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.

Home Guy wrote in :

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


Sure they can; it's just less likely for that to happen.




--
Tegger

Home Guy 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.

--
All is as it is.

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

On Tue, 15 Mar 2011 20:38:56 -0400, 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:


snip

You forgot this:
"The main difference between CANDUs and other water moderated reactors
is that CANDUs use heavy water for neutron moderation. The heavy water
surrounds the fuel assemblies and primary coolant.
The heavy water is unpressurized, and a cooling system is required to
keep it from boiling."

The big problem with ALL nukes is cooling.
Lose cooling and you get disaster.
You see what's going on in Japan?
Think there's 6 reactors on one site.
And cooling pools for depleted rods.
Those also need cooling or you get a disaster.
They cool depleted rods for 6-10 years before they can encase them for
disposal.
And the cooling pools aren't in a containment vessel like the active
rods are.
That's what's happening in Japan.
Even the depleted rods in the cooling pools are melting down and
releasing radiation to the atmosphere.

I think nukes are a good energy source, but when it goes wrong, it
goes VERY wrong.
After this Japan disaster, I only see 2 options for nukes going
forward. You need to do both.
1. Radical redesign so cooling loss can't cause disaster.
By "disaster" I mean environmental disaster.
That's what's scary about nukes. Last I saw 140k people have been
evacuated from around the Japan nuke plant.
No wonder nukes are subject to NIMBY.
If things go bad you can abandon the site, and no harm is done except
loss of investment and real estate.
This means cooling pools must also be in containment.

2. NEVER have "too much" fissionable material at one site.
Go smaller, not bigger.
That way when one breaks, there's no way it can be a huge disaster
like what might happen in Japan.
And they will break. Nobody believes that won't happen.
Building more and smaller nuke plants would be more expensive, but
that's how it is.

Anyway, that's my cracker barrel view as a newsgroup physicist.

--Vic

Vic Smith wrote:

You forgot this:
"The main difference between CANDUs and other water moderated reactors
is that CANDUs use heavy water for neutron moderation. The heavy water
surrounds the fuel assemblies and primary coolant.
The heavy water is unpressurized, and a cooling system is required to
keep it from boiling."

That's when it's operating. A Candu core can be shut down without
needing a cooling system to remain functioning after shutdown.

This is the key point:

----------
Criticality of CANDU fuel bundles in light water is impossible, avoiding
one concern of severe accident analyses that light-water reactors must
contend with. Furthermore, since the geometry of the CANDU core is near
optimal from a reactivity standpoint, any rearrangement under severe
accident conditions ensures shutdown.
---------

http://www.nuclearfaq.ca/cnf_sectionD.htm

http://www.nuclearfaq.ca/cnf_sectionD.htm#q

The CANDU system is a strong example of safety through both engineered
redundancy and passive design. The core has numerous triple-redundant
detectors that feed to two logically, conceptually and physically
separate shutdown systems (shut-off rods and high-pressure poison
injection). Each system is capable of shutting down the core within 2
seconds following a LOCA ("Loss-of-Coolant Accident" -- the design-basis
accident for CANDU reactors), without credit given to operator
intervention.

In addition to engineered safety systems, CANDU reactors have a number
of inherent safety features that distinguish it from other reactor
designs (e.g. PWRs, BWRs):

* The subdivision of the core into two thermalhydraulic loops (in
most CANDU designs), and hundreds of individual pressure tubes within
each loop, localizes a LOCA (Loss-of-Coolant Accident) to one small
region of the core, and reduces the reactivity effect of a LOCA
accordingly. Furthermore, the two core-passes per loop mean that only a
quarter of the core would likely suffer a mismatch between heat
generation and removal under such conditions (and only the highest-power
fuel elements within this one-quarter-core region).

