Shippingport Atomic Power Station steam generator tube damage and water chemistry control (1965--1975)

The four stainless steel tubed steam generators in the Shippingport Atomic Power Station were replaced in 1964 with larger, horizontal, NiCrFe Alloy 600 tubed units consistent with a power uprating of the plant. Each of the four Alloy 600 tubed units experienced tube leakage attributed to corrosion by water treatment chemicals (sodium phosphates) which concentrated locally on the tubes in inadequately flushed crevices. Corrective and preventive actions include tube plugging, flow blockage, conversion to all-volatile (hydrazine-morpholine) chemistry and replacement of the two steam generators with the straight tube design. Eddy current inspection after four years of all-volatile chemistry use showed a diminished rate of crevice corrosion and no tube denting

Steam generator tube denting simulation testing. [PWR]

Tube denting has been reported in steam generators in a number of commercial nuclear power plants in recent years. In order to aid in understanding of the mechanism leading to tube denting in the steam generators, a Bettis laboratory test program was initiated to attempt to reproduce tube denting and to investigate the effects of chemistry, design, and temperature. The results of the tests indicate that denting can be reproduced in the small model steam generator test apparatus devised for this testing. Denting was observed under carbon steel support plates in seawater-contaminated secondary water in a test with hydrazine-ammonia chemistry and a primary water inlet temperature of 590/sup 0/F and in a test with hydrazine-morpholine chemistry and a primary water inlet temperature of 545/sup 0/F. The parameters of these two tests simulate conditions in a typical commercial steam generator and the Shippingport Atomic Power Station steam generators, respectively