Newsgroups: sci.energy
From: jgd@dixie.com (John De Armond)
Subject: Re: Breeders
Message-ID: <489v5!_@dixie.com>
Date: Tue, 11 May 93 17:21:39 GMT
Keywords: Rx is NOT a bomb!

mrjg8679@uxa.cso.uiuc.edu (Michael R James) writes:

>I thought that the water was carried through the the core
>in the RBMKs in separate channels in the graphite.  I don't
>think the water ever contacted the fuel cladding.
>One "advantage" of the RBMK was on-line refueling ( a leftover
>from the design's weapons production days).  I can't imagine
>removing fuel that's in contact with coolant.
>

You're right. Sollows has simply argued himself into a corner and is trying
to wiggle out.

From the literature I've collected on the subject, here is what seems to
have happened at Chernobyl. (I'd not dispute variations on the theme.
It seems most everything associated with Chernobyl is clouded by official
lies.)

When the scram button was pressed, there was a total positive reactivity
insertion of 2.5 (HUGE!) which led to a local power transient estimated
to be in excess of 500 MWt.  This transient cause enough steam pressure
and water hammer to rupture the cooling channels and jam the control rods
while they were still mostly out.  The reactor continued running.
The water, now in contact with very hot fuel cladding and graphite,
chemically reacted with both, releasing hydrogen and carbon monoxide.
The fuel did not react because it is an oxide.  The hydrogen and
carbon monoxide collected under the upper biological shield and when it
reached a flammable ratio, exploded, ignited by the still-running but
now-uncooled reactor.  THIS hydrogen explosion is what blew the
top off the reactor building and scattered part of the core around
the compound.  The reactor, or what was left of it, continued
running after this explosion.  The heat generated vaporized the fuel
and set the graphite on fire.  This nuclear-fed inferno is what
vaporized a large fraction of the core's fission product inventory.
It should be remembered a) that the core was at the end of its life
and thus ladden with fission products and b) the core was over 3 times
larger than free world designs, containing over 300 tons of fuel.

Explosions figured into Chernobyl only as a triggering event for a much
larger disaster - a still-critical, uncooled core with a fire in it that
burned for several days.

John
--
John De Armond, WD4OQC               |Interested in high performance mobility?
Performance Engineering Magazine(TM) | Interested in high tech and computers?
Marietta, Ga                         | Send ur snail-mail address to
jgd@dixie.com                        | perform@dixie.com for a free sample mag
Lee Harvey Oswald: Where are ya when we need ya?

Newsgroups: sci.energy
From: whitlock@dcss.mcmaster.ca (Jeremy Whitlock)
Subject: Re: Breeders
Message-ID: <1993May11.193619.18924@mcshub.dcss.mcmaster.ca>
Keywords: Rx is NOT a bomb!
Date: Tue, 11 May 1993 19:36:19 GMT

Just to set the record a little straighter...

In article <489v5!_@dixie.com> jgd@dixie.com (John De Armond) writes:
>mrjg8679@uxa.cso.uiuc.edu (Michael R James) writes:
>
>>I thought that the water was carried through the the core
>>in the RBMKs in separate channels in the graphite.  I don't
>>think the water ever contacted the fuel cladding.
>>One "advantage" of the RBMK was on-line refueling ( a leftover
>>from the design's weapons production days).  I can't imagine
>>removing fuel that's in contact with coolant.
>>
>You're right.

No, he's wrong.  The fuel is immersed in pressurized water, and removed
while still immersed in pressurized water.  A fuelling machine latches on
to the end of each tube and pressurizes.  This is the same as with CANDU's.

>The water, now in contact with very hot fuel cladding and graphite,
>chemically reacted with both, releasing hydrogen and carbon monoxide.

The chemical reaction that produced hydrogen is between Zircalloy fuel
cladding and very hot steam.  Thus, it is not a problem under normal
operation.


