KR102409501B1 - method for manufacturing neutron absorbing material - Google Patents
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- G21F1/00—Shielding characterised by the composition of the materials
- G21F1/02—Selection of uniform shielding materials
- G21F1/08—Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
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- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/06—Metallic material
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
- C23C4/129—Flame spraying
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/34—Spacer grids
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- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
원자력 발전소의 사용후핵연료의 임시 저장 시설에서 사용하는 사용후 연료 저장용기 및 방사선 폐기물 포장용기에서 연료 및 폐기물로부터 중성자 방사를 흡수하기 위해 적용되는 내부식 중성자 흡수 코팅에 관한 기술이 개시된다. 보론카바이드(B4C) 또는 보론나이트라이트(BN) 분말과, 바인더(binder)로서 오스테나이트(Austenite) 조직을 가진 고내식강 분말을 혼합한 혼합분말은 열용사 및 저온분사 방식에 의해 모재에 코팅된다.Disclosed is a technology for a corrosion-resistant neutron absorbing coating applied to absorb neutron radiation from fuel and waste in a spent fuel storage container and a radiation waste packaging container used in a temporary storage facility for spent nuclear fuel in a nuclear power plant. The mixed powder mixed with boron carbide (B 4 C) or boron nitrite (BN) powder and high corrosion-resistant steel powder with an austenite structure as a binder is applied to the base material by thermal spraying and low-temperature spraying. coated
Description
내부식성 재료(corrosion resistant material)의 코팅, 특히 원자력 발전소의 사용후핵연료의 임시 저장 시설인 습식 저장(wet storage) 수조에서 사용하는 사용후핵연료의 지지 격자 구조체인 조밀랙(조밀저장대, spent fuel rack)이나, 건식 저장(dry storage)에서 사용하는 사용후핵연료 저장용기(spent fuel storage), 그리고 원전 해체 시 발생되는 방사선 폐기물의 포장 용기에서 연료 및 폐기물의 중성자 방사를 흡수하기 위한 저장용기에 적용되는 내부식성 중성자 흡수 코팅(corrosion resistant neutron absorbing coating)에 관한 기술이 개시된다.Coating of corrosion resistant material, especially, used fuel support grid structure in wet storage tank, which is a temporary storage facility for spent fuel in nuclear power plants (dense storage tank, spent fuel) rack), spent fuel storage used in dry storage, and storage containers for absorbing neutron radiation of fuel and waste from packaging containers for radioactive waste generated during nuclear decommissioning. Disclosed is a technology for a corrosion resistant neutron absorbing coating that is
원자력 발전소에서 사용후핵연료는 원전내 습식저장시설(wet storage)에서 일정 기간 냉각 후 건식저장시설(dry storage)에 저장된다. 그리고 원전 해체 시 발생하는 방사선 폐기물들은 적절한 용기에 포장하여 처분시설이 건설·운영될 때까지 안전하게 저장·관리되어야 한다. 이러한 저장시설에 사용되는 사용후핵연료의 지지 격자 구조체와 저장용기, 그리고 방사선폐기물 포장 용기는 장기간 동안 방사되는 중성자를 흡수하고 동시에 부식으로부터 우수한 저항성을 가지는 재료가 적용되어야 한다. 국내에서는 현재 사용후핵연료의 지지 격자 구조체 및 저장용기에 사용되는 소재의 경우 전량 외국 제작사에 의존하고 있다.In a nuclear power plant, spent nuclear fuel is stored in a dry storage facility after cooling for a certain period in a wet storage facility in the nuclear power plant. In addition, radioactive waste generated during the decommissioning of a nuclear power plant should be packaged in an appropriate container and stored and managed safely until a disposal facility is constructed and operated. The support grid structure and storage container for spent nuclear fuel used in these storage facilities, and the radioactive waste packaging container must be made of a material that absorbs neutrons radiated for a long period of time and has excellent resistance to corrosion at the same time. In Korea, the materials used for the support grid structure and storage containers of spent nuclear fuel are entirely dependent on foreign manufacturers.
