Up to: Sustainability FAQ
Facts from Cohen and others
How long will nuclear energy last?
These facts come from a 1983 article by
Nuclear energy, assuming breeder
reactors, will last for several billion
years, i.e. as long as the sun is in a state to support life on earth.
Here are the basic facts.
- In 1983, uranium cost $40 per pound. The known uranium reserves at
that price would suffice for light water reactors for a few tens of years.
Since then more rich uranium deposits have been discovered including a very
big one in Canada. At $40 per pound, uranium contributes about 0.2 cents
per kwh to the cost of electricity. (Electricity retails between 5 cents and
10 cents per kwh in the U.S.)
- Breeder reactors use uranium more than 100 times as efficiently as
the current light water reactors. Hence much more expensive uranium can
be used. At $1,000 per pound, uranium would contribute only 0.03 cents
per kwh, i.e. less than one percent of the cost of electricity. At that
price, the fuel cost would correspond to gasoline priced at half a cent
- How much uranium is available at $1,000 per pound?
There is plenty in the Conway granites of New England and in shales in
Tennessee, but Cohen decided to concentrate on uranium extracted from
seawater - presumably in order to keep the calculations simple and
certain. Cohen (see the references in his article) considers it certain
that uranium can be extracted from seawater at less than $1000 per pound
and considers $200-400 per pound the best estimate.
In terms of fuel cost per million BTU, he gives (uranium at
$400 per pound 1.1 cents , coal $1.25, OPEC oil
$5.70, natural gas $3-4.)
- How much uranium is there in seawater?
Seawater contains 3.3x10^(-9) (3.3 parts per billion) of uranium,
so the 1.4x10^18 tonne of seawater contains 4.6x10^9 tonne of uranium.
All the world's electricity usage, 650GWe could therefore be supplied
by the uranium in seawater for 7 million years.
- However, rivers bring more uranium into the sea all the time, in fact
3.2x10^4 tonne per year.
- Cohen calculates that we could take 16,000 tonne per year of uranium
from seawater, which would supply 25 times the world's present electricity
usage and twice the world's present total energy consumption. He
argues that given the geological cycles of erosion, subduction and uplift,
the supply would last for 5 billion years with a withdrawal rate of
6,500 tonne per year. The crust contains 6.5x10^13 tonne of uranium.
- He comments that lasting 5 billion years, i.e. longer than the sun
will support life on earth, should cause uranium to be considered a
- Here's a Japanese site discussing
extracting uranium from seawater.
The main point to be derived from Cohen's article is that energy
is not a problem even in the very long run. In particular, energy
intensive solutions to other human problems are entirely
- Cohen neglects decay of the uranium. Since uranium has a half-life
of 4.46 billion years, about half will have decayed by his
postulated 5 billion years.
- He didn't mention thorium, also usable in breeders. There is 4 times
as much in the earth's crust as there is uranium. There's less thorium
in seawater than there is uranium.
- He did mention fusion, but remarks that it hasn't been developed yet.
He has certainly provided us plenty of time to develop it.
site contains links to many of his articles. He's a particular
expert on radiation hazards. His 1990 book
The Nuclear Energy Option is on the web page. Its chapter on solar
energy is especially interesting in its description of the 1990 hopes
for solar energy.
Up to: Energy FAQ
Bernard Cohen is
Professor Emeritus of Physics at Pittsburgh University. He is former
president of the Health Physics Society, the main scientific society
concerned with radiation safety. He has written several books on nuclear energy.
Several of Cohen's papers are reproduced on
Russ Paielli's nuclear page
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