--
Jeremy Whitlock                          "My thoughts are mine, not Mac's"
Dept. Engineering Physics
McMaster University                      e-mail: whitlock@mcmaster.ca
Hamilton, Ontario, Canada, L8S 4L7       phone: 416-525-9140 ext.7140

Newsgroups: sci.energy
From: jgd@dixie.com (John De Armond)
Subject: Re: Breeders
Message-ID: <h00v+6j@dixie.com>
Date: Wed, 12 May 93 18:22:50 GMT
Keywords: Rx is NOT a bomb!

sollows@UNBSJ.CA (KENNETH SOLLOWS) writes:

>In article <489v5!_@dixie.com> jgd@dixie.com (John De Armond) writes:

>John, cull the comic books out of your library; they have no place in a
>serious discussion of the merits of nuclear power.  Michael is misinformed;
>you're just ignorant!

Apparently then so is Grigori Mendvedev (Former section chief of
Soyuzatomenergo, Ministry of Energy & Electrification).  In his book he
pretty clearly describes a dry channel design.  Other of his facts
are at odds with other accounts so I'd not be terribly suprised that he
is wrong.

>500 MWt in what portion of a reactor rated at 3000 MWt or so?  If you're
>going to throw numbers about, throw enough to be meaningful.

In a region described as a flattened sphere occupying approximately
50 tons of the 3000 tons of fuel.  The power density obviously was
not uniform, the bulk probably occuring in the inner 2/3s.

>>This transient cause enough steam pressure
>>and water hammer to rupture the cooling channels and jam the control rods
>>while they were still mostly out.

>I love it.  "Enough steam pressure and water hammer".  John, just how much
>is "enough", and how was it generated?  No hand waving please, just reasoned
>physical insight.  How long will it take even a step change in internal heat
>generation rate in the fuel pin to significantly affect the cladding
>temperature?  Is this time scale consistant with the accident?  What happens
>to the heat transfer coefficient, and thus the steam generation rate, when
>the critical heat flux is exceeded?

Not the issue.  Film boiling is only part of the equation in a transient
such as this.  Gamma and neutron heating contributes more than enough
to flash the water long before heat transport from the fuel pins occurs.

>It's clear that you don't have even a passing familiarity with the design of
 the reactor in question, or the basic
>physical principles that come into play in the event you purport to describe?

I can see the ignorance but not on this side.  Why don't you go back and
look at the analysis of the SL-1 reactor steam explosion?  This steam
explosion was also caused by a prompt criticality.  And just like
Chernobyl, the initial mechanism of destruction was steam-driven water
hammer slamming into the top of the reactor vessel with enough force to
blow off the control rod drives, pull out the closure studs, shear the
cooling pipes and jack the whole vessel several feet upward.  Unlike
chernobyl, the large negative moderator coefficient shut the reaction
down in microseconds.  And unlike Chernobyl, bulk fuel failuer of the
ALUMINUM-clad fuel did not occur.  The fuel was distorted and the
control blades were locked in place (greatly assisting the analysis of
the accident) but the cladding did NOT bulk melt.  Hey, if you're really
reading-impaired, there's even a video available from DOE.  SL-1 (and
BORAX, for that matter) is a classic example of the relatively minor
aftermath of a prompt criticality accident in a properly designed
reactor.

I cite this example because unlike Chernobyl the facts are well known and
undisputed.

Back to the explosion thread, the power transient at Chernobyl did NOT
cause an explosion.  It is described in the literature as a series of
rumbles.  The reactor foreman, Valery Perevozchenko, who was above the
biological shield at that instant, described the shield plates as
"dancing as if shook by a giant hand" from the vibration.  He was able
to report this because the explosion happened 40 seconds later after the
cladding/graphite/water reaction had produced enough hydrogen and oxygen
to explode under the biological shield.  He (fairly rapidly, I'd
imagine) returned to the control hall to report what he had seen BEFORE
the explosion.

>Just a suggestion.  Before you give up your day job and start lecturing on
>energy policy and public safety, why not develop a passing familiarity with
>the subject?

