Nevada Test Research Articles

Waveform Tomography Improves Far-Regional Distance Simulations of Underground Nuclear Explosions and Earthquakes from the Former Nuclear Test Site, Western United States

Abstract We investigated the efficacy of seismic Earth models to simulate complete regional distance waveforms from underground nuclear explosions and earthquakes on and near the former Nevada Test Site in Nevada, western United States. We focused on two far-regional stations (∼1000 km) in two period bands 20–50 and 15–40 s, for which path propagation effects over many wavelengths accumulate and pose challenges to low-magnitude nuclear explosion monitoring (NEM). Four seismic models were considered: two average radially symmetric 1D and two fully 3D models. Model performance was evaluated with metrics of waveform phase (cross-correlation delay time), shape (correlation coefficient), and amplitude (variance reduction with delay time shift) and averaged into a summary score. We found that a recent 3D model based on full waveform inversion (FWI) tomography including radial anisotropy and crustal thickness variations performs on average better than the alternatives. Results suggest that FWI based on crustal depth earthquakes can provide useful 3D models for NEM. Such models can be used for the simulation of Green’s functions for source characterization including moment tensor inversion and source type characterization (e.g., explosion–earthquake–collapse identification, moment and yield estimation).

Assessing Radiation Fallout in Public Zones near the Nevada National Security Site (NNSS): A Recent Study.

A comprehensive radiological study was conducted in the surrounding public zones of the Nevada National Security Site to identify traces of resuspended radioactivity and heavy elemental contamination that might have resulted from various activities. The study used passive and active nuclear methods, specifically gamma spectrometry and instrumental neutron activation analysis, respectively. Passive gamma spectra analysis of air filter papers from various Community Environmental Monitoring Program stations conclusively verified the presence of radionuclides exclusively originating from the natural decay series of 238U and 232Th. Furthermore, gamma spectrometry and instrumental neutron activation analysis of plant samples from surrounding areas of the Nevada National Security Site revealed the absence of any unusual elemental contamination in the environment. These results demonstrated that there was no measurable radiological impact on the public zones surrounding the site resulting from the spread of radioactive materials or toxic heavy metals associated with previous or ongoing activities at Nevada National Security Site. Therefore, the safety of public zones concerning retained radioactivity and harmful elemental contamination arising from Nevada National Security Site operations is negligible. The significance of this study is further pronounced in the current geopolitical context, as it establishes the baseline elemental composition for various desert plants for future reference.

Airblast observations and near-field modeling of the large surface explosion coupling experiment

Seismoacoustic wave generation for two consecutive surface chemical explosions of the same yield (approximately 1 ton TNT-equivalent) was studied during the Large Surface Explosion Coupling Experiment (LSECE) conducted at Yucca Flat on the Nevada National Security Site (NNSS) site in alluvium geology. We have performed numerical simulations for both chemical explosions to investigate how the non-central source initiation, site topography and soil mechanical properties affect the evolution of the explosion (fireball and cloud), its crater, and variations in the generated blast waves. The results can be used to improve the understanding of surface explosions and their effects and how those effects can be used to infer source information such as explosive yield and emplacement. We find that the non-central detonation of the explosive cube results in non-axisymmetric blast overpressures which persist through the strong and weak shock regimes, in this case out to 200 m and more. The pattern of the secondary shock (i.e., shock created due to slowing explosive products within the expanding fireball) is also affected and its arrival relative to the main shock and may be indicative of explosive type due to its dependence on the explosive products ratio of heats. Small reflections are visible within the overpressure signal that are most probably due to small artifacts in blast path. Importantly, the fireball growth, cavity generation, and cloud formation also depart from spherical and ideal approximations due to ground interactions and material dependence, which shows the importance of realistic geomaterial models for accurate prediction. The asymmetry in peak overpressure is diminished for the second chemical explosion, which was placed in the crater of the first. Numerical modeling shows that the explosive jetting created by the non-central detonation is reduced upon interaction with the crater walls and this has the effect of making the blast generation more axisymmetric.

Spot size measurement of a deuterium-tritium dense plasma focus using neutron radiography.

