Pressure pipe made of zirconium alloy

Abstract

Abstract PURPOSE:To provide a pressure pipe made of Zr alloy used for heavy water reactors or the like with a protective oxidized film on the surface of the body maintaining residual compressive stress through a hot water autoclave treatment at a temperature lower than that of relaxation following peening of the surface. CONSTITUTION:After a drawing of the body of a pressure pipe, a shot peening is applied to smooth fine cracks on the surface thereof employing a steel ball or the like while a residual compressive stress is given up to about 1 mm under the surface. Then, the body of the pipe is inserted into a hot water autoclave and retained for about 5 hours at a temperature below 400 deg.C under which a creep deformation is hard to take place whereby a protective oxidation film 3 is formed on the surface of the body. This makes the residual compressive stress by the peening larger than the stress W' when an inner pressure P is applied on the body of the pipe. Consequently, the inner surface thereof is invariably subjected to a compressive stress allowing hydride 2 to be parallel to the stress thereby minimizing the possibility of flucture due to a delay in hydrogen. In addition, oxidation by cooling water can be prevented.

Inventors

• 👤 Tsutomu Masumoto
• 👤 Saburo Usami

Bibliographic Details