Good suggestion, Ken.  Follow it.  Actually it worked the other way for
me, Ken.  I quit my day nuclear job to pursue this magazine venture.
I'm a health-physicist and a former ARO (not licensed only because I
took a higher paying job in engineering before my plant, Sequoyah, was
licensed.) with over 15 years experience and hundreds of hours on the
reactor simulators.  (BWR and Westinghouse PWR).  I've consulted to
about a third of the US utilities on radiation and emergency planning
matters.  The post- accident radiation monitoring system at TMI-1 is my
design and installation, for example.  And as the past TEMA radiological
safety officer for East Tennessee, a region that encompasses Oak Rdige
and the Sequoyah and Watts Bar nuclear plants, I've had a significant
positive impact on public policy in the area.  I take at least partial
credit for emergency workers in the region being educated enough about
nuclear matters not to go ballistic when they see a magenta and yellow
propeller.

You're right about one thing.  I don't know as much about the RMBK as
I'd like.  I've been collecting literature for a couple of years as a
hobby.  If you had done the same thing, you'd realize that the accounts
even by the people who were there vary widely.  I was on the DOE
volunteer team that the Soviets declined to accept so I didn't get the
first-hand view of Chernobyl I desired.  Nontheless, I know enough about
reactor dynamics to be able to filter the BS from the descriptions of
the events.  And unlike you, I freely admit my areas of weakness, the
details of the RMBK being one.  Also unlike you, I won't get in a public
forum and make an ass out of myself by claiming a reactor can undergo a
nuclear explosion.  And then continuing to claim same after any number
of experts have shown you the error of your ways.  One would almost
believe Yackadamn artificial ignorance automation had forked itself and
taken on the name "Ken".

John
--
John De Armond, WD4OQC               |Interested in high performance mobility?
Performance Engineering Magazine(TM) | Interested in high tech and computers?
Marietta, Ga                         | Send ur snail-mail address to
jgd@dixie.com                        | perform@dixie.com for a free sample mag
Lee Harvey Oswald: Where are ya when we need ya?

Newsgroups: sci.energy
From: whitlock@dcss.mcmaster.ca (Jeremy Whitlock)
Subject: Re: Breeders
Message-ID: <1993May13.142404.13998@mcshub.dcss.mcmaster.ca>
Keywords: Rx is NOT a bomb!
Date: Thu, 13 May 1993 14:24:04 GMT

In article <h00v+6j@dixie.com> jgd@dixie.com (John De Armond) writes:
>sollows@UNBSJ.CA (KENNETH SOLLOWS) writes:
>>In article <489v5!_@dixie.com> jgd@dixie.com (John De Armond) writes:
>>John, cull the comic books out of your library; they have no place in a
>>serious discussion of the merits of nuclear power.  Michael is misinformed;
>>you're just ignorant!
>
>Apparently then so is Grigori Mendvedev (Former section chief of
>Soyuzatomenergo, Ministry of Energy & Electrification).  In his book he
>pretty clearly describes a dry channel design.

If Medvedev said this, he is mistaken.  To give him benefit of doubt,
however, I'd first suspect the Russian-English translation.

> Nontheless, I know enough about
>reactor dynamics to be able to filter the BS from the descriptions of
>the events.

Too bad you didn't filter the BS about a power reactor running with dry
fuel channels.

>John De Armond, WD4OQC

--
Jeremy Whitlock                          "My thoughts are mine, not Mac's"
Dept. Engineering Physics
McMaster University                      e-mail: whitlock@mcmaster.ca
Hamilton, Ontario, Canada, L8S 4L7       phone: 416-525-9140 ext.7140

Newsgroups: sci.energy
From: whitlock@dcss.mcmaster.ca (Jeremy Whitlock)
Subject: Re: Breeders
Message-ID: <1993May14.164544.24249@mcshub.dcss.mcmaster.ca>
Keywords: Rx is NOT a bomb!
Date: Fri, 14 May 1993 16:45:44 GMT

In article <8l#wf__@dixie.com> jgd@dixie.com (John De Armond) writes:
>whitlock@dcss.mcmaster.ca (Jeremy Whitlock) writes:
>>Too bad you didn't filter the BS about a power reactor running with dry
>>fuel channels.
>
>Interesting comment, Jeremy, particularly given your first statement above.
>Dry channel reactors aren't exactly unheard of, after all.

