JP6197264B2 - Neutron absorber, method for producing the same, and method for treating molten fuel - Google Patents
Neutron absorber, method for producing the same, and method for treating molten fuelDownload PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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Description
Translated fromJapanese本発明は、炉心溶融を起こした軽水炉から溶融燃料を取り出す際、およびその後の輸送や貯蔵の際に、粉砕した溶融燃料に混合させて臨界安全性を確保するための中性子吸収材に関する。 The present invention relates to a neutron absorber for ensuring critical safety by mixing molten fuel with a pulverized molten fuel at the time of taking out the molten fuel from a light water reactor that has undergone core melting, and subsequent transportation and storage.
軽水炉においては、被覆管や燃料が溶けて崩れ落ちる炉心溶融となった場合、溶融燃料の回収は、事故後１０年程度経過して溶融燃料の崩壊熱が低下していると思われる頃に行われる。溶融燃料を取り出すには、放射線の遮蔽と除熱の観点から水につけた状態で行う。もし溶融燃料が原子炉圧力容器を貫通して格納容器の底部に溜まり、格納容器にまで損傷を与えている場合には、格納容器を修復したうえで冠水して溶融燃料を水没させ、溶融燃料を粉砕して取り出す必要がある。 In light water reactors, when the core melts as the cladding tube or fuel melts and collapses, the recovery of the molten fuel is carried out when it seems that the decay heat of the molten fuel has decreased about 10 years after the accident. . The molten fuel is taken out in a state where it is immersed in water from the viewpoint of shielding radiation and removing heat. If molten fuel penetrates the reactor pressure vessel and accumulates at the bottom of the containment vessel and damages the containment vessel, repair the containment vessel, submerge it, submerge the molten fuel, and melt the molten fuel. Need to be crushed and taken out.
溶融燃料の取り出し作業において、軽水炉燃料はもともと低濃縮度燃料であることから、臨界になることは殆どないと考えられる。さらに、臨界の危険性を下げる要因として以下が考えられる。 In the operation of taking out the molten fuel, the light water reactor fuel is originally a low-concentration fuel, so it is considered that it will hardly become critical. In addition, the following factors can be considered as factors that reduce the risk of criticality.
１．燃料の燃焼に伴い、実質的な濃縮度はさらに下がっている。
２．中性子吸収物質である核分裂生成物（ＦＰ）が存在する。
３．溶融燃料は構造材やコンクリートとの混合物で存在している。1. As the fuel burns, the substantial enrichment is further reduced.
2. Fission products (FP), which are neutron absorbing materials, exist.
3. Molten fuel exists in a mixture with structural materials and concrete.
逆に臨界の危険性を高める要因としては、以下が考えられる。
４．燃料の燃焼に伴いプルトニウム（Ｐｕ）が蓄積している。
５．水中で溶融燃料を粉砕すると燃料と水の体積比が変わり、溶融燃料の状態によっては局所的に最適減速状態（臨界安全上最も厳しい比率で水と混じり合った状態）を引き起こす可能性がある。
６．中性子効率を高めるに十分な水の反射体が存在する。Conversely, the following factors can be considered as factors that increase the critical danger.
4). As the fuel burns, plutonium (Pu) accumulates.
5. When the molten fuel is pulverized in water, the volume ratio of the fuel to water changes, and depending on the state of the molten fuel, there is a possibility of locally causing an optimal deceleration state (a state in which water is mixed with water at the strictest ratio for critical safety).
6). There are enough water reflectors to increase neutron efficiency.
炉物理的には４〜６を考慮しても臨界にはならないと考えられる。しかしながら、２０１１年の福島第１原発の事故のように、燃料が格納容器にまで漏れ出すような大規模な炉心溶融は前例が無く、１９７９年の米国スリーマイル島原発事故に比べても大規模で、その溶融燃料の取り出しは世界的にも経験のない困難な取り組みのため、安全管理上は臨界安全にも十分に配慮して万全の防止策をとることは必須である。 It is considered that the reactor does not become critical even if 4-6 are considered. However, unlike the 2011 accident at the Fukushima Daiichi nuclear power plant, there was no unprecedented large-scale core melting that caused fuel to leak into the containment vessel, which was larger than the 1979 US Three Mile Island nuclear accident. Since the removal of the molten fuel is a difficult effort that has no experience in the world, it is essential to take thorough prevention measures with sufficient consideration for criticality safety.
