Radionuclide signals from underground nuclear explosions (UNEs) are strongly influenced by the surrounding hydrogeologic regime. One effect of containment is delay of detonation-produced radioxenon reaching the surface as well as lengthening of its period of detectability compared to uncontained explosions. Using a field-scale tracer experiment, we evaluate important transport properties of a former UNE site. We observe the character of signals at the surface due to the migration of gases from the post-detonation chimney under realistic transport conditions. Background radon signals are found to be highly responsive to cavity pressurization suggesting that large local radon anomalies may be an indicator of a clandestine UNE. Computer simulations, using transport properties obtained from the experiment, track radioxenon isotopes in the chimney and their migration to the surface. They show that the chimney surrounded by a fractured containment regime behaves as a leaky chemical reactor regarding its effect on isotopic evolution introducing a dependence on nuclear yield not previously considered. This evolutionary model for radioxenon isotopes is validated by atmospheric observations of radioxenon from a 2013 UNE in the Democratic People’s Republic of Korea (DPRK). Our model produces results similar to isotopic observations with nuclear yields being comparable to seismic estimates.
This report is presented as a compilation of data and is intended to be used for future CAU-specific flow and transport models. 7.7.2 Projecf History This report is an account of work accomplished in late 1995 and early 1996, which was documented in a draft report distributed by IT Corporation (IT) for limited external review in April 1996 (IT, 1996a). Reviewers' comments have been addressed in this final report, but the scope and conclusions have not changed significantly fiom those presented in the IT draft publication. ' The hydrostratigraphic nomenclature used in this report follows that used for the UGTA Phase I regional groundwater modeling efforts (IT, 1996b). However, hydrogeologic characterization of the NTS area is a continuing process, and changes in the definitions of some hydrostratigraphic. units have occurred as a result of work conducted after publication of the draft report that forms the basis of this document (IT, 1996a). These changes have not been incorporated into this final report. Conclusions fiom the data presented in this fracture analysis report have, however, been assimilated into subsequent reports. For a more in-depth look at the hydrostratigraphy of the Pahute Mesa study area, the reader is directed to these recent works, which include Drellack and Prothro (1 997) and Prothro and Drellack (1 997). 1.2 Objecfives The objective of this study was to obtain information about fiactures in volcanic hydrogeologic and hydrostratigraphic units at Pahute Mesa to determine important hydrologic parameters for future CAU-specific flow and transport models. Critical fracture information gathered during this study included: ' Fracturedensity Aperture Orientation Secondary mineral coatings 1-3 7.3 Methodology 7.3. 7 Core Fracture Analysis A core fracture analysis was performed on conventional core samples from eight drill holes on or in the vicinity of Pahute Mesa. The drill holes were UE-18r, UE-18t, UE-lgx, UE-20bh #1, U-~OC, U E-~O C , UE-20e #1, and UE-20f. A summary of pertinent information about these wells is presented in Table 1-1. These drill holes were selected because cummulatively they provide representative core through five of the six hydrostratigraphic units (J3SUs) defined in the Phase I regional groundwater flow model, and they provide the opportunity to compare fractures in core to the BHTV and/or FMS borehole fracture logs. A total of 1,578 meters (m) (5,177 feet [a]) of core w k examined from December 1995 to February 1996 by geologists from Bechtel Nevada Corporation (BN), IT Corporation, Daniel B. Stephens and Associates, and GeoTrans, Inc. This study was conducted at the U. S. Geological Survey's (USGS) Geologic Data Center and Core Library in Mercury, Nevada. Typically, core was examined megascopically; however, lox-to 4Ox-zoom binocular microscopes were used routinely for more detailed examination. The fracture data collected during the fracture analysis as well as stratigraphic, lithologic, hydrogeologic, hydrostratigraphic, and geophysical information were entered into a ...
Portions of thisDrilling problems included hole deviation and hole instability that prevented the timely completion of this borehole. Drilling methods used include rotary tri-cone and rotary hammer drilling with conventional and reverse circulation using aidwater, aidfoam (Davis mix), and bentonite mud.Geologic cuttings and geophysical logs were obtained from the well. The rocks penetrated by the ER-12-1 drillhole are a complex assemblage of Silurian, Devonian, and Mississippian sedimentary rocks that are bounded by numerous faults that show substantial stratigraphic offset.The final 7.3 m (24 ft) of this hole penetrated an unusual intrusive rock of Cretaceous age. The geology of this borehole was substantially different from that expected, with the Tongue Wash Fault encountered at a much shallower depth, paleozoic rocks shuffled out of stratigraphic sequence, and the presence of an altered biotite-rich microporphyritic igneous rock at the bottom of the borehole.Conodont CAI analyses and rock pyrolysis analyses indicate that the carbonate rocks in ER-12-1, as well as the intervening sheets of Eleana siltstone, have been thermally overprinted following movement on the faults that separate them. The probable source of heat for this thermal disturbance is the microporphyritic intrusion encountered at the bottom of the hole, and its age establishes that the major fault activity must have occurred prior to 102.3+0.5 Ma (middle Cretaceous).Geophysical logs run in the saturated and unsaturated sections of the borehole were invaluable for interpretation of stratigraphy and structure. Problems encountered during logging were lack of service tables for stacked logs, lack of calibration tables for the ER-12-1 hole size, and lack of written procedures for running these logs in the field. Hydrologic investigations consisted of water level monitoring, flow logging, aquifer tests, and drill-stem tests. The results indicate that the static composite fluid level in well ER-12-1 was 469 m ( 1540 ft) below land surface. Drill-stem tests and flow logs determined that the lower two intervals in the well are underpressured relative to the upper zones by approximately 396 m (1 300 ft). Aquifer tests, drill-stem tests, and flow logs determined that the transmissivity of the well ranged from 7.5 x m2/s, with the most transmissive zone being 518 to 555 m (1700 to 1820 ft) below land surface followed by the 9 14 to 963 m (3000 to 3 160 ft). The pressure differential between these zones allowed for substantial crossflow to occur while the well was open.to 4 x Two types of geochemical samples were acquired from this well. Water quality samples taken during drilling and testing indicated very few problems associated with the well. Those identified consisted of elevated quantities of volatile and semivolatile organics (sample 10006) and metals (sample 10007) associated with the drilling process. Geochemical characterization samples were taken only from the uppermost zone, 518 to 555 m (1700 to 1820 ft). The results from this sample vii indica...
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