Of course not, but given that the RBMK isn't a gas-cooled reactor or
radiative/convection-cooled nuclear battery, I can only assume that when
you say the coolant doesn't touch the fuel cladding you are implying that
there is no cooling medium at all touching the fuel cladding.

> Perhaps someone
>will post a description in which the russian-english translation is
>"better."

No translation needed.  The RBMK's description can be found in any decent
book on reactor designs.  It is a vertically-oriented, graphite-moderated,
direct cycle (ie. boiling water) pressure tube reactor, comprised of a
vertical cylinder 12 m in diameter and 7 m high (roughly twice the diameter of
a CANDU with approximately the same height), filled with graphite blocks that
are penetrated with about 1700 vertical Zirconium-2.5%Nb alloy pressure tubes
containing fuel (2.0% enriched pre-Chernobyl, 2.4% enriched post-Chernobyl)
and control rods.  Coolant is pumped up through the pressure tubes from a
common inlet header, reaching an average steam quality of 14% (max. 22%),
and into a common steam drum.  The graphite is immersed in Helium and Nitrogen
to maintain an inert environment and to aid in heat transfer to the coolant
via the pressure tube walls.  (Perhaps this last point is the source of
confusion?)

This is taken from a rather unimposing little book called "Reactor Accidents"
by David Mosey (Nuclear Engineering International Special Publications, 1990).

--
Jeremy Whitlock                          "My thoughts are mine, not Mac's"
Dept. Engineering Physics
McMaster University                      e-mail: whitlock@mcmaster.ca
Hamilton, Ontario, Canada, L8S 4L7       phone: 416-525-9140 ext.7140

Newsgroups: sci.energy
From: jgd@dixie.com (John De Armond)
Subject: Re: Reactor explosions (was Re: Breeders)
Message-ID: <tl!wb-a@dixie.com>
Date: Thu, 13 May 93 04:40:18 GMT
Keywords: Rx is NOT a bomb!

sollows@UNBSJ.CA (KENNETH SOLLOWS) writes:

I'm wrapping several of Ken's babblings into this one post

>The problem with your line of arguement is that there was no "sealed"
>container.

Sure there was.  When the AZ switch (scram) was pressed, the reactor
was sealed because the reactor protection has previously been disabled

>Any local overpressure that could burst the open tube must
>therefore derive from a very high rate of vapour generation, so that the
>inertia of the coolant is sufficient to restrain the vapour, causing an
>overpressure.

Nope.  Again, according to Medvedev, the power transient lasted some
20 seconds according to both stripchart recordings and the plant computer.
At the instant the AZ switch was triggered, the total power level was at
about 60 MWt with almost all the rods out trying to burn out of an
iodine well.  The turbines had been tripped and the reactor coolant pumps
had begun to spin down.  The reduced flow led to steam voiding which lead
to a slow but uncontrollable power increase.  The pressure increase
was at about 0.5 atm/second.  When the aZ switch was triggered, starting
control rod insertion and the final 0.5 beta of positive reactivity, the
power surged in the upper part of the core to around 550 MWt.  This surge
caused the coolant pressure to increase at the rate of 15 atm/sec (220 psi/sec)
until the first coolant pipes ruptured.  If one assumes it would take double
the normal pressure to rupture a channel, something in the range of 10-20
seconds fits the scenario rather well.

