Why do nuclear power plants have those huge hyperboloid shaped towers?


Every time I see those towers (in a movie, draw or picture) I instantly recognize it as a nuclear power station. But I’ve never asked why…

Why such a big and specific shaped tower? Is it something exclusive for nuclear power? Do all nuclear stations need those towers, or is it optional? Why that shape? What’s inside?

In: Engineering

Nuclear power plants are just giant kettles. They use nuclear energy to boil water, and they run that steam past turbines which generate electricity when spun. The concrete towers you see are specially designed to remove the excess heat from the steam produced, so the water can be reused. Some large nuclear power plants can use up to 1 billion gallons of water a day, so it’s important they recycle as much as they can.

They are for cooling by convection. The hot pipes from the plant are in the base of the tower. The bottom of the tower is open, supported above the ground. The air inside heats and rises, pulling in cold air from around the tower base, cooling the pipes. The shape is to make the rising airflow as effective as possible while allowing for a huge, hollow construction.

They’re used on many power plants, not just nuclear.

Those structures are called cooling towers. There are many shapes. But, the hyperbolic structure is preferred. At the bottom, the widening of the tower provides a large area for installation of fill to promote thin film evaporative cooling of the circulated water. As the water first evaporates and rises, the narrowing effect helps accelerate the laminar flow, and then as it widens out, contact between the heated air and atmospheric air supports turbulent mixing.

They are superior in stability towards outside forces compared with “straight” buildings.

They’re the cooling towers the plant uses for the steam cycle the plant uses to produce power. Most plants have the water in the reactor at a very high pressure to keep it from boiling even heated up to several hundred degrees. That water is used as a heat source to boil a separate mass of water to make steam. The steam spins a turbine (effectively a big mechanical pinwheel) and then gets cooled by a third set of water so the condensed steam can be sent back to become steam again.

That third set of water is what goes to the cooling tower. It sprays out of a huge network of sprinklers and some becomes steam. The shape of the tower acts like a chimney to direct steam and warm air up and drafting new, cooler air in at the bottom to cool off the rest of the water which falls into a pool before being sent back into the plant to condense more turbine steam. The cloud coming out at the top is simply that humid air venting out the top into the cooler outside air.

Basically, the shape is strong / materially efficient (comparable to an archway), and it’s good for airflow (because it permits the air to slow down as it escapes the tube, resulting in less turbulence).

Anywhere that needs to discard ample heat could use this tower design (some coal plants do), but there are other options to cool a nuke plant (ideally a large, flowing body of water).

The inside is… usually empty. It’s filled with warm, rising air (and optionally: water vapor). Maybe a fan sonewhere in there. The bottom contains heat exchangers/radiators (and usually: fans and/or sprays of water).

wiki for more info: https://en.wikipedia.org/wiki/Cooling_tower#Air_flow_generation_methods

A nuclear plant, like coal and gas, uses steam to run a turbine+generator and generate power.

This steam is created by heating water using the fuel, and after being used in the turbine it is returned to a main condenser to be reused. This main condenser is also under a heavy vacuum (imagine how in movies when a spaceship or something has a hole and things get sucked out quickly) in order to allow for efficient exhaust and condensing of the steam.

These two things are vital to the turbine, as it allows increased efficiency by reusing the steam as it condenses, and to protect the turbine (low vacuum/higher back pressure can cause higher temperatures and vibration issues before protective devices trip your turbine).

In order to actually function, the condenser needs a lot of cooling water (A gas plant can use 100000 gallons per minute per turbine as an example). This water can be provided by a lot of sources. Cooling towers like you describe are one of these things. Other sources can be water from rivers and oceans which just are returned to the source after use, or even air cooling via large fans.