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Old_comfy_shoes t1_j5za47o wrote

Reply to comment by MTGamer in How hot is the steam coming out of nuclear power plants? by ivy-claw

If you have some water and it touches something very hot, the water can't exceed 100C, because as soon as it does, it becomes steam. But the steam can be crazy hot. So with enough temperature difference, if you plunge something crazy hot into water, the vapour won't instantly escape, and the heat transfer could be very rapid creating larger pockets of really hot steam, only the outside of which would be cooled by the water. So, the steam can be much hotter. But the water must stay at 100C in order to be water.

Steam, should always be hotter than 100C, which is why it converted to steam. It's essentially water that is hotter than 100C at 1 ATM, by definition. But usually it would only be a little bit hotter in conventional use. 300C seems like a lot though. Idk anything about reactors, but I think they plunge massive insanely hot rods into water?

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Seraph062 t1_j63qqh0 wrote

> But usually it would only be a little bit hotter in conventional use. 300C seems like a lot though. Idk anything about reactors, but I think they plunge massive insanely hot rods into water?

You generally want steam for turbines to be pretty hot, the ones I'm familiar with usually run about 500°C. There are a few reasons for this, hotter steam is generally easier (and more efficient) to extract energy from, it's also better for the turbines because droplets can cause damage and higher steam temperatures help avoid droplet formation.

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