“Sustainable” power from nuclear fission

Figure 24.1 shows how much electricity was generated globally by nuclear
power in 2007, broken down by country.

Could nuclear power be “sustainable”? Leaving aside for a moment the
usual questions about safety and waste-disposal, a key question is whether
humanity could live for generations on fission. How great are the world
wide supplies of uranium, and other fissionable fuels? Do we have only a
few decades’ worth of uranium, or do we have enough for millennia?

To estimate a “sustainable” power from uranium, I took the total recov-
erable uranium in the ground and in seawater, divided it fairly between 6
billion humans, and asked “how fast can we use this if it has to last 1000

Almost all the recoverable uranium is in the oceans, not in the ground:
seawater contains 3.3 mg of uranium per m3 of water, which adds up to
4.5 billion tons worldwide. I called the uranium in the ocean “recoverable”
but this is a bit inaccurate – most ocean waters are quite inaccessible, and
the ocean conveyor belt rolls round only once every 1000 years or so; and
no-one has yet demonstrated uranium-extraction from seawater on an in
dustrial scale. So we’ll make separate estimates for two cases: first using
only mined uranium, and second using ocean uranium too.

The uranium ore in the ground that’s extractable at prices below $130
per kg of uranium is about one thousandth of this. If prices went above
$130 per kg, phosphate deposits that contain uranium at low concentra-
tions would become economic to mine. Recovery of uranium from phosp-
hates is perfectly possible, and was done in America and Belgium before
1998. For the estimate of mined uranium, I’ll add both the conventional
uranium ore and the phosphates, to give a total resource of 27 million tons
of uranium (table 24.2).

We’ll consider two ways to use uranium in a reactor: (a) the widely-used
once-through method gets energy mainly fromthe 235U (which makes
up just 0.7% of uranium), and discards the remaining 238U; (b) fast breeder
, which are more expensive to build, convert the 238U to fission
able plutonium-239 and obtain roughly 60 times as much energy from the

Once-through reactors, using uranium from the ground

A once-through one-gigawatt nuclear power station uses 162 tons per year
of uranium
. So the known mineable resources of uranium, shared between
6 billion people, would last for 1000 years if we produced nuclear power at
a rate of 0.55 kWh per day per person. This sustainable rate is the output
of just 136 nuclear power stations, and is half of today’s nuclear power
production. It’s very possible this is an underestimate of uranium’s poten-
tial, since, as there is not yet a uranium shortage, there is no incentive for

million tons
Australia 1.14
Kazakhstan 0.82
Canada 0.44
USA 0.34
South Africa 0.34
Namibia 0.28
Brazil 0.28
Russian Federation 0.17
Uzbekistan 0.12
World total
(conventional reserves
in the ground)
Phosphate deposits 22
Seawater 4500
Table 24.2. Known recoverable resources of uranium. The top part of the table shows the “reasonable assured resources” and “inferred resources,” at cost less than $130 per kg of uranium, as of 1 Jan 2005. These are the estimated resources in areas where exploration has taken place. There’s also 1.3 million tons of depleted uranium sitting around in stockpiles, a by-product of previous uranium activities.
Figure 24.3. Workers push uranium slugs into the X-10 Graphite Reactor.