Name: Kate P.
Date: November 2002
What is the efficiency of nuclear energy?
This is not an easy question, because it depends upon how you define
"efficiency". From a fundamental perspective, efficiency can be defined as:
Efficiency = 100x [Th -Tc] / Th where:
Th and Tc are the temperature of the reactor core and Tc is the temperature
at which the heat is expelled from the generator (all temperatures in
kelvins). So, let's say Th = 1000 K and Tc = 300 K, then: Efficiency is:
100x [1000 - 300] / 1000 or 70%. This is an ideal maximum. It does not take
into account heat exchanger efficiency, heat losses in pipes, the energy
used to pump fluids around, and all the other "machinery" necessary to
produce energy in an operating power plant. All of those losses could cut
this "efficiency" in half. Some models for efficiency go into more detail by
incorporating "down time". For example, if a power plant has to be put on
hold for 36.5 days per year for maintenance, then its efficiency would be
decreased by another 10%.
Other efficiency "models" incorporate the "cost" of operation in terms
energy output. Such costs involve dollars required for monitoring, cost of
waste disposal, and so on.
So the answer to your question has a lot to do who and why the calculation
is being done.
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Update: June 2012