EP0773555B1 - Hydraulisch erhärtendes Neutronschutzmaterial und Verfahren zur Neutronschutzherstellung derselben - Google Patents

Hydraulisch erhärtendes Neutronschutzmaterial und Verfahren zur Neutronschutzherstellung derselben Download PDF

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Publication number
EP0773555B1
EP0773555B1 EP96118207A EP96118207A EP0773555B1 EP 0773555 B1 EP0773555 B1 EP 0773555B1 EP 96118207 A EP96118207 A EP 96118207A EP 96118207 A EP96118207 A EP 96118207A EP 0773555 B1 EP0773555 B1 EP 0773555B1
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EP
European Patent Office
Prior art keywords
weight
neutron
shielding
particles
hardening material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP96118207A
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English (en)
French (fr)
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EP0773555A1 (de
Inventor
Takayuki c/o Doryokuro Kakunenryo Kaihatsu Nagai
Takuya c/o Doryokuro Kakunenryo Kaihatsu Seshimo
Hiroyuki c/o Mitsui Eng. & Shipbd.Co.Ltd. Tanuma
Masaaki c/o Takenaka Corporation Otagawa
Masafumi c/o Takenaka Corporation Terai
Shunichiro Chichibu Onoda Cement Corp. Uchida
Yasuhisa Chichibu Onoda Cement Corp. Takuma
Hideki Chichibu Onoda Cement Corp. Fujita
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Takenaka Corp
Taiheiyo Cement Corp
Mitsui Engineering and Shipbuilding Co Ltd
Japan Atomic Energy Agency
Original Assignee
Takenaka Corp
Japan Nuclear Cycle Development Institute
Taiheiyo Cement Corp
Mitsui Engineering and Shipbuilding Co Ltd
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Publication date
Application filed by Takenaka Corp, Japan Nuclear Cycle Development Institute, Taiheiyo Cement Corp, Mitsui Engineering and Shipbuilding Co Ltd filed Critical Takenaka Corp
Publication of EP0773555A1 publication Critical patent/EP0773555A1/de
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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F1/00—Shielding characterised by the composition of the materials
    • G21F1/02—Selection of uniform shielding materials
    • G21F1/04—Concretes; Other hydraulic hardening materials
    • G21F1/042—Concretes combined with other materials dispersed in the carrier