再臨界予防のための方策としては、中性子を吸収するホウ酸水を原子炉圧力容器および格納容器内の水に注入する方策が考えられる（例えば特許文献１参照）。ホウ酸水はボロン（ホウ素）の化合物の水溶液である。ボロンの同位体のうち１０Ｂは非常に大きな中性子吸収断面積を持つため、原子炉内において中性子吸収のための制御棒に使用されている。しかしながら、水に溶解できるホウ酸の濃度（溶解度）には限度があり、温度が低いほど溶解度は低下する。そのため崩壊熱が低下している溶融燃料取り出しの時点では、ホウ酸水に高い濃度は期待できない。また、仮にホウ酸水が臨界安全の確保に十分な濃度だとしても、溶融燃料取り出し後の保管の段階でも同様なホウ酸水濃度を維持する必要がある。As a measure for preventing recriticality, a measure of injecting boric acid water that absorbs neutrons into water in the reactor pressure vessel and the containment vessel is conceivable (see, for example, Patent Document 1). Boric acid water is an aqueous solution of boron (boron) compound. Among boron isotopes,10 B has a very large neutron absorption cross section, and is therefore used as a control rod for neutron absorption in a nuclear reactor. However, there is a limit to the concentration (solubility) of boric acid that can be dissolved in water, and the lower the temperature, the lower the solubility. Therefore, a high concentration of boric acid water cannot be expected at the time of taking out the molten fuel where the decay heat is low. Even if the boric acid water has a concentration sufficient for ensuring critical safety, it is necessary to maintain the same boric acid water concentration even at the storage stage after the molten fuel is taken out.
再臨界予防のための他の方策としては、ボロンまたは炭化ボロン (Ｂ４Ｃ)、酸化ボロン (Ｂ２Ｏ３) 、窒化ボロン(ＢＮ) などの粉末を、原子炉圧力容器および格納容器内の水に混入させる方策が考えられる。これらは粒径が数ミクロン程度の粉末として入手が可能で、水中に投入して攪拌すれば均等に混じり合う。したがって、上述のホウ酸水よりも高い中性子吸収能力が期待できる。しかしながら、これらの粉末を水に混入させると、長時間水中に滞留し、水が黒く濁って水中の視界が失われるため、水中のカメラでモニターしながら遠隔操作で行う溶融燃料の取り出しには不適当である。また、仮に溶融燃料の取り出しができたとしても、その後の保管の段階で水が失われると、上記粉末も水と共に失われる可能性がある。Other measures for recriticality prevention include boron, boron carbide (B4 C), boron oxide (B2 O3 ), boron nitride (BN) powders, etc. in reactor pressure vessels and containment vessels. Measures for mixing in water are conceivable. These are available as powders having a particle size of about several microns, and are mixed evenly if they are put into water and stirred. Therefore, higher neutron absorption capability than the above boric acid water can be expected. However, if these powders are mixed in water, they will stay in the water for a long time, and the water will become black and cloudy, and the visibility in the water will be lost. Is appropriate. Even if the molten fuel can be taken out, if the water is lost at the subsequent storage stage, the powder may be lost along with the water.
したがって、本発明は、十分な中性子吸収能力を持ち、かつ、溶融燃料取り出し時のみならず、その後の保管および貯蔵時にも失われることなく有効な中性子吸収能力を長期にわたり維持できる中性子吸収材を提供することを目的としている。 Therefore, the present invention provides a neutron absorber that has a sufficient neutron absorption capability and can maintain an effective neutron absorption capability for a long time without being lost not only when the molten fuel is taken out but also during subsequent storage and storage. The purpose is to do.
本発明は、炉心溶融を起こした軽水炉の水中に投入される中性子吸収材の製造方法であって、ボロンおよびボロン化合物の粉末のうち１種類または数種類からなるボロン系粉末とステンレス鋼粉末および／またはアルミニウム粉末と混合して１ｍｍ以上２００ｍｍ以下の大きさの塊状に成形し、次いで焼結してボロンの見かけの原子数密度を５０％以上とすることを特徴とする。The present invention relates to a method for producing a neutron absorber that is introduced into the water of a light water reactor that has undergone core melting, and includes one or several types of boron and boron compound powders,stainless steel powders and / or boron powders. It is characterized in that it is mixed with aluminum powder and formed into a lump with a size of 1 mm or more and 200 mm or less, and then sintered to make the apparent atom number density of boron 50% or more.
