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RE: jet engine penetration depth
Group
If you hit the containment head on, the engines won't hit the containment at
all. The engine to engine span is quite wide... The engines if they did
hit would be glancing off of a curved surface... I have physically
witnessed test results of non-explosive, high velocity hardened munitions
striking concrete structures and there is a significant reduction in
penetration if the impact vector is anything other than normal to the impact
surface. Even if the containment were flat, if the shaft of the engine did
not strike the surface perpendicularly, the shaft will rotate and slam
broadside into the contaiment. The force instead of being over the cross
sectional area of the end of the shaft is then dispersed over the entire
cross sectional are of the long side of the shaft. The resultant
penetration is <5% of that for a normally incident crash.
In addition to rebar, there are post-tension tendons to provide additional
resistance to cracking. Even if you crack and significantly crumble the
concrete, the steel rebar would analagous to kevlar, which deforms but is
tough and difficult to break. The steel inner liner would be dented inward
like a Pepsi can, but most likely intact.
I'm neither for or against, it's just that this is much more than smashing a
sledge hammer into a cynder block. I also trying to model the real world
with a high degree of accuracy could require detailed analysis of many
variables. Someone please forward these points to the persons performing
the calcs.
I miss good old fashioned geeky health physics. My delete key is getting
worn out lately.
Glen Vickers
> -----Original Message-----
> From: Marvin Resnikoff [SMTP:radwaste@RWMA.COM]
> Sent: Wednesday, November 07, 2001 9:11 AM
> To: radsafe; Franta, Jaroslav
> Subject: Re: jet engine penetration depth
>
> Jaro:
> You're right on two fronts: 1) we did not assume rebar. Steel poses more
> effective resistance than concrete. We could take rebar into account. At
> PFS, the dry storage casks are constructed of steel shells and concrete.
> We and PFS took that into account by energy loss through each of the
> steel, concrete, steel shells. But remember again that some reactor
> containments are only 2' thick. Because of that, within a few days of the
> WTC attack, we asked the NRC to monitor their web site, an action they
> took over 4 weeks later.
> 2) The issue of the speed that a 767 (not a 757, which has a lighter
> engine and less fuel) could strike a low profile target is a matter of
> probabilities. We did not investigate this matter. Here is what the news
> media said:
> Wash Post, CBS.com: 460 mph, Pentagon
> MSNBC: 600 mph, WTC; 450 mph, Pentagon
> Wash Post: 400 - 550 mph into all targets
> Wash Post: 345 mph, Pentagon
> Since video clips on the second WTC attack exist, at least for that crash,
> where the plane banked, one could precisely determine that speed.
> Another issue involves flight path. Some reactors, such as those next to
> the ocean, are on a clear flight path and many reactors are as tall as the
> Pentagon. On the other hand, some reactors lie in valleys next to
> curving rivers. Striking such reactors at cruising speed would have a low
> probability.
> Thanks for your email and for maintaining a professional dialogue on this
> important issue.
> Marvin Resnikoff
>
> ----- Original Message -----
>
> From: Franta, Jaroslav <mailto:frantaj@AECL.CA>
> To: Radsafe (E-mail) <mailto:radsafe@list.vanderbilt.edu>
> Sent: Tuesday, November 06, 2001 5:05 PM
> Subject: RE: jet engine penetration depth
>
> Marvin,
> According to the reference document,
> Davis, P. R., D. L. Strenge, and J. Mishima, 1998, Final Accident
> Analysis for Continued Storage, Revision 0, Jason Technologies
> Corporation, Las Vegas, Nevada. [244118],
> posted at
> <http://www.ymp.gov/deisref/collection/disk17/tic_244118.pdf>,
> page 7 paragraph one states :
>
> Table 2 indicates that the maximum thickness of concrete
> penetrated by a jet engine (2.80 ft.) under the assumed conditions is
> considerably less than the thickness of the concrete storage modules (3.33
> ft.). Thus, unless the concrete in the storage modules becomes degraded,
> aircraft penetration would not be expected.
>
> ....where the "assumed conditions" were 500 fps impact velocity and
> a Boeing 757 with Rolls Royce engines.
> Note also, that the "concrete" assumed in this document is just that
> -- there is no steel rebar, as one would find in a reactor containment
> dome wall (or the impact target in the 1988 Sandia F-4 Phantom impact
> test, where penetration depth was trivial).
> I also think that your assumed speed of 500mph is way too high --
> while its certainly possible to hit the end of an airport runway
> accurately at ~100mph, trying to steer an airliner into a relatively small
> building at FIVE TIMES that speed would be virtually impossible. The WTC
> attacks occurred at a little over 300mph, and you could see that the
> terrorist pilot had his hands full trying not to miss -- the plane banked
> quite sharply just prior to impact ( BTW, the ref. doc. speed of 500 fps
> is about 550 kph, or 340 mph).
>
> Jaro
>
> -----Original Message-----
> From: Marvin Resnikoff [mailto:radwaste@RWMA.COM]
> Sent: Monday November 05, 2001 7:18 PM
> To: radsafe
> Cc: Matt Lamb
> Subject: jet engine penetration depth
>
>
>
> Jaroslav Franta:
> Thanks for pointing us in the direction of the Sandia full-scale
> tests of an F-4 Phantom jet. This paper is important to our work in
> analyzing the impact of a jet engine on a nuclear fuel dry storage cask.
> We've now evaluated the Sandia paper presented at a symposium, rather than
> the abstract.
> Sandia states, "The primary purpose of the test was to determine the
> impact force versus time due to the impact of a complete F-4 Phantom onto
> a massive, essentially rigid reinforced concrete target." You were
> correct to state that the F-4 Phantom had intact engines. The penetration
> depth by the fuselage was 2 cm, as you stated; the penetration depth of
> the engines was 6 cm.
> However, the massive concrete block, weighing almost 25 times the
> weight of the F-4 Phantom, absorbed almost all the impact. The 469 tonne
> block was floated on an air cushion and moved 1.83 m until it hit the
> backup structure and rebounded.
> Our calculations for concrete penetration do not assume the
> structure moves. As must be clear to you, one cannot infer from the
> Sandia test that a 767 engine moving 500 mph will penetrate 6 cm of
> concrete. If the building or storage cask were stationary, the
> penetration depth of the 767 jet engine is closer to 4 feet, and several
> U.S. reactors have a thinner concrete containment. Our method of
> calculating the penetration depth is identical to the method used by NRC
> staff and DOE contractors.
> Marvin Resnikoff
>
>
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