Underground Nuclear Explosions Research Articles

Long-Range Consequences of Emergency Underground Nuclear Explosions in Yakutia: Incidence of Malignant Neoplasms

The paper evaluates the possibility of interrelation of emergency underground nuclear explosions with an increased incidence of cancer among the population of areas bordering the area of emergency underground nuclear explosions, for example, in Suntarsky and Nyurbinsky districts, in which the incidence of malignant neoplasms, mortality from malignant neoplasms is higher than the average in the Republic of Sakha (Yakutia). For this purpose, the radiation situation of the sites of underground nuclear explosions “Kraton-3” and “Kristall” was investigated: the radionuclide composition of soil and vegetation was studied by semiconductor gamma-ray spectrometry and a water sample by liquid scintillation spectrometry; dosimetric measurements were carried out: the power of exposure doses. Based on the results of water analysis, it is possible to determine the possibility of migration of tritium from the cavities of emergency underground nuclear explosions. The results of the study of vegetation and soil showed the presence of artificial radionuclides 137Cs, 241Am and traces of 60Co. High values of the specific activity of radiocesium are observed in several samples taken near the area “Kraton-3”. Also in this area, the results of dosimetric measurements showed a slight decrease in the gamma background level, but which still remains elevated and exceeds the safe level by 2.5 times. It is possible that the increased incidence rate in