本発明によれば、軽水炉の溶融燃料を粉砕して捕集する際に、捕集手段に本発明で製造した中性子吸収材を適量混入することにより、臨界安全性を確保することができる。たとえば、水中において溶融燃料を粉砕し、上記中性子吸収材よりも小さな網目を有する網状体に、水中において中性子吸収材と粉砕した溶融燃料とを投入することができる。そして、取り出した溶融燃料を網状体に収容して輸送および貯蔵することにより、中性子吸収材は失われることがなく、十分な臨界安全性を長期にわたり維持することができる。 According to the present invention, when the molten fuel in the light water reactor is pulverized and collected, critical safety can be ensured by mixing an appropriate amount of the neutron absorber produced in the present invention into the collecting means. For example, the molten fuel can be pulverized in water, and the neutron absorber and the crushed molten fuel in water can be put into a network having a mesh smaller than that of the neutron absorber. Then, by storing the taken molten fuel in the mesh body and transporting and storing it, the neutron absorber is not lost, and sufficient critical safety can be maintained for a long time.
ここで、「見かけの原子数密度」とは、中性子吸収材を構成する物質全体の原子の数を分母としたときのボロンの原子数の割合をいう。中性子吸収材としての機能を確保するために、ボロンの見かけの原子数密度は５０％以上必要である。 Here, the “apparent atom number density” refers to the ratio of the number of boron atoms when the total number of atoms constituting the neutron absorbing material is used as the denominator. In order to ensure the function as a neutron absorber, the apparent atom number density of boron needs to be 50% or more.
中性子吸収材の大きさは、原子炉圧力容器および格納容器内の水中で粉砕し捕集した溶融燃料に混入させることから、水中に中性子吸収材が滞留しても視界を妨げない程度の大きさであり、かつ、保管の段階で仮に水が失われても、水とともに流出しない程度の大きさが必要であることから１ｍｍ以上は必要である。一方、中性子吸収材の大きさが２００ｍｍを超えると、中性子吸収材の中心部分のボロンに対してはその外側のボロンによる遮蔽のために中性子が到達しにくくなる現象（自己遮蔽効果）が生じるため、中性子吸収材の重量当たりの中性子吸収性能は低下する。粉砕した溶融燃料は大きさが数ｍｍから数ｃｍ程度の破片と予想されるため、これらの破片を捕集する際に、同程度の大きさの中性子吸収材を適量混入することが望ましいことから、中性子吸収材の大きさは５〜２０ｍｍが望ましい。 The size of the neutron absorber is mixed with molten fuel that has been crushed and collected in the reactor pressure vessel and the containment vessel, so that the neutron absorber does not interfere with visibility even if it stays in the water. In addition, even if water is lost at the stage of storage, it is necessary to have a size that does not flow out together with water, so 1 mm or more is necessary. On the other hand, if the size of the neutron absorber exceeds 200 mm, a phenomenon (self-shielding effect) that neutrons are difficult to reach due to the shielding of the boron at the center of the neutron absorber due to the outer boron occurs. The neutron absorption performance per weight of the neutron absorber is reduced. Since the crushed molten fuel is expected to be fragments of several mm to several centimeters in size, it is desirable to mix an appropriate amount of a neutron absorber of the same size when collecting these fragments. The size of the neutron absorber is preferably 5 to 20 mm.
中性子吸収材の形状については特に制約はなく、中性子吸収性能については、上述の自己遮蔽効果が問題とならないような大きさである限り、ボロンの含有量（原子数密度）にほぼ依存し、その形状とは無関係である。しかしながら、鋭角的な形状ではその一部が微少な破片となって原子炉圧力容器および格納容器内の水に混入して視界を妨げる恐れがある。以上の観点から、中性子吸収材の形状は、球、円柱、立方体またはこれらに近い形状が望ましい。また中性子吸収材は、原子炉圧力容器および格納容器内の水中にて、粉砕し捕集した溶融燃料に混入させるため、当然ながら遠隔操作機器により供給と混入を行う必要がある。この観点からは球またはそれに近い形状が最適である。 There is no particular limitation on the shape of the neutron absorber, and the neutron absorption performance is almost dependent on the boron content (atomic number density) as long as the above-described self-shielding effect is not a problem. It has nothing to do with shape. However, if the shape is acute, a part of the shape becomes a minute fragment and may mix with the water in the reactor pressure vessel and the containment vessel and hinder the visibility. From the above viewpoint, the shape of the neutron absorber is preferably a sphere, a cylinder, a cube, or a shape close to these. Further, since the neutron absorber is mixed in the molten fuel crushed and collected in the water in the reactor pressure vessel and the containment vessel, it is naturally necessary to supply and mix it by a remote control device. From this viewpoint, a sphere or a shape close thereto is optimal.