* The large-volume, low-pressure, low-temperature moderator
surrounding the pressure tubes acts as a heat sink in large LOCA
scenarios, rendering negligible the risk of "fuel meltdown". The
moderator, in turn, is surrounded by a thick light-water shield tank
(used for biological and thermal shielding) which can also act as a heat
sink in severe accident scenarios.

* The moderator also provides a low-pressure environment for the
control rods, eliminating the "rod-ejection" scenarios considered in PWR
safety analyses. In addition, the location of neutronics measurement
devices in the moderator avoids subjecting this equipment to a hot,
pressurized environment.

* Heavy-water neutron kinetics is slower by several orders of
magnitude than light-water kinetics, reducing the discontinuity between
prompt and delayed kinetic behaviour, and making control easier.

* Criticality of CANDU fuel bundles in light water is impossible,
avoiding one concern of severe accident analyses that light-water
reactors must contend with. Furthermore, since the geometry of the CANDU
core is near optimal from a reactivity standpoint, any rearrangement
under severe accident conditions ensures shutdown.

* On-power refuelling means that the power distribution reaches an
equilibrium within a year of start-up, and remains virtually unchanged
for the reactor's operating life. This greatly simplifies the analysis
of core behaviour as a result of postulated accidents.

* On-power refuelling also allows defective fuel to be detected and
removed from the core, reducing the contamination of the reactor coolant
piping and simplifying maintenance.

* The low excess reactivity of the CANDU core leads to relatively
low reactivity worth of the control devices, limiting the potential
severity of postulated loss-of-regulation accidents.

* The positioning of the steam generators well above the core
promotes natural thermosyphoning (i.e. movement due to the coolant's own
density differences), which can remove decay heat if shut-down cooling
is lost. At the same time, the large amount of small-diameter piping in
the feeder network acts as a natural "radiator" under such conditions.

This significant amount of inherent, or "passive", safety in the CANDU
system, in conjunction with fast-acting, robustly engineered safety
systems and backup safety systems, is the reason why a complex
technology like nuclear power can be one of the safest and most reliable
energy options available.

In article , Home Guy wrote:

That's when it's operating. A Candu core can be shut down without
needing a cooling system to remain functioning after shutdown.

This is the key point:

Just my cynicism, but I'm guessing that nuclear power just got shoved
back another 40 years. Yer average lay person doesn't give a damn about
facts, or science, or about how the reactors in Japan differ from the
ones you advocate. "Nuke" just resumed its status as a dirty word.

On Mar 16, 3:57*am, Home Guy wrote:
Vic Smith wrote:
You forgot this:
"The main difference between CANDUs and other water moderated reactors
is that CANDUs use heavy water for neutron moderation. The heavy water
surrounds the fuel assemblies and primary coolant.
The heavy water is unpressurized, and a cooling system is required to
keep it from boiling."

That's when it's operating. *A Candu core can be shut down without
needing a cooling system to remain functioning after shutdown.

This is the key point:

----------
Criticality of CANDU fuel bundles in light water is impossible, avoiding
one concern of severe accident analyses that light-water reactors must
contend with. Furthermore, since the geometry of the CANDU core is near
optimal from a reactivity standpoint, any rearrangement under severe
accident conditions ensures shutdown.
---------

http://www.nuclearfaq.ca/cnf_sectionD.htm

http://www.nuclearfaq.ca/cnf_sectionD.htm#q

The CANDU system is a strong example of safety through both engineered
redundancy and passive design. The core has numerous triple-redundant
detectors that feed to two logically, conceptually and physically
separate shutdown systems (shut-off rods and high-pressure poison
injection). Each system is capable of shutting down the core within 2
seconds following a LOCA ("Loss-of-Coolant Accident" -- the design-basis
accident for CANDU reactors), without credit given to operator
intervention.

