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I received the following private communication from a DOE
employee during a previous discussion on this topic:
The TMI containments were designed against a Boeing 720 at
Mach .85. The Boeing
720 was the prototype to the 707. This was
the largest aircraft at the time of
the construction permit. By the
time of the operating license, interveners
raised objections since Boeing
747s were around, and a used DC-8 stretch was
kept at the airport by a travel
club. The operating license went through since
engineering studies were
able to show that the body of the 747 wouldn't knock
down the containment,
and only the jet engine shafts had a chance of
penetration. And, of
course, the reactor itself (except for the pressurizer) is
actually below the
operating floor inside the containment building, so damage to
the containment
does not lead to a reactor accident directly.
Jack Earley
Radiological Engineer
Enercon Services, Inc. 6525 N. Meridian, Suite 503 OKC, OK
73116 phone: 405-722-7693 fax:
405-722-7694 jearley@enercon.com
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----- Original Message -----
Sent: September 28, 2001 7:30 a.m.
Subject: RE: NRC News release on
Terrorists.
Jaro,
Thanks for the reply. I do not have access to this information,
but have noted that comments have been made that the confinement building can
take the impact of a 707, etc., but have never seen anyone backup these
statements.
-- John
Jaro,
I don't think
you would say that the WTC buildings were fragile. They stood for
over an hour after inpact. Will a four foot thick, reinforced concrete
wall do as well? If you don't know, say so.
-- John
<><><><><><><><><><>
John, the
reference books I have say that sprayed asbestos or mineral fiber covering
on steel columns has a fire resistance rating of roughly 2hrs per inch of
thickness (more precise numbers depend on construction details,
materials, quality, etc.).
Concrete offers
roughly the same fire protection per unit of thickness, for the steel rebar
inside.
But with wall
thickness measured in FEET for NPP containment domes, we're looking at a
fire rating measured in DAYS, not hours (there is, in addition, usually a
steel plate liner on the inside surface of the dome).
PS. thanks for your
expression of confidence, saying "I don't
think you would say that the WTC buildings were fragile."
...indeed, if you check what I actually wrote (see below), you will note
that I was talking about the sprayed-on fireproofing material, not the steel
structure. I don't have any figures handy at the moment on the relative
strength of sprayed-on fibrous material versus concrete in dome walls, but I
presume its quite substantial (flame away if you
must....).
Jaro
OOOOPS -- I guess John meant burning jet fuel from the
airliner ! (thanks Phil !)
...but if nothing gets through the wall, what difference
does it make ? (ignoring destruction of the "balance of plant" for the
moment).
As we saw in the WTC disaster, much of the fuel was gone
in the initial fireball. I suspect this would be even more so in the case
of a disintegration of an airliner on the outside of a containment
dome.... in contrast to the WTC, where a significant fraction spilled
throughout the interior of the structure and ignited any combustible
materials there....
Also, in chemical/petrochemical industry, large concrete
basins are used for emergency/accidental spills to safely burn-off the
flammable liquid.
I think there is a big difference between the relatively
skimpy & fragile fireproofing of steel structures in highrises, and
rebar embedded in four-foot thick concrete walls !
Jaro
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