On 29 Jul 2004 19:17:46 -0700, (Dan Caster) wrote:
There was an article is the Wall Street Journal a while back about a
different design for nuclear power plants that use helium as the heat
transfer agent. It sounded pretty good. No melt down possibility.

Also you do know that China is building nuclear power plants?

You're talking about Generation IV reactors. There are two styles
of helium cooled reactors, the gas cooled fast reactor (GCFR), and
the very high temperature gas cooled reactor (VHTGCR). The former
is a breeder, the latter is not. General Atomics worked on the GCFR
in the 1970s, but none have actually been built.

The VHTGCR, developed by China as the HTR-10, operates at 1,000 C,
the highest operating temperature of any nuclear reactor yet built. This
is hot enough to thermally crack hydrogen from water, so this design
can produce electricity *and* directly produce hydrogen from water for
mobile power usage.

Japan's (HTTR), General Atomics' (GTMHR), and South Africa's
(PBMR) are variants on this design. There are daunting materials
issues with this style of reactor because of the high temperature
involved, and it is *not* a breeder, but working reactors of this style
have been built and successfully operated.

Other Gen IV designs include lead cooled, molten salt cooled,
sodium cooled, and supercritical high pressure water cooled
designs. The Clinch River plant, killed by Carter, was to have
been a sodium cooled breeder. France operates a number of
molten salt (lithium salts) cooled breeders. The Japanese are
working on a supercritical high pressure water cooled reactor.

The molten lead cooled design is of most interest for our present
discussion because of a number of desirable properties. It is
passively safe. It is a completely closed cycle breeder, with
a 20 year fuel cycle. In other words no off-site reprocessing
is required. Models have been built in modular sizes from
50 to 1200 megawatts. Candidate designs are the US STAR,
the Japanese LSPR, and Russia's BREST.

While the lead cooled reactor isn't quite as efficient as the
high temperature gas cooled reactor, I like it better because
of its closed breeder cycle, long unrefueled life, its inherent
safety properties, and the ease with which it can be scaled
to different modular sizes. You can essentially treat it as a
drop in long life primary battery available in a range of standard
sizes.

This design also has the simplest waste disposal method. Since
it is fully closed cycle, you can simply shut down and unplug the
reactor core, shielded by its own (now solid) lead coolant, and
store it at a long term disposal site, no disassembly or chemical
reprocessing steps are required. Since burn up is so complete,
there isn't much high level radioactivity left in the spent core.

Gary