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