Definitions

  • the present invention relates to a neutron-shielding material which is useful in the fields of nuclear power plants, reprocessing of spent nuclear fuels, spent nuclear fuel disposal or medicine and particularly useful for shielding neutrons generated from various sources in such fields.
  • the invention also relates to a method of manufacturing neutron shields.
  • the energetic neutrons be slowed down to thermal neutrons using elements having a small atomic mass number, e.g., hydrogen (H), and that the thermal neutrons be absorbed by a suitable substance such as boron (B).
  • H hydrogen
  • B boron
  • FR-A-2 546 331 describes a neutron-shielding material comprising inter alia 40 to 60% by weight of aluminium hydrate, 15 to 25% by weight of aluminate cement, 1 to 3% of boron carbide and 20 to 30% by weight of water.
  • Cement is a relatively good material for shielding neutrons because, when transformed into mortar or concrete, it is mixed with water so as to form a hydrate that traps water therein.
  • the amount of water bound as a constituent of hydrate is small, and the greater part of mixed water is free water, which is likely to be lost due to evaporation, etc.
  • Plastics such as polyethylene may also contain a relatively large amount of hydrogen.
  • plastics are weak against heat and have poor long-term durability. In addition, they are difficult to form into large members of high density. For these reasons, uses of plastics are limited.
  • Exemplary substances containing boron include natural minerals such as colemanite (2CaO ⁇ 3B 2 O 3 ⁇ 5H 2 O) and kurnakovite (2MgO ⁇ 3B 2 O 3 ⁇ 13H 2 O).
  • these minerals In order to shield neutrons, use of these minerals as aggregate of concrete may be conceivable.
  • the boron content in these minerals is as low as 12-17% by weight, so it is difficult to secure boron content at a high concentration.
  • these minerals release B 2 O 3 , which inhibits cement from setting or hardening.
  • To suppress release of B 2 O 3 there has been made an attempt to coarsen the grain size of aggregate to thereby reduce specific surface area. This approach, however, cannot avoid uneven distribution of boron in concrete.
  • control of grain size of powdery aggregate is difficult. As a result, it is not only impossible to obtain highly plasticized concrete, but it also becomes difficult to place concrete into a formwork uniformly.
  • conventional neutron shields and materials therefor have the following drawbacks: Limited hydrogen content and boron content; low strength against heat and external physical force; a tendency to leave large voids in concrete products; difficulty in forming large members or members having complex shapes; and difficulty in obtaining shields having a uniform composition. Therefore, they are not satisfactory as neutron shields around nuclear reactors or high level radioactive waste.
  • hydraulic hardening materials containing hydraulic cement, aluminum hydroxide, and boron carbide at certain proportions have excellent neutron shielding properties, strength of afterhardening products, and workability of fresh mortar, and that they are capable of forming uniform shields.
  • the present invention was accomplished based on these findings.
  • the present invention provides a hydraulic hardening material for shielding neutrons (hereinafter may be referred to as neutron-shielding material) characterized by containing 10-50% by weight of Portland cement, 30-88% by weight of aluminum hydroxide, and 0.1-35% by weight of boron carbide, and which is constituted by particles comprising, when sieved through a mesh of 1 mm, not more than 5% by weight of oversize particles, 60-80% by weight of particles having a diameter of equal to or smaller than 100 ⁇ m, and not more than 20% by weight of particles having a diameter of 60-90 ⁇ m.
  • neutron-shielding material characterized by containing 10-50% by weight of Portland cement, 30-88% by weight of aluminum hydroxide, and 0.1-35% by weight of boron carbide, and which is constituted by particles comprising, when sieved through a mesh of 1 mm, not more than 5% by weight of oversize particles, 60-80% by weight of particles having a diameter of equal to or smaller than 100
  • the present invention also provides a method of manufacturing a neutron shield including the steps of mixing 100 parts by weight of the above-mentioned neutron-shielding hydraulic hardening material, 15-50 parts by weight of water, and not more than 5 parts by weight of at least one chemical admixture selected from the group consisting of air-entraining (AE) agents, air-entraining and water reducing agents, high-range water reducing agents, plasticizers, air-entraining and high-range water reducing agents, and foaming agents; and kneading the resultant mixture.
  • AE air-entraining
  • the Portland cement provides the target afterhardening structure with strength when mixed with water
  • aluminum hydroxide provides hydrogen atoms that slow down highly energetic neutrons to thermal neutrons
  • boron carbide provides boron atoms that absorb thermal neutrons which have been slowed down by hydrogen atoms.
  • they may be any one of ordinary Portland cement and high-early-strength Portland cement; blended cements such as Portland blast-furnace slag cement, or Portland pozzolan cement, and Portland fly-ash cement. If needed, there may also be used additives that are ordinarily used in mortar and concrete; e.g., expansive additives, accelerator, corrosion inhibitor, and waterproofing agents.
  • Aluminum hydroxide may take a polymorphism such as diaspore, boemite, and gibbsite. In consideration of stability at high temperatures, gibbsite is most preferred. The theoretical hydrogen content of gibbsite is 3.8% by weight.
  • B 4 C Boron carbides take the form of B 4 C, B 8 C, B 13 C 2 , etc. Under general circumstances, B 4 C is the easiest one to obtain. Moreover, B 4 C is preferred because of its good stability. The theoretical boron content of B 4 C is as high as 78% by weight.
  • hydraulic cement When a neutron-shielding hydraulic hardening material neutrons is mixed with water and thereby hardens to develop enough strength as a structure, it is necessary that hydraulic cement be present in the amount of at least 10% by weight. If hydrogen and boron are both co-present, the neutron absorbing effect may be exerted more effectively. Therefore, it is concluded that proper ranges for the content of hydraulic cement, aluminum hydroxide, and boron carbide are 10-50% by weight, 30-88% by weight, and 0.1-35% by weight, respectively.
  • Portland cement is obtained through grinding the clinker that has been burned in a rotary kiln, and mixing it with suitable admixtures such as gypsum.
  • Aluminum hydroxide is usually manufactured using a Bayer's process for industrial production.
  • Boron carbide is normally manufactured through carbonizing of boron oxide (B 2 O 3 ) using carbon, and the resultant mass is used after being pulverized.
  • hydraulic hardening materials obtained by the mixture of these heterogeneous powders have poor fluidity when mixed with water. In extreme cases, flow and slump are barely obtainable.
  • ordinary tamping bars cannot achieve uniform filling of the cement into a flow cone or a slump cone; therefore a vibrator is usually required for achieving a uniform placing.
