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The Gravel Gertie was developed in 1957 by Sandia National Laboratories as a modification of existing igloo-style conventional munitions bunkers, which are designed to contain internal explosions by venting much of the overpressure out the main door.
While this represents a good strategy for minimizing the risks posed by normal bombs, the low order detonation of a nuclear warhead's high explosives would spread vaporized plutonium, tritium and uranium over the surrounding area via the air. Full nuclear detonation was highly unlikely and impossible to design against, but low-order detonations were a very real risk during assembly, disassembly and maintenance, especially of older gun-type fission weapons.
A Gravel Gertie has thick reinforced concrete walls but a ventilated roof covered internally by approximately 7 meters of loosely compressed porous gravel suspended from steel cables above a false ceiling over the work area. In the event of an explosion, the mass of gravel is designed to compress and move upward with the initial blast, sealing the hole in the roof while allowing some of the gas pressure to escape by passing through the gravel. This "filters" the escaping gases and prevents the building from rupturing. The mass of gravel then falls down into the room when the gases cool, trapping large amounts of radioactive particles under and within the gravel, further minimizing leakage. According to tests at Sandia, the Gravel Gertie successfully reduced the expected level of external airborne contamination by a factor of 10, which was considered satisfactory to limit exposure to the immediate area.
Gravel Gertie is named after the character of the same name from the Dick Tracy comics; the compressed mass of gravel forming the ceiling of the bunker reportedly reminded researchers of Gertie's grey, curly hair.
|This section requires expansion. (June 2008)|
- http://cryptome.org/pantex-gertie/pantex-gertie.htm (pictures of the type of rooms discussed)
- Where Nuclear Weapons Go to Die Article in Foreign Policy