What is a Nuclear Cooling Tower?
Nuclear fission generates an unbelievable amount of heat. If this heat is not carefully managed, temperatures in the reactor core will rise quickly and to potentially dangerous levels. To avoid this, heat must be constantly and rapidly removed from the core. This is typically done via a system of cooling loops which transfer heat to where it can be used to produce energy (Visit our ‘Turning Heat into Electricity‘ page for a full explanation).
There are two main ways of dealing with any waste heat which remains in the tertiary cooling water. The most recognisable one is recirculating it using nuclear cooling towers, where the heat is emitted to the atmosphere. This is typically done in power stations located close to rivers or lakes, to avoid increasing the temperature of the body of water. Alternatively, power stations located on the coast will simply release the heated water into the sea and suck in fresh seawater to replace it. It is important to note that this water is not radioactive at all.
How does a Nuclear Cooling Tower work?
Nuclear power plant cooling towers are designed to maximize the cooling efficiency through a process called evaporative cooling. Heated water from the tertiary cooling loop enters the cooling tower through large pipes. The water is distributed evenly across the top of the cooling tower using spray nozzles. These nozzles break the water into fine droplets, increasing the surface area for heat exchange.
Spray nozzles at the top of a cooling tower
As the water droplets fall through the tower, they come into contact with the upward-moving air. A small portion of the water evaporates, absorbing heat from the remaining water. This evaporation process is highly efficient in removing heat. The remaining water cools down as it transfers heat to the air through direct contact. The cooled water collects at the bottom of the tower. The cooled water collects in a basin at the bottom of the cooling tower. Pumps then recirculate this cooled water back to the condenser in the tertiary loop, where it absorbs more heat from the secondary loop, and the cycle repeats.
Cooled water descends into the basin. Gaps around the base of the tower allow air to be drawn in.
Drift eliminators are installed to minimise the loss of water droplets that escape with the exhaust air. They capture and return these droplets to the cooling tower, reducing water loss and preventing excessive release of water vapour to the environment. Despite the efficiency of drift eliminators, some water is lost through evaporation and drift. The makeup water system compensates for these losses by adding fresh water to the cooling tower to maintain the required water level.
Types of Nuclear Cooling Towers
Natural Draft Cooling Towers
Natural draft towers make up the vast majority of cooling towers used at nuclear power stations. They rely on the natural buoyancy of hot air. As the warm air inside the tower rises, cooler air is drawn in from the bottom, creating a continuous airflow without the need for mechanical assistance. Natural draft cooling towers are typically hyperboloid in shape, which enhances structural stability and airflow efficiency. These towers are quite tall, often reaching heights of 100 meters or more, to facilitate natural convection.
Advantages
Energy Efficiency: Since they do not require fans or other mechanical devices to move air, natural draft towers are highly energy-efficient.
Low Operating Costs: With fewer mechanical components, these towers have lower maintenance and operational costs.
Durability: The simple design with fewer moving parts generally results in a longer lifespan.
Disadvantages
High Initial Cost: The construction of natural draft towers is expensive due to their size and complexity.
Space Requirements: They require significant space, making them less suitable for areas with limited land availability.
Climate Dependency: Their efficiency can be affected by local climate conditions, particularly in areas with low ambient temperatures.
Mechanical Draft Cooling Towers
Mechanical draft towers use fans to force or draw air through the tower. Fans are either located at the top of the tower, pulling air through the system, or at the bottom, pushing air into the tower. Similar to natural draft towers, water is sprayed from the top and falls through the air, cooling as it exchanges heat with the air. While cooling towers of this type are commonly used on a small scale across many industries, they are incredibly rare as the main heat sink for a nuclear power station.
Advantages
Flexibility: Mechanical draft towers can be installed in a variety of locations, including areas with limited space.
Consistent Performance: They provide reliable cooling regardless of ambient temperature, making them suitable for diverse climates.
Control: The airflow can be adjusted by controlling the fan speed, allowing for precise temperature regulation.
Disadvantages
Energy Consumption: The fans consume significant amounts of energy, increasing operational costs.
Maintenance: More mechanical components mean higher maintenance requirements and potential for mechanical failure.
Noise: The operation of fans can generate noise, which may be a concern in certain locations.
Explore Further
Choose from the articles below to continue learning about nuclear.
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Below you can find references to the information and images used on this page.
Content References
Image References
- Singularity – tinyfugu – CC BY-NC 2.0
- Staircase to heaven – tinyfugu – CC BY-NC 2.0
- Cooling tower 2 – tinyfugu – CC BY-NC 2.0
- Inside the cooling tower – tinyfugu – CC BY-NC 2.0
- 500ft drop on either side – tinyfugu – CC BY-NC 2.0
- Sunrise – Peter Miller – CC BY-NC-ND 2.0
- Charleroi Urbex – Electrabel Cooling Tower – Robert GLOD – CC BY-NC-ND 2.0
- Showers in natural draft cooling tower – Jan Beránek – CC BY-SA 4.0
- Video – Kraftwerk Lippendorf Kühlturm – High Contrast – CC BY 3.0 DE
- De Molen (windmill) and the nuclear power plant cooling tower in Doel – Trougnouf – CC BY 4.0
- Neckarwestheim Nuclear Power Plant from Liebenstein – Felix König – CC BY-SA 3.0
- Kernkraftwerk Neckarwestheim (GKN) – German Federal Archive – CC BY-SA 3.0 DE
- Kuehlturm – Kraftwerk Rostock – Morloc – Public Domain
