermal neutron transmittances of the boron compound boron carbide (B 4 C), the gadolinium compound gadolinium acid sulfide (Gd 2 O 2 S), and the gadolinium oxide (Gd 2 O 3 ).
- FIG. 15 is a diagram showing the analysis results of the neutron transmittance for each thickness of the material.
- the thickness is 20 ⁇ m and the thermal neutron transmittance of boron carbide is about 0.40, but the thermal neutron transmittance of the gadolinium compound is attenuated to 0.10. This indicates that the gadolinium compound has a high shielding ability for thermal neutrons.
- High-energy neutrons can be decelerated by a moderator (hydrogen) and absorbed in the thermal neutron region for efficient shielding.
- Boron and gadolinium react with neutrons and emit gamma rays.
- Boron has a maximum of 478 keV and gadolinium has a maximum of 8 MeV.
- 16 and 17 are schematic views for explaining neutron capture gamma rays of gadolinium. As shown in FIGS. 16 and 17, gadolinium neutron capture gamma rays are divided into two types, a continuous spectrum of (1) and a discrete spectrum of (2), and are mainly the continuous spectrum of (1). In this case, the generation rate in the energy region lower than the rate at which 8MeV is actually emitted increases, including scattering.
- FIG. 18 shows the results of calculating the ⁇ -ray energy and the attenuation ratio when the thickness of the shielding material is 5 cm.
- boron carbide can be shielded by only about 20%, but gadolinium oxide can be shielded by 70% or more like iron.
- Boron carbide is about 40% of the 2.2 MeV ⁇ -rays emitted by the reaction of neutrons with hydrogen, 80% of the gadolinium oxide is emitted, and boron carbide is emitted at about 500 keV of 478 keV emitted by the reaction with boron.
- Gadolinium oxide can shield more than 9.8% of the amount of about 30%.
- boron carbide is less than 90%, while gadolinium oxide absorbs more than iron and has a high shielding performance of 1/42. ..
- the radiation shielding block is made of concrete, which is the radiation shielding body.
- the concrete block which is a radiation shielding block, is manufactured by, for example, the following method.
- the composition is cement, a powder with a gadolinium compound that is a fine aggregate and a size (average particle size) of less than 5 mm, and a coarse aggregate with a gadolinium compound and a size (average particle size) of 5 mm or more, with cement as 1 by volume.
- the volume ratio is 1: 2 to 3: 4 to 6.
- the cement and the fine aggregate powder of the gadolinium compound are mixed well, and 50 to 60% of water is added as a ratio to the cement to make a cement paste. Instead of adding all the water from the beginning, mix it little by little, add coarse aggregate to the cement paste, and adjust the amount of water to be added according to the kneading condition and the state of putting in the mold.
- FIG. 19 is a schematic top view showing a structural example of the concrete block 10.
- FIG. 20 is a front schematic view showing another structural example of the concrete block 10.
- FIG. 21 is a schematic side view showing another structural example of the concrete block 10.
- 22 and 23 are schematic views showing a structural example of a concrete block structure which is a radiation shielding structure.
- a cement frame is used for manufacturing, but since the weight of the manufactured block becomes heavy, here, one of the concrete blocks 10 shown in FIGS. 19 to 20 is integrally used. They are combined and connected to form a wall-shaped (plate-shaped) concrete block structure 100 shown in FIG. 22 or a box-shaped concrete block structure 100 shown in FIG. 23.
- These concrete blocks 10 have a connecting through hole 10a for connecting to another concrete block 10.
- the block 10 shown in FIGS. 19, 20, and 21 suppresses radiation from leaking from the gap by forming an uneven structure on the overlapping surfaces. Furthermore, assuming that the individual concrete blocks 10 become heavy and fall or collapse when the surfaces are overlapped, the concrete blocks 10 are bolted through the connecting through holes 10a in the vertical or horizontal direction through structural materials such as iron and stainless steel. In some cases, it is connected with such a bolt and fixed to the floor with this bolt to form an anchor.
- the size of one piece of FIGS. 19, 20, and 21 can be standardized to 50 mm or 100 mm, and further combined in multiple stages depending on the situation of the shielding effect to form a shielding body.
- the concrete which is the radiation shield of the embodiment can be used alone, or can be combined with the conventional heavy concrete containing boron and iron to form a radiation shield.
- the radiation shield of the embodiment has a high radiation shielding ability. For example, after forming a shield with the radiation shield block of the embodiment around the source of radiation, a conventional heavy-duty concrete block is combined behind the shield to shield the radiation. By forming the structure, radiation can be shielded more effectively. By such a combination, a margin can be given to the thickness of the entire shield, and the applicability of the shield to the installation space can be expanded.
