Nuclear Test Scenarios for Discussion of On-Site Inspection Technologies
The purpose of the ISS OSI Invited Meeting being held in Vienna March 24-27, 2009 is to obtain a better understanding of the phenomenology of underground nuclear explosions for On-Site Inspection (OSI) purposes. In order to focus the technology discussions, we have developed two very general scenarios, or models, of underground nuclear test configurations and phenomena that will help us explore the application of OSI methodologies and techniques. The scenarios describe testing environments, operations, logistics, equipment, and facilities that might be used in conducting an underground nuclear test. One scenario involves emplacement of a nuclear device into a vertical borehole in an area with relatively flat terrain; the other involves emplacement within a tunnel (horizontally) in an area with mountainous terrain. Vertical borehole geometry The example for this scenario is an intermediate yield nuclear explosion carried out in a flat desert area. The ground was cleared and smoothed over a 200 X 200 m fenced area for operational support activities, access to the borehole, and in order to place a few structures to house diagnostics equipment and control functions. Power lines were provided for local electrical power. The vertical emplacement borehole was 2 m in diameter and bored to a depth of 350 m. The emplacement hole was lined with steel pipe in order to keep the hole open and to avoid cave-ins during emplacement of the nuclear device. Emplacement was above the local water table, and the top of the saturation zone is about 30 m below the bottom of the emplacement hole. The detonation point was at a depth of 340 m. All of the rock material removed while drilling the borehole was removed to another place. Diagnostics and control for the test were relatively simple: about 2 dozen high capacity coaxial cables feed from the down hole instruments to the surface and then about 100 m laterally to a diagnostics trailer. Two strong steel cables were used to emplace the device and diagnostic instruments and to support the down hole cables. The borehole was stemmed after the device was emplaced. The stemming material was relatively simple: the hole was backfilled with sand or gravel about 20-30 m above the nuclear experiment package, a grouted plug about 3 m thick is added, and the hole backfilled with a mixture of sand and gravel to the surface. After the test, the testing party removed all structures and power lines and covered the top of the borehole with a small building. Geologic environment before the test--The geology for the test consists of flat-lying alluvium and tuff, with 50 m of poorly consolidated alluvium near the surface and moderately welded tuff from 50 m depth to 50 m below the bottom of the hole. The upper tuff is underlain by a densely welded tuff unit, with basement Paleozoic sedimentary rock beginning at a depth of about 1000 m. The tuff is intact with a few fractures. There are no known faults located within 500 m of the borehole. Alteration of the underground environment--The blast created a spherical or near spherical cavity with a lens of vitrified material at the bottom. There are several zones surrounding the detonation point with decreasing levels of rock damage. The zones are: (1) the crushed zone (several tens of meters)where the rock has lost all prior integrity; (2) the fractured zone (out to a couple of hundred meters) characterized by radial and concentric fissures; and (3) the zone of irreversible strain (out to a couple of thousand meters) with local media deformation. A collapse chimney formed one hour after the detonation, in which overlying material fell into the explosion cavity. This chimney zone reached up to within 50 m of the surface and a small apical void formed (10 m high and 80 m in diameter) at the top of the rubble chimney. The rubble chimney is dry and density is about 20% less than the surrounding intact rock. Alteration at the surface--No surface depression formed, but there is significant 'fluffing' of the surface soil from the effects of the initial shock wave. A few radial and concentric fractures formed from the shock effects within a radius of 200 m of the borehole. Radionuclide environment--No particulates or aerosol radiological material reached the surface. However, the stemming is not completely impervious to gas release and a small amount of gas and vapor was released along the emplacement pipe immediately after the explosion and before the rubble chimney formed. Most of the gas venting stopped as soon as cavity collapse occurred. After the rubble chimney formed and the pressure in the explosion cavity reached equilibrium, gases began to migrate up through the rubble chimney aided by barometric pumping. There is also an unknown fault located 300 m from the explosion cavity that provided another gas migration pathway between the damage zone of the cavity and the surface.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 950618
- Report Number(s):
- LLNL-TR-411364; TRN: US200911%%38
- Country of Publication:
- United States
- Language:
- English
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