本発明では焼結を行うため、円柱、立方体またはこれらに近い形状とすることは容易である。球に近い形状とする場合は、仮焼結した円柱、立方体またはこれらに近い形状の素材を融点以上に加熱して溶融させることで、表面張力の作用により球形に近い形状が得られる。一方、ボロンまたは炭化ボロン（Ｂ４Ｃ）、酸化ボロン（Ｂ２Ｏ３）または窒化ボロン（ＢＮ）などのボロン化合物粉末を樹脂製のバインダーと混合して成形する方法であれば、球、円柱、立方体またはこれらに近い形状とすることは容易であり、その製造方法は公知である。In the present invention, since sintering is performed, it is easy to form a cylinder, a cube, or a shape close to these. In the case of a shape close to a sphere, a shape close to a sphere can be obtained by the action of surface tension by heating and melting a pre-sintered cylinder, cube, or a material having a shape close to these to a melting point or higher. On the other hand, as long as it is a method in which boron compound powder such as boron or boron carbide (B4 C), boron oxide (B2 O3 ) or boron nitride (BN) is mixed with a resin binder and molded, a sphere, a cylinder It is easy to form a cube or a shape close to these, and its manufacturing method is known.
すなわち、本発明の他の炉心溶融を起こした軽水炉の水中に投入される中性子吸収材の製造方法は、ボロン粉末およびボロン化合物の粉末のうち１種類または数種類からなるボロン系粉末をバインダーと混合して塊状に成形し、その表面に、ボロン系粉末よりも融点の低い金属粉末および／またはセラミック粉末を付着させて１ｍｍ以上２００ｍｍ以下の大きさとし、次いで加熱して金属粉末および／またはセラミック粉末の焼結体からなる外殻の内部にボロン系粉末を充填し、ボロンの見かけの原子数密度を５０％以上とすることを特徴とする。なお、上記塊状のものの表面に、金属粉末および／またはセラミック粉末をバインダーとともに混合したものを付着させることもできる。That is, according to another method of manufacturinga neutron absorbing materialintroduced into the water of a light water reactor that has caused core melting of the present invention, one or several types of boron powder and boron compoundpowder are mixed with a binder. Then, a metal powder and / or ceramic powder having amelting point lower than that of theboron-based powder is adhered to the surface so as to have a size of 1 mm or more and 200 mm or less, and thenheated to bak themetal powder and / or ceramic powder. A boron-based powder is filled in the outer shell made of a combined body, and the apparent atomic number density of boron is 50% or more. In addition, what mixed metal powder and / or ceramic powder with the binder can also be made to adhere to the surface of the said lump-shaped thing.
上記製造方法で製造された中性子吸収材は、焼結によりバインダーが蒸発し、金属および／またはセラミックの外殻の中にボロン粉末やボロン化合物の粉末が収容された構成である。この中性子吸収材では、金属やセラミックの材質を適宜選定することにより、耐食性や強度に優れ長期に亘って使用可能である。また、上記中性子吸収材では、ボロン粉末やボロン化合物の粉末をバインダーとともに混合するから成形が容易である。 The neutron absorber manufactured by the above manufacturing method has a configuration in which the binder is evaporated by sintering, and boron powder or boron compound powder is accommodated in the outer shell of metal and / or ceramic. This neutron absorber is excellent in corrosion resistance and strength and can be used over a long period of time by appropriately selecting a metal or ceramic material. Further, the neutron absorber is easy to mold because it mixes boron powder or boron compound powder together with a binder.