Neutron radiography is a technique uniquely suited to applications in nuclear diagnostics, non-destructive testing, and subcritical experiments. The spatial resolution of neutron radiographs is degraded by optical blur in the imaging system and the neutron source size, where the ideal source is point-like to optimize the point-spread function. A potential neutron source for radiography is the dense plasma focus (DPF), a coaxial Z-pinch that produces thermonuclear and beam-target neutrons. To assess if the source size is suitable for radiography, a neutron imaging system was used to measure the source size of the 4 MA Sodium DPF at the Nevada National Security Site operating with deuterium-tritium gas-fill. The source size was measured using the edge-spread function of tungsten objects, each having a rolled (convex) edge. The spot size was found to be 7-12mm full-width at half-max(FWHM) assuming a Gaussian source, though comparison is presented for Lorentzian and Bennett distributions. The average FWHM was found to be 8.6 ± 1.2mm vertically and 10.8 ± 1.2mm horizontally with respect to the image plane, averaging over varied edges and alignments. The results were sensitive to source alignment and edge metrology, which introduced notable uncertainties. These results are consistent with separate experimental measurements as well as magnetohydrodynamics simulations of this DPF, which suggest that neutron production can originate from pinches ∼5-7mm off-axis. These results suggest that the DPF should be used for radiography at low magnification (M < 1) where spot size does not dominate spatial blur.

Godiva IV central cavity neutron environment characterization with threshold neutron detectors

Godiva IV is a cylindrical fast burst reactor comprised of approximately 65 kg of highly enriched uranium that is operated by Los Alamos National Laboratory and sited at the National Criticality Experiments Research Center at the Nevada National Security Site in Nevada in the United States. Godiva IV is typically operated at delayed critical and in the regime spanning from sub-prompt to super-prompt bursts. Godiva IV is used for sample irradiations, criticality safety demonstrations, dosimetry studies, and for studying super-prompt behavior. In preparation for both an upcoming experiment to reduce uncertainties in the prompt fission spectrum for 235U using threshold neutron detectors, and for future research using Godiva IV, it was desired to exercise the process of the selection of threshold neutron detectors/activation foils, radiation metrology, and the subsequent adjustment of the neutron spectrum. For this exercise, nine high purity threshold neutron detectors/activation foils were irradiated in a Godiva IV burst. The foils were then analyzed using a high-purity germanium detector in the NCERC counting laboratory to determine end of irradiation specific activities for available IRDFF-II reactions. This work summarizes the Godiva IV foil irradiation, radiation metrology results, and adjusted neutron spectrum. The results of this exercise ultimately characterized the neutron environment inside the sample irradiation cavity inside Godiva IV to a higher degree than previously performed, informed decisions for the upcoming larger scale experiment, and will inform future neutron spectrum characterizations at NCERC.

Hydrologic Impacts of a Strike-Slip Fault Zone: Insights from Joint 3D Body-Wave Tomography of Rock Valley

ABSTRACT The Rock Valley fault zone (RVFZ), an intraplate strike-slip fault zone in the southern Nevada National Security Site (NNSS), hosted a series of very shallow (&amp;lt;3 km) earthquakes in 1993. The RVFZ may also have hydrological significance within the NNSS, potentially playing a role in regional groundwater flow, but there is a lack of local hydrological data. In the Spring of 2021, we collected active-source accelerated weight drop seismic data over part of the RVFZ to better characterize the shallow subsurface. We manually picked ∼17,000 P-wave travel times and over 14,000 S-wave travel times, which were inverted for P-wave velocity (VP), S-wave velocity (VS), and VP/VS ratio in a 3D joint tomographic inversion scheme. Seismic velocities are imaged as deep as ∼700 m in areas and generally align with geologic and structural expectations. VP and VS are relatively reduced near mapped and inferred faults, with the most prominent lower VP and VS zone around the densest collection of faults. We image VP/VS ratios ranging from ∼1.5 to ∼2.4, the extremes of which occur at a depth of ∼100 m and are juxtaposed across a fault. One possible interpretation of the imaged seismic velocities is enhanced fault damage near the densest collection of faults with relatively higher porosity and/or crack density at ∼100 m depth, with patches of semiperched groundwater present in the sedimentary rock in higher VP/VS areas and drier rock in lower VP/VS areas. A relatively higher VP/VS area beneath the densest faults persists at depth, which suggests percolation of groundwater via the fault damage zone to the regionally connected lower carbonate aquifer. Potentially, the presence and movement of groundwater may have played a role in the 1993 earthquake aftershocks.

