Effects of high velocity of steam turbine valves and inlet piping

This paper discusses an approach to the evaluation of the effects of high steam velocity on high pressure turbine control valves and inlet piping. These concerns resulted from proposed modifications to the SONGS Unit 1 high pressure turbine steam path. SONGS 1 is a 450 MW PWR nuclear generating station. Over the 20 years of operation, steam generator performance degraded such that the plant shifted from being reactor limited to turbine limited. Today, the plant can only operate at 92% reactor power. A project was initiated to regain some of the lost power generation capabilities by redesign of the turbine steam path. While evaluating the effects on systems external to the turbine, concerns were raised regarding the adequacy of the steam turbine valves and piping for the expected future conditions. SONGS 1 has two 24 inch (0.6m) turbine stop valves and four 14 inch (0.36m) control valves