In addition to engineered safety systems, CANDU reactors have a number
of inherent safety features that distinguish it from other reactor
designs (e.g. PWRs, BWRs):

* * * The subdivision of the core into two thermalhydraulic loops (in
most CANDU designs), and hundreds of individual pressure tubes within
each loop, localizes a LOCA (Loss-of-Coolant Accident) to one small
region of the core, and reduces the reactivity effect of a LOCA
accordingly. Furthermore, the two core-passes per loop mean that only a
quarter of the core would likely suffer a mismatch between heat
generation and removal under such conditions (and only the highest-power
fuel elements within this one-quarter-core region).

* * * The large-volume, low-pressure, low-temperature moderator
surrounding the pressure tubes acts as a heat sink in large LOCA
scenarios, rendering negligible the risk of "fuel meltdown". The
moderator, in turn, is surrounded by a thick light-water shield tank
(used for biological and thermal shielding) which can also act as a heat
sink in severe accident scenarios.

* * * The moderator also provides a low-pressure environment for the
control rods, eliminating the "rod-ejection" scenarios considered in PWR
safety analyses. In addition, the location of neutronics measurement
devices in the moderator avoids subjecting this equipment to a hot,
pressurized environment.

* * * Heavy-water neutron kinetics is slower by several orders of
magnitude than light-water kinetics, reducing the discontinuity between
prompt and delayed kinetic behaviour, and making control easier.

* * * Criticality of CANDU fuel bundles in light water is impossible,
avoiding one concern of severe accident analyses that light-water
reactors must contend with. Furthermore, since the geometry of the CANDU
core is near optimal from a reactivity standpoint, any rearrangement
under severe accident conditions ensures shutdown.

* * * On-power refuelling means that the power distribution reaches an
equilibrium within a year of start-up, and remains virtually unchanged
for the reactor's operating life. This greatly simplifies the analysis
of core behaviour as a result of postulated accidents.

* * * On-power refuelling also allows defective fuel to be detected and
removed from the core, reducing the contamination of the reactor coolant
piping and simplifying maintenance.

* * * The low excess reactivity of the CANDU core leads to relatively
low reactivity worth of the control devices, limiting the potential
severity of postulated loss-of-regulation accidents.

* * * The positioning of the steam generators well above the core
promotes natural thermosyphoning (i.e. movement due to the coolant's own
density differences), which can remove decay heat if shut-down cooling
is lost. At the same time, the large amount of small-diameter piping in
the feeder network acts as a natural "radiator" under such conditions.

This significant amount of inherent, or "passive", safety in the CANDU
system, in conjunction with fast-acting, robustly engineered safety
systems and backup safety systems, is the reason why a complex
technology like nuclear power can be one of the safest and most reliable
energy options available.

I think the main point is not to build them in tsunami prone zones.
It was the tsunami that nobbled it not the quake. So they need to be
built away from the coast.

We have a nuclear reactor in the Severn estuary in the UK. There was a
Tsunami there some 300 years ago.
Not all Tsunamis arise from earthquakes. Some come from undersea
avalanches.

On Tue, 15 Mar 2011 23:57:39 -0400, Home Guy wrote:

Vic Smith wrote:

You forgot this:
"The main difference between CANDUs and other water moderated reactors
is that CANDUs use heavy water for neutron moderation. The heavy water
surrounds the fuel assemblies and primary coolant.
The heavy water is unpressurized, and a cooling system is required to
keep it from boiling."

That's when it's operating. A Candu core can be shut down without
needing a cooling system to remain functioning after shutdown.

This is the key point:

----------
Criticality of CANDU fuel bundles in light water is impossible, avoiding
one concern of severe accident analyses that light-water reactors must
contend with. Furthermore, since the geometry of the CANDU core is near
optimal from a reactivity standpoint, any rearrangement under severe
accident conditions ensures shutdown.
---------

http://www.nuclearfaq.ca/cnf_sectionD.htm

http://www.nuclearfaq.ca/cnf_sectionD.htm#q


Didn't know about CANDU reactors. But I've read up a bit.
I can't argue about heavy water versus light water reactors.
But they both use uranium.
Saying a CANDU can't melt down when it loses cooling is just wrong.
That's what they all say.
Let's wait until a CANDU loses cooling, then we'll see.
I'll stick with what I said.
Good containment of cores and depleted rod cooling pools, and never
put too much uranium in one place.
Smaller reactors/generating plants, and spread them around.
Then when the **** hits the fan it's not a huge disaster.
Just a small disaster.