Chemical explosion of October 18, 2023 at the Nevada Test Site

The results of processing the seismic event of October 18, 2023 in the area of the Nevada Test Site (NTS) are presented using digital records of seismic arrays and three-component stations available in open sources, at local and regional distances. Kinematic and dynamic parameters of the seismic event were obtained. A comparison with well-known reference explosions and tectonic earthquakes on the territory of the NTS in order to estimate the event’s yield, as well as determination of the source’s nature was made. It is highly likely that the event under study is a chemical explosion with yield of at least two tons

Capturing plume behavior in complex terrain: an overview of the Nevada National Security Site Meteorological Experiment (METEX21)

Capturing plume behavior in complex terrain: an overview of the Nevada National Security Site Meteorological Experiment (METEX21)

Time-Varying Moment-Tensor Analysis with Application to Buried Chemical Explosions

Abstract The Source Physics Experiment (SPE) Phase I consisted of a series of over-buried, horizontally colocated chemical explosions at the Nevada National Security Site. Seismic waveforms from these explosions recorded at near-source accelerometers, local geophone arrays, and regional seismic stations provided a rich suite of observations suitable for resolving fine source details. To investigate the time-varying source history of the explosions, we used the frequency-domain moment-tensor inversion method described in Yang et al. (2018) with added regularization and reconstruction to suppress the nonuniqueness evident in unconstrained inversion results. The inverted moment-rate spectra are accurate within the response band of the local geophones and, in all cases, display predominately isotropic characteristics. For SPE-4Prime, SPE-5, and SPE-6, we resolve predominately isotropic moment release followed by double couple and compensated linear vector dipole (CLVD) release later in the time-varying source history. We interpret these results both in terms of absolute depth and scaled depth of burial. The apparent non-isotropic release from SPE-4Prime and SPE-5 may simply reflect increased resolving power related to improved Earth model accuracy at greater absolute depths, whereas the non-isotropic release from SPE-6 likely reflects the larger damage associated with an event at a shallower scaled depth. These results provide insight into the time-varying source characteristics of shallow explosions and motivation to study shear-wave generation by inverting for fracture, spallation, induced slip, and other temporally delayed source processes through time-varying methods.

The Observed Inefficiency of Explosions to Produce Large Aftershocks: Båth’s Law for Explosions is 2.5

Abstract Underground explosions are observed to produce fewer and smaller aftershocks than similar size earthquakes. The seismic magnitude difference Δmx between an explosion and its largest aftershock is an expression of Båth’s law for explosions. Based on an analysis of a compilation of aftershock studies from Soviet testing at the Semipalatinsk test site in Kazakhstan and observations from American testing at the Nevada National Security Site (NNSS), we find that the average magnitude difference for explosions Δmx‾ is about 2.5. Based on the NNSS data, two standard deviations of Δmx is about 1.5. In all the cases studied, from ton to megaton yield, from shallow to overburied depth, and chemical or nuclear source, no explosion aftershock has been larger than the explosion that preceded it. In fact, the two events at the NNSS with the largest aftershock magnitudes relative to the explosion are associated with the collapse of the cavity created by the explosion. This is similar to observations from North Korean testing at the Punggye-ri Test Site, where the largest seismic event following the test is attributed to the collapse after the 2017 explosion and is from 0.8 to 2 magnitude units less than the mainshock.