사용후핵연료의 지지 격자 구조체 및 저장용기에 적용할 수 있는 상용화된 중성자 흡수 제품에는 3M사의 BORALTM, Holtec International 사의 METAMICTM 등이 알려져 있다. 3M사의 BORALTM 은 얇은 두께의 알루미늄 합금으로 클래딩(cladding)된 B4C와 알루미늄 혼합분말의 열간압연 복합재로, 높은 붕소함량 (최대 67 부피%)의 장점이 있으나, 알루미늄 합금 클래딩과 B4C와 알루미늄의 복합재 계면에서 블리스터링(blistering) 및 벌징(bulging)이 발생하는 문제점이 있다. Holtec International 사의 METAMICTM은 B4C와 알루미늄 합금 분말을 혼합한 후 고압 프레스를 이용하여 압출한 제품으로 블리스터링에 대한 문제점은 해결하였으나 국부부식이 발생한다는 단점을 지니고 있다. 또한 이러한 복합재들은 복잡한 제조공정과 높은 단가의 공통의 단점이 있다.3M's BORAL TM and Holtec International's METAMIC TM are known as commercially available neutron absorption products applicable to the support grid structure and storage container of spent nuclear fuel. 3M's BORAL TM is a hot-rolled composite of B 4 C and aluminum mixed powder clad with thin aluminum alloy. There is a problem in that blistering and bulging occur at the interface of the aluminum and composite materials. METAMIC TM of Holtec International is a product that is extruded using a high-pressure press after mixing B 4 C and aluminum alloy powder. Although the problem of blistering has been solved, it has the disadvantage of local corrosion. In addition, these composite materials have the common disadvantages of a complicated manufacturing process and a high unit cost.
미국특허 8,580,350은 이러한 분야에 적용될 수 있는 내부식성 중성자 흡수 코팅 기술을 개시하고 있다. 이 공보에는 붕소를 함유하는 철 기반 비정질(amorphous) 금속 합금을 코팅의 재료로 제시하고 있으며 열용사(thermal spray) 방식, 플레임용사(flame spray), 스퍼터링(sputtering) 혹은 PVD(Physical Vapor Deposition), CVD (Chemical Vapor Deposition), 전착(electro deposition) 등의 다양한 방식에 의해 코팅하는 기술을 개시하고 있다. 하지만 제시된 합금, 예를 들어 SAM1651 합금은 약 1.2 무게%의 붕소를 함유하고 있어 우수한 중성자 흡수 성능을 기대하기 어렵다. 또 이를 해결하기 위해 붕소를 함유하는 중성자 흡수 재료를 첨가하여 복합재를 만드는 방법도 제시하고 있으나, 새로운 합금소재의 개발에 따른 부담과 높은 단가의 단점을 가질 것으로 보인다. 또한, 건식용기에 저장되는 사용후핵연료의 농축도 및 연소도 등의 조건이 가혹해짐에 따라 예상되는 B4C의 함량 요건에 적절하게 대응하기 어려울 것으로 보인다.U.S. Patent 8,580,350 discloses a corrosion-resistant neutron absorbing coating technology that can be applied in this field. In this publication, an iron-based amorphous metal alloy containing boron is presented as a material for coating, and thermal spray method, flame spray method, sputtering or PVD (Physical Vapor Deposition), Disclosed is a coating technique by various methods such as CVD (Chemical Vapor Deposition) and electro-deposition. However, the proposed alloy, for example, SAM1651 alloy, contains about 1.2 wt% of boron, so it is difficult to expect excellent neutron absorption performance. Also, to solve this problem, a method of making a composite material by adding a neutron-absorbing material containing boron is also proposed, but it is likely to have disadvantages of a burden and a high unit price due to the development of a new alloy material. In addition, it seems difficult to adequately respond to the expected B 4 C content requirements as conditions such as the concentration and burn-up of spent nuclear fuel stored in dry containers become more severe.