>You just aren't going to get that from an intact fuel
>bundle because of some very fundamental heat transfer physics.  If you work
>really hard at it, you might get the fuel to melt and form a puddle, but you
>won't get very high vapour generation rates because the vapour insulates the
>water-fuel interface.  To get very high vapour generation rates you need to
>finely divide and distribute the hot fuel and cladding thru the water, so
>you get a large area for heat transfer and large vapour generation rates.

Nope.  If the power excursion is large enough, gamma, neutron and radiant
heating will do it just fine, particularly in a saturated steam environment as
existed in the core prior to the excursion.  The sequence of fuel disassembly
vs channel failure is of course, speculation because the core was
destroyed later and in any event is irrelevant since the chemical explosion
that destroyed the reactor occured a millennium later on the nuclear time scale.

>People design and build a device like this, that can take itself apart in
>such a spectacular manner, and you can say it's not about explosions!?!
>What planet are you from?

Let me ask you a little different question.  Was TMI about nuclear explosions?
This is directly related to Chernobyl, as I will explain in the next
installment.

>>So you would *advocate* the making of public policy based on scientific
>>ignorance and misconception?

>More amateur sophistry!  I've known 1st year law students that could argue a
>better case for nuclear power than you can.  Of course I don't, I just
>advocate making public policy through debate by thoughtful, feeling people
>with a concern for society and the world.  Scientific ignorance and
>misconception, of the kind demonstrated by you in these exchanges, has no
>legitimate place in reasoned policy debates.

Interesting comment comming from you, a person who admitted in another post
that you are technically illiterate in this field and who is relying
on an AECL executive summary for his facts.  It is interesting to see you
clain you don't advocate making public policy based on ignorant faddism while
at the same time you've spent almost 2 weeks trying to argue yourself
of your corner of claiming Chernobyl was a nuclear explosion.  I did
notice your amateurish technique of trying to drop "nuclear" out of your
later statements.  Are you a lawyer?  You certainly smell like one.


>He was clearly refering to an explosion.  I happen to think his approach to
>public discussion of these matters is much more productive than the simple-
>minded mantra "Reactors can't explode like bombs".  Like any mantra, one
>might feel better to say it over and over, but it only affects the
>individual.  The rest of the public is left with the impression of someone
>with a primitive belief in magic.

So you think a sensationalistic sound byte using language chosen for
its color is more productive than actual fact.  Not surprising.

>And this is just how the industry loses it credibility.  It says, for years
>and years, that reactors can't blow up like bombs.  When a reactor blows up,
>we say: "Well yes, it can blow up, but it wasn't like a bomb!"

Reactors cannot blow up like bombs regardless of how many times you
chant to the contrary.  Chernobyl didn't blow up like a bomb.  TMI
didn't blow up like a bomb.  SL-1 didn't blow up like a bomb, Hanford
didn't blow up like a bomb.  Chemical and/or steam explosions were involved
in some of these (see if you can figure out which.) but the nuclear
part had only a tangental involement.

>It
>degenerates into a debate about the number of angels that can dance on the
>head of a pin and the public gets suspicious or tunes out.

Unlike the "TV scientists" you worship, scientists and engineers with
any degree of personal integrity will NOT dumb down technical issues
to some public lowest denominator nor will they lie. Were that you
had a fraction of such standards.

>True enough, but irrelevant.  The "sealed system" in this case includes a
>heat sink, and up until the power transient the whole works is in quasi-
>staedy state.  The reactor physics is all screwed up, but the sucker is
>running.

Ohhh, such exquisitely precise scientific terms.  "Sucker".  "All screwed
up."  I'll have to remember these, as they convey soooo much more information
than conventional terms.

>running.  The question is:  How does a localized power transient cause such
>a spectacular tube failure?

The answer is it can't and it didn't.

>>This is why reactors are designed to scram
>>if you increase power to rapidly.  If you watched the film on Chernobyl you
>>will see the morons running the plant over rode that safety feature.
>
>Actually, the latest reports tend to shift more of the blame to the
>designers, and place a little less on the operators.