--Vic

On Mar 15, 8:38*pm, 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.


Here's a fact. Unless the Canadians have re-invented the laws of
physics,
your whole premise and understanding of what's going on is wrong. No
nuclear reactor can go from 100% power to zero power instantly or
within
even a few hours. That has nothing to do with the reactor design,
but
has everything to do with physics. The fission of uranimum produces
radioactive byproducts that in turn decay over time. That decay
continues
for hours and days after the control rods are inserted. The control
rods
absorb neutrons and stop the uranium chain reaction, but do nothing
to stop the self decay of the other radioactive elements. Every power
reactor has to have some means of removing that waste heat or the
reactor will start to melt down.

Also, nothing in that cite says anything
close to what you claim it does. It comments on one narrow aspect
of the design. Show us where it says cooling water is not critical
after inserting the control rods.

I'ts also particularly foolish to start claiming some Canadian
reactor,
which your obvioulsy don't understand, is superior and would have
prevented the accident. Wouldn't it be better to first at least
find
out the full story and sequence of events from an investiation?

wrote in message
...


Also, nothing in that cite says anything
close to what you claim it does. It comments on one narrow aspect
of the design. Show us where it says cooling water is not critical
after inserting the control rods.

I'ts also particularly foolish to start claiming some Canadian
reactor,
which your obvioulsy don't understand, is superior and would have
prevented the accident. Wouldn't it be better to first at least
find
out the full story and sequence of events from an investiation?

Canadian reactors don't use uranium, they are fueled by worn-out hockey
pucks of which Canada has an infinite supply. And they can stop their
reactors instantly, the control rods look like a big goalie stick and a big
goalie glove and once they're in there a whistle blows and nothing happens
after that until the restart procedure which is known as a face-off.

In article ,
"DGDevin" wrote:



Canadian reactors don't use uranium, they are fueled by worn-out hockey
pucks of which Canada has an infinite supply. And they can stop their
reactors instantly, the control rods look like a big goalie stick and a big
goalie glove and once they're in there a whistle blows and nothing happens
after that until the restart procedure which is known as a face-off.

You forgot to append your comments with the disclaimer:

"I was just kidding, this is a joke, please don't respond as though I
was actually being serious."

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.



--
All is as it is.

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.

dgk wrote in news:f8l4o6h4au5o2b0jaibm2k6sivicpu29hl@
4ax.com:

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


???
There is no disturbing of the ground if a road splits down the yellow
centerline and one half is suddenly 4 feet below the other half??

--
Best regards
Han
email address is invalid

On 3/15/2011 6:02 PM, Home Guy wrote:
Canadian CANDU nuclear reactors can't melt down or go critical the way
that these GE reactors are doing in Japan.

....

If they can't go critical they wouldn't be of much use...

And, they have emergency cooling systems for large and small LOCA just
as do LWRs...

http://canteach.candu.org/library/20040724.pdf

--

In article , dpb wrote:
On 3/15/2011 6:02 PM, Home Guy wrote:
Canadian CANDU nuclear reactors can't melt down or go critical the way
that these GE reactors are doing in Japan.

....

If they can't go critical they wouldn't be of much use...

I think you need to look up the meaning of critical... If it *does* go
critical, it becomes a bomb.

On 3/16/2011 7:05 AM, Doug Miller wrote:
In , wrote:
On 3/15/2011 6:02 PM, Home Guy wrote:
Canadian CANDU nuclear reactors can't melt down or go critical the way
that these GE reactors are doing in Japan.

....

If they can't go critical they wouldn't be of much use...

