I was reading that a nuke power plant in MA had to reduce its electrical power output because of warm ocean water temperatures of 75.3 degrees. Apparently this was. 3 degrees above specs and affected the ability of the plant to cool the reactor. How does 75 degree water affect nuke power plant reactor cooling? One would think that the reactor is quite hot and 100 degree water (for example) would still have a cooling effect. Are these nuke power plant cooling systems designed with such little excess cooling margin that 75 degree ocean water makes that much of a difference?
The cooling system is rated for a maximum temperature change when running flat out. If the incoming cooling water temperature is too high then the outgoing cooling water will be heated above the safe temperature of what it is cooling. The same thing goes for air conditioning in a car. Running on max it can only cool the air a maximum of say for example 20 degrees. So when the outside air is 80 degrees, the car can only go down to 60 degrees. Outside 85 / inside 65. Outside 95 / inside 75. Outside 105 / inside 85. It's physics. When the air or water (depending) coming in is too hot, the heat generator power needs to be turned down for the proper amount of cooling. (Yeah, I'm an ubergeek...)
...could also be there is a lot of fouling (gunk/dirt) build-up in the pipes (from the water) which cuts down on the heat exchange efficiency.
Interesting. I never would have guessed that just a few degrees of water temperature difference would affect nuclear plant cooling that much, though. So it sounds like when one uses water as a cooling medium for nuclear power, the fact that one is using water as a coolant is the limitation, not necessarily the cooling "system," so the reactors are limited to how much power they can produce by the ability of water to cool?
fortunately, the heat is supposed to break tonite, and they haven't had to cut back too much. not too many blackouts in the past week, but shows we need improved efficiencies for peak demand. not that any of the powers that be could give two cents.
The information provided has explained it well. The one thing to add is that the operational range and limits are agreed upon design decisions by all parties involved, not theoretical limits. The plant could have been designed to run at full power with these temperatures if the considerable additional expense was thought to be needed (i.e. profitable over the life of the plant). It's much like designing a dam. Do you design for the once every 100 year flood, the once every 1000 year flood, etc. Pick a number too big and no dam gets built. So don't take this situation as being an inadequate design. It may that ocean temperatures are getting a lot hotter than what were reasonable predictions many decades ago. I would also add that this has more to do with power plant turbine steam requirements and not the nuclear part near as much.
When we think of design, we should also note that the original license was though 2012, and it served well in that 40 year period. Should it have gotten its license renewed for 20 years? I am not sure, but Indian point surely was not designed for conditions and populations in 2013. Yes, absolutely reducing output to keep cooling in spec was the right thing to do for pilgrim.
