午夜福利1000集合

FOR the home that has everything, how about a mini nuclear reactor? Small
enough to fit in the basement and needing a top-up with uranium only once every
10 years, it will eliminate greenhouse gas emissions along with worries about
power cuts.

It sounds wonderfully retro鈥攕omething from the days when researchers
talked confidently of nuclear-powered planes and trains. Yet thanks to some
clever passive safety features, a miniature reactor along these lines is almost
a reality. It is being developed in Japan and could, in theory, provide local
urban power
(see p 4). But perhaps the most remarkable thing about it is that it
is being seriously discussed. It is a sign of a new confidence in the nuclear
industry. There鈥檚 now talk all around the world of building brand-new reactors
with safe designs, even though the industry appeared dead just a few years ago.
What鈥檚 going on?

The change is partly due to Bush鈥檚 support for nuclear power. In May,
Vice-President Dick Cheney said: 鈥淚t鈥檚 a safe technology and doesn鈥檛 emit any
greenhouse gases at all. With the gas prices rising the way they are, nuclear is
looking like a good alternative.鈥�

Given that no new nuclear reactor has been ordered in the US for almost 30
years, it seems a surprisingly positive view. But it鈥檚 little more than a
reflection of prevailing economics: despite all the past problems, many nuclear
power plants are performing well. Their safety records are good, there are plans
to extend their working lives further into the future, and they are making
money.

That is encouraging companies to look for new designs that will be cheap,
safe and efficient. The top contender is the pebble-bed reactor. The concept
couldn鈥檛 be simpler: build a graphite-lined hopper and pour in hundreds of
thousands of tennis-ball sized 鈥減ebbles鈥�, each made up of uranium dioxide
particles wrapped in layers of graphite and a silicon carbide ceramic. The
fission reaction from the mass of uranium produces heat which is removed by a
stream of helium pumped through the hopper and then used to drive steam
turbines.

In principle, the design offers big advantages. The reactor is cheap to
build. New modules can be added to boost output. It can be refuelled simply by
pouring in new pebbles at the top of the hopper and taking old ones out from the
bottom. The density of the uranium in the reactor is not sufficient to start a
runaway meltdown. As the uranium fuel comes in small ceramic-wrapped pebbles, it
is easier to handle and store than uranium fuel rods. And the reactor can
operate at higher temperatures than a conventional one, making it more
efficient.

Is this the bright future for nuclear power? Not necessarily. Even in an
intrinsically safer reactor, there is potential for problems. Manufacturing
defects in the nuclear pebbles could allow radioactivity to escape. Although
graphite doesn鈥檛 burn until far beyond the operating temperature of the reactor,
there have been past accidents where graphite has caught fire鈥攏otably at
Windscale in Cumbria and Chernobyl. And there has already been a mishap at an
experimental pebble-bed reactor in Germany, when a pebble jammed in a feed pipe.
You can bet there鈥檒l be strong public resistance even to the new, safe
design.

But there鈥檚 a deeper problem, too, and it鈥檚 likely to be a show-stopper.
Nuclear power only looks brighter now because the accounting rules allow past
development costs to be written off. Inspect the books more closely and a
horrible truth emerges: no one has the remotest idea what the true cost of the
nuclear industry has been, nor what expenses will be incurred to decommission
reactors and dispose of nuclear waste.

It should be perfectly possible to run existing reactors efficiently for
another 20 years or more. But that doesn鈥檛 justify major outlays on a nuclear
technology when we still can鈥檛 calculate all the true costs. Plans to build a
prototype pebble-bed reactor in South Africa will scarcely change that. In a
world where electricity supply is everywhere being deregulated, the marketplace
is not going to vote for nuclear power without much clearer numbers. The nuclear
industry may be enjoying a little sunshine right now, but it鈥檚 still a setting
sun.