고가의 중성자 흡수 재료를 국산화하기 위해 국내에서도 기술 개발이 진행되고 있다. 한국원자력연구원은 해외에서 수입하고 있는 중성자 차폐 소재에 비해서 보다 가볍고, 기계적 물성 및 건정성, 차폐성능이 우수한 에폭시 기반 나노복합 중성자 차폐소재 개발을 2010년-2013년에 걸쳐 진행하였다. 또 한양대학교, 한국원자력연구원, ㈜래드코어는 공동으로 원전 소내·외 저장시설의 임계제어를 위한 인공희토류 기반 신개념 중성자흡수체 핵심기술의 개발을 2012년-2015년에 걸쳐 진행하였다. 한스코, 한국생산기술연구원, 단국대학교 등은 공동으로 사용후핵연료 저장 및 운송용기에 적용하기 위한 중성자 흡수재(Gd, Er, Sm)을 함유하는 이상 스테인리스 강의 개발을 2015년-2019년에 걸쳐 진행하였다. 한국재료연구원에서는 용탕 교반 공정 개발 및 공정 개선을 통하여 B4C의 분산성을 향상시킨 5~20 vol% B4C/Al 금속복합소재 개발을 2017년-2021년에 걸쳐 진행하고 있는 중이다. 이러한 선행 기술 개발들은 중성자 흡수 및 구조재료의 기능을 함께하는 고강도, 고내식성, 고내열성의 신합금 및 신소재를 설계하는 것을 목적으로 하고 있으며, 여전히 제조공정의 복잡성과 가격 경쟁력 면에서 문제를 가질 것으로 보인다.In order to localize expensive neutron absorbing materials, technology development is underway in Korea. The Korea Atomic Energy Research Institute developed an epoxy-based nanocomposite neutron shielding material that is lighter than the neutron shielding material imported from abroad, and has excellent mechanical properties, dryness, and shielding performance from 2010 to 2013. In addition, Hanyang University, Korea Atomic Energy Research Institute, and Radcore Co., Ltd. jointly developed a new concept neutron absorber core technology based on artificial rare earth for critical control of storage facilities inside and outside the nuclear power plant from 2012 to 2015. Hansco, Korea Institute of Industrial Technology, Dankook University, etc. jointly developed stainless steel containing neutron absorbers (Gd, Er, Sm) for storage and transportation of spent nuclear fuel from 2015 to 2019 did. The Korea Institute of Materials Science and Technology is developing a 5-20 vol% B4C/Al metal composite material that improves the dispersibility of B 4 C through the development and process improvement of the molten metal agitation process over 2017-2021. These prior art developments are aimed at designing new alloys and materials with high strength, high corrosion resistance, and high heat resistance that have the functions of neutron absorption and structural materials. .
이러한 새로운 소재 혹은 합금의 개발과 다른 접근법으로, 박진주 외, Application of flame spraying coatings of neutron absorbing boron-polymer composite powder for spent nuclear fuel container, 한국원자력학회, October 24-25, 2013에는 저밀도 폴리에틸렌(Low density polyethylene : LDPE) 폴리머 분말을 B4C 분말 40무게% 혼합하여 알루미늄 모재에 플레임 열용사(flame thermal spray) 방식에 의해 코팅하는 기술을 개시하고 있으나, 짧게는 10,000년 길게는 300,000년 동안 사용후핵연료를 저장하기 위한 저장용기에 적용하기에는 폴리머 열화에 대한 잠재적인 문제점이 남아있다.As a different approach to the development of these new materials or alloys, Jinju Park et al., Application of flame spraying coatings of neutron absorbing boron-polymer composite powder for spent nuclear fuel container, Korea Atomic Energy Society, October 24-25, 2013, low density polyethylene (Low density) polyethylene: LDPE) polymer powder is mixed with B 4 C powder 40% by weight and coated on an aluminum base material by flame thermal spray method, but it is used for as little as 10,000 years and as long as 300,000 years as spent nuclear fuel. Potential problems with polymer degradation remain to be applied to storage containers for the storage of polymers.