Atmospheric Atomic Testing in Nevada, Shot Harry, and the Agency of Nature

Abstract Harry, a 32-kiloton tower shot in May of 1953, was the dirtiest atmospheric detonation ever conducted at the Nevada Test Site in terms of population exposure to radioactive contamination. Fallout descended upon St. George, Utah, and residents were instructed to shelter in place for approximately two hours. The timeline regarding Harry’s arrival in St. George and when the shelter in place directive was issued, however, remains the subject of controversy, as do the potential health effects. Harry not only illustrated the inadequacies of the Atomic Energy Commission’s (AEC) management of offsite fallout, but also called into question modernist assumptions of the command and control of nature. Based on archival analysis of AEC memorandum and reports as well as documents associated with civil litigation against the federal government, I more fully articulate the events surrounding shot Harry and highlight the implications for historical analysis more broadly.

Seismoacoustic Signatures Observed During a Long-Term Deployment of Infrasound Sensors at the Nevada National Security Site

ABSTRACT Earthquakes have repeatedly been shown to produce inaudible acoustic signals (&amp;lt;20 Hz), otherwise known as infrasound. These signals can propagate hundreds to thousands of kilometers and still be detected by ground-based infrasound arrays depending on the source strength, distance between source and receiver, and atmospheric conditions. Another type of signal arrival at infrasound arrays is the seismic induced motion of the sensor itself, or ground-motion-induced sensor noise. Measured acoustic and seismic waves produced by earthquakes can provide insight into properties of the earthquake such as magnitude, depth, and focal mechanism, as well as information about the local lithology and atmospheric conditions. Large earthquakes that produce strong acoustic signals detected at distances greater than 100 km are the most commonly studied; however, more recent studies have found that smaller magnitude earthquakes (Mw&amp;lt;2.0) can be detected at short ranges. In that vein, this study will investigate the ability for a long-term deployment of infrasound sensors (deployed as part of the Source Physics Experiments [SPE] from 2014 to 2020) to detect both seismic and infrasonic signals from earthquakes at local ranges (&amp;lt;50 km). Methods used include a combination of spectral analysis and automated array processing, supported by U.S. Geological Survey earthquake bulletins. This investigation revealed no clear acoustic detections for short range earthquakes. However, secondary infrasound from an Mw 7.1 earthquake over 200 km away was detected. Important insights were also made regarding the performance of the SPE networks including detections of other acoustic sources such as bolides and rocket launches. Finally, evaluation of the infrasound arrays is performed to provide insight into optimal deployments for targeting earthquake infrasound.

Rural healthcare: A retrospective review of lung carcinoma demographics and screening in the northern Arizona healthcare system.

e18696 Background: In the United States, lung carcinoma is the leading cause of cancer mortality. In 2022, the National Cancer Institute estimated 236,740 new cases of lung cancer, or 12.3% of all new cancer cases, and 130,180 deaths, or 21.4% of all cancer deaths. The risk factors for lung cancer include cigarette smoking, secondhand smoke, the non-Hispanic population, air pollution, or prior radiation therapy. The fatality and common risk factors emphasize the importance of the screening guidelines. Northern Arizona is considered an area affected by downwinder syndrome which is defined as individuals exposed to radiation from the explosion of nuclear devices at the Federal Nevada Test Site with radioactive materials being disturbed by winds. Northern Arizona Healthcare (NAH) has a large population located in these affected counties and lung cancer demographics were reviewed to observe for any variation when compared to the general population. The patients were also reviewed to determine if there were any major deficits in screening guidelines. Methods: This retrospective review included patients diagnosed with lung carcinoma based on the ICD 9 and 10 codes between 2015 to 2020 in the NAH systems. The total number of charts included 559 but 184 were excluded for the following reasons: concern for lung cancer, but not confirmed, patients located not in Northern Arizona, diagnosed prior to 2015, duplicate name but same medical record number, malignancy other than lung cancer, metastatic cancer with unknown primary, and lung cancer was eventually ruled out. The total number of patients remaining in the review was 375. Demographics and lung carcinoma screening information were obtained through NAH medical records. Results: Demographics: median age of 71 with 286 of 375 patients &gt; 65; gender 53.06% males, 46.4% female; race: 88.8% Caucasian, 4.8% Hispanic, Native American 4%, African American 2.1%, Asian 0.3%; smoking history 56.8% active, 31.4% former, 10.6% never; Lung Cancer Pathology: Adenocarcinoma 49.3%, Squamous Cell 18.9%, NSCLC (other than adenocarcinoma or squamous cell) 11.78%, Small Cell 17%, undetermined 2.7%; Lung Cancer Screening: 64.50% no screening vs 7.2% who did, 28.3% were indeterminable. Conclusions: Despite Northern Arizona being considered an area affected by downwinder syndrome, a five-year review of lung carcinoma demographics did not expose any major variation when compared to the generalized population. A limitation was molecular markers were not included and a potential area of further investigation. The review did expose deficits in lung carcinoma screening. 64% of the 375 patients were not screened for lung cancer. A formal presentation was held at NAH grand rounds to raise awareness of lung carcinoma screening guidelines. For future advancement, a collaboration with IT to develop outpatient screening alerts to optimize healthcare in rural areas.

