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Thermal Energy Production in Nuclear Power Plants
Published in Robert E. Masterson, Nuclear Reactor Thermal Hydraulics, 2019
Cladding materials used today have a very high thermal conductivity, and as a rule of thumb, they also have good resistance to the radiation produced by the fuel. Zircaloy is a much better material than stainless steel is in this regard. It has a very low absorption cross section for thermal neutrons, and because of this, it does not absorb as many neutrons. There are two versions of Zircaloy in widespread use today: Zircaloy-2, which is used primarily in BWRs, and Zircaloy-4, which is used primarily in PWRs. The properties of these two alloys are compared in Table 5.6. Notice that Zircaloy-4 has a slightly more iron and chromium than Zircaloy-2. It also has much less nickel. The amount of tin and zirconium in both of these alloys is about the same. Most reactors use cladding that is between 0.40 and 0.70 mm thick. An excellent article discussing the physical properties of these two alloys is available at the following URL: http://web.ornl.gov/info/reports/1962/3445605716311.pdf.
Essentials of Nuclear Power
Published in David Hart, Nuclear Power in India, 2019
The fabrication stage of fuel processing involves the production of either uranium metal or refractory uranium dioxide, and their encasing in the form of long thin rods in a suitable material. This material must retain the radioactive fission products (the new atoms consisting of the fragments of 235U) in the fuel, and yet not hinder the chain reaction process through neutron absorption. The material usually used these days is zircaloy. Zircaloy is an alloy of zirconium which is commonly used as a structural material in reactor cores because it has a low neutron capture cross-section and good resistance to corrosion even in water at high temperatures. It is, however, rather expensive. Fabrication is carried out in very clean conditions to avoid contaminating the fuel with neutron-absorbing foreign bodies.
Pressurized Water Reactors
Published in Kenneth D. Kok, Nuclear Engineering Handbook, 2016
The fuel assembly design provides optimum core performance by minimizing neutron absorption in structural materials and maximizing heat-transfer capabilities. Mixing vane grids increase the heat-transfer capability of the fuel rods. High fuel utilization is achieved by minimizing the parasitic absorption of neutrons in the core. In the assembly design, the only structural materials in the fuel region are the spring clip grids, Zircaloy control rod guide thimbles, and Zircaloy fuel cladding. Zircaloy is used because it absorbs relatively few neutrons and has good mechanical and heat-transfer properties.
Machining of Zircaloy-2 using progressive tool design in EDM
Published in Materials and Manufacturing Processes, 2022
Jitendra Kumar, Tarun Soota, S.K. Rajput
Decreasing trend of SR was observed on increase in rake angle (T3, T5, and T7), and minimum SR was observed with tool T7, which was also less than conventional tool (T1) as shown in Fig. 5(c). The rake angle provides proper flushing of debris particle from machined surface, and therefore deposition of debris (metal oxide and carbide)[18] were reduced (Figs. 6(c,d)) and 7(c,d)). An increase in value of SR was observed on increase in relief angle (T2, T8, and T10), and maximum SR was on T10 (6.523 µm), which was also more than conventional tool (T1) as shown in Fig. 5(c). Zircaloy-2 is used in BWR (boiling water reactor), power plant core and structural components of nuclear power plant. In these applications low SR value is required[29] to minimize the hydrogen ingress on machined surface.[19] When through hole is made on the surface of Zircaloy-2 using different designed tools, the diameter of hole at inlet is larger than the tool diameter and is known as radial over cut (Roc). Equation 4 is used to calculate Roc, and the outcomes of Roc are enlisted in Table 4. If the diameter of the produce hole in exit is smaller than the tool diameter then it is called radial undercut (Ruc), and calculated by Eq. 5 and given in the Table 4. Figure 10 shows inlet and outlet diameter of the machined hole.
Investigative Study of Neutronic Safety Parameters of HPR and EPR Using the MCNP Code
Published in Nuclear Technology, 2020
R G. Abrefah, P. M. Atsu, R. B. M. Sogbadji
The HPR-1000 reactor core generates 3050 MW (thermal) of thermal power with an average linear power density of 173.8 W‧cm–1 (Ref. 6). The reactor core is loaded with 177 China Fuel Series (CF3) fuel assemblies, ensuring sufficient thermal margin while increasing output power. The CF3 fuel assembly is composed of 264 fuel rods arranged within a 17 × 17 supporting structure. The fuel rods contain UO2 pellets or Gd2O3-UO2 pellets.6 Zircaloy is used as cladding material for the fuel pins. The CF3 has excellent performance and is applicable for a long refueling cycle. Three independent means exist for core reactivity and power distribution control: burnable absorber of gadolinium (Gd2O3) poisons, rod cluster control assemblies (RCCAs), and soluble boron absorber. The RCCA comprises 24 control rods fastened to a spider connector. The absorber material used in the control rod is Ag-In-Cd alloy or stainless steel. The HPR-1000 is designed with a thermal margin greater than 15% to improve safety and operational performance.6
Machining and optimization of Zircaloy-2 using different tool electrodes
Published in Materials and Manufacturing Processes, 2021
Jitendra Kumar, Tarun Soota, S.K. Rajput, Kuldeep K. Saxena
Zirconium alloys have high corrosion resistance, low thermal neutron absorption capacity, and high ductility. Due to bio-compatibility, it is used in knee and hip implants in human body. High corrosion resistance makes it suitable for use in chemical, liquefied natural gas, and oil industries. In nuclear industry, Zircaloy-2 was used for cladding fuel rod. Non-traditional machining EDM (electrical discharge machining) has a capability to produce dies and molds, parts for the aerospace industry, structural component of the nuclear power plant, surgical components, and so on with high precision and accuracy.[1] High strength material can undoubtedly machine utilizing EDM with high precision and accuracy.