Los Angeles Times
June 11, 2005


By H. Josef Hebert

WASHINGTON -- The new-generation nuclear reactors being talked about
after a pause of three decades are not much different from those of
the past, though the designs should make them safer, more efficient
and easier to build.

Two designs likely to be pursued adopt a passive safety system
requiring less involvement by operators to shut the system down and
ensure that the reactor core doesn't overheat. A third design would
have more redundant and isolated safety systems than current reactors
plus a double-walled concrete containment dome better able to
withstand an airplane crash.

Still awaiting Nuclear Regulatory Commission approval, all three
designs are "evolutionary" advancements from the "light-water"
reactors in use in the United States and Europe today. These reactors
use ordinary water to slow, or moderate, the fission process as well
as for emergency cooling if needed. A Generation IV gas-cooled reactor
would be the next step in design advancements, probably after 2030, in
the United States.

The three reactor designs attracting the most interest are being
developed by Westinghouse, a subsidiary of the British company BNFL;
General Electric; and the French conglomerate AREVA, whose Framatome
subsidiary designed France's reactors. All three manufacturers say
their new designs have been simplified to increase safety and have
fewer moving parts, valves and pumps.

Here are some characteristics of each of the top three light-water
reactor designs and a next-generation gas-cooled reactor:

* The Westinghouse AP1000:

This would have one-third fewer pumps, half as many valves, and more
than 80 percent fewer pipes than current reactors. It can be built
using modular units manufactured in a factory and transported to the
reactor site, cutting construction time to three years.

It relies on a largely passive safety system. The cooling water for
use in event of a buildup of excess heat is above the reactor core and
uses gravity and natural circulation for emergency cooling if needed.
In current reactors, cooling water must be pumped into the core.

* General Electric's ESBWR:

This has a 1,500 megawatt boiling water design, meaning the cooling
water is not under pressure and is allowed to boil with steam passing
over the top of the reactor into the turbines.

ESBWR stands for "Economic Simplified Boiling Water Reactor,"
reflecting that its design removes many complexities of current
reactors. It has 25 percent fewer pumps, valves, motors, piping and
cabling and is designed to respond more quickly to a loss of coolant
situation. Modular construction and a smaller plant size allow for
faster construction.


A 1,500 megawatt pressurized water reactor that's an evolutionary
design based on the French and German reactors designed by Framatome
and Siemans. It is a simplified design using existing technologies,
with fewer parts.

While it maintains an active rather than passive safety system, the
EPR has a number of design improvements, including a double-wall
concrete containment dome for greater protection against an aircraft
crash. The design also extends the dome over the spent fuel pool and
two of the four safety buildings.

If there is a severe accident and meltdown, the reactor vessel is
designed to capture the core melt in a cavity below the containment

* Generation IV reactors:

These reactor technologies reflect a "revolutionary" step from the
"Generation III" and earlier design light-water reactors. Development
for commercial use won't occur until 2030.

They produce more heat and less waste with different cooling
mechanisms than the light water reactors, and would be able to produce
hydrogen as a replacement for fossil fuels to power everything from
cars to electric lamps. An international effort has been under way
since 2000 to examine various technologies, using a gas such as carbon
dioxide, water, liquid metal or even molten salt for cooling.

A gas-cooled reactor known as the pebble bed is being developed in
South Africa and was touted for the U.S. market until Exelon, the
Chicago-based utility, pulled out of the project. Instead of fuel
rods, the pebble bed uses coated graphite pebbles filled with uranium
fuel. The decay heat is transferred to helium, an inert gas, that
eventually moves to a gas turbine to produce electricity.

The Energy Department is planning a $1.25 billion program to build a
gas-cooled Generation IV experimental reactor in Idaho. It would
produce both hydrogen and electricity and could become a prototype for
future commercial reactors.

Copyright 2005 Los Angeles Times