Why is it that part of all nuclear facilities I’ve ever seen photos of have the same kind-of-hourglass shape, although with a lower base that’s of a larger radius than the upper?
Example picture, structures in upper part of picture:
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Also, on a related note, what exactly IS this structure and its function?
Those are cooling towers. The reactors are in the dome shaped buildings in the center of the photo.
There are large power plants that are non-nuclear that also have them, but generally the cooling requirements are lower in conventional plants.
The shape is to best funnel cool air from the base up through the stack. The warmed air causes an updraft. The shape optimizes airflow.
As stated they are cooling towers… and you see them in non nuclear facilities as well and some nuclear power stations do not have them.
AFAIK, neither Chernobyl nor Fukushima had the.
Not all nuclear plants have them. The infamous Fukushima Daiichi (flip to 2nd photo), for example.
Nuclear & fossil-fuel power plants work by boiling water and making steam, which is used to turn a turbine. The steam is then cooled down and turned back into water, so it can be used again. Some plants use air cooling; that’s what those hourglass- shaped cooling towers do. Others use water from a nearby river or ocean to cool down the steam, so they don’t need cooling towers.
The cooling requirement is a function of the total thermal power of the plant and the efficiency of the steam cycle they’re using. are nuke plants typically larger (power-wise) than coal plants, or is there something about them that facilitates a more efficient steam cycle? Or both?
I always find it faintly amusing that people have come to associate that shape with all things scary and nuclear, when it’s actually one of the most innocuous parts of the whole process. The cooling towers take hot water and turn it into cooler water.
I don’t know why it’s become associated with nukes in the popular consciousness, but it has.
The cooling towers are better in that they are a fail-safe method of cooling. Thermal air currents just happen (“hot air rises”), while water-cooled facilities work only as long as the pumps moving the water are working. When the electricity to the pumps fails, the cooling stops (like in Japan), with predictable results.
Had Chernobyl nor Fukushima had cooling towers, perhaps they would have still provided enough cooling to have prevented or minimized these meltdowns.
I’m fairly sure no (current) reactor design uses cooling towers to cool the primary coolant (the stuff that actually goes through the reactor). Since the primary coolant is radioactive and the cooling towers are open to the atmosphere, this would be a major radiation hazard.
Usually the primary coolant is run through a heat exchanger (inside the reactor containment) that generates non-radioactive steam to run the turbines. After going through the turbines, the steam is run through a condenser so it can be recycled back to the heat exchanger. The cooling towers cool the condenser (you can also use a river or lake for the same purpose, which is why not all power stations have them).
Definitely not. At Fukushima, the primary pumps which circulate water through the core didn’t have power. Without those, you don’t have coolant exchange between the core and the cooling tower, so having a cooling tower wouldn’t help.
At Chernobyl there was a massive reactivity excursion where the core was put into an unstable state and briefly produced over a hundred times its design maximum power. No amount of cooling could keep up with that. The meltdown came after the core had been blown apart and scattered across the landscape by the initial steam and hydrogen explosions, at which point the cooling systems were wrecked and useless anyway.
The reactor that melted down at Chernobyl had too many design issues to list. I don’t think cooling towers would have made any difference.
The funny thing is that light water reactors with classic cooling towers were under construction at Chernobyl, intended to replace the dangerous graphite-stack models. You can see their partially-built ruins just southeast of the sarcophagus and abandoned reactor building.
The soon-to-be-decommissioned San Onofre Nuclear Power Plant in Southern California, like Fukushima, used seawater for cooling and therefore does not have the iconic cooling towers. Part of the reason for its shutdown was due to new water-use regulations which would have required constructing new cooling towers – which was not only cost-prohibitive, but because of space restrictions, the towers would have to be built on the opposite side of Interstate 5.
I’d imagine it would’ve been very disconcerting to drive THROUGH a nuclear power plant on your daily commute! :eek:
Nuclear plants generate much hotter steam than coal or gas-fired plants. The thing is nuclear plants have a primary and secondary water “loops”, if you will. The water in the reactor vessel passes through the outlet piping, passes through one side of a heat exchanger and then returns through the inlet piping back into the reactor vessel. This is the primary loop and the water/steam is radioactive and is NOT, at all, intended for release. It’s a closed system. The secondary system is water passing through the other side of the heat exchanger where it gets VERY hot and turns the turbines to generate the electrical power. Then this water/steam is pumped into the cooling tower where some probably evaporates and the rest is cooled and is pumped back to the inlets of the secondary side of the heat exchanger. This water is NOT radioactive.
Very interesting and all, but it doesn’t answer my question. If the cooling requirements for nukes are generally higher than for coal-fired plants, as butler1850 implies, then why is this so?
Why are cooling requirements higher for nuke plants? Because the superheated steam coming from the outlet pipe of the reactor vessel to the input of the primary side of the heat exchanger is much hotter than the steam output of a coal or oil-fired boiler.
There’s also the matter of compactness. Nukes produce all of their power in a very small physical space, meaning the temperatures of operation and cooling requirements are much, much higher. In coal- and oil-fueled plants, the heat cores are much larger, relatively cooler and distributed, meaning that the overall cooling needs might be as great but can be diffused.
Possibly its resemblance to an incomplete mushroom cloud.
Butler1850 has implied that nukes have a higher cooling requirement than coal-fired plants. This is in reference to the total thermal power that must be dissipated. You can have as high a temperature as you want, but if you aren’t flowing much fluid, the total thermal power will be low.
If a nuke is dumping a lot of thermal power in a cooling tower, then either it is much less efficient than a coal-fired plant, or it is much more powerful than a coal-fired plant (or both). So which is it?
So you’re saying that cooling towers don’t require that anything be pumped?