I think you need to look up the meaning of critical... If it *does* go
critical, it becomes a bomb.

I know the meaning of critical but I'll look it up and explain it for
you...

For a chain-reacting system, the mean number of fission neutrons
produced by a neutron during its life within the system is known as the
"multiplication factor" termed "keff" or "k-effective". It follows that
keff = 1 if the system is critical; keff 1 and the system is
subcritical; keff 1 and the system is supercritical.

It does _not_ follow that if the system is supercritical there is a
nuclear explosion; it requires going slightly super critical to raise
power levels (or to initially startup the reactor in the first place);
once the new desired power level is achieved, control rod and/or other
poisons (soluble boron in form of boric acid in LWRs) are adjusted to
bring keff back to precisely 1 (which is obtained by observing that
neutron fluxes are maintained at a constant level by the reactor
instrumentation.

chain reaction, fission: A sequence of nuclear fission reactions in
which fissions are induced by neutrons emerging from preceding fissions.
Depending on whether the number of fissions directly induced by
neutrons from one fission is on the average less than, equal to, or
greater than unity, the chain reaction is convergent, (subcritical),
self-sustaining (critical), or divergent (supercritical).

Note that "supercritical" does _not_ on its own imply the reactor or
reaction is out of control; it requires being supercritical for a period
to either startup the reactor or to raise the operating power level
from, say, 75% to 100% FOP. If the reactor were to remain subcritical
its entire lifetime it would never start up and never, therefore, be of
any actual practical use.

Nuclear explosions only occur when the value of keff 1 and the
reaction becomes critical on prompt neutrons alone. That is a
physically unrealizable situation in commercial reactors; neither the
geometry nor enrichment are adequate.

A pretty good glossary of nuclear terms; not for the totally faint of
heart, however, ...

http://docs.google.com/viewer?a=v&q=cache:fjjM1LufiUwJ:www.osti.gov/bridge/servlets/purl/5609066-o4S1LS/+critical+definition+nuclear+ans&hl=en&gl=us&pid=b l&srcid=ADGEESg0uV0cj6tbQW6eF-x7W6tPhFkW6KXSVOExz2Nx4AQ2r2ET_MuaF_Q4jRjWVMJKgXrV rMwCYvZ2FEZNEJJ2JppYRojEhx2ssmz6vyWrbp4hZSXY6_UDRl BXJJ5momSZE6F86ch5&sig=AHIEtbTGQLNFf-U_xYcrKFLGI4YvlLvbzw

--

On Mar 15, 4:02*pm, Home Guy 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.

Here's a question nobody is asking:

Since the problem always seems to be with outdated reactors; how many
outdated reactors are decommissioned every year?

Molly Brown wrote:

Here's a question nobody is asking:

Since the problem always seems to be with outdated reactors; how many
outdated reactors are decommissioned every year?

Nobody's asking that question because the question is based on a faulty
premis - that the reactors are "outdated".

It's like if I asked you if you still beat your wife (or in your case,
maybe your husband).

The basic design of that reactor (and many others made by GE USA in
Japan and in the US) requires that it always has a functional cooling
system. It doesn't matter if it was old or new - it always needs a
functioning cooling system, because the nuclear chain reaction can't be
fully stopped in that design.

On Mar 15, 6:24*pm, Home Guy wrote:
Molly Brown wrote:
Here's a question nobody is asking:

Since the problem always seems to be with outdated reactors; how many
outdated reactors are decommissioned every year?

Nobody's asking that question because the question is based on a faulty
premis - that the reactors are "outdated".

It's like if I asked you if you still beat your wife (or in your case,
maybe your husband).

The basic design of that reactor (and many others made by GE USA in
Japan and in the US) requires that it always has a functional cooling
system. *It doesn't matter if it was old or new - it always needs a
functioning cooling system, because the nuclear chain reaction can't be
fully stopped in that design.