Regional infrasonic observations from surface explosions – influence of atmospheric variations and realistic terrain

SUMMARY A pair of 1-ton, conventional surface explosions were conducted at the Nevada National Security Site in the fall of 2020 producing seismoacoustic signatures observable hundreds of kilometres from the source location. Regional infrasonic observations include tropospheric ducting at large distances to the south, a wide stratospheric waveguide with signals observed more than 700 km to the east, and anomalous arrivals in the stratospheric shadow zone. Notable differences in propagation between the events are identified despite the explosions being conducted just two days apart due to a sharp temporal shift in the tropospheric winds as well as structural changes in the stratospheric winds. Propagation simulations of the two events have been completed using a combination of ray tracing and parabolic equation (PE) methods. Simulations have been conducted to quantify the impact of the temporal variations in the atmosphere as well as the influence of terrain on propagation. Temporal variations in reflection locations are found to produce notable changes in downrange propagation due to spatially varying terrain features. Finite frequency effects modelled by the PE are found to predict ensonification not included in corresponding 2D ray tracing simulations. Notable variations in predicted signal amplitude are found due to focusing by along-path and cross-path terrain gradients; though, the later of these is only modelled using fully 3D ray tracing analysis.

Seismoacoustic Explosion Yield and Depth Estimation: Insights from the Large Surface Explosion Coupling Experiment

ABSTRACT The Large Surface Explosion Coupling Experiment (LSECE) is a chemical explosion experiment conducted in Yucca Flat at the Nevada National Security Site in 2020. The experiment included two surface detonations of ∼1000 kg trinitrotoluene equivalent. The main goal of this experiment was to provide the ground-truth data for seismoacoustic wave excitation by large chemical explosions near the ground surface. The seismic and acoustic energy partitioning between the surface is strongly governed by the depth or height of explosions, and either seismic or acoustic-only analysis may have inherent ambiguity in determining explosion yield and depth simultaneously. Previous studies suggested that joint seismoacoustic analysis can resolve the trade-off and reduce the uncertainty of yield and depth estimation dramatically. We demonstrate the capability of seismoacoustic analysis to improve the accuracy of explosion yield and depth estimation with the LSECE data. Local acoustic wave propagation in the atmosphere can be substantially affected by constantly varying weather conditions. Consisting of two detonations before dawn and in the afternoon, LSECE provides unique data to evaluate the model accuracy of acoustic wave propagation and seismoacoustic energy partitioning depending on local atmospheric conditions. We quantitatively evaluate the accuracy of yield and depth estimation depending on atmospheric variability and the improvement achieved by the joint seismoacoustic approach.

Nuclear Fission or Fusion on Meeting Electricity Demand of Future Energy Source Economy and Policy

