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Heat Wave Shuts Down Alabama Reactor

Posted by CowboyNeal on from the weathering-the-heat dept.

mdsolar writes "In a first for the US, one of three nuclear reactors at the Browns Ferry nuclear plant in Alabama has been shut down because the Tennessee River is too hot to provide adequate cooling for the waste heat produced by the reactor. This is happening as the TVA faces its highest demand for power ever, reports the Houston Chronicle. This effect has been seen in Europe in the past, forcing reduced generation, but the US has until now been immune to the problem. The TVA will buy power elsewhere and impose higher rates, blaming reduced river flow as a result of drought."

14 of 401 comments (clear)

  1. Reasons right? by Anonymous Coward · · Score: 5, Informative

    I work at a nuclear power plant. We have a limit for the temperature of the river downstream of our returned cooling water for environmental reasons, not reasons related to the power generation process. I suspect the TVA has a similar requirement.

    I noted from the nrc website (www.nrc.gov) that their other reactors are operating at reduced load, which is what our reactors must do to limit the heat input into the river.

    So this is nothing remarkable.

    1. Re:Reasons right? by Wonko+the+Sane · · Score: 4, Informative

      Physics: It's not just a good idea, it's the law.

    2. Re:Reasons right? by hankwang · · Score: 5, Informative

      How efficient is a power generation plant that throws away gigawatts of power as waste heat?

      From the heat source to electrical power output is usually in the range 35--50%, depending on the plant design. A fundamental problem is the theoretical limit of the efficiency of a heat engine, a device that converts a temperature difference into mechanical power. It is 1 - Tcold/Thot, where Tcold and Thot are the temperatures of the cold and hot parts, in kelvin. For a steam-operated heat engine, the cold end is around the boiling point of water (373 K), and the hot end might be 1000 K, which limits the efficiency to 63% if there are no other losses. But one can use the waste heat for other purposes in a cogeneration plant, for example for residential heating in cold climates or for the industry.

      --
      Avantslash: low-bandwidth mobile slashdot.
    3. Re:Reasons right? by Cyberax · · Score: 3, Informative

      Nope. You can't beat http://en.wikipedia.org/wiki/Carnot_cycle in efficiency. The practical upper limit for nuclear power plants is about 50%. And we're already getting closer to this limit.

      We can use some insane things like high temperature (thousands degrees) reactors with gas cooling to get another 10%-15% of efficiency, but it is just not practical.

    4. Re:Reasons right? by Dachannien · · Score: 3, Informative

      Actually, if you really do read the article carefully, nowhere does it state that the water itself is incapable of cooling the reactor. It merely states that the river water is "too hot", which could just as well indicate that adding more warm water - especially in drought conditions where the river level is probably lower than normal - would make the river temperature too hot to safely sustain its ecosystem.

  2. Re:In Soviet Russia by Belacgod · · Score: 3, Informative

    Soviet Russia doesn't refer to USSR. It's to distinguish it from Tsarist Russia, or Kievan Russia, or any of the other regimes that ruled Russia. Similar usages in other countries: Napoleonic France, Imperial Rome, Colonial America, Nazi Germany.

  3. Some people sell their "waste" heat by Colin+Smith · · Score: 4, Informative

    To heat domestic water, space heating and even to power adsorption chillers which can reduce AC requirements. Even coal power stations can hit 88% efficient.

    http://www.helsinginenergia.fi/en/tuotanto/benefit s.html

    US power stations are still only 40% efficient because ... Well you decide for yourself.

    --
    Deleted
    1. Re:Some people sell their "waste" heat by Waffle+Iron · · Score: 3, Informative
      That's because so many people in Denmark are close enough to a power plant to run steam tunnels to their locations. The trend in the US over the past decades has been to build huge power plants in the middle of nowhere, so it just wouldn't work here.

      Recently, a new trend has been to build smaller cogeneration facilities in populated areas in the US, but due to valid political and environmental concerns, the only viable fuel for these is natural gas. That fuel is already in short supply and dwindling fast, so that's not going to solve the problem by itself.

  4. Re:What "waste heat"? by Wonko+the+Sane · · Score: 3, Informative
    A carnot cycle is indeed a closed cycle, but:

    Carnot's theorem is a formal statement of this fact: No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same reservoirs.

    Your open-cycle system will never be more efficient than a carnot cycle at the same temperatures.
  5. Re:What "waste heat"? by SEMW · · Score: 3, Informative

    I'm afraid Wonko's right. The total efficiency converges to Carnot's. If there is any *usable* waste heat left at the end of a cycle to put into another heat engine, then the first cycle wasn't running at full (reversible) Carnot efficiency.

