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Reactor Heat Transfer
Published in G. Vaidyanathan, Dynamic Simulation of Sodium Cooled Fast Reactors, 2023
Boron in the form of boron carbide (B4C) is used as absorber rod material for controlling the power of the nuclear reactors. Natural boron contains 20% B10, and the rest is the B11 isotope. B10 is the isotope with neutron absorption properties. While water reactors use natural boron, fast reactors use boron enriched in B10 to ~60–70%. Boron swells on absorption of a neutron due to the production of helium. This necessitates replacement of control rods once in ~2 years. Tantalum is being considered as a possible substitute, primarily because of its favorable swelling characteristics and availability. The disadvantage is the 115-day half-life gamma decay from Ta182 to W182, which causes long-term decay heat removal problems. Also, Ta is soluble in sodium. Europium oxide is another candidate. It has twice the neutron absorption capability compared to boron. However, it has many disadvantages from reactivity and low thermal conductivity considerations. In light of this, boron is continued to be used as an absorber material in control rods.
Recent Advances in Boron-Based Flame Retardants
Published in Yuan Hu, Xin Wang, Flame Retardant Polymeric Materials, 2019
Boron carbide is produced industrially by the carbo-thermal reduction of B2O3 in an electric arc furnace. It is a black powder and has a melting point of 2445°C. It was reported (Kobayashi et al. 1995) that the addition of boron carbide (10–15 wt%) in a variety of intumescent coatings containing ammonium polyphosphate, and blowing agent resulted in improving weight retention, compression strength, and peel strength during fire. More important, it can retard oxidative weight loss of the foamed layer at 1000°C or even higher. The effect of boron carbide nanoparticles on fire resistance of carbon fiber/epoxy composite was evaluated (Rallini et al. 2013). The flame resistance was evaluated through residual mechanical properties after the exposure of the specimens to a direct torch with a heat flux of 500 kW/m2. It was demonstrated that boron carbide improves the thermal stability of the composite and inhibits the thermal oxidation of the carbon fiber.
Advances and Applications of Nontraditional Machining Practices for Metals and Composite Materials
Published in T. S. Srivatsan, T. S. Sudarshan, K. Manigandan, Manufacturing Techniques for Materials, 2018
Ramanathan Arunachalam, Rajasekaran Thanigaivelan, Sivasrinivasu Devadula
Boron carbide is one of the most widely used ceramics. Boron carbide nozzles are manufactured by hot-pressing. Because of its improved mechanical property, such as high hardness, high melting point, better wear resistance, high Young’s modulus, good chemical inertness, and high thermal conductivity, boron carbide is a widely used material in modern engineering applications and is a promising candidate for wear resistance components (Deng 2005). The third hardest material after diamond and cubic boron nitride is boron carbide. Abrasive jet machining nozzles are made of dense sintered boron carbide (Deng 2005); these nozzles are extremely hard and wear resistant and have a long life. Because of their low wear rate, boron carbide nozzles can maintain the internal geometry and minimum compressor requirement and deliver maximum blasting effectiveness as well as save nozzle replacement downtime.
Laser powder bed fusion as a net-shaping method for reaction bonded SiC and B4C
Published in Virtual and Physical Prototyping, 2022
Sebastian Meyers, Miquel Turón Vinãs, Jean-Pierre Kruth, Jef Vleugels, Brecht Van Hooreweder
Carbide ceramics have a number of desirable properties that make them highly suitable for various engineering applications. Two of the most widely used carbide ceramics are silicon carbide and boron carbide. Silicon carbide (SiC) is a lightweight ceramic with a high Young’s modulus, excellent corrosion resistance, a high thermal conductivity and a low thermal expansion coefficient. It is used as a structural material in high-temperature furnaces, in the automotive industry as high-performance brake discs and diesel particulate filters, in thermal management applications and in the aerospace industry for precision instrumentation, telescope mirrors or heat exchangers. Boron carbide (B4C) can be found in applications that make use of its excellent wear resistance, like nozzles for water jet cutting or grit blasting, but also as a structural material in armour and in nuclear applications such as control rods or radiation shielding.
Influence of tool traverse speed on microstructure and mechanical properties of CuNi/B4C surface composites
Published in Transactions of the IMF, 2021
G. Suganya Priyadharshini, T. Satish Kumar, N. Anbuchezhian, R. Vaira Vignesh, R. Subramanian, T. Velmurugan, K. Kamal Basha
Among the various particulates available as reinforcements, boron carbide (B4C) possesses a unique combination of properties such as high melting point, good hardness and mechanical properties, and low specific weight.16 Hence, it is a material of choice for engineering applications.17 B4C with its high hardness and adequate fracture toughness improves the hardness and impact strength in aluminium alloys.18 Beside this, reinforcing B4C improves the hardness, wear-resistance, and ultimate compression strength of aluminium matrix composites.19 Composites of magnesium alloy reinforced with B4C have shown improved density, microhardness, bending strength, and elastic modulus compared to that of the base material.20
Features of a control blade degradation observed in situ during severe accident conditions in boiling water reactors
Published in Journal of Nuclear Science and Technology, 2019
Anton Pshenichnikov, Saishun Yamazaki, David Bottomley, Yuji Nagae, Masaki Kurata
Boron carbide is being used in BWR reactors for regulation of neutron spectrum for absorbing and reducing the number of neutrons and is the chain reaction control mechanism. The configuration of absorber material in the test sample is important to be representative; therefore, in order to approach real accident conditions as much as possible, we used a typical Japanese BWR test assembly design. Two groups of claddings were encased in two channel boxes. The distance between claddings was maintained by original spacers from the Japanese BWR reactor in order to have prototypic gaps between parts of an experimental assembly. This is very important because it is one of the main factors directly influencing the absorber melt relocation features and its impact on the channel box (Figure 3).