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RE: NRC News release on Terrorists.

BTW, with respect to the question of relative strength of sprayed-on fibrous material fireproofing versus concrete in RB dome walls,  I forgot to mention those impact tests demonstrating great strength.
Also relevant is the incident, in the early eighties (I believe), when some antinuclear direct-action types fired an antitank missile at the containment dome of the 1200MWe Creys-Malville ("Superphénix") FBR in France (then under construction, but with dome finished). As I recall, it left only superficial damage on the exterior of the wall.
(And incidentally, what those direct-action types failed to accomplish with missiles, the Green politicians achieved in the Socialist-coalition government -- Creys-Malville is shut down, and FFbillions are down the toilet...).

Jaro 

From: Franta, Jaroslav
Sent: Thursday September 27, 2001 2:05 PM
To: Radsafe (E-mail)
Subject: RE: NRC News release on Terrorists.

-----Original Message-----
From: Jacobus, John (OD/ORS) [mailto:jacobusj@ors.od.nih.gov]
Sent: Thursday September 27, 2001 1:14 PM
To: Franta, Jaroslav; Radsafe (E-mail)
Subject: RE: NRC News release on Terrorists.

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