제안된 발명은 B4C의 함량 규제요건 강화에 대응이 가능하도록 B4C의 함량에 유연성을 가지는 사용후핵연료 및 방사선폐기물의 중성자 흡수재 제조 기술을 제시하는 것을 목적으로 한다.The proposed invention aims to present a technology for manufacturing a neutron absorber for spent nuclear fuel and radioactive waste that has flexibility in the content of B 4 C so as to be able to respond to the strengthening of regulatory requirements for the content of B 4 C.
나아가 제안된 발명은 우수한 중성자 흡수 성능과 내구성을 지니면서 가격경쟁력까지 갖춘 사용후핵연료 및 방사선폐기물의 중성자 흡수재 제조 기술을 제시하는 것을 목적으로 한다.Furthermore, the proposed invention aims to present a technology for manufacturing a neutron absorber for spent nuclear fuel and radioactive waste, which has excellent neutron absorption performance and durability, and has price competitiveness.
더 나아가 제안된 발명은 낮은 비용으로 적용 가능하고 넓은 면적에 걸쳐 균일한 성능을 가지는 사용후핵연료 및 방사선폐기물의 중성자 흡수재 제조 기술을 제시하는 것을 목적으로 한다. Furthermore, the proposed invention aims to provide a technology for manufacturing a neutron absorber for spent nuclear fuel and radioactive waste that is applicable at low cost and has uniform performance over a large area.
제안된 발명의 일 양상에 따르면, 결정질(crystalline)의 고내식성 합금 분말과 보론카바이드 또는 보론나이트라이드 분말을 혼합한 혼합분말을 열용사에 및 저온분사 의해 모재에 코팅하여 중성자 흡수재가 제조된다.According to an aspect of the proposed invention, a neutron absorber is manufactured by coating a mixed powder of a crystalline high corrosion-resistance alloy powder and boron carbide or boron nitride powder on a base material by thermal spraying and low-temperature spraying.
제안된 발명에 따라, 낮은 비용으로 중성자 흡수재를 제조하는 방법이 제시되었다. 보론 함량을 50 wt %까지 높일 수 있고 이에 따라 기존의 중성자 흡수재에 비해 더 우수한 중성자 포획 성능을 나타낼 수 있다. According to the proposed invention, a method for manufacturing a neutron absorber at low cost has been proposed. It is possible to increase the boron content up to 50 wt % and thus exhibit better neutron trapping performance compared to the conventional neutron absorber.
도 1은 일 실시예에 따른 중성자 흡수재 제조 방법의 구성을 도시한 흐름도이다.
도 2는 B4C와 316SS 스테인레스강을 50:50 비율로 혼합한 분말을 열용사 방식에 의해 코팅된 상태를 보여주는 단면 사진이다.1 is a flowchart illustrating a configuration of a method for manufacturing a neutron absorber according to an embodiment.
FIG. 2 is a cross-sectional photograph showing a state in which powder obtained by mixing B 4 C and 316SS stainless steel in a 50:50 ratio is coated by thermal spraying.