  • the powder in a dry state preferably has a filling ratio of not lower than a threshold value.
  • the filling rate be not less than 55%, more preferably not less than 60%, when measured in such a manner that the powder in a dry state is put in a hollow cylindrical container having an inner diameter of 5 cm and a height of 5 cm, and then compacted by 180 tappings from the height of 2 cm.
  • the particles when sieved through a mesh of 1 mm, have such distribution that oversize particles are present in an amount of not more than 5% by weight, particles having a diameter of equal to or smaller than 100 ⁇ m are present in an amount of 60-80% by weight, and particles having a diameter of 60-90 ⁇ m are present in an amount of not more than 20% by weight.
  • the neutron-shielding hydraulic hardening material of the present invention provides a neutron-shielding product after being mixed with water and then setting. It is not necessarily preferred if the mixing ratio of powders to water is defined by the ratio of water content to cement content as in the case of ordinary mortar and cement. Instead, it is proper that the ratio be defined in terms of the entirety of powders and water. The ratio is preferably such that water is used in an amount of 15-50 parts by weight with respect to 100 parts by weight of the neutron-shielding hydraulic setting material of the present invention.
  • the neutron-shielding hydraulic hardening material of the present invention when it is mixed with water, this may be achieved by the addition of water reducing agents or high-range water reducing agents. If lighter neutron-shielding products are desired, this may be achieved by adding air-entraining agents, foaming agents, or similar agents to thereby introduce very fine air bubbles in the material while maintaining the uniformity of the composition.
  • the neutron-shielding hydraulic hardening material of the present invention may contain at least one chemical admixture selected from the group consisting of air-entraining agents, air-entraining and water reducing agents, high-range water reducing agents, plasticizers, air-entraining and high-range water reducing agents, and foaming agents.
  • these are incorporated in a total amount of not more than 5 parts by weight per 100 parts by weight of the neutron-shielding hydraulic hardening material of the present invention. If the total amount of the additives is in excess of 5 parts by weight, the additives may become separated when mixed with water; thus these amounts are not preferred.
  • a fresh mortar obtained through mixing neutron-shielding hydraulic hardening material of the present invention with water is uniform and has an appropriate softness and fluidity. Therefore, it can be uniformly placed into a formwork without the application of violent mechanical vibration as generated by a vibrator.
  • This is advantageous because mortar can be placed uniformly and without leaving large voids into complex members to which rod type vibrators cannot be inserted. Consequently, placing work can be considerably simplified, dispersion in quality of afterhardening product that tends to occur due to the application of vibration is reduced, and separation of materials that tends to occur due to the application of vibration can also be avoided.
  • neutron-shielding hydraulic hardening material of the present invention and the method of manufacturing neutron shields of the present invention will next be described in detail by way of example, which is given for the purpose of illustration only.
  • the neutron-shielding hydraulic hardening materials shown in Table 1 were prepared.
  • the hydraulic cement employed was an high-early-strength Portland cement having a specific surface area of not less than 4,000 cm 2 /g.
  • Three types of aluminum hydroxide having different particle sizes were used including A (particle size centered between 1 and 5 ⁇ m), B (particle size centered between 10 and 20 ⁇ m), and C (particle size centered between 90 and 110 ⁇ m).
  • the boron carbide employed was B 4 C (particle size centered between 100 and 150 ⁇ m). Given proportions of powders were mixed using a Henschel mixer for 10 minutes.
  • each powder sample was mixed with water at a water/powder ratio of 27% by weight, and a flow value was determined in accordance with the flow test method provided in JIS R5201, to thereby assess the fluidity.
  • the compressive strength is as small as 2.0 N/mm 2 , which cannot provide the resultant structure with sufficient strength.
  • the cement content is 10% by weight or greater (Samples 2 through 11) a certain level of strength is secured and thus the material can be used in practice.
  • the flow values are 220 or greater, with the mortar exhibiting even more improved fluidity with excellent results of visual observation of voids.
  • Example 7 a typical sample that exhibited excellent fluidity was used. This sample was mixed with water and additives at the indicated water/powder proportions and in the amounts indicated in Table 2.
  • the high-range water reducing agent employed was a product of Onoda Cement Corporation (SP-X), and the air-entraining agent was a product of Yamaso Chemical Co., Ltd. (Vinsol W).
  • the air volume and the flow value without tapping (unit: mm) of the fresh mortar were determined.
  • the flow value without tapping indicates the diameter of mortar spread in a circle on a plane when a cone filled with mortar was placed on the plane and the cone was then removed by being lifted upward.
  • a mortar sample having the same composition was placed into a formwork having an inner diameter of 10 cm and a height of 20 cm without the application of vibration, and was then cured for 14 days.
  • the size of voids in the cross section of the resultant afterhardening product was determined in the manner described in Example 1. The results are shown in Table 2.
  • Sample 21 representing the standard in which no additives were added, exhibited a flow value without tapping of 105, which was almost the same as that of the bottom size of the flow cone, and an air volume of 2% by volume.
  • Sample 22 in which a high-range water reducing agent had been added in an amount of 0.4% by weight
  • Sample 23 in which an air-entraining agent had been added in an amount of 0.04% by weight
  • Sample 24 in which a high-range water reducing agent and an air-entraining agent were simultaneously added
  • Sample 24 exhibited slightly reduced effect of the additives, but still was considered satisfactory in terms of achievement of fluidity and a reduction in weight.
  • Samples 22 and 24 (in which a high-range water reducing agent was added) show sufficient fluidity, and uniform afterhardening products having no large woids have been obtained by placing without being applied mechanical vibration.
  • the neutron-shielding hydraulic setting material of the present invention is a material that provides an excellent neutron shielding effect, satisfactory strength of afterset product, and good workability of fresh mortar. Therefore, when neutron shields are manufactured by the method of the present invention, neutron shields with enhanced uniformity can be obtained.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Claims (4)