    BTW, if a heat engine were ever to be used in a closed system, then its efficiency would quickly converge to 0%, since the hot source would cool down and the cold source would heat up! The Carnot cycle, as I said in my other post, assumes infinite, constant temperature hot and cold sources, i.e. effectively the same as a system where heat is constantly added to the hot source (by a nuclear reactor) and taken away from the cold source (by a running river) to maintain a constant temperature.

    --
    What's purple and commutes? An Abelian grape.
  6. Meanwhile Back In Alabama by cluckshot · · Score: 5, Informative

    A little noted fact of the cold war is that a very large amount of the US total electrical generation capacity is in the TVA region (Tennessee River - Dependent) The loss of this reactor is serious as the whole USA has no reserve capacity at peak load and with the heat wave over the East USA this is a critical loss. If it were the only reactor in danger this might be of no concern. The US TVA operates 5 big reactors and numerous coal fired plants all of which have the Tennessee River at thermal capacity to cool them and the river is dropping daily.

    If heavy sustained rain does not fall on the Tennessee River Valley over the next 3 to 4 months an event which is historically unlikely, the loss of something close to 15 times the Browns Ferry reactor in capacity is likely to hit the USA. There is nothing to pick up the load. The loss of this one reactor is nearly equal to all the wind energy the USA generates. This loss threatens the operations of every one of the 48 US States. With the possible loses in Alabama Power pools and their reactors etc as well as Georgia Power, this poses the very real risk of cutting the energy supply of the USA by a very large fraction. As I write the North Alabama region is short 60 inches of rain over the past 18 months. The US TVA has been drawing down storage for 5 years now. There is no reserve and little prospect of one for some years to come.

    I had warning of this imminent event when the City of Huntsville requested from TVA more water for its treatment plant and was turned down for supply. I knew then that the supply was gone.

    --
    Never Politically Correct ~ I prefer the facts If you don't like what I say, get a life, or comment yourself.
    1. Re:Meanwhile Back In Alabama by Ecks · · Score: 4, Informative

      TFA has the engineering wrong. The problem isn't the river temperature as much as the air temperature. A nuclear power plant needs to be located near a river so it can have a large supply of relatively cool water to use as a working fluid. The river water gets boiled into steam by reactor water in the nuclear reactors primary coolant loop. This is steam is what turns the turbines and generates the electricity. When it exits the turbines it's still steam, it's just cooler and wetter. You can't return it in this state because doing that would dramatically raise the river's temperature. You have to cool it down before you can put it back. To do that you use a passive air to water heat exchanger. But they're having a heatwave down there. Between the starting temperature of the river and the reduced efficiency of the passive heat exchanger using all three reactors in the plant would heat the river to unacceptable levels.

      Unacceptable is not boiling it's probably something in low 90F range because if the mean temperature of the river was over 90F for any period of time you raise the risk of algae blooms and fish kills.

      Physical conditions are not preventing the plant from running, environmental considerations are. And if the river's temperature is close to or exceeds the contracted discharge temperature without being heated by the plant then reevaluating the environmental decision may be in order.

      -- Ecks

  7. Re:paddle wheels in the heat stream by QuickFox · · Score: 5, Informative

    Are you thinking a forest of insulated two-foot steam pipes running all around town? Sounds pretty ugly, noisy, expensive and environmentally disruptive. Here in Sweden we've had this in the cities forever. It's not ugly, noisy, expensive and environmentally disruptive. Instead it's underground.

    Generally they don't transport steam, they transport hot but liquid water.

    See, engineers are not idiots. You must be new here.
    --
    Terrorists can't threaten a country's freedom and democracy. Only lawmakers and voters can do that.
  8. Actually... by danwesnor · · Score: 3, Informative

    The reactor was shut down because the water exiting the plant's cooling system exceeded an average of 90 degrees F over a 24 hour period. The plants have an agreement with the state to limit the temperature of the water they put into the river. The water in the river is not even remotely 90 degrees F.

    Brown's Ferry also just recently started one of its reactors after a long downtime, so this only kicked us back a few months. It's not a big impact to the nation's grid, not even to the local area.

    As for why we don't recapture the energy in the heated water to make even more power, well, they just didn't think it was necessary back when we used to build power plants back in the 60's. Investing money in anything nuclear in the US is political suicide.