Nope.  The experiment was formulated by people with no nuclear training.
The execution of the test was managed by Anatoly Dyatlov, an electrical
engineer with no nuclear training.  And after the reactor sunk into
an iodine well while setting the test up, Dylatlovn overrode his Senior
Reactor Operator and ordered the attempt to burn out of it.  Gross
human error was the direct cause of the accident.  A very poor reactor
design contributed to the accident but it did NOT cause it.
One could postulate a situation where a person of Dyatlov's stature
could cause an excursion in most any reactor.

John
--
John De Armond, WD4OQC               |Interested in high performance mobility?
Performance Engineering Magazine(TM) | Interested in high tech and computers?
Marietta, Ga                         | Send ur snail-mail address to
jgd@dixie.com                        | perform@dixie.com for a free sample mag
Lee Harvey Oswald: Where are ya when we need ya?

Newsgroups: sci.energy
From: jgd@dixie.com (John De Armond)
Subject: Reactor explosions (was Re: Breeders)
Message-ID: <ln9v4rp@dixie.com>
Date: Tue, 11 May 93 05:41:27 GMT
Keywords: Rx is NOT a bomb!

sollows@UNBSJ.CA (KENNETH SOLLOWS) writes:

>>"Slow atomic bomb?"  Why not say that a reactor is brought up to power like
>>a "slow atomic bomb?"  Or, what not just call a reactor a "slow atomic bomb?"

>Because when they operate normally they don't produce an explosion that
>causes damage to the environs.  On the other hand, when they operate as the
>Chernobyl reactor did immediately prior to blowing the roof off its
>building, calling it an ~unanticipated core disassembly event~ or any
>other such technospeak gobbledygook does great damage to the credibility
>of the speaker.  The damn thing blew up.  It was like a bomb.  Was it like
>a glob of plastique, 3 sticks of dynamite, a truck load of fertilizer and
>fuel oil, a tank full of napalm?  I don't know, but Marshall said it was
>like a "slow atomic bomb" and I see no reason to disbelieve him.  I also
>note that, in addition to understanding something of the physics of the
>event, he is in a better position than most of us (me, anyway) to judge
>the kind of language appropriate to the description of the event in a
>public forum.

This would be funny if it weren't so tragically ignorant. I wonder if
you so blindly accept the explanation of other non-nuclear events that
you don't understand without question.  If so, your worldview must be
exceedlingly simple.  Let's do this real slowly.

If I take a few million curies of high level waste, wrap it in dynamite
and set it off in the World Trade center, was that a nuclear explosion?

Say "No".  Very good.

if I take a few million curies of HLW, put it in a sealed container
along with some water, build a fire under the container and allow it
to burst from steam pressure, was THAT a nuclear explosion?

Say "No".  Very very good.  We're making progress.

If I take a few million curies of HLW, put it in a sealed container along
with some water, insulate the whole thing very well and allow it
to burst from the decay-heat-generated-steam, was THAT a nuclear
explosion?

Say "No".

If I take a few million curies of HLW containing some fissionable
uranium, put it in a sealed container along with some water, insulate
the whole thing very well, arrange the geometry such that fission takes
place and allow it to burst from the fission-heat-generated-steam, was
THAT a nuclear explosion?

Say "No."  Heeeyyy, we're getting there.

If I take a few million curies of HLW containing some fissionable
uranium, put it in a sealed container along with some water, insulate
the whole thing very well, arrange the geometry such that real fast
fission takes place and allow it to burst from the
fission-heat-generated-steam, was THAT a nuclear explosion?

You know the drill.

Now suppose I take a couple of sub-critical masses, arrange some
contraption capable of holding them together long enough for a substantial
portion of the mass to fission, thus raising the whole mass to 300,000,000
degrees or so, emitting zillions of gamma, X-rays and neutrons and vaporizing
the assembly and some amount of surrounding real estate, is THAT a
nuclear explosion?

