THE DEFINITION OF TRUE CRATER DIMENSIONS BY POST-SHOT DRILLING.
LAWRENCE RADIATION LAB UNIV OF CALIFORNIA LIVERMORE
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The Danny Boy event of March 5, 1962, was a nuclear cratering explosion of 0.42-kt yield at a depth of 110 ft in a basalt flow capping Buckboard Mesa in Area 18, Nevada Test Site. In May-June 1962, three slant holes were drilled from the northwest side of the crater lip base into the vicinity of the shot point for purposes of recovering samples for radiochemical yield determination, assessing the fracture state in the inelastic zone, and locating the true crater surface at several points in order to estimate the explosion cavity radius at the time of venting. Percent core recovery data and radiation logs failed to define the fallback-true crater interface nor was any radioactive glass lining the cavity surface found in the cores. Rock in a 2-ft-thick zone immediately beyond this surface was intensely crushed and fractured in a manner readily descernible by a petrographic microscope examination. Core samples from all three holes examined thusly over 1-ft intervals revealed these microfractures to occur consistently at points 35-38 ft radially from the shot point. A radius of 36 plus or minus 2 feet is therefore assigned to the explosion cavity. The true crater cavity surface is a hemisphere radially symmetrical about the shot point at depths below approximately 110 ft. Author
- Geology, Geochemistry and Mineralogy