In the 1950’s many countries were interested in using energy from nuclear fission to make electricity. The heat from the nuclear reaction would be transferred to a liquid or gas and ultimately to steam to drive turbines. If water was to be used to transfer the heat then it had to be under high pressure to remain liquid. Many countries opted to contain the pressure in a large steel vessel and use thin tubes to guide the water over the fuel.
In Canada AECL, Ontario Hydro and Canadian General Electric (CGE) were working on a small reactor to demonstrate the feasibility of Nuclear Power. The initial design used a steel pressure vessel, but it was then found that no Canadian company could manufacture the vessel to the required quality standard.
In the USA a reactor had been designed to use tubes made from Zircaloy-2 to both guide the flow of water over the fuel and contain the required water pressure. The 1004 tubes were 53 feet long, 3 inches inside diameter and a wall thickness of 0.275 inches. At that time only small diameter, thin-walled tubes had been made from Zircaloy-2 to contain nuclear fuel. Three American companies that had large enough extrusion presses and suitable equipment to cold work the extruded tubes to size and increase their strength were given contracts to try and make the tubes, Harvey Aluminum, Carborundum and The Chase Brass and Copper Company. Each company made tubes to the specifications and these tubes were used to construct Hanford N reactor.
Based on this information the NPD (Nuclear Power Demonstration) reactor, the first CANDU reactor, was redesigned to use 132 Zircaloy-2 pressure tubes 20 feet long, 3 1/4 inches inside diameter and wall thickness of 0.165 inches to contain the fuel bundles and heavy water for heat transfer. The Chase Brass and Copper Company were given a contract to make a trial batch of tubes using a process similar to the Hanford N reactor tubes. The tubes were satisfactory and CGE built NPD. The Chase Brass and Copper Company, which later became Nu Tech, has made almost all the tubes for subsequent CANDU reactors.
