Reactor nickel-clad

To avoid corrosion, cast iron, enamel or nickel-clad reactors, and plastic HCl pipelines (e.g. from phenol-formaldehyde resins or polyvinylidene fluoride) or glass or enamel pipes are employed iron Raschig rings are used as the catalyst, placed as a layer on the reactor base. 

Because of its low neutron absorption, zirconium is an attractive stmctural material and fuel cladding for nuclear power reactors, but it has low strength and highly variable corrosion behavior. However, ZircaHoy-2, with a nominal composition of 1.5 wt % tin, 0.12 wt % iron, 0.05 wt % nickel, 0.10 wt % chromium, and the remainder zirconium, can be used ia all nuclear power reactors that employ pressurized water as coolant and moderator (see... 

Most LWR fuel rod cladding is made of Zircaloy (and its derivatives), which is an alloy of primarily zirconium and tin. Other alloying elements include niobium, iron, chromium, and nickel. Zircaloy was chosen because it has a very low cross section for thermal neutrons. Naturally occurring zirconium contains about l%-5% hafnium. The hafnium must be removed because it has a very high thermal neutron cross section and is often used in making control rods for reactors. The separation process used in the United States is a liquid-liquid extraction process. It is based on the difference in solubility of the metal thiocyanates in methyl isobutyl ketone. In Europe, a process known as extractive distillation is used to purify zirconium. This method employs a separation solvent that interacts differently with the zirconium and hafnium, causing their relative volatilities to change. This enables them to be separated by a normal distillation process. The separated zirconium is then alloyed with the required constituents. 

In the nuclear industry, stainless steel was used to clad the uranium dioxide fuel for the first-generation reactors. But by 1965, the force of neutron economy had made zirconium alloys the predominant cladding material for water-cooled reactors. There was a widespread effort to develop strong, corrosion-resistant zirconium alloys. Noticeably, the Ozhennite alloys were developed in the Soviet Union for use in pressurized water and stream. These alloys contain tin, iron, nickel, and niobium, with a total alloy content of 0.5-1.5%. The Zr-1% Nb alloy also is used in the Soviet Union for pressurized water and steam service. Researchers at Atomic Energy of Canada Ltd. took a lead from the Russians zirconium-niobium alloys and developed the Zr-2.5% Nb alloy. This alloy is strong and heat-treatable. It is used either in a cold-worked condition or a quenched-and-aged condition. 

S. Kasahara, J. Kuniya, K. Moriya, N. Saito, S. Shiga, General Corrosion of Iron, Nickel and Titanium Alloys as Candidate Materials for the Fuel Claddings of the Supercritical-water Cooled Power Reactor, in GENES4/ANP2003, Paper 1132, September 15—19, 2003, Kyoto, Japan. 

The first fast reactors designed as power producers, which will be built within the next decade, will have cylindrical ceramic fuel, clad with stainless steel or nickel alloys, and cooled by liquid sodium. The fuel pins of such a reactor will have the following characteristics ... 

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