BINGO!!  You get to say "yes."

Nothing to do with steam, vaporized fuel, reactor vessels, conventional
explosives or any of the other tripe mentioned in this thread to justify
calling anything that explodes and involves radioactive materials a
"nuclear explosion."

Now that we've figured out what a nuclear explosion is and is not, let's
look at Chernobyl.

>No, but if a gas explosion ignited a fire that burned the house, I
>would say it exploded and burned.  I would say the same for Chernobyl.  As
>to what the expolsion was like, I have no problem with Lord Marshall's
>phrase ". . . like a slow atomic bomb."

Chernobyl is NOT about explosions.  The steam explosion did relatively
little damage as far as the outside world was concerned.  Sure the
core was destroyed and the reservation contaminated but that had
no effect on the civilians outside the plant.  What DID have an effect
on the outside world was the nuclear fueled fire that burned for several
days AFTER the explosion.  Because of the core design, the portions that
were not destroyed continued fissioning.  The heat caused the graphite
to burn and vaporized the fuel and fission products.  THIS SLOW BURN is
what generated the massive contamination that blanketed the region.
Had the reactor NOT continued fissioning, the impact would have been
orders of magnitude less.  I know these are subtle details but they
MATTER not only from a scientific perspective but from a political
perspective.  If public policy is to be set to fix some problem, it helps
to know the problem.  Public policy would have prevented a flawed reactor
design like Chernobyl from ever beening built.  For the record, Soviet
public policy, as it were, DID prohibit the construction of chernobyl-like
reactors.  Problem was it was ignored.  That is also a political problem
having nothing to do with explosions OR fires.

>Appropriate terminology depends upon context.  As I acknowledged in my post
>on April 25, the timescales are important in engineering and physics.  They
>just are just no so critical when it comes to policy.  The important
>words are "explode" and "bomb".

So you would *advocate* the making of public policy based on scientific
ignorance and misconception?  If so  words fail me to describe the
revulsion I feel toward you.  Understanding the difference between a
nuclear explosion and a thermal explosion from nuclear generated heat
has EVERYTHING to do with public policy.  No one in his right mind
would support a design that could undergo even a nuclear fizzle.
Thermally generated explosions are easy to handle with conventional
containments.  Indeed, I challenge anyone to distinguish between a steam
explosion and a "double ended guillotine break" of a primary coolant
pipe and the resultant release of a half million gallons of water at 650
degrees.  This double ended guillotine break is the design-basis accident
for conventional LWR plants.

Acknowledging public policy is sometimes made in a factual vacuum is one
thing; accepting and perpetuating it is a whole 'nuther ball game.  I
hope your position is one of technical ignorance rather than deceit.
I even more hope I misunderstood your position but I doubt it.

John

--
John De Armond, WD4OQC               |Interested in high performance mobility?
Performance Engineering Magazine(TM) | Interested in high tech and computers?
Marietta, Ga                         | Send ur snail-mail address to
jgd@dixie.com                        | perform@dixie.com for a free sample mag
Lee Harvey Oswald: Where are ya when we need ya?

Newsgroups: sci.energy
From: jgd@dixie.com (John De Armond)
Subject: Re: Reactor explosions (was Re: Breeders)
Message-ID: <j80vgyh@dixie.com>
Date: Wed, 12 May 93 17:07:05 GMT
Keywords: Rx is NOT a bomb!

stephens@geod.emr.ca (Dave Stephenson) writes:

>Almost true. The steam/hydrogen explosion a Chernobyl was powerful
>enough to shoot bits of the reactor core in to the local company
>town. The firefighters reported that some of their number were
>picking up bits that glowed blue in the street. Most are now dead.
>The comment about the slow burn is true. A water cooled graphite
>moderated reactor is about the  most unsafe  reactor design. The
>British graphite moderated reactors used carbon dioxide for cooling,
>and of course have a containment vessel.

