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. / text

Frequency-dependent earthquake coda attenuation values are often reported; however such measurements usually depend on the types of the attenuation models employed. In this thesis, I use numerical modeling of Peaceful Nuclear Explosion (PNE) codas at far regional to teleseismic distances to compare two of such models, namely the conventional frequency-dependent attenuation with parameters (Q0, ¦Ç) defined by Qcoda(f) = Q0f¦Ç and frequency-independent effective attenuation (Qe) with geometrical attenuation (¦Ã). The results favour strongly the (¦Ã, Qe) model and illustrate the mechanisms leading to apparent Qcoda(f) dependencies. Tests for variations of the crustal velocity structures show that the values of ¦Ã are stable and related to lithospheric structural types, and the inverted Qe values can be systematically mapped into the true Swave attenuation factors within the crust. Modeling also shows that ¦Ã could increase in areas where relatively thin attenuating layers are present within the crust; such areas could likely be related to younger and active tectonics. By contrast, when interpreted by using the traditional (Q0,¦Ç) approach, the synthetic coda shows a strong and spurious frequency dependence with ¦Ç ¡Ö 0.5, which is also similar to many published observations.<p> Observed Lg codas from two Peaceful Nuclear Explosions located in different areas in Russia show similar values of ¦Ã ¡Ö 0.75¡¤10-2 s-1, which are also remarkably close to the independent numerical predictions in this thesis. At the same time, coda Qe values vary strongly, from 850 in the East European Platform to 2500 within the Siberian Craton. This suggests that parameters ¦Ã and Qe could provide stable and transportable discriminants for differentiating between the lithospheric tectonic types and ages, and also for seismic coda regionalization in nuclear-test monitoring research.

Frequency-dependent earthquake coda attenuation values are often reported; however such measurements usually depend on the types of the attenuation models employed. In this thesis, I use numerical modeling of Peaceful Nuclear Explosion (PNE) codas at far regional to teleseismic distances to compare two of such models, namely the conventional frequency-dependent attenuation with parameters (Q0, ¦Ç) defined by Qcoda(f) = Q0f¦Ç and frequency-independent effective attenuation (Qe) with geometrical attenuation (¦Ã). The results favour strongly the (¦Ã, Qe) model and illustrate the mechanisms leading to apparent Qcoda(f) dependencies. Tests for variations of the crustal velocity structures show that the values of ¦Ã are stable and related to lithospheric structural types, and the inverted Qe values can be systematically mapped into the true Swave attenuation factors within the crust. Modeling also shows that ¦Ã could increase in areas where relatively thin attenuating layers are present within the crust; such areas could likely be related to younger and active tectonics. By contrast, when interpreted by using the traditional (Q0,¦Ç) approach, the synthetic coda shows a strong and spurious frequency dependence with ¦Ç ¡Ö 0.5, which is also similar to many published observations.<p> Observed Lg codas from two Peaceful Nuclear Explosions located in different areas in Russia show similar values of ¦Ã ¡Ö 0.75¡¤10-2 s-1, which are also remarkably close to the independent numerical predictions in this thesis. At the same time, coda Qe values vary strongly, from 850 in the East European Platform to 2500 within the Siberian Craton. This suggests that parameters ¦Ã and Qe could provide stable and transportable discriminants for differentiating between the lithospheric tectonic types and ages, and also for seismic coda regionalization in nuclear-test monitoring research.

When a nuclear explosion occurs certain radionuclides are emitted, notably xenon. Due to the fact that xenon is a noble gas, it is hard to contain and can therefore be detected far from the explosion site. There are four isotopes of xenon that are of interest in the detection of a nuclear explosion: 131mXe, 133mXe, 133Xe and 135Xe. By constantly measuring the amount of these isotopes in the air, changes in the concentration in an indication that a nuclear explosion has occurred. In this thesis a detector was modelled in GEANT4 and focuses on one kind of noble gas detector: SAUNA - the Swedish Automatic Unit for Noble gas Acquisition. SAUNA uses the coincidence technique in order to determine the concentration of xenon there is in the air. By using the coincidence technique, it is possible to reduce the impact of the background radiation and therefore increase the efficiency of the detector. 133Xe has a coincidence when it first undergoes beta decay, with an endpoint energy of 346 keV, and then emits a 80 keV gamma particle. 135Xe has also a dual coincidence, a beta decay with an endpoint energy of 910 keV together with a 250 keV gamma-ray. However both these isotopes have a triple coincidence decay that also can be exploited: for 133Xe, a beta particle with endpoint energy of 346 keV, a 30 keV X-ray and a 45 keV conversion electron, while for 135Xe there is instead of the gamma particle a 30 keV X-ray and a 214keV conversion electron that can be emitted together with the beta particle. The 30 keV X-ray together with the beta particle for 133Xe can also be used as a dual coincidence, in that case the conversion electron is ignored. For 133Xe, when a beta particle, a 45 keV conversion electron, and a 30 keV X-ray are emitted, the model was able to detect all three particles in 69.2% ± 0.1 of the cases. However, when only the particles with a detected energy within a 5 keV interval of their generated energies are considered to be in coincidence, then for 133Xe triple coincidence occurs in 22.9% ± 0.2 of the cases. For 135Xe the model was able to detect the triple coincidence (between a beta, 214 keV CE and 30 keV X-ray) in 63.5% ± 0.1 of the cases. This work shows that adding another particle in a coincidence reduces the chance to detect the coincidence. The positive effect of adding another particle in a coincidence is that the minimum detectable concentration of xenon should be smaller. The goal for future detectors should be to make it possible for the detector to take advantage of the triple coincidences but at the same time be also able to use the dual coincidences.

