Effects Of Alloys And Flow Velocity On Welded Pipeline Wall Thinning In Simulated Secondary Environment For Nuclear Power Plants

The pipelines and equipments are degraded by flow-accelerated corrosion (FAC), and a large-scale test facility was constructed for simulating the FAC phenomena in secondary coolant environment for PWR type nuclear power plants. Using this facility, the FAC test was performed on a weld pipe (carbon steel and low alloy steel) under the high velocity flow conditions (> 10 m/s). Wall thickness was measured by high temperature ultrasonic monitoring systems (four-channel buffer rod type and waveguide type) during the test period and the room temperature manual ultrasonic method before and after the test period. This work deals with the complex effects of flow velocity on wall thinning of a weld pipe, and the test results showed that higher flow velocity induced different increments in the wall thinning rate for the carbon steel and low alloy steel pipe.