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RE: abc news on nukes-terror targets; containments magically grow



Title: RE: abc news on nukes-terror targets; containments magically grow

Norm & Radsafers,

Most reactor containment domes in North America have walls about 3½ feet thick, but often with some sections (such as the ring around the roof of Canadian CANDU 6s) up to 6+ feet thick.

Its true that the concrete target slab in the Sandia test, at 12-foot thickness, was much thicker than a reactor containment dome wall... but it might as well have been a hundred feet thick, since the maximum penetration was only 60 mm (2½").

The extra thickness merely served to ensure the worst possible case - a completely unyielding target (like driving an axe into a log placed on an unyielding base - as opposed to placing it on soft ground or on wood chips, which renders the impact ineffective).

The rigidity w.r.t external impacts of an actual reactor containment wall is ensured by its anchoring to the concrete "base mat" and to the ground below, as well as by its convex cylindrical shape, and by the solid disc roof (which restrains the top end of the cylindrical structure).

It is conceivable that in a small local impact area (ex. the point where an airliner engine hit, in case of a WTC-type terrorist attack) there might be some plastic deformation of the rebar (with cracking of the concrete in which they are embedded), since the wall is typically much thinner (3½ ft). Any such yielding however, would diminish the depth of penetration below the 60 mm maximum achieved with a completely unyielding target.

Please remember also, that within the reactor containment dome there is typically at least one or more reinforced concrete walls, before you get to the reactor vessel itself. Some of these walls are four feet or more thick (see graphic posted at http://www.magma.ca/~whitlock/cnf/containment.jpg and discussion at http://www.ncf.ca/~cz725/cnf_sectionD.htm#terrorist ).

FYI, Sandia has posted the videos of the crash test (two - one long-distance view & one close-up) at http://www.sandia.gov/media/NRgallery00-01.htm  .........I found them a bit tricky to download, but eventually succeeded -- so if anyone wants a copy, just say so & I will send (warning - they are 1.1MB & 2.2MB mpg files, which some servers may not let people receive messages that size, unfortunately..).

I thought that the currently posted Sandia introduction to the videos is a bit short on words, and could be misinterpreted :

" The 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 (3.66 meters thick). The test was not intended to demonstrate the performance (survivability) of any particular type of concrete structure to aircraft impact. The impact occurred at the nominal velocity of 215 meters per second  [=774 kph = 478 mph] . The mass of the jet fuel was simulated by water; the effects of fire following such a collision was not a part of the test. The test was performed by Sandia National Laboratories under terms of a contract with the Muto Institute of Structural Mechanics, Inc., of Tokyo. "

..........In my opinion, there needs to be a bit more complete explanation of the test set-up, certainly some mention of the published results (the 60 mm penetration depth), and the relevance to actual reactor containment structures. They might also consider reinforcing the statement, "complete F-4 Phantom" with one which appeared in an official report, "A flyable F-4 aircraft was acquired by Sandia" -- ie. one with both its engines in place (contrary to some claims that the engines were removed prior to the test...).

As I said previously, according to information from Jane's All the World's Aircraft, the Phantom jet in the Sandia crash test has two General Electric J79-GE-17 turbojets, each of them weighing 1,740 kg (3,835 lbs) and having a diameter of 992 mm (39"), with a total weight of 3,480 kg (7,656 lbs) for the two side-by-side mounted engines, and an average impact area density of 3.21 psi. Large commercial airliners like the Boeing 767 and 747 use engines with a weight of some 4,200 kg (9,200 lbs), and a diameter of 2,463 mm (97"), for an average impact area density of only 1.24 psi, which is apparently  about 2.6  times less severe than the Phantom's engines (corrected figure).

Actually however, much of that large engine frontal area is due to the high-bypass fan (which the military jet doesn't have), while much of the weight is concentrated in the "core" part of the engine, which contains the compressor and turbine stages. This core part of the engine has an average impact area density roughly the same as the Phantom's engines, possibly slightly higher. The shafts BTW are thin-wall hollow pipes, several inches in diameter.

Regards,

Jaro