The announcement of the United States Department of Energy (DOE) on Tuesday, December 13, 2022 was a monumental milestone in nuclear Fusion research, where a “net energy gain driven by Inertia Fusion Confinement (ICF)” eventually, after almost 40 years of scientific efforts achieved for the first time in history by scientists from the Lawrence Livermore National Laboratory (LLNL) in California through its National Ignition Factify (NIF) program. For a long time since aftermath of “Manhattan Project”, scientists knew and had some clear concept of bringing sun energy to earth by means of “Fusion” process either via Magnetic Fusion Confinement (MFC)or ICF after their success of exploding their nuclear fission bomb through Nevada Test Site (NTS) via “Fission” process. Announcement of such an achievement by simply put it is one of the most impressive scientific feats of the 21st century as “Jennifer Granholm, secretary of U.S. Department of Energy said at a press conference. Such success puts production of electricity from nuclear energy of fusion puts it in different perspectives and it shows that researchers have been working on this for decades alongside of MCF and their efforts behind nuclear fission of Generation - IV (GEN-IV) reactors technology and manufacturing. In this short review paper, we describe all these issues of the differences between Fission and Fusion and each aspect of them being source of generating electricity to meet national and global demand for the source of it from nuclear point of view and not going to detail of renewable source of energy at this point.

Doom Town, Nevada Test Site, and the Popular Imagination of Atomic Disaster

This article explores the effect of Doom Town, a civil defense experiment conducted at Nevada Test Site in March 1953 and May 1955, on American attitudes toward the atom. Initially conceived by the Federal Civil Defense Administration (FCDA) as a means to progress knowledge and understanding of how to survive nuclear attack, the creation and destruction of two “Survival Towns” in the Nevadan desert instead accelerated national anxieties. My article looks at how local and national media negatively framed the two experiments, and how the public responded, with two specific images of Doom Town undermining public confidence in the atom: the ruined city (or homegrown Hiroshima) and the projected death of the American nuclear family.

The National Criticality Experiments Research Center and its role in support of advanced reactor design

The National Criticality Experiments Research Center (NCERC) located at the Nevada National Security Site (NNSS) in the Device Assembly Facility (DAF) and operated by Los Alamos National Laboratory (LANL) is the only general purpose critical experiments facility in the United States. Experiments from subcritical to critical and above prompt critical are carried out at NCERC on a regular basis. In recent years, NCERC has become more involved in experiments related to nuclear energy, including the Kilopower/KRUSTY demonstration and the recent Hypatia experiment. Multiple nuclear energy related projects are currently ongoing at NCERC. This paper discusses NCERC’s role in advanced reactor design and how that role may change in the future.

TRAVEL TIME CURVES FOR YUCCA TEST SITE (NEVADA TEST SITE) – SEISMIC ARRAYS «OZHEREL’E» (GEOPHYSICAL OBSERVATORY «BOROVOYE»)

This paper presents the travel times of P waves for 8 Yucca Flat (Nevada Test Site NTS) explosions from 1979 to 1984, with magnitudes mb = 4.9–5.9. Travel times were obtained by revising seismograms from the archives Sadovsky Institute of Geosphere Dynamics for the subsystem “Ozherel’e” (Necklace) of peripheral points Zerenda, Vostochniy, Chkalovo of the large-base seismic array system (SAS) of the geophysical observatory Borovoye. This system has been operating since 1979 on the territory of Kazakhstan. By the example of registration of underground nuclear explosions at the Yucca site of the Nevada Test Site (NTS), local travel time curves and linear trends in the P wave travel time in the range of epicentral distances 89.3110°–90.3701° are investigated. We estimate of the velocities of effective P waves for the Yucca-“Ozherel’e” and peripheral points.

Estimating the Geological Structure and Transport Properties of Denied and Limited Access Sites

AbstractOnsite measurements are the standard for establishing geological conditions and related transport properties. However, making direct measurements is not always possible, either because a location is too remote, too vast, or access is outright denied. The latter is typically the case at nuclear test sites, or military installations. Here we describe a systematic method to characterize geology and estimate fracture width, spacing, tortuosity, permeability, and porosity at locations where direct measurements cannot be made. Fractures are treated as fractals with their respective fractal dimensions determined using surface images. Tortuosity in the geological matrix (i.e., bulk media) is determined using rock class with the latter also being used to determine distributions for permeability and porosity. The approach is tested using areal images and rock class for the Nevada Test Site and validated by comparison to field and core measurements. Past work has shown that testing a nuclear weapon underground can affect not only the migration time for gases to the surface but also their isotopic ratios. Accurately modeling gas transport and isotopic fractionation requires knowledge of the geology. However, suspected tests are typically conducted at sites to which the international community has no access.