本発明のさらに他の炉心溶融を起こした軽水炉の水中に投入される中性子吸収材の製造方法は、ボロン粉末およびボロン化合物の粉末のうち１種類または数種類からなるボロン系粉末をバインダーと混合して塊状に成形し、その表面に、ボロン系粉末よりも融点の低いボロン化合物の粉末を付着させて１ｍｍ以上２００ｍｍ以下の大きさとし、次いで加熱してボロン化合物の粉末の焼結体からなる外殻の内部にボロン系粉末を充填し、ボロンの見かけの原子数密度を５０％以上とすることを特徴とする。なお、上記塊状のものの表面に、ボロン化合物の粉末をバインダーとともに混合したものを付着させることもできる。According to another aspect of the present invention, there is provided a method for producinga neutron absorberthat is introduced into the water of a light water reactor that has melted acore by mixing one or severalboron-based powders of boron powder and boron compoundpowder with a binder. molded into lumps on its surface, ofboron based powder having a low melting point boron compoundsthan powder to adhere 1mm or more 200mm or less in size Satoshi, thenthe outer shell made of a sintered product of powderheated toboron compound The inside is filled with boron-based powder, and the apparent atomic number density of boron is 50% or more. In addition, what mixed the powder of the boron compound with the binder can also be made to adhere to the surface of the said block-shaped thing.
上記製造方法で製造された中性子吸収材は、焼結によりバインダーが蒸発し、ボロンおよび／またはボロン化合物の外殻の中にボロン粉末やボロン化合物の粉末が収容された構成である。この中性子吸収材においても、耐食性や強度に優れ長期に亘って使用可能である。 The neutron absorber manufactured by the above manufacturing method has a configuration in which the binder is evaporated by sintering, and boron powder and / or boron compound powder is contained in the outer shell of boron and / or boron compound. This neutron absorber is also excellent in corrosion resistance and strength and can be used for a long time.
本発明によれば、十分な中性子吸収能力を持ち、かつ、溶融燃料取り出し時のみならずその後の保管および貯蔵時にも失われることなく有効な中性子吸収能力を長期にわたり維持することができる。 ADVANTAGE OF THE INVENTION According to this invention, it has sufficient neutron absorption capability, and can maintain effective neutron absorption capability for a long term, without being lost not only at the time of taking out molten fuel but at the time of subsequent storage and storage.
（１）第１実施形態
図１は本発明の第１実施形態を示す図である。この図に示す中性子吸収材１０は、ボロンの粉末と、ステンレスなどの鉄系金属粉末やアルミニウム粉末とを混合し、球状または円柱状に成形して焼結したものである。この中性子吸収材１０の大きさは、１ｍｍ以上２００ｍｍ以下、好ましくは５ｍｍ以上２０ｍｍ以下である。また、ボロンの見かけの原子数密度は５０％以上である。(1) First Embodiment FIG. 1 is a diagram showing a first embodiment of the present invention. The
ボロンに対して混合する金属やセラミックの比率については以下の観点から決定する。すなわち、中性子吸収性能の観点からは前者の比率が高いことが望ましいが、ボロン単独での焼結には、その融点（約２３００℃）直下に保持する必要がある。一方、ボロン粉末に他の金属またはセラミックの粉末と適量混合させれば、より低い温度での焼結が可能である。たとえば、ボロンとステンレス鋼（融点：約１４００℃）の粉末とを混合して焼結する際の温度は約１０００℃である。また、ボロン粉末と黒鉛の粉末から炭化ボロン（Ｂ４Ｃ）の焼結体を作ることもでき、この際の焼結温度は約１６７０℃である。炭化ボロン（Ｂ４Ｃ）は原子炉の制御棒として使われている実績がある。ボロンとアルミナ（融点：２０５４℃）の粉末で焼結する際の温度は約１６００℃である。The ratio of metal or ceramic to be mixed with boron is determined from the following viewpoints. That is, from the viewpoint of neutron absorption performance, it is desirable that the former ratio is high, but for sintering with boron alone, it is necessary to maintain the melting point (about 2300 ° C.) directly below. On the other hand, if boron powder is mixed with an appropriate amount of other metal or ceramic powder, sintering at a lower temperature is possible. For example, the temperature at which boron and stainless steel (melting point: about 1400 ° C.) are mixed and sintered is about 1000 ° C. A sintered body of boron carbide (B4 C) can also be made from boron powder and graphite powder, and the sintering temperature at this time is about 1670 ° C. Boron carbide (B4 C) has been used as a control rod for nuclear reactors. The temperature when sintering with powder of boron and alumina (melting point: 2054 ° C.) is about 1600 ° C.
