The Comprehensive Nuclear Test Ban Treaty Technical Issues for the United States (2012) / Chapter Skim
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APPENDIX E Dealing with Evasive Underground Nuclear Testing
APPENDIX E Dealing with Evasive Underground Nuclear Testing
Pages 161-180
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From page 161... ...
. For a fully2 decoupled nuclear explosion, most of the explosive energy goes into increasing the gas pressure in the cavity by as much as 100 times atmospheric pressure.3 This is in contrast to a normal "well coupled" underground explosion where much of the energy goes into melting and deforming the surrounding rock and in generating larger seismic waves.
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From page 162... ...
The following sections discuss three decoupled nuclear explosions and what can be learned from them, cavities created by past nuclear explosions in salt that might be used for future clandestine testing, use of large cavities in thick salt deposits, and testing in mined cavities in hard rock. Salt is emphasized because cavities likely exist in that material from past nuclear explosions in the Former Soviet Union, and very large cavities at depth are easiest to construct in salt.
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From page 163... ...
. The Seismology Subcommittee judged that some of those calculations for salt have overestimated DF for fully decoupled nuclear explosions and all of them for partially decoupled tests.
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From page 164... ...
. SOURCE: Adapted from Glen and Goldstein, 1994; Murphy, 2009; and Sykes, 1996 Observed decoupling factors for the Cowboy chemical explosions in salt in 1959 also are smaller than those from code calculations (Murphy, 2009)
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From page 165... ...
(1991) that very large decoupling factors can be obtained for explosions that are overdriven6 by large amounts in salt compared with those for Sterling, are not supported by the data of the 1976 Azgir nuclear explosion and the 1961 Cowboy chemical explosions.
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From page 166... ...
Frequencies up to 20 Hz are often recorded for regions characterized by efficient propagation of seismic waves -- such as most of Russia, the areas near the Chinese and Indian test sites, and all of North Korea. Hence, for areas characterized by efficient propagation of seismic waves of high frequencies, the detection of decoupled tests of 1 kiloton and larger can
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From page 167... ...
Decoupled testing in existing cavities created by past explosions in salt Both the decoupled 1966 Sterling and the partially decoupled Azgir nuclear explosions were detonated in cavities in salt domes created by well-coupled nuclear explosions. Salt is one of the few Earth materials in which a cavity produced by a nuclear explosion is not likely to collapse on a time scale of months to years.
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From page 168... ...
Hence, extrapolating the properties of salt in the region surrounding a cavity formed by a nuclear explosion such as Salmon to a solution-mined cavity is uncertain. Disposal of brine is a major problem because a rule of thumb in the industry is that the solution mining of 1 cubic foot of salt requires about 7 cubic feet of injected fresh water (Leith, 2001)
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From page 169... ...
. Fifteen nuclear explosions with yields of about 3 to 15 kilotons were conducted during the 1980s at depths of 3,000 to 3,600 feet (900 to 1,100 meters)
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From page 170... ...
An early plan for permanent disposal of radioactive waste from commercial nuclear reactors in an abandoned salt mine near Lyons, Kansas, was cancelled in part because all previous boreholes had not been cataloged and containment could not be assured. No decoupled nuclear explosions are known to have been conducted in cavities created in salt by either solution or conventional mining.
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From page 171... ...
Explosions in coal and similar soft rocks do not produce as large seismic waves as those in hard rock. Decoupling factors of about 20 to 40 have been observed for chemical explosions in hard rock that range in size from a few pounds to about 10 tons.
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From page 172... ...
• Take into account that noble gases can be detected today at much smaller concentrations than a decade ago. • Take into account that radionuclides have leaked from many previous nuclear explosions in hard rock at Novaya Zemlya and eastern Kazakhstan and the few in granite at the Nevada Test Site.
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From page 173... ...
The issue with mine-blast signals then became whether detectable blasting activity could be used to mask or disguise the signals from an underground nuclear explosion. This section provides further details, additional references to papers and a website that describe relevant aspects of the seismic signals from chemical explosions, and some specific mining regions where blasting activity is detected at monitoring networks, and summarizes assessments of the size of the largest underground nuclear explosion whose seismic signals might be successfully masked by mine-blasting.
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From page 174... ...
(1998) surveyed chemical explosion activity on the territory of the former Soviet Union, finding that this reduction in signal strength (compared to a single-fired shot, or an underground nuclear explosion)
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From page 175... ...
Answers can come from taking examples of signals from large mine blasts, and signals from small underground nuclear explosions, then adding them together before subjecting them to the methods used to discriminate between various types of seismic events. What is typically found is that the maximum size of the identifiable waves (for example, 9 See: http://earthquake.usgs.gov/earthquakes/eqarchives/mineblast/.
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From page 176... ...
For this reason, the use of mine-blasts for masking nuclear explosion signals, though they might afford some possibilities, are not very effective for concealing large releases of energy. The seismic signal from an underground nuclear event is an expression of the instantaneous release of nuclear energy, and unless the yield is very small, it stands out in comparison with the size of the energy released in a sub-blast "delay." TABLE E-1: Example Mining Events in the 2007-2008 REB Catalog.
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From page 177... ...
. Several authors have studied rock bursts and mine collapses with the goal of finding a method of discriminating their signals from those of underground nuclear explosions, and a reliable method has emerged that is based upon the distinguishing characteristic that in underground explosions the rocks in the vicinity of the shot point are pushed outward from the source, whereas in a rock burst or a mine collapse the rocks in the vicinity of the source move inward toward the source (see, for example, Bowers and Walter, 2002; Dreger et al., 2008)
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From page 178... ...
Unsuccessful Proposals for Clandestine Underground Nuclear-Explosion Testing Several other scenarios have been proposed for clandestine underground testing, but none is considered likely to be successful: • Hiding signals of an explosion in that of an earthquake -- Modern instruments detect seismic waves from earthquakes and nuclear explosions over a very broad range of frequencies and at many different distances. Signals from small nuclear explosions can be separated from those of large earthquakes by simple filtering in the frequency domain, using arrays to separate signals arriving from different azimuths and wave speeds, and looking at data from regional stations closest to the presumed explosion.
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From page 179... ...
179 Appendix E: Evasive Underground Nuclear Testing Seismic waves from nuclear explosions in the Degelen Mountain subsite of the Semipalatinsk Test Site, Kazakhstan, reportedly were about ten times smaller than expected for an explosion conducted close to the underground location of an earlier nuclear test (results reported by Sokolova, 2008)
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