Nuclear power reactors alloys

Zirconium is used as a containment material for the uranium oxide fuel pellets in nuclear power reactors (see Nuclearreactors). Zirconium is particularly usehil for this appHcation because of its ready availabiUty, good ductiUty, resistance to radiation damage, low thermal-neutron absorption cross section 18 x 10 ° ra (0.18 bams), and excellent corrosion resistance in pressurized hot water up to 350°C. Zirconium is used as an alloy strengthening agent in aluminum and magnesium, and as the burning component in flash bulbs. It is employed as a corrosion-resistant metal in the chemical process industry, and as pressure-vessel material of constmction in the ASME Boiler and Pressure Vessel Codes. 

Nuclear power reactors have the following safety issues nuclear waste, plutonium buildup and radioactivity. Nuclear waste from the reactor fuel consists of uranium that has been formed into a usable metal alloy and provided as small pellets, rods, or plates. The fuel is encapsulated with a metal cladding, such as zircaloy, which adds mechanical strength and also prevents radioactive contamination. 

The LI 2 phase ZrjAl, which forms peri-tectically from ZrjAl and Zr, was studied extensively for use as the cladding material for water-cooled, nuclear power reactors since it has a low cross section for the absorption of thermal neutrons (Schulson, 1984 Liu et al., 1990 Parameswaran et al., 1990). In particular, the mechanical behavior was the subject of detailed studies (Schulson, 1984) according to which the strength is high with an anomalous temperature dependence for the flow stress. The work hardening rate exceeds that for any disordered or ordered f.c.c. alloy. ZrjAl, with polished surfaces, has a ductil-... 

Corrosion of metals and alloys—Aqueous corrosion testing of zirconium alloys for use in nuclear power reactors... 

The development of water-cooled nuclear power reactors brought about the use of zirconium and its alloys for uranium fuel cladding and for structural components. As a result of these developments in the nuclear industry, the cost of zirconium and its alloys decreased considerably and became competitive... 

Sheeks, C. J., Moshier, W. C., Ballinger, R. G., Latanison, R. M., Pelloux, R. M. N., Fatigue crack growth of Alloys X750 and 600 in simulated PWR and BWR environments , Proc. 1st Int. Conf. on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, Myrtle Beach, USA, 22-25 Aug. 1983, NACR pp. 701-25 (1984)... 

Nuclear and magneto-hydrodynamic electric power generation systems have been produced on a scale which could lead to industrial production, but to-date technical problems, mainly connected with corrosion of the containing materials, has hampered full-scale development. In the case of nuclear power, the proposed fast reactor, which uses fast neutron fission in a small nuclear fuel element, by comparison with fuel rods in thermal neutron reactors, requires a more rapid heat removal than is possible by water cooling, and a liquid sodium-potassium alloy has been used in the development of a near-industrial generator. The fuel container is a vanadium sheath with a niobium outer cladding, since this has a low fast neutron capture cross-section and a low rate of corrosion by the liquid metal coolant. The liquid metal coolant is transported from the fuel to the turbine generating the electric power in stainless steel... 

The most important applications of zirconium involve its alloys, Zircaloy. The aUoy offers excellent mechanical and heat-transfer properties and great resistance to corrosion and chemical attack. This, in conjunction with the fact that zirconium has a low neutron absorption cross section, makes this ahoy a suitable choice as a construction material for thermal nuclear reactors and nuclear power plants. Other uses are as an ingredient of explosive mixtures, as getter in vacuum tubes, and in making flash bulb, flash powder (historical), and lamp filaments, in rayon spinnerets, and in surgical appliances. 

The most important application of zirconium is in the formulation of the base metal in an alloy of 98% zirconium. 1.5% tin, 0.35% lron-chromium-mckel. and 0.15% oxygen, This alloy is widely used in water-cooled nuclear reactors because of its excellent corrosion resistance up to about 350 in H 0, and its low neutron cross section. Currendy, about 90% of the zirconium produced is used for this application. The excellent corrosion resistance of zirconium to both strong acids and alkalis, particularly its resistance to strong caustic solutions at all concentrations and temperatures, is attracting increasing attention for application in chemical processing equipment, See also Nuclear Power Technology. 

Another potential use for holmium is a result of its very unusual and strong magnetic properties. It has been used in alloys with other metals to produce some of the strongest magnetic fields ever produced. Holmium also has some limited use in the manufacture of control rods for nuclear power plants. Control rods limit the number of neutrons available to cause the fission of uranium in nuclear reactors, thus controlling the amount of energy produced in the plant. 

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