焼結可能なボロンの最大混合比率は、混合する粉末の組み合わせのみならず両者の粒子の寸法にも依存する。たとえば、大きい粒子直径のボロン粉末と小さい粒子直径のステンレス粉末を焼結する場合、ボロン粉末の比率を高めることができる。 The maximum mixing ratio of sinterable boron depends not only on the combination of powders to be mixed but also on the size of both particles. For example, when sintering a large particle diameter boron powder and a small particle diameter stainless steel powder, the ratio of boron powder can be increased.
（２）第２実施形態
図２および図３は本発明の第２実施形態を示すものである。この実施形態では、ボロンまたは炭化ボロン（Ｂ４Ｃ）、酸化ボロン（Ｂ２Ｏ３）または窒化ボロン（ＢＮ）などのボロン化合物の粉末２１をバインダーとともに混合して球状にし、図２に示すように、その表面にステンレス鋼、アルミニウムなどの金属粉またはアルミナなどのセラミックの粉末２２をバインダーとともに混合して付着させる。次いで、図２に示すものを焼結することにより、図３に示すように、粉末２２が焼結されて形成された外殻２３の内部にボロン等の粉末２１が密閉された中性子吸収材２０が作製される。この中性子吸収材１０の大きさは、１ｍｍ以上２００ｍｍ以下、好ましくは５ｍｍ以上２０ｍｍ以下である。また、ボロンの見かけの原子数密度は５０％以上である。(2) Second Embodiment FIGS. 2 and 3 show a second embodiment of the present invention. In this embodiment, a
（３）第３実施形態
図４および図５は本発明の第３実施形態を示すものである。この実施形態では、ボロンの粉末３１をバインダーとともに混合して球状にし、図４に示すように、その表面に炭化ボロン（Ｂ４Ｃ）の粉末３２をバインダーとともに混合して付着させる。次いで、図４に示すものを焼結することにより、図５に示すように、粉末３２が焼結されて形成された外殻３３の内部にボロンの粉末３１が密閉された中性子吸収材３０が作製される。この中性子吸収材３０の大きさは、１ｍｍ以上２００ｍｍ以下、好ましくは５ｍｍ以上２０ｍｍ以下である。また、ボロンの見かけの原子数密度は５０％以上である。(3) Third Embodiment FIGS. 4 and 5 show a third embodiment of the present invention. In this embodiment,
炭化ボロン （Ｂ４Ｃ）は原子炉の制御棒としても使用されており、焼結が容易である。なお、ボロンの粉末をバインダーとともに混合して球状にし、その表面にボロンおよび黒鉛の粉末を付着させて焼結することにより、炭化ボロン（Ｂ４Ｃ）の外殻にボロンの粉末が密封された中性子吸収材を製造することもできる。Boron carbide (B4 C) is also used as a control rod for a nuclear reactor and is easily sintered. Boron powder was mixed with a binder to form a sphere, and boron and graphite powders were adhered to the surface and sintered to seal the boron powder to the outer shell of boron carbide (B4 C). Neutron absorbers can also be manufactured.
（１）第１実施例
平均粒径が２０μｍのボロンの粉末と平均粒径が１０μｍのステンレス鋼の粉末を用意し、体積比率が８０：２０、重量比率が６６：３４、原子数比率が８３：１７となるように配合した。その混合粉末を１０ｍｍの大きさの塊に圧粉成形し、５Ｐａの真空中にて１２５０℃で１時間焼結し塊状の中性子吸収材を作製した。(1) First Example A boron powder having an average particle diameter of 20 μm and a stainless steel powder having an average particle diameter of 10 μm are prepared. The volume ratio is 80:20, the weight ratio is 66:34, and the atomic ratio is 83. : It mix | blended so that it might be set to 17. The mixed powder was compacted into a lump with a size of 10 mm and sintered in a vacuum of 5 Pa at 1250 ° C. for 1 hour to produce a lump neutron absorber.