- high-energy neutron rays can be scattered by water mixed with cement to absorb energy and reduce energy, and in addition to the originally generated radiation, it reacts with neutrons and emits. Radiation can also be efficiently absorbed by a high-density gadolinium compound, which is industrially useful.
Abstract
Description
Claims (13)
- 中性子線、X線、及びγ線を遮蔽する放射線遮蔽体であって、
10体積%以上90体積%以下のガドリニウムを具備する、
放射線遮蔽体。 - 前記ガドリニウムを含み、水に溶けないガドリニウム化合物を含む、請求項1に記載の放射線遮蔽体。
- 前記ガドリニウム化合物の粉体又は前記ガドリニウム化合物の焼結体を具備し、
前記粉体又は焼結体は、6.5g/cm3以上の密度を有する、請求項2に記載の放射線遮蔽体。 - 前記ガドリニウム化合物は、賦活剤を含む請求項2に記載の放射線遮蔽体。
- 前記ガドリニウム化合物は、酸化ガドリニウム、ガドリニウムガリウムガーネット、酸硫化ガドリニウム、及びケイ酸ガドリニウムからなる群より選ばれる少なくとも一つのガドリニウム化合物を含む、請求項2又は請求項3に記載の放射線遮蔽体。
- 平均粒径、平均長さ、又は平均厚さが5mm未満であり、第1のガドリニウム化合物を含む、第1の骨材と、
平均粒径、平均長さ、又は平均厚さが5mm以上であり、第2のガドリニウム化合物を含む、第2の骨材と、を具備する、請求項1に記載の放射線遮蔽体。 - 前記第1及び第2のガドリニウム化合物のそれぞれは、酸化ガドリニウム、ガドリニウムガリウムガーネット、酸硫化ガドリニウム、ケイ酸ガドリニウムからなる群より選ばれる少なくとも一つを含み、
前記第1及び第2のガドリニウム化合物は、互いに同じ又は異なる、請求項6に記載の放射線遮蔽体。 - タングステン、ビスマス、鉛、モリブデン、及びヘビアロイからなる群より選ばれる少なくとも一つを更に具備する、請求項1ないし請求項7のいずれか一項に記載の放射線遮蔽体。
- 前記放射線遮蔽体は、コンクリートである、請求項1ないし請求項8のいずれか一項に記載の放射線遮蔽体。
- 中性子線、X線、及びγ線を遮蔽する放射線遮蔽体の製造方法であって、
セメントと、
平均粒径、平均長さ、又は平均厚さが5mm未満であり、第1のガドリニウム化合物を含む、第1の骨材と、
平均粒径、平均長さ、又は平均厚さが5mm以上であり、第2のガドリニウム化合物を含む、第2の骨材と、
水と、
を混合する工程を具備し、
前記セメントに対する前記細骨材の体積比率は、2以上3以下であり、
前記セメントに対する前記粗骨材の体積比率は、4以上6以下であり、
前記セメントに対する前記水の体積比率は、0.5以上0.6以下である、
製造方法。 - 前記第1及び第2のガドリニウム化合物のそれぞれは、酸化ガドリニウム、ガドリニウムガリウムガーネット、酸硫化ガドリニウム、ケイ酸ガドリニウムからなる群より選ばれる少なくとも一つを含み、
前記第1及び第2のガドリニウム化合物は、互いに同じ又は異なる、請求項10に記載の方法。 - 一体的に組み合わされた複数の放射線遮蔽ブロックを具備し、
前記複数の放射線遮蔽ブロックのそれぞれは、請求項1ないし請求項9のいずれか一項に記載の放射線遮蔽体を有する、放射線遮蔽構造体。 - 請求項1ないし請求項9のいずれか一項に記載の放射線遮蔽体と、
ホウ素又は鉄を含む第2の放射線遮蔽体と、
を具備する、放射線遮蔽構造体。
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EP21848985.4A EP4191612A4 (en) | 2020-07-27 | 2021-07-27 | RADIATION SHIELDING BODY, METHOD FOR PRODUCING A RADIATION SHIELDING BODY AND RADIATION SHIELDING STRUCTURE |
JP2022539477A JPWO2022025036A1 (ja) | 2020-07-27 | 2021-07-27 | |
CN202180061435.5A CN116134552A (zh) | 2020-07-27 | 2021-07-27 | 放射线屏蔽体、放射线屏蔽体的制造方法及放射线屏蔽结构体 |
US18/155,937 US20230154637A1 (en) | 2020-07-27 | 2023-01-18 | Radiation shield unit, method of manufacturing radiation shield unit, and radiation shield structure |
JP2023212965A JP2024026395A (ja) | 2020-07-27 | 2023-12-18 | 放射線遮蔽体、放射線遮蔽体の製造方法、及び放射線遮蔽構造体 |
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See also references of EP4191612A4 |
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