Integration of Noble Gas and Seismic Measurements for Small Yield Event Discrimination and Yield Estimation: A Multidisciplinary Experimental Study
Abstract
Radioactive noble gases (RNG) 131Xe, 133Xe and 135Xe are ubiquitous products of underground nuclear detonations. Because of their uniqueness, such noble gas signatures can confirm the nuclear nature of an event. However, gas transport through fractured rock, especially near the ground surface, is not fully understood. One of the important parameter is the half-life of the RNGs, which varies between 9.2 hours (135Xe) and 11.9 days (131mXe). Because of such short half-lives, there is a narrow window of opportunity for the isotope detection on the order of a few weeks to 2 months before they decay below detectability. Thus prediction of the timing of gas breakthrough in different emplacement conditions is very important for nuclear monitoring. We propose to conduct a Gas Diffusion Experiment (GDE) to obtain observational measurements of trace gases as they migrate from an explosive fractured rock source region to the ground surface. This experiment will provide observational data to validate the numerical model recently developed by Los Alamos National Laboratory (LANL, Anderson et al., 2011 and Jordan, et al., 2014) and provide insight into previous numerical model studies related to explosive tests such as the Non-Proliferation Experiment (Carrigan et al., 1996). The experiment series will include four explosions above and below the water table to evaluate the influence of water saturation on gas transport. The explosions will have different yields and depths of burial in order to examine the effects of these important parameters on the gas transport as well as on seismic wave radiation. The below water table GDE will be the first of its kind. Even if SF6 is completely sequestered beneath the water table due to capillary effects, it would be an important result. We will perform extensive pre- and post-explosion subsurface site characterization, including cross-hole tomography, TEM/DC resistivity formation fracture aperture mapping, slug testing, and rock coring to characterize the subsurface properties (density, porosity, fracture density, and permeability) as a function of distance from the explosion source. In addition, we will collect and analyze seismic data from the explosions. Seismic data from the explosions with different emplacement conditions (combined with known gas signatures) could provide additional information for detection and yield estimation of small explosions, such as those apparently being conducted by N. Korea. We are particularly interested in determining whether there is correlation between the shear wave amplitudes, the formation of long fractures and the prompt venting of the tracer gas following the formation of the long fractures
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2017
- Source ID
- HDTRA11710040
Entities
People
- Anastasia Stroujkova
Organizations
- Defense Threat Reduction Agency