SEDL / STP / STP754-EB / STP37055S

High-Strength, Creep-Resistant Excel Pressure Tubes

Cheadle, BA
Research officers, Atomic Energy of Canada Limited, Research Company, Chalk River, Ont.

Holt, RA
Research officers, Atomic Energy of Canada Limited, Research Company, Chalk River, Ont.

Fidleris, V
Research officers, Atomic Energy of Canada Limited, Research Company, Chalk River, Ont.

Causey, AR
Research officers, Atomic Energy of Canada Limited, Research Company, Chalk River, Ont.

Urbanic, VF
Research officers, Atomic Energy of Canada Limited, Research Company, Chalk River, Ont.

Pages: 15    Published: Jan 1982

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Abstract

Pressure tubes for CANada Deuterium Uranium Pressurized Heavy Water reactors are made from Zr-2.5Nb by extruding preheated hollow billets into tubes that are cold-worked 30 percent to size. The fabrication process produces fine elongated α-grains with a high dislocation density which makes a large contribution to the tensile strength of the tubes but increases in-reactor creep and growth rates.

The alloy Excel (Zr-3.5Sn-0.8Mo-0.8Nb) is stronger and more creep resistant than Zr-2.5Nb and is being developed as a pressure tube material. Tubes have been fabricated that are as strong as the Zr-2.5Nb tubes but they have more equiaxed α-grains with much lower dislocation densities. The tubes corrode faster than the Zr-2.5Nb tubes and will require 0.1 mm more corrosion allowance on the 4.1-mm-thick walls. However, their in-service axial elongation and diametral expansion due to irradiation creep and growth will be 70 percent less than the Zr-2.5Nb tubes.