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Rotary Gear Pumps: Chemical feed water treatment applications at nuclear power plants

Huge quantities of water are used in nuclear power plants for a variety of operations. As such, there are a number of chemical processes that the water has to go through before it can be released back into the environment. When it comes to water treatment applications, small rotary gear pumps can be used as a means of improving performance rates, maintenance and costs.
 
By Karen Eisemann, Director of Customer Service / Rotary Product Manager, Pulsafeeder Engineered Products.

There’s a reason nuclear power plants are located near an abundant water source, such as a river, lake or an ocean. It is because they typically pump more than 500,000 gallons of water per minute through heat exchangers in their circulating water systems. These systems cool the plant’s condensers and they remove heat from the steam that exits the plant’s main turbine. Nuclear plants also have service water systems that are used to cool air compressors, lube oil systems and other systems related to the safe shutdown of the reactor. Without enormous quantities of water, nuclear power plants cannot operate. However, quantity alone is not all that matters – the quality of the water has a direct impact on the plant’s efficiency. That’s why all of the water used must be filtered and cleaned during use and before being discharged back into the environment.   

The initial screening comes from large external filters that trap large debris. Once the water has entered the plant’s circulating system it must be cleaned via chemical feed processes in order to manage micro-bio organisms and to prevent scaling, corrosion and foulants from hindering the efficiency of the condenser. Clean condenser heat transfer surfaces have a direct impact on a plant’s operating efficiency and failing to prevent micro-bio fouling can lead to expensive plant de-rates and unplanned outages. To clean the water, chemicals such as sulfuric acid and sodium hypochlorite solutions are metered via rotary gear pumps. These applications feature exceedingly high flow rates and relatively low pressures.

Traditional demineralizer systems are also utilized in the power industry to purify water for the steam generating loop. These systems remove contaminants that can negatively affect the steam generator’s performance. Large ion exchange resin beds remove contaminants by substituting H+ ions and OH- ions for dissolved salts in the source water. The resultant water is pure and essentially free of any dissolved salts. When exhausted, the resins are re-generated by using sulfuric acid and sodium hydroxide. This re-generation requires large dosing rates at relatively low pressures. After the water is used it is discharged back into the environment, but before doing so, it is treated with a de-chlorination chemical, such as sodium meta-bisulfite. In cases where high dosing rates are required, the de-chlorination chemicals can be metered out by rotary gear pumps.

To read more of this article please contact the editor, Deirdre Morgan.


 

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