  1. Hydraulisch härtendes Neutronenabschirmmaterial, umfassend 10 bis 50 Gew.% Portlandzement, 30 bis 88 Gew.% Aluminiumhydroxid und 0,1 bis 35 Gew.% Borcarbid und das sich aus Teilchen zusammensetzt, die nach Sieben durch ein Sieb mit 1 mm nicht mehr als 5 Gew.% Teilchen mit Übergröße, 60 bis 80 Gew.% Teilchen mit einem Durchmesser von gleich oder weniger als 100 µm und nicht mehr als 20 Gew.% Teilchen mit einem Durchmesser von 60 bis 90 µm.
  2. Hydraulisch härtendes Material zum Abschirmen von Neutronen nach Anspruch 1, das eine Füllrate von nicht weniger als 55% hat, die so gemessen wird, dass das Material in einem trockenen Zustand in einen zylindrischen Hohlbehälter mit einem Innendurchmesser von 5 cm und einer Höhe von 5 cm gegeben und dann durch 180-maliges Klopfen von der Höhe von 2 cm kompaktiert ist.
  3. Verfahren zur Herstellung eines Neutronenabschirmmaterials, umfassend die folgenden Schritte: Mischen von 100 Gew.Teilen eines hydraulisch härtenden Neutronenabschirmmaterials nach Anspruch 1 oder 2, 15 bis 50 Gew.Teilen Wasser und nicht mehr als 5 Gew.Teile von zumindest einer chemischen Zumischung, ausgewählt aus der Gruppe, bestehend aus Luftporenzusatzstoffen, Luftporen- und Wasserreduktionsmittel, Mittel zum starken Vermindern von Wasser, Weichmacher, Mittel zum Luftporenbilden und starken Vermindern von Wasser und Schäummittel; und Kneten der resultierenden Mischung.
  4. Verfahren zur Herstellung einer Neutronenabschirmung nach Anspruch 3, worin das geknetete Material in eine Verschalung gegeben wird, ohne dass eine mechanische Vibration auferlegt wird.
EP96118207A 1995-11-13 1996-11-13 Hydraulisch erhärtendes Neutronschutzmaterial und Verfahren zur Neutronschutzherstellung derselben Expired - Lifetime EP0773555B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP29438595 1995-11-13
JP294385/95 1995-11-13
JP7294385A JP2929077B2 (ja) 1995-11-13 1995-11-13 中性子遮蔽用水硬性材料及びこれを用いた中性子遮蔽体の製造方法