（２）第２実施例
平均粒径が２０μｍのボロンの粉末とバインダー（メチルセルロース）とを混合し、直径１０ｍｍ、高さ１０ｍｍの円柱体に形成した。この円柱体の表面にステンレス鋼粉末を厚さ１ｍｍとなるように付着させた。このときのボロン粉末とステンレス鋼粉末の比率は以下のとおりである。
円柱体の体積：０．７８ｃｃ
ボロン粉末の有効体積：０．７０ｃｃ
ステンレス鋼粉末層の体積：０．４７ｃｃ
ステンレス鋼粉末の有効体積：０．４２ｃｃ(2) Second Example Boron powder having an average particle diameter of 20 μm and a binder (methylcellulose) were mixed to form a cylindrical body having a diameter of 10 mm and a height of 10 mm. Stainless steel powder was adhered to the surface of this cylindrical body to a thickness of 1 mm. The ratio of boron powder and stainless steel powder at this time is as follows.
Volume of cylinder: 0.78cc
Effective volume of boron powder: 0.70cc
Stainless steel powder layer volume: 0.47cc
Effective volume of stainless steel powder: 0.42cc
以上より、ボロン粉末とステンレス鋼粉末の混合比率は以下のとおりである。
体積比率：０．７０：０．４２＝６２：３８
原子数比率：６４：３６From the above, the mixing ratio of boron powder and stainless steel powder is as follows.
Volume ratio: 0.70: 0.42 = 62: 38
Atomic ratio: 64:36
以上の混合比率で成形した直径１２ｍｍ、高さ１２ｍｍの円柱体を５Ｐａの真空中にて１２５０℃で１時間焼結し塊状の中性子吸収材を作製した。
（３）第３実施例
平均粒径が２０μｍのボロンの粉末とバインダー（メチルセルロース）とを混合し、直径１０ｍｍ、高さ１０ｍｍの円柱体に形成した。この円柱体の表面に炭化ボロン（Ｂ４Ｃ）粉末を厚さ１ｍｍとなるように付着させた。このときボロン粉末とＢ４Ｃ粉末の比率は以下のとおりである。
円柱体の体積：０．７８ｃｃ
Ｂ４Ｃ粉末の有効体積：０．７０ｃｃA cylindrical body having a diameter of 12 mm and a height of 12 mm molded at the above mixing ratio was sintered at 1250 ° C. for 1 hour in a vacuum of 5 Pa to produce a massive neutron absorber.
(3) Third Example Boron powder having an average particle diameter of 20 μm and a binder (methylcellulose) were mixed to form a cylindrical body having a diameter of 10 mm and a height of 10 mm. Boron carbide (B4 C) powder was adhered to the surface of this cylindrical body to a thickness of 1 mm. At this time, the ratio of boron powder to B4 C powder is as follows.
Volume of cylinder: 0.78cc
Effective volume of B4C powder: 0.70cc
以上より、ボロン粉末と炭化ボロン（Ｂ４Ｃ）粉末の混合比率は以下のとおりである。
体積比率：０．７０：０．４２＝６２：３８From the above, the mixing ratio of boron powder and boron carbide (B4 C) powder is as follows.
Volume ratio: 0.70: 0.42 = 62: 38
また、ボロンと炭素の原子数比率は以下のとおりである。
原子数比率：９８：２The atomic ratio of boron and carbon is as follows.
Atomic ratio: 98: 2
以上の混合比率で成形した直径１２ｍｍ、高さ１２ｍｍの円柱体を５Ｐａの真空中にて１６７０℃で１時間焼結し塊状の中性子吸収材を作製した。 A cylindrical body having a diameter of 12 mm and a height of 12 mm molded at the above mixing ratio was sintered at 1670 ° C. for 1 hour in a vacuum of 5 Pa to produce a massive neutron absorber.
本発明は、炉心溶融を起こした軽水炉から溶融燃料を取り出す際、およびその後の輸送や貯蔵の際に、中性子を吸収する材料として利用することができる。 The present invention can be used as a material that absorbs neutrons when taking out molten fuel from a light water reactor that has undergone core melting, and during subsequent transport and storage.
１０ 中性子吸収材
２０ 中性子吸収材
２１ 粉末
２２ 粉末
２３ 外殻
３０ 中性子吸収材
３１ 粉末
３２ 粉末
３３ 外殻DESCRIPTION OF
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| CN106782714A (en)* | 2017-01-10 | 2017-05-31 | 上海核工程研究设计院 | A kind of interpolation type neutron-absorbing component for irradiated fuel assembly |
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