So what you're saying is that you would let your wife and two children
drive around in a

http://stationwagonforums.com/forums...onwagon 1.jpg

even though it's outdated.

On 3/15/2011 11:21 PM, Molly Brown wrote:
....
So what you're saying is that you would let your wife and two children
drive around in a

.... even though it's outdated.

Ignore this bozo, Molly; he's totally wrong.

The CANDU reactor also has emergency core cooling systems and requires
core cooling after shutdown; see the earlier link I posted that
describes the systems.

The issue is that fission reactors of _ALL_ types produce fission
products (well, DOH! ) which are radioactive and therefore, decay.
The process of radioactive decay gives of heat as the decay products are
absorbed in the various materials of the reactor and this gives rise to
the (amazingly well-named ) decay heat which must be removed even
after the reactor is shut down.

The fission nuclear reaction has been shut down by "scramming" the
reactor and once so, that reaction does (essentially) cease. That is no
different in a LWR (BWR or PWR) as it is in the CANDU heavy water design.

(I am, btw, degreed NucE w/ 30+ yrs in commercial nuclear generation
with both a reactor vendor and as consultant to power utilities, various
US national laboratories, US DOE and commercial clients)

--

dpb wrote in
:

On 3/15/2011 11:21 PM, Molly Brown wrote:
...
So what you're saying is that you would let your wife and two
children drive around in a

... even though it's outdated.

Ignore this bozo, Molly; he's totally wrong.

The CANDU reactor also has emergency core cooling systems and requires
core cooling after shutdown; see the earlier link I posted that
describes the systems.

The issue is that fission reactors of _ALL_ types produce fission
products (well, DOH! ) which are radioactive and therefore, decay.
The process of radioactive decay gives of heat as the decay products
are absorbed in the various materials of the reactor and this gives
rise to the (amazingly well-named ) decay heat which must be
removed even after the reactor is shut down.

The fission nuclear reaction has been shut down by "scramming" the
reactor and once so, that reaction does (essentially) cease. That is
no different in a LWR (BWR or PWR) as it is in the CANDU heavy water
design.

(I am, btw, degreed NucE w/ 30+ yrs in commercial nuclear generation
with both a reactor vendor and as consultant to power utilities,
various US national laboratories, US DOE and commercial clients)

Well, I am a biochemist of sorts, but I do believe I can reason.
Opinions on that vary, but you are not allowed to question my spouse or
kids.

Question here is, can you explain how a CANDU reactor gets cooled after a
total power loss, and once it is scrammed, fission of the fuel has
stopped (mostly), but the fission products still produce prodigious
amounts of heat.

TIA!
(I'm in favor of nuclear energy, but the problems haven't all been
solved, I think.)
--
Best regards
Han
email address is invalid

"dpb" wrote in message
...
On 3/15/2011 11:21 PM, Molly Brown wrote:
...
So what you're saying is that you would let your wife and two children
drive around in a

... even though it's outdated.

Ignore this bozo, Molly; he's totally wrong.

The CANDU reactor also has emergency core cooling systems and requires
core cooling after shutdown; see the earlier link I posted that
describes the systems.

The issue is that fission reactors of _ALL_ types produce fission
products (well, DOH! ) which are radioactive and therefore, decay.
The process of radioactive decay gives of heat as the decay products are
absorbed in the various materials of the reactor and this gives rise to
the (amazingly well-named ) decay heat which must be removed even
after the reactor is shut down.

The fission nuclear reaction has been shut down by "scramming" the
reactor and once so, that reaction does (essentially) cease. That is no
different in a LWR (BWR or PWR) as it is in the CANDU heavy water design.

(I am, btw, degreed NucE w/ 30+ yrs in commercial nuclear generation
with both a reactor vendor and as consultant to power utilities, various
US national laboratories, US DOE and commercial clients)

This is all about money. Reactors *could* be built to withstand tsunamis
AND earthquakes but no one would be able to afford them. It's only after
disasters that business and governments are willing to spend money on
additional protections against theoretically rare events.

