@dtech said:
@morbiuswilters said:
And clearly they are cooling the water (since the effectiveness of the cooling reduces on hot days). Most likely they will have to increase the cooling capabilities of the plants or build more plans to add extra capacity for the times when they can't run at 100%.
I don't believe they cool the water: I believe the water (from the river/sea/environment) is used to cool the innermost fluid so you get: heated by reactor => through turbine => cooled by water => heated by reactor etc.). The problem is you can't just "cool water", you need to transfer the (heat) energy to some other medium, which then obviously gets warmer.
When the (river) water is warmer because of higher temperatures, the inner fluid can't get cooled enough, hence the need to run at a lower capacity.
"Cooling the river water" isn't possible (well, at least not in an energy-efficient way) because the water is already used as a coolant, you'd need another more efficient coolant, but if that was available it would've been used in the first place.
Another option (used where there is no cooling water available) are cooling towers, where energy is transferred to the atmosphere by evaporating water. Howerer, I believe they are more inefficient and more expensive (I'm not sure though)
Also, these problems aren't nuclear-power-plant specific, all turbine (nuclear, fossil, solar-heat) would have this issue I would think.
You are correct. In a nuke plant, there are three main coolants. The primary coolant is in contact with the fuel and transfers heat to the steam generator. It is a completely closed cycle, and the primary coolant is usually somewhat radioactive. Secondary coolant circulates from the steam generator to the turbines and other bits and pieces of the power plant. It's also a closed cycle (less some minor losses through turbine seals and such), and is no more dangerous than any other kind of steam. The third coolant is river (or ocean) water, and is used in very high volumes compared to the other two. It's function is to cool the 'spent' steam so it can condense and be returned to the steam generator.
All steam plants have the second two 'coolant' circuits, no mater how the steam is generated, though the steam part (the nuke plant secondary circuit) isn't usually refered to as 'coolant' in those plants. Coal, natural gas, oil, garbage, solar thermal, ect. - they all have the same potential problem as the nuke plants if the river or ocean is too hot. Even gas-turbine plants have that problem to some degree - they usually use the gas turbine exhaust to generate steam that's used to make more power. That's part of why gas-turbine and diesel peaking plants, as well as interconnect arrangements with other utilities, are necessary.
Cooling towers are used to cool the output from the third curcit I menitoned above. They are basicly large radiators, and are not nearly efficent enough to provide sufficcent cooling for any kind of steam plant on thier own. Plants built where there isn't much water need an artifical lake or some other large source of water (aqueduct or under ground aquifier) for cooling.