On Wed, 16 Mar 2011 09:27:31 -0400, Fuddy Dud
wrote:

Home Guy wrote:
Fuddy Dud wrote:

Canadian CANDU nuclear reactors can't melt down or go critical
the way that these GE reactors are doing in Japan.

It's too bad that they were basically forced into using the GE
rectors in Japan. Now we will have a new generation of people
in Japan that can thank the US for the nuclear "gift" that
keeps on giving.

That wasn't the problem. It was the back up generators and fuel
tanks that were taken out by the tsunami. No back up cooling,
not reactor design that is causing the problem.

It is the reactor design.

Even when all the control rods are inserted to stop the reaction, the
core still operates at 7% heat output - not zero percent. A constantly
operating coolant system must be available at all times to maintain this
type of reactor in a safe state, even during shut-down. Clearly in an
area prone to earth quakes and tsunami's, such a requirement seems to be
practically infeasible.

============
Canadian CANDU reactor overview:

The large thermal mass of the moderator provides a significant heat sink
that acts as an additional safety feature. If a fuel assembly were to
overheat and deform within its fuel channel, the resulting change of
geometry permits high heat transfer to the cool moderator, thus
preventing the breach of the fuel channel, and the possibility of a
meltdown. Furthermore, because of the use of natural uranium as fuel,
this reactor cannot sustain a chain reaction if its original fuel
channel geometry is altered in any significant manner.

Today there are 29 CANDU reactors in use around the world, and a further
13 "CANDU-derivatives" in use in India (these reactors were developed
from the CANDU design after India detonated a nuclear bomb in 1974 and
Canada stopped nuclear dealings with India). The countries the reactors
are located in a

* Canada: 17 (+3 refurbishing, +5 decommissioned)
* South Korea: 4
* China: 2
* India: 2 (+13 in use, +3 under construction)
* Argentina: 1
* Romania: 2 (+3 under construction, currently dormant)
* Pakistan: 1

CANDU fuel bundles, each about 50 cm in length and 10 cm in diameter,
weight approx. 20 kg (44 lb), generate about 1 GWh of electricity during
its time in the reactor.

The Bruce Nuclear Generating Station, the second multi-unit CANDU
station, was constructed in stages between 1970 and 1987 by the
provincial Crown corporation, Ontario Hydro. It consists of eight units
each rated at approximately 800 MWe each, and is currently owned by
Ontario Power Generation (OPG) and run by Bruce Power.

The Bruce station is the largest nuclear facility in North America, and
second largest in the world (after Kashiwazaki-Kariwa in Japan),
comprising eight CANDU nuclear reactors having a total output of 6,232
MW (net) and 7,276 MW (gross) when all units are online. Current output
with six of the eight reactors on line is 4,640 MW. Restart of the
remaining two units is planned by 2012.

(note: The Kashiwazaki-Kariwa reactor mentioned above is NOT a
CANDU-type reactor. It is a Boiling Water varient of a Light Water
Reactor, made by General Electric).
===========

http://en.wikipedia.org/wiki/Candu

Well it the generators and generator fuel tanks were underground like in
the US they would all be cooling just fine right now with no problems.

It's good that an earthquake doesn't actually disturb the ground.