전술한, 그리고 추가적인 양상들은 첨부된 도면을 참조하여 설명하는 실시예들을 통해 구체화된다. 각 실시예들의 구성 요소들은 다른 언급이나 상호간에 모순이 없는 한 실시예 내에서 또는 타 실시예의 구성 요소들과 다양한 조합이 가능한 것으로 이해된다. 발명자는 그 자신의 발명을 가장 최선의 방법으로 설명하기 위해 용어의 개념을 적절하게 정의할 수 있다는 원칙에 입각하여 본 명세서 및 청구범위에 사용된 용어는 기재 내용 혹은 제안된 기술적 사상에 부합하는 의미와 개념으로 해석되어야만 한다. 이하 첨부된 도면을 참조로 본 발명의 바람직한 실시예를 상세히 설명하기로 한다.The foregoing and additional aspects are embodied through the embodiments described with reference to the accompanying drawings. It is understood that various combinations of the elements of each embodiment are possible within the embodiment or with the elements of other embodiments as long as there is no contradiction between them or other mentions. Based on the principle that the inventor can appropriately define the concept of a term to describe his invention in the best way, the terms used in the present specification and claims shall have meanings consistent with the description or the proposed technical idea. and should be interpreted as a concept. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
제안된 발명의 일 양상에 따르면, 중성자 흡수재는 보론카바이드(B4C) 또는 보론나이트라이트(BN) 분말과, 바인더(binder)로서 결정질(crystalline)의 고내식성 합금 분말을 혼합한 혼합분말을 열용사(thermal spray) 및 저온분사 (cold spray)방식에 의해 모재에 코팅하여 제조된다.According to one aspect of the proposed invention, the neutron absorber is a mixed powder of boron carbide (B 4 C) or boron nitrite (BN) powder and a crystalline high corrosion resistance alloy powder as a binder. It is manufactured by coating the base material by thermal spray and cold spray methods.
도 1은 일 실시예에 따른 중성자 흡수재 제조 방법의 구성을 도시한 흐름도이다. 도시된 바와 같이, 먼저 보론카바이드 또는 보론나이트라이드 분말이 준비된다(110). 열압축 보론카바이드는 다이아몬드, 입방형 질화 붕소(Cubic Boron Nitride), 산화 붕소(Boron Oxide) 다음으로 높은 경도를 가진 물질이며, 함유된 보론에 의해 중성자 포획에 유리한 구조를 가지고 있다. 보론카바이드 또는 보론나이트라이드 분말의 입경은 크게 중요하지 않으나, 50μm 이하인 것이 바람직하다.1 is a flowchart illustrating a configuration of a method for manufacturing a neutron absorber according to an embodiment. As shown, first boron carbide or boron nitride powder is prepared (110). Thermal compression boron carbide is a material with the highest hardness after diamond, cubic boron nitride, and boron oxide, and has an advantageous structure for capturing neutrons by the boron contained therein. The particle size of boron carbide or boron nitride powder is not very important, but is preferably 50 μm or less.
보론카바이드 분말과 별도로, 부식저항성이 우수한 Fe, Ni, Al, Ti, Ni 기반의 결정질(crystalline) 합금 분말이 준비된다(130). 일 예로, 18Cr 과 8Ni 을 기본 조성으로 하고 오스테나이트(Austenite) 조직을 가진 304SS 혹은 316SS 스텐레스강의 분말이 사용될 수 있다. 강철을 담금질(quenching)하여 느리게 냉각하면 726℃ 이상의 고온에서 안정된 오스테나이트 조직으로 변하게 된다. 304SS 혹은 316SS 스텐레스강은 오스테나이트(austenite) 조직을 가지며, 자성이 없고, 뛰어난 내식성을 가지며, 충격에 강하고, 연신률이 크다. 또한 열처리에 의해 경화되지 않는 특성을 가진다.Separately from the boron carbide powder, a crystalline alloy powder based on Fe, Ni, Al, Ti, and Ni having excellent corrosion resistance is prepared (130). For example, a powder of 304SS or 316SS stainless steel having 18Cr and 8Ni as a basic composition and having an austenite structure may be used. When the steel is quenched and cooled slowly, it changes to a stable austenite structure at a high temperature of 726°C or higher. 304SS or 316SS stainless steel has an austenite structure, has no magnetism, has excellent corrosion resistance, is strong in impact, and has a high elongation. In addition, it has a characteristic that is not hardened by heat treatment.
