How efficient is a nuclear power station?

In percentages

1 Answer

  • 1 decade ago
    Best Answer

    Efficiency is in terms of output divided by input. What is your output and what is your input?

    For power stations, the output is usually the electric energy produced, but the input is less clear.

    In a coil or oil-fired power plant, the fuel is burned, heats water to steam, and drives a steam turbine which generates the electricity.

    As input, you can take the energy in the steam, the energy in the fuel (if it were burned perfectly), the energy that is actually extracted from the fuel (as it is burned), etc.

    For a nuclear power station, there are even more choices. The fissioning process generates heat which creates steam from water. After a while, the rate at which the fuel generates energy by fissioning goes down (remember half-life?) so the fuel is replaced even when it still has a good bit of energy left to give up.

    So are you going to use:

    1. The heat that is actually transferred to the water to produce steam?

    2. The heat that is actually produced by the fissioning process?

    3. The heat that could be extracted from the "fuel" over the same time period?

    4. All the fission energy in the original fuel?

    Clearly, the efficiency figure you get depends on which input you choose.

    The steam in to electricity out ratio is not as good for nuclear power plants as it is for coal and oil plants because of the lower temperatures (350 degrees C) and pressures used in nuclear power plants - figures around 30% (depending on the age of the plant) are typical.

    Add in the other energy losses, and from an energy efficiency point of view, nuclear power looks like a loser.

    But no one really cares about the energy efficiency. What they care about is cost per unit energy out. And that is not a percentage.

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