Oriented Spray Cooling System Ultimate Heat Sink for Future Nuclear Plants

The reference safety-related ultimate heat sink (UHS) for the evolutionary advanced light water reactor nuclear plants that require a safety-related reactor service water system (RSWS) is a spray pond. Spray ponds offer significant advantages over mechanical draft cooling towers including superior simplicity and operability, lower preferred power requirements, and lower capital and maintenance costs. The UHS for the Columbia Generating Station (CGS), one of the last nuclear plants that was licensed during the last round of nuclear plant construction in the United States of America (USA), is the Oriented Spray Cooling System (OSCS), an evolutionary spray pond design. Unlike a conventional spray pond in which spray nozzles are arranged in a flat bed and spray upward, the OSCS nozzles are mounted on spray trees arranged in a circle and are tilted at an angle oriented towards the center of the circle. As a result, the water droplets drag air into the spray region while the warm air that is concentrated in the center of the circle rises. Both of these effects work together to increase air flow through the spray region. Increased air flow reduces the local wet-bulb temperature (LWBT) of the air in the spray pattern, promoting heat transfer and more efficient cooling. During the late 1970’s while working for the Tennessee Valley Authority, the author developed a purely analytical model to predict the thermal performance of the OSCS which was successfully compared with the OSCS at the CGS in the mid 1980’s. This paper describes the OSCS and the analytical model that is used to predict its performance and compares the predicted performance of the OSCS at the CGS with the full-scale field test results. The paper describes how this technology has been successfully used to design the UHS for a future nuclear plant that requires a safety-related RSWS that must not exceed a peak temperature of 95 °F.