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EP0773555A1 EP0773555A1 (de) 1997-05-14
EP0773555B1 true EP0773555B1 (de) 2000-07-05

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JP (1) JP2929077B2 (de)
DE (1) DE69609144T2 (de)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10327466B4 (de) * 2003-01-13 2008-08-07 Jan Forster Baukörper für Strahlenschutzbauwerke
JP2008157801A (ja) * 2006-12-25 2008-07-10 Fujita Corp 中性子遮蔽低放射化コンクリートおよびモルタル
JP4883634B2 (ja) * 2007-06-07 2012-02-22 株式会社フジタ 中性子遮蔽体および該中性子遮蔽体により形成された加速器室
CZ2011730A3 (cs) * 2011-11-14 2013-08-28 Ústav anorganické chemie AV CR, v.v.i. Anorganický materiál s absorbátory neutronu a zpusob jeho prípravy
JP5347075B1 (ja) * 2013-01-25 2013-11-20 石川島建材工業株式会社 中性子遮蔽コンクリート
JP6867567B2 (ja) * 2017-01-16 2021-04-28 富士化学株式会社 臨界防止被覆層の形成方法
DE102017006902A1 (de) * 2017-07-20 2019-01-24 Theodor Pieper GmbH & Co. KG Betonzusammensetzung und Verfahren zum Herstellen einer solchen Betonzusammensetzung
CN107342113A (zh) * 2017-07-21 2017-11-10 中国核动力研究设计院 一种耐高温耐辐照无机屏蔽材料
CN111943612B (zh) * 2020-08-13 2022-10-11 中国核动力研究设计院 一种耐辐照耐高温快中子屏蔽材料及制备方法
CN114171215A (zh) * 2021-12-01 2022-03-11 中国核电工程有限公司 一种中子毒物材料及其制备方法、以及核临界安全贮槽

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JPS5416098A (en) * 1976-05-12 1979-02-06 Nippon Asbestos Co Ltd Neutron shielding heat insulator
FR2546331A1 (fr) * 1983-05-20 1984-11-23 Robatel Slpi Perfectionnements aux materiaux hydrogenes de protection antineutronique
JPH01147399A (ja) * 1987-12-02 1989-06-09 Kuraray Co Ltd 繊維強化中性子遮蔽モルタルコンクリート
JP3203269B2 (ja) * 1992-09-01 2001-08-27 花王株式会社 空気連行剤
JP3618001B2 (ja) * 1993-12-13 2005-02-09 大同コンクリート工業株式会社 多孔質連通気泡コンクリ−ト成形体及び同コンクリ−ト複合体の製造方法

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JP2929077B2 (ja) 1999-08-03
DE69609144T2 (de) 2001-03-22
JPH09133790A (ja) 1997-05-20
DE69609144D1 (de) 2000-08-10
EP0773555A1 (de) 1997-05-14

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