I think the real problem here was believing the tsunami barriers would work.
It turns out they had multiple modes of failure. We do learn an awful lot
with each near meltdown. From what I've been reading, designs subsequent to
the GE MK1 have incorporated a lot of improvements, much of it learned from
failures at TMI and Chernobyl. This accident will probably cause regulators
to up the requirements for cooling system survivability, armoring them up
perhaps as much as the reactor containment vessels. In all the designs I've
seen posted on the net, the cooling systems seem to be a pretty serious
Achilles' heel.

As a NucE, what would you say the worst case scenario is in the Japanese
crisis? What would it look like compared to Chernobyl?

--
Bobby G.

On Mar 16, 10:32*am, dpb wrote:
On 3/15/2011 11:21 PM, Molly Brown wrote:
... So what you're saying is that you would let your wife and two children
drive around in a

... even though it's outdated.

Ignore this bozo, Molly; he's totally wrong.

TheCANDUreactor also has emergency core cooling systems and requires
core cooling after shutdown; see the earlier link I posted that
describes the systems.

The issue is that fission reactors of _ALL_ types produce fission
products (well, DOH! * ) which are radioactive and therefore, decay.
The process of radioactive decay gives of heat as the decay products are
absorbed in the various materials of the reactor and this gives rise to
the (amazingly well-named ) decay heat which must be removed even
after the reactor is shut down.

The fission nuclear reaction has been shut down by "scramming" the
reactor and once so, that reaction does (essentially) cease. *That is no
different in a LWR (BWR or PWR) as it is in theCANDUheavy water design.

(I am, btw, degreed NucE w/ 30+ yrs in commercial nuclear generation
with both a reactor vendor and as consultant to power utilities, various
US national laboratories, US DOE and commercial clients)

--

He's not "totally" wrong and you're glossing over the differences in
fundamental design and safety margins of PHWR (Candu) vs BWR. In the
event of Station Black Out (SBO) + loss of ECCS w/o operator
intervention, a Candu reactor, due to the heat sinks provided in the
design from the low pressure/low temp moderator and water filled
reactor core, will very likely not "melt down" while a BWR certainly
will and did.

On Tue, 15 Mar 2011 21:24:44 -0400, Home Guy wrote:

Molly Brown wrote:

Here's a question nobody is asking:

Since the problem always seems to be with outdated reactors; how many
outdated reactors are decommissioned every year?

Nobody's asking that question because the question is based on a faulty
premis - that the reactors are "outdated".

It's like if I asked you if you still beat your wife (or in your case,
maybe your husband).

The basic design of that reactor (and many others made by GE USA in
Japan and in the US) requires that it always has a functional cooling
system. It doesn't matter if it was old or new - it always needs a
functioning cooling system, because the nuclear chain reaction can't be
fully stopped in that design.


When the control rods are dropped, as they were in Japan within
seconds of the earthquake being detected, the reaction stops. All
that's left is the secondary radioactive byproducts producing heat as
they enter their half-life phase, which is a few days to a couple
weeks.

On Mar 15, 9:24*pm, Home Guy wrote:
Molly Brown wrote:
Here's a question nobody is asking:

Since the problem always seems to be with outdated reactors; how many
outdated reactors are decommissioned every year?

Nobody's asking that question because the question is based on a faulty
premis - that the reactors are "outdated".

It's like if I asked you if you still beat your wife (or in your case,
maybe your husband).

The basic design of that reactor (and many others made by GE USA in
Japan and in the US) requires that it always has a functional cooling
system. *It doesn't matter if it was old or new - it always needs a
functioning cooling system, because the nuclear chain reaction can't be
fully stopped in that design.

No, nitwit. All nuclear power reactors need a functioning cooling
system
for days after the fission reaction is stopped. That's because the
heat
continues to come from radioactive byproducts of the fission. You can
stop the fission, but you cannot stop the natural decay of those
radioactive byproducts. Ever hear of a spent fuel pool? Why do you
think they generate heat and must be cooled as well?

