Infrared applications for steam turbine condenser systems

Infrared inspection of the main steam condensers at the Peach Bottom Atomic Power Station has been utilized successfully in detecting condenser air in-leakage problems. Air in-leakage lowers the condenser's vacuum, thus decreasing the condenser's efficiency. This creates backpressure on the turbine which lowers its efficiency, resulting in fewer megawatts generated. Air in-leakage also creates an increase in off-gas flow which is a radiological concern for both the plant and the public. Inspections are normally performed on the condenser's manway covers and rupture disks prior to an outage during coast down and post outage. The optimum conditions are 100% power and temperature, however, a high radiation field prevents the inspection until reactor power is down to 65% or less. Anomalies are typically indicated by cooling in the effected areas of the air in-leakage. The anomalies are not limited to air in-leakage. Intermittent water out-leakage, due to a heater dump valve cycling, has been detected when visual inspections find nothing. Infrared inspections have also detected delamination on various rupture disk surfaces. Although air in-leakage has not been associated with the rupture disk delamination anomalies, their conditions are trended to determine any changes. The use of infrared reduces the amount of radiological dose normally associated with smoke tube inspections by shortening the inspection time. The accuracy of locating condenser air in-leakage is also improved with the use of infrared.