이후에 30-70 wt%의 보론카바이드 또는 보론나이트라이트 분말과, 70-30 wt%의 오스테나이트(Austenite) 조직을 가진 고내식성 합금 분말을 균일하게 혼합하여 혼합분말을 준비한다 (150). 보론카바이드 분말의 비율이 50 wt% 인 실시예에서 가장 양호한 품질이 달성되었으며, 도 2는 이러한 B4C와 316SS 스테인레스강을 50:50 비율로 혼합한 분말을 열용사 방식에 의해 코팅된 상태를 보여주는 단면 사진이다. 또 상기 실시예에서 제조된 중성자 흡수재에 대한 중성자 차폐 특성 평가를 통해 중성자 흡수 성능을 확인하였다.After that, 30-70 wt% of boron carbide or boronnitrite powder and 70-30 wt% of a high corrosion-resistant alloy powder having an austenite structure are uniformly mixed to prepare a mixed powder (150). The best quality was achieved in the example in which the ratio of boron carbide powder was 50 wt%, and FIG. 2 shows a state in which the powder mixed with B 4 C and 316SS stainless steel in a 50:50 ratio was coated by thermal spraying. This is a cross-sectional picture showing. In addition, the neutron absorption performance was confirmed through the evaluation of the neutron shielding characteristics of the neutron absorber prepared in the above example.
보론카바이드 분말의 비율이 70%를 넘어가면 국부적으로 바인딩이 약한 곳이 나타난다. BORALTM 이나 METAMICTM 등과 같이 합금으로 제작되는 기존의 상용화된 사용후핵연료 중성자 흡수재와 달리 혼합분말을 코팅하여 제조하는 방식은 보론의 함량을 높일 수 있다는 점에서 중성자 흡수면에서 유리하다. BORALTM 이나 METAMICTM 등과 같은 보론을 포함한 알루미늄 합금의 경우 제조시 30% 이상의 보론을 첨가하면 기계적 성능이 저하되어 필요한 내구성을 지닌 중성자 흡수재로서는 가공성에 문제점을 유발한다.If the proportion of boron carbide powder exceeds 70%, local weak binding appears. Unlike the existing commercially available spent nuclear fuel neutron absorbers made of alloys such as BORAL TM or METAMIC TM , the method of coating mixed powder is advantageous in terms of neutron absorption in that it can increase the content of boron. In the case of aluminum alloys containing boron, such as BORAL TM or METAMIC TM , if 30% or more of boron is added during manufacturing, mechanical performance is lowered, which causes problems in workability as a neutron absorber with required durability.
이후에, 모재에 준비된 혼합분말을 열용사(thermal spray coating) 방식에 의해 코팅하여 중성자 흡수재가 제조된다. 열용사 방식은 3500-15,000K의 고온의 열원에 의한 열에너지와 고압 공정가스의 유입에 의한 운동 에너지가 유동장 내에서 열/운동량 전달을 통해 입자를 용융시키고, 일정 이상의 속도로 가속시킴으로써 코팅 대상 모재 면과의 충돌 시 입자의 퍼짐 혹은 일부 소성변형과 급속 응고과정을 거쳐 모재와 접합을 형성한다. 열용사에 의해 형성된 코팅의 미세조직은 층상 구조(lamellar structure)를 가진다. 열용사 방식에는 플레임용사(flame spray), 플라즈마용사(plasma spray), 아크용사(arc spray), 고속 산소-연료 (High Velocity Oxygen-Fuel : HVOF) 용사, 고속 공기-연료 (High Velocity Air Fuel : HVAF) 용사 등의 방식이 알려져 있다. 제안된 발명은 이러한 알려진 열용사 방식 중 하나를 채택하여 적용할 수 있으며, 혼합분말의 입자가 매우 작은 경우 저온분사 방식도 채택할 수 있다.Thereafter, the neutron absorber is manufactured by coating the mixed powder prepared on the base material by a thermal spray coating method. In the thermal spray method, thermal energy from a high-temperature heat source of 3500-15,000K and kinetic energy from the inflow of high-pressure process gas melt the particles through heat/momentum transfer within the flow field and accelerate it to a certain speed. When colliding with the material, it forms a bond with the base material through the spread of particles or some plastic deformation and rapid solidification. The microstructure of the coating formed by thermal spraying has a lamellar structure. Thermal spray methods include flame spray, plasma spray, arc spray, High Velocity Oxygen-Fuel (HVOF) thermal spray, and High Velocity Air Fuel: HVAF) thermal spraying and the like are known. The proposed invention can be applied by adopting one of these known thermal spraying methods, and when the particles of the mixed powder are very small, a low-temperature spraying method can also be adopted.
