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Declared Net Capacity in Mega Watts Electrical

  1. Jun 27, 2011 #1
    If a nuke units has a DNC of 1000 MWe, is this capacity per sec, hour, day, or year???

    I'm "assuming" this capacity is per hour but then again a Watt is a unit of seconds.

    In other words, If a nuke unit has declared net capacity (DNC) of 1000 MWe, how long would the unit have to run at 100% capacity before it actually supplied a 1000 MWe to the switchyard?

    Any reference material that answers this question is greatly appreciated - NRC/ IAEA or the likes.

  2. jcsd
  3. Jun 27, 2011 #2


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    1 W = 1 J/s. Watt is a unit of power, Joule is a unit of energy. Power is just the rate of energy per unit time.

    With a DNC 1000 MWe (or 1 GWe) unit is expected to produce 1 GWe of electrical energy (net) with the unit at full rated (thermal) end and all equipment running. A 1 GWe unit will use about 50 MWe for pumps and various electrical systems on site, so there is also gross capacity. The net electrical generation is what can be sold on the grid to generate revenue.

    The supply from generator to switchyard is more or less instantaneous.


    The NRC website refers to Net Electric (Energy) Generation

    Net Electric Generation would be based on integrating the Net Power over time (usually on a monthly or annual basis),
    Last edited by a moderator: Apr 26, 2017
  4. Jun 28, 2011 #3
    1 W = 1 J/s. Watt is a unit of power; Joule is a unit of energy. Power is just the rate of energy per unit time. Thanks Astronuc

    So basically my previous question was erroneously worded due to your above explanation.

    Let me try a different question to see if I’m getting the hang of this. Anybody feel free to comment.


    Palo Verde Nuclear Generating Station is the largest nuclear plant in the United States averaging over 3.3 gigawatts (GW) of electrical power production and is located in Wintersburg, Arizona. The facility consists of three pressurized water reactors each with a max electrical generating capacity of 1.2 gigawatts. Assuming the plant is on a two year refueling cycle, how much electrical energy will Palo Verde Nuclear Generating Station produce between refueling cycles? Note: All three units refuel at the same time.


    24 hours/day x 365 days/year x 2 years = 17,520 hours, and 17,520 hours x 3.3 gigawatts (GWe) = 57.8 terawatt hours (TWh) of energy. Now, 1 Watt = 1 Joule/second, so, 57.8 TJh/s x 3600 sec/hour = approx 0.2 exajoule (EJ).

    So, in a given two year refueling period Palo Verde Nuclear Generating Station produces approximately 57.8 terawatt hours (TWh) or 0.2 exajoule (EJ) of energy.

    To put this into perspective, Wikipedia stats “the 2011 earthquake and tsunami in Japan had 1.41 EJ of energy according to its 9.0 on the Richter magnitude scale. Energy in the United States used per year is roughly 94 EJ.”
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