Re: Nuclear Power: Unsafe, Uneconomical, Unsustainable
- From: xnichols@xxxxxxxxxxx
- Date: 4 Feb 2007 14:06:50 -0800
On 4 Feb, 20:16, richard schumacher <no-s...@xxxxxxxxxxx> wrote:
You need to educate yourself about
- reprocessing
- fast breeders
- thorium fuel
and then check back with us.
Nuclear Waste and the real economics of nuclear power
by Peter Bunyard (extract)
"A critical point about the practicability of nuclear power to provide
clean energy under global warming is the quality and grade of the
uranium ore. The quality of uranium ore varies inversely with their
availability on a logarithmic scale. The ores used at present, such as
the carnotite ores in the United States have an uranium content of up
to 0.2 per cent, and vast quantities of overlying rocks and subsoil
have to be shifted to get to the 96,000 tonnes of uranium-containing
rock and shale that will provide the fresh fuel for a one gigawatt
reactor [1].
In addition, most of the ore is left behind as tailings with
considerable quantities of radioactivity from thorium-230, a daughter
product of the radioactive decay of uranium. Thorium has a half-life
of 77 000 years and decays into radium-226, which decays into the gas
radon-222. All are potent carcinogens.
Fresh fuel for one reactor contains about 10 curies of radioactivity
(27 curies equal 1012 becquerels, each of the latter being one
radiation event per second.) The tailings corresponding to that
contain 67 curies of radioactive material, much of it exposed to
weathering and rain run-off. Radon gas has been found 1 000 miles from
the mine tailings from where it originated. Uranium extraction has
resulted in more than 6 billion tonnes of radioactive tailings, with
significant impact on human health [2].
Once the fuel is used in a reactor, it becomes highly radioactive
primarily because of fission products and the generation of the
'transuranics' such as neptunium and americium. At discharge from the
reactor, a tonne of irradiated fuel from a PWR (pressurized water
reactor such as in use at Sizewell) will contain more than 177 million
curies of radioactive substances, some admittedly short-lived, but all
the more potent in the short term. Ten years later, the radioactivity
has died away to about 405 000 curies and 100 years on to 42 000
curies, therefore still 600 times more radioactive than the original
material from which the fuel was derived [3].
Today's reactors, totalling 350 GW and providing about 3 per cent of
the total energy used in the world, consume 60 000 tonnes of
equivalent natural uranium, prior to enrichment. At that rate,
economically recoverable reserves of uranium - about 10 million tonnes
- would last less than 100 years. A worldwide nuclear programme of 1
000 nuclear reactors would consume the uranium within 50 years, and if
all the world's electricity, currently 60 exajoules (1018Joules) were
generated by nuclear reactors, the uranium would last three years [4].
The prospect that the amount of economically recoverable uranium would
limit a worldwide nuclear power programme was certainly appreciated by
the United Kingdom Atomic Energy in its advocacy for the fast breeder
reactor, which theoretically could increase the quantity of energy to
be derived from uranium by a factor of 70 through converting non-
fissile uranium-238 into plutonium-239.
In the Authority's journal [5], Donaldson, D.M., and Betteridge, G.E.
stated that, "for a nuclear contribution that expands continuously to
about 50 per cent of demand, uranium resources are only adequate for
about 45 years."
The earth's crust and oceans contain millions upon millions of tonnes
of uranium. The average in the crust is 0.0004 per cent and in
seawater 2 000 times more dilute. One identified resource, the
Tennessee shales in the United States, have uranium concentrations of
between 10 and 100 parts per million, therefore between 0.1 and 0.01
per cent. Such low grade ore has little effective energy content as
measured by the amount of electricity per unit mass of mined ore [6].
Below 50 parts per million, the energy extracted is no better than
mining coal, assuming that the uranium is used in a once-through fuel
cycle, and is not reprocessed, but is dumped in some long-term
repository. Apart from the self-evident dangers of dissolving spent
fuel in acid and keeping the bulk of radioactive waste in stainless
steel tanks until a final disposal is found, reprocessing offers very
little if at all in terms of energy gained through the extraction and
re-use of uranium and plutonium in mixed oxide fuel (MOX) [7].
To date, nuclear power has been built and subsidised through the use
of fossil fuels, which have provided the energy for mining,
extraction, enrichment and construction. Hence, nuclear power cannot
be considered to be free of greenhouse gas emissions. Use of the next
grade down could lead to a greenhouse gas inventory every bit as bad
as for a gas-fired electricity generation plant, and considerably
worse than for a gas-fired co-generation plant, in which both
electricity and end-use heating are produced."
http://www.i-sis.org.uk/DTNPM.php
.
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