Cold-worked Zr—2.5 wt% Nb pressure tubes for Canada Deuterium Uranium pressurized heavy water reactors are made by hot extruding hollow billets into tubes that are cold-worked to size and to develop their tensile strength. All manufacturing steps are closely controlled, and the tubes meet very stringent specifications. To ensure that the tubes are free of unacceptable defects, the ingots, billets, and finished tubes are ultrasonically inspected. The strength and flaw tolerance of the tubes have been measured. Tubes removed from both research and operating power reactors have been examined to measure changes in each of these properties due to the effects of reactor operation. All tests show that cold-worked Zr—2.5 wt% Nb pressure tubes have excellent tensile strength and resistance to failure.