I'd like to see a credible reference that says the fission process
cannot
be stopped by inserting all the control rods in the GE reactor. Link
please......

And what kind of nitwit starts speculating without having any of the
basic
facts? We need a full investigation. So far, we hardly have any
data
at all as to what happened.

On Mar 15, 6:02*pm, Home Guy 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.

What a piece of **** you are, true crap, Put 30 feet of water over any
plant not designed to operate flooded and what do you have you ass
hole. There are always smart asses like you around. You are the true
****tard.

Home Guy 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.

Hmm. So far, no one has died (or even gotten sick) from the Japanese nuclear
power plants.

A pundit who studied Chernobyl for 30 years recently concluded that more
people died from WORRY over the events at Chernobyl than from radiation
poisoning or its aftermaths.

This worry manifested itself in agitation over relocation, heart disease,
Type II diabetes, consternation, upheavals, etc. There was a ten-fold
increase in abortions as women feared their children might be born with god
knows what.

It might be said, to coin a phrase, we have nothing to fear but fear.

On 3/16/2011 9:02 PM, HeyBub wrote:
Home Guy 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.

Hmm. So far, no one has died (or even gotten sick) from the Japanese nuclear
power plants.


Always good to make jokes especially when you know that except in the
case of exposure to mega quantities of radiation health effects are not
instantaneous.


A pundit who studied Chernobyl for 30 years recently concluded that more
people died from WORRY over the events at Chernobyl than from radiation
poisoning or its aftermaths.


The FSU was really open about all of their doings so we can certainly
count on accurate statistics....





This worry manifested itself in agitation over relocation, heart disease,
Type II diabetes, consternation, upheavals, etc. There was a ten-fold
increase in abortions as women feared their children might be born with god
knows what.

It might be said, to coin a phrase, we have nothing to fear but fear.

George wrote:
On 3/16/2011 9:02 PM, HeyBub wrote:
Home Guy 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.

Hmm. So far, no one has died (or even gotten sick) from the Japanese
nuclear power plants.


Always good to make jokes especially when you know that except in the
case of exposure to mega quantities of radiation health effects are
not instantaneous.



No joke. There are three possible bad effects from radiation:

* Radiation sickness - you either get over it or you die. There is no
lasting effect.
* Genetic mutation - there is no case on record of a mutated fetus surviving
to term.
* Cancer - Cancer is the most studied disease on the planet.

Next, there are no "mega quantities" of radiation in Japan (or at least none
reported).

The point the pundit was making is that there is a fourth deleterious health
effect: Fear. Fear, and the accompanying trepidation, causes heart problems,
psychological dysfunction, and irrational actions, such as tens of thousands
of elective abortions.

What does this have to do with home repair? Unless the discussion
touches on how much lead is needed to wrap a house near a reactor, then
this is the wrong newsgroup.

On 3/16/2011 8:02 PM, HeyBub wrote:
Home Guy 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.

Hmm. So far, no one has died (or even gotten sick) from the Japanese nuclear
power plants.

A pundit who studied Chernobyl for 30 years recently concluded that more
people died from WORRY over the events at Chernobyl than from radiation
poisoning or its aftermaths.

This worry manifested itself in agitation over relocation, heart disease,
Type II diabetes, consternation, upheavals, etc. There was a ten-fold
increase in abortions as women feared their children might be born with god
knows what.

It might be said, to coin a phrase, we have nothing to fear but fear.

R. F. Duffer wrote:
What does this have to do with home repair? Unless the discussion
touches on how much lead is needed to wrap a house near a reactor,
then this is the wrong newsgroup.


Complaining about the content of various posts doesn't really fit the
portfolio of the group either.

On Tue, 15 Mar 2011 19:02:37 -0400, Home Guy 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.

were candu reactors around 50 years ago?