바람직한 실시예에서, 플레임용사(flame spray) 방식이 적용되었다. 플레임용사 방식은 산소와 같은 연료가스의 연소를 통해 분말을 가열, 용융하여 코팅한다. 연소에 사용되는 연료가스는 아세틸렌(Acetylene)은 29 NLPM(Normal litre per minute), 산소는 43 NLPM의 속도로 스프레이 건(spray gun)에 공급되고, 혼합분말은 30 g/min의 속도로 공급된다. 일 실시예에서, 316SS 스텐레스강 분말은 밀도가 7.99g/cm2 이고, 녹는점(melting temperature)은 1,371-1,399℃이며, 보론 카바이드 분말은 밀도가 2.52g/cm2 이고, 녹는점은 2,763℃, 끓는점(boiling temperature)은 3,500℃이다. 이때 스프레이 건의 노즐 헤드와 모재간의 거리(standoff)는 5-9인치 정도가 적당하다. In a preferred embodiment, a flame spray method is applied. The flame spray method heats and melts powder through combustion of fuel gas such as oxygen to coat it. The fuel gas used for combustion is supplied to the spray gun at a rate of 29 NLPM (Normal liter per minute) for Acetylene and 43 NLPM for oxygen, and the mixed powder is supplied at a rate of 30 g/min. . In one embodiment, 316SS stainless steel powder has a density of 7.99 g/cm 2 , a melting temperature of 1,371-1,399° C., boron carbide powder has a density of 2.52 g/cm 2 , and a melting point of 2,763° C. , the boiling point is 3,500 °C. In this case, the appropriate distance (standoff) between the nozzle head of the spray gun and the base metal is about 5-9 inches.
이상에서 본 발명을 첨부된 도면을 참조하는 실시예들을 통해 설명하였지만 이에 한정되는 것은 아니며, 이들로부터 당업자라면 자명하게 도출할 수 있는 다양한 변형예들을 포괄하도록 해석되어야 한다. 특허청구범위는 이러한 변형예들을 포괄하도록 의도되었다. Although the present invention has been described above with reference to the accompanying drawings, the present invention is not limited thereto, and it should be construed to encompass various modifications that can be apparent from those skilled in the art. The claims are intended to cover such modifications.
Claims (7)
상기 혼합분말을 열용사(thermal spray coating) 방식 및 저온분사 방식 의해 모재에 코팅하는 단계;
를 포함하는 중성자 흡수재 제조 방법.Boron carbide (B 4 C) or boron nitrite (BN) powder with a weight ratio of 30-70%, and crystalline high corrosion resistance alloy powder with a weight ratio of 70-30% as a binder. Iron (Fe), chromium (Cr) and nickel (Ni) as a basic composition and preparing a mixed powder mixed with a stainless steel alloy powder having an austenite structure;
coating the mixed powder on a base material by a thermal spray coating method and a low temperature spray method;
A neutron absorber manufacturing method comprising a.
The method according to claim 6, The thermal spray coating is a fuel gas used for combustion, Acetylene is supplied to the spray gun at a rate of 29 NLPM (Normal liter per minute) and oxygen is 43 NLPM, and the mixed powder is A method of manufacturing a neutron absorber, supplied at a rate of 30 g/min, with a standoff between the nozzle head and the base material in the range of 5 to 9 inches.
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