Westinghouse Electric Corporation

Fredric W Pement

Bruce W Bevilacqua

Robert D Burack

Wenche W Cheng

Donald R Stoner

Richard J Jacko

George C Economy

Judith B Esposito

John N Esposito

Joseph M Gilkison

Alfred W Klein

A primary coolant circuit for cooling a nuclear reactor has wetted mechanically stressed nickel base alloy components such as Alloy 600 tubes in steam generators having oxidized surfaces comprising 1-10 w/o zinc, which tubes are inhibited against primary water stress corrosion cracking. The crack initiation times may be delayed by a factor of two in pressurized water nuclear reactors.

Inhibiting stress corrosion cracking in the primary coolant circuit of a

Both an improved method and apparatus for determining, on an accelerated basis, the susceptibility of a nickel-based alloy to suffer stress corrosion cracking within a steam generator environment is disclosed herein. The method generally comprises the steps of subjecting a mechanically stressed specimen of the alloy to a mixture of steam and hydrogen at a temperature of between about 365.degree. C. to 435.degree. C., wherein the partial steam pressure is between about 10.4 MPa to 30.4 MPa, and the partial hydrogen pressure is between about 32 kPa to 500 kPa. The improved testing apparatus of the invention generally comprises a vessel for containing a stressed specimen and a pressurized atmosphere formed of steam and hydrogen, and an inlet cell for injecting a selected amount of hydrogen into the pressurized atmosphere of the vessel which includes a diffusion membrane which is permeable to hydrogen but impermeable to the remainder of the pressurized atmosphere. The inlet cell has a tubular housing having a wall formed from a thin layer of hydrogen permeable palladium-silver alloy. The tubular housing contains a gas permeable sponge formed by sintered particles of stainless steel to prevent the thin layer of palladium-silver alloy used in the hydrogen diffusion membrane from imploding in response to the pressure within the vessel.

Apparatus for conducting accelerated corrosion testing of nickel alloys

A process for thermally stress-relieving a stressed portion of a metallic tube is disclosed herein. The process generally comprises the steps of inserting a small diameter radiant heater into the open end of the metallic conduit and then positioning it adjacent to the portion to be stress relieved, and heating this portion to a temperature between about 1150.degree. F. to 1500.degree. F. for a time period of between about four and twelve minutes, depending upon wall thickness. In order to determine the proper amount of electrical power to apply to the radiant heater, the emissivity of the stressed portion of the conduit is first measured by heating a portion of the section to incandescence at a known power level, and then determining the temperature of the incandescent tube by means of a pyrometer which compares the intensity of two selected colors or wavelengths of the transmitted light. This process is particularly useful in thermally stress-relieving the U-bends of heat exchanger tubes formed from Inconel.RTM. 600 that are used in nuclear steam engines. It may also be used to stress-relieve such heat exchanger tubes in regions where the reinforcing sleeves have been welded into their interiors. Such thermal stress relieving renders the tubes less susceptible to intragranular stress corrosion cracking.

Process for thermally stress-relieving a tube

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Pittsburgh, PA, United States of America

Fredric W Pement