Improvement technique of sensitized HAZ by GTAW cladding applied to a BWR power plant
A SCC(Stress Corrosion Cracking)-resistant technique, in which the sleeve installed by expansion is melted by GTAW process without filler metal with outside water cooling, was developed. The technique was applied to ICM (In-Core Monitor) housings of a BWR power plant in 1993. The ICM housings of which materials are type 304 Stainless Steels are sensitized with high tensile residual stresses by welding to the RPV (Reactor Pressure Vessel). As the result, ICM housings have potential of SCC initiation. Therefore, the improvement technique resistant to SCC was needed. The technique can improve chemical composition of the housing inside and residual stresses of the housing outside at the same time. Sensitization of the housing inner surface area is eliminated by replacing low-carbon with proper-ferrite microstructure clad. High tensile residual stresses of housing outside surface area is improved into compressive side. Compressive stresses of outside surface are induced by thermal stresses which are caused by inside cladding with outside water cooling. The clad is required to be low-carbon metal with proper ferrite and not to have the new sensitized HAZ (Heat Affected Zone) on the surface by cladding. The effect of the technique was qualified by SCC test, chemical composition check, ferrite content measurement and residual stresses measurement etc. All equipment for remote application were developed and qualified, too. The technique was successfully applied to a BWR plant after sufficient training.
- OSTI ID:
- 234167
- Report Number(s):
- CONF-9411168-; ISBN 0-87171-444-2; TRN: IM9624%%208
- Resource Relation:
- Conference: Maintenance and repair welding in power plants V, Orlando, FL (United States), 30 Nov - 2 Dec 1994; Other Information: PBD: 1995; Related Information: Is Part Of Maintenance and repair welding in power plants 5: Proceedings; PB: 269 p.
- Country of Publication:
- United States
- Language:
- English
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