No.  Bits of fuel and graphite were scattered over part of the other
reactor buildings and the compound.  Pripyat, the company town is about
3 km away from the compound.  The firefighters who died fought the
reactor fire and work in the midst of the heaviest debris immediately
around the crater.  An aerial photo of the plant pretty clearly shows the
blast radius and the debris.  Many of the people who died were soviet
soldiers (nicknamed "bio-robots") brought in to remove the core debris
from the reactor building and immediately surrounding area.  This was
done after the intense radiation scrambled even the nuclear-rated
robots loaned the Soviets by DOE.

A water cooled graphite reactor is not inherently unsafe.  A graphite
reactor with large positive temperature coefficient and a large positive
void coefficient IS, as would be any other design with the same
characteristics.

John
--
John De Armond, WD4OQC               |Interested in high performance mobility?
Performance Engineering Magazine(TM) | Interested in high tech and computers?
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Newsgroups: sci.energy
From: whitlock@dcss.mcmaster.ca (Jeremy Whitlock)
Subject: Re: Reactor explosions (was Re: Breeders)
Message-ID: <1993May12.195913.21347@mcshub.dcss.mcmaster.ca>
Keywords: Rx is NOT a bomb!
Date: Wed, 12 May 1993 19:59:13 GMT

In article <forrere.131.0@ccmail.orst.edu> forrere@ccmail.orst.edu (Gene Forrer) writes:
>I forgot to ask something.  Perhaps it would help if you went into more
>detail as to how the core pukes all of its fuel and cladding into the
>coolant.  You see the fuel and cladding will melt at about 2200 degrees,
>long after all of the water in the plant has flashed to steam.

The fuel temperature rises with a milli-second time constant, the power
density exceeds the fuel's limit, the fuel flies apart into the coolant.

The coolant temperature rises much, much more slowly (remember the ceramic's
high thermal inertia) and doesn't begin to take off until the fuel -- at
around 2000 deg. C. -- hits it.

--
Jeremy Whitlock                          "My thoughts are mine, not Mac's"
Dept. Engineering Physics
McMaster University                      e-mail: whitlock@mcmaster.ca
Hamilton, Ontario, Canada, L8S 4L7       phone: 416-525-9140 ext.7140

Newsgroups: sci.energy
From: whitlock@dcss.mcmaster.ca (Jeremy Whitlock)
Subject: Re: Reactor explosions (was Re: Breeders)
Message-ID: <1993May18.172725.21741@mcshub.dcss.mcmaster.ca>
Date: Tue, 18 May 1993 17:27:25 GMT

In article <forrere.143.0@ccmail.orst.edu> forrere@ccmail.orst.edu (Gene Forrer) writes:
>>As for why this happened, I suspect the fact that the first meter of
>>Chernobyl's control rods was graphite (more moderator) may have
>>had a good bit to do with that.
>>
>Actually there was water in the bottom of the control rod channel (really
>bad design feature) so when the reactr was scrammed the water acted as a
>moderator and caused the initial power pulse.

It is wrong (and LWR-centric) to think of cooling water in a pressure-tube
reactor as a moderator.  These reactors have so much bulk moderator outside
the pressure tubes (graphite or heavy water) that they really couldn't care
less about the water in the pressure tubes -- as far as neutron moderation
goes.  In fact, a reactor like the CANDU uses light water as a "liquid
control rod" for zone control.  Relatively speaking, it is a poison to the
chain reaction.

At Chernobyl the water at the bottom of the control rod channels was displaced
by the graphite follower attached to the bottom of the control rods, ie, the
scram replaced a poison with a lesser poison.  If it makes you feel better to
think of the water as a moderator, think of the graphite as an even better
(*much* better) moderator.

--
Jeremy Whitlock                          "My thoughts are mine, not Mac's"
Dept. Engineering Physics
McMaster University                      e-mail: whitlock@mcmaster.ca
Hamilton, Ontario, Canada, L8S 4L7       phone: 416-525-9140 ext.7140