In a Nuclear Power Station, cooling ponds are used to store “spent” Magnox fuel rods prior to transportation for re-processing. The ponds need reliable level control and monitoring for safe operation. The cooling ponds are divided into three separate sections, and each section requires a continuous level measurement with backup high and low alarm points. If the level gets too high, there is risk of overfilling the pond. If the level gets too low, there is indication of a system leak.
The maintenance engineers sought to improve the reliability of the cooling pond system by upgrading the level measurement and adding redundant alarms. They wanted a simple solution to provide alarm monitoring and continuous level measurement that could relay back to a Programmable Logic Controller (PLC). Additionally, access was limited and clearance for an over-head crane had to be allowed above the level instruments. Therefore, the new system would have to be installed on a simple cantilevered mounting plate secured to the cooling pond dividing walls. Without an upgraded system, this customer risked increasing maintenance costs and overfilling the ponds. The cooling ponds are mildly radioactive and create a safety and environmental risk if flooded into a non-hazardous area. Likewise, an unreliable level measurement might not detect a pond leak which also resulted in a safety and environmental risks.
This could installed three Ultrasonic Level transmitters on a flat mounting plate to provide a continuous measurement of level in all three chambers of the cooling pond. Additionally, six Vibrating Fork Switches were installed on three separate plates (2 per mounting plate) to provide a back-up alarm for High and Low level in each section. The new system of level controls was easy to install and provided a low maintenance solution which reduced maintenance costs. The overall system reliability was increased which reduced the safety and environmental risks of overfills and leakage.