In fact, keeping the nuclear material — or whatever fuel supply — at the core of a power plant cool is absolutely essential and so maintenance of those huge cooling towers we see in photos and news stories is incredibly important.
Since the catastrophic nuclear power plant damage in Japan earlier this year from an earthquake and tsunami, power plants have been more in the news than usual.
The meltdown in Japan occurred mainly due to loss of power to the cooling systems at the plant.
Types of Cooling Towers
Open Cooling Towers – water in these towers comes into contact with the outside air and can pick up contaminants and pollutants.
Closed Loop Cooling Towers – the water in these towers does not come into contact with the outside air.
Forced Draft Cooling Towers – this type of tower has a fan at the top and other fans in the body of the tower to force air through the system.
Mechanical Draft Cooling Towers – connected to a chimney, fans keep air moving.
Factory Assembled Cooling Towers – these towers are shipped almost completely assembled. I’d like to see that truck!
Field Assembled Cooling Towers – these are shipped in their component parts and assembled on site.
All cooling towers need regular maintenance and cleaning.
The water used in cooling towers collects whatever contaminants that can be found in the outside air: dirt, pollen, bacteria, mold; and since power plants are often built near the ocean, they can also collect salt and algae. The frequency with which a cooling tower needs to be cleaned depends on the level of contaminants in the air where it is located.
Keeping in mind that cooling towers are pretty efficient at cleaning the air, they will still accumulate particles of contaminants in the basin which collects the water droplets left after going through the cooling system. How fast these particles accumulate determines how often the cooling tower must be cleaned.
Possible Effects of Improperly Maintained Cooling Towers
If a cooling tower is not cleaned on a proper schedule, the results can range from lower efficiency to environmental disaster.
- A nuclear power plant’s cooling system already uses a tremendous amount of energy. If scale, salt or dust affect the “fill,” which provides the water droplets for cooling, it takes even more energy to run the cooling system.
- Proper cleaning will keep a nuclear power plant cooling system running for more years, amortizing the tremendous cost of building and maintenance.
- Legionnaire’s Disease is a real danger from unmaintained cooling towers. There is a 50% chance of any cooling tower containing these deadly bacteria, even if it is kept clean!
Methods of Cleaning Cooling Towers
There are a few main ways of cleaning nuclear plant cooling towers:
In this method, the basin which collects the water droplets is drained fully and the technician goes into the basin to shovel out or otherwise remove the deposit of bacteria, silt and mud that has collected there. The technician must wear protective garments and a full-face shield or respirator.
This method is wasteful of water, since all of the water in the basin is discarded and it has to be entirely refilled with hundreds of thousands of gallons.
Using the vacuuming method means the technician can stay out of the basin itself and only involves draining about 25% of the water, which can be discarded or re-used. This method is less dangerous to the operator and less wasteful of water — an important and limited resource.
“Diving the tower” can be accomplished while the cooling tower is at work. Wearing a dry-suit — which is completely sealed and attached to tube for air and communications — divers use a vacuum to clean the tower basin, or inspect and even repair the tower while it is running!
The San Onofre nuclear power plant here in Southern California does not have cooling towers. It uses ocean water to cool the nuclear fuel and a lot of it — plants with cooling towers use 5% of the water that ocean cooled plants use and that is a big savings in resources. The cost of building the cooling towers has been a consideration in the decision about whether to change the cooling system at San Onofre.
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A big Thank You to the NADCA for helping with this article!
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