Production and subsurface vertical transport of radioxenon resulting from underground nuclear explosions

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Title: Production and subsurface vertical transport of radioxenon resulting from underground nuclear explosions
Author: Lowrey, Justin David
Abstract: Atmospheric monitoring of radionuclides as part of the International Monitoring System requires the capability to differentiate between a radionuclide signature emanating from peaceful nuclear activity and one emanating from a well -contained underground nuclear explosion . While the radionuclide signatures of nuclear weapons are generally well known , radionuclides must first pass through hundreds of meters of earth to reach the surface where they can be detected and analyzed . Less well known is the affect that subsurface vertical transport has on the isotopic signatures of nuclear explosions . In this work , a model is developed , and tested , simulating the detonation of a simple underground nuclear explosion and the subsequent vertical transport of resulting radioxenon to the surface . First , the fast -fission burn of a fissile spherical core surrounded by a layer of geologic media is modeled , normalized to 1 kton total energy . The resulting source term is then used in the testing and evaluation of the constructed vertical transport model , which is based on the double -porosity model of underground fluid transport driven by barometric pumping . First , the ability of the vertical transport code to effectively model the underground pressure response from a varying surface pressure is demonstrated . Next , a 100 -day simulation of the vertical migration of a static source is examined , and the resulting cumulative outflow of roughly 1 % initial inventory outflow per cycle is found to closely follow the analytical predictions . Finally , calculated radioxenon source terms are utilized to model the resulting vertical transport and subsequent surface outflow . These results are found to be consistent with the physical expectations of the system , and lastly a cursory sensitivity analysis is conducted on several of the physical parameters of the model . The result is that the vertical transport model predicts isotopic fractionation of radioxenon that can potentially lie outside of currently accepted standard bounds .
URI: http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2331
Date: 2011-02-16

Citation

Production and subsurface vertical transport of radioxenon resulting from underground nuclear explosions. Master's thesis, University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /ETD -UT -2010 -12 -2331 .

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