Current trends in the use of Zirconium Alloys

THE development of zirconium and its alloys for use in nuclear reactors began in the United Statesin 1948 when it was found that hafnium-free zirconium had a much lower neutron-absorption crosssection than had previously been suspected. Structural materials for use in water-cooled power reactors must possess a combination of high stre-ngth, corrosion resistance and low neutron capture cross-section. Zirconium alloys alone have the required combi-nation of these. For almost a decade the standard zirconium alloy for use in water-cooled reactors has been zircalov-2. A very considerable body of experience in the fabrication and use of zirconium alloys has been built up. It has been demonstrated that zircaloy tubes can be manufactured to specifications far more exacting in their requirements than is the case for standard code specifications for heat exchanger and condenser tubes

Eddy Current Testing of Zirconium Wires

FUEL bundles for Rajasthan Atomic Power Reactor, as per the design, consist of a cluster of 19 elements held together by zircaloy end plates and spaced by wire helices on the six elements of the inner ring and alte-rnate elements of the outer ring. Each element is a zircaloy-2 tube 495 min long,1524 mm in diameter and of 0.4 nom wall thickness containing the nuclear fuel in the form of sintered uranium dioxide pellets and sealed at both ends. In order to provide the required spacing between the elements, zircaloy wire of 1.25 mm dia. is spot-welded around the elements in the helix form. The wire helices serve to separate the elements to maintain the dimensions of the coolant sub-channels between them and to increase the mixing of coolant between inner and outer sub-channels. Zircaloy wire of 1.63 mm dia. is spot-welded on the outer elements so as to provide bearing surfaces for the bundle when it moves through the fuel channels in the coolant assemblies