This thesis, Earth satellites and detection of air andground based activities by Ulf Ekblad of the Physics departmentat the Royal Institute of Technology (KTH), addresses theproblem of detecting military activities in imagery. Examplesof various techniques are presented. In particular, problemsassociated with "novelties" and "changes" in an image arediscussed and various algorithms presented. The imagery usedincludes satellite imagery, aircraft imagery, and photos offlying aircraft. The timely delivery of satellite imagery is limited by thelaws of celestial mechanics. This and other information aspectsof imagery are treated. It is e.g. shown that dozens ofsatellites may be needed if daily observations of a specificsite on Earth are to be conducted from low Earth orbit. New findings from bioinformatics and studies of small mammalvisual systems are used. The Intersecting Cortical Model (ICM),which is a reduced variant of the Pulse-Coupled Neural Network(PCNN), is used on various problems among which are changedetection. Still much more could be learnt from biologicalsystems with respect to pre- and post-processing as well asintermediate processing stages. Simulated satellite imagery is used for determining theresolution limit for detection of tanks. The necessary pixelsize is shown to be around 6 m under the conditions of thissimulation. Difference techniques are also tested on Landsat satelliteimagery with the purpose of detecting underground nuclearexplosions. In particular, it is shown that this can easily bedone with 30 m resolution images, at least in the case studied.Satellite imagery from SPOT is used for detecting undergroundnuclear explosions prior to the detonations, i.e. under certainconditions 10 m resolution images can be used to detectpreparations of underground nuclear explosions. This type ofinformation is important for ensuring the compliance of nucleartest ban treaties. Furthermore, the necessity for havingcomplementary information in order to be able to interpretimages is also shown. Keywords: Remote sensing, reconnaissance, sensor,information acquisition, satellite imagery, image processing,image analysis, change detection, pixel difference, neuronnetwork, cortex model, PCNN, ICM, entanglement, Earthobservation, nuclear explosion, SPOT, Landsat, verification,orbit.

<p>This thesis, Earth satellites and detection of air andground based activities by Ulf Ekblad of the Physics departmentat the Royal Institute of Technology (KTH), addresses theproblem of detecting military activities in imagery. Examplesof various techniques are presented. In particular, problemsassociated with "novelties" and "changes" in an image arediscussed and various algorithms presented. The imagery usedincludes satellite imagery, aircraft imagery, and photos offlying aircraft.</p><p>The timely delivery of satellite imagery is limited by thelaws of celestial mechanics. This and other information aspectsof imagery are treated. It is e.g. shown that dozens ofsatellites may be needed if daily observations of a specificsite on Earth are to be conducted from low Earth orbit.</p><p>New findings from bioinformatics and studies of small mammalvisual systems are used. The Intersecting Cortical Model (ICM),which is a reduced variant of the Pulse-Coupled Neural Network(PCNN), is used on various problems among which are changedetection. Still much more could be learnt from biologicalsystems with respect to pre- and post-processing as well asintermediate processing stages.</p><p>Simulated satellite imagery is used for determining theresolution limit for detection of tanks. The necessary pixelsize is shown to be around 6 m under the conditions of thissimulation.</p><p>Difference techniques are also tested on Landsat satelliteimagery with the purpose of detecting underground nuclearexplosions. In particular, it is shown that this can easily bedone with 30 m resolution images, at least in the case studied.Satellite imagery from SPOT is used for detecting undergroundnuclear explosions prior to the detonations, i.e. under certainconditions 10 m resolution images can be used to detectpreparations of underground nuclear explosions. This type ofinformation is important for ensuring the compliance of nucleartest ban treaties. Furthermore, the necessity for havingcomplementary information in order to be able to interpretimages is also shown.</p><p>Keywords: Remote sensing, reconnaissance, sensor,information acquisition, satellite imagery, image processing,image analysis, change detection, pixel difference, neuronnetwork, cortex model, PCNN, ICM, entanglement, Earthobservation, nuclear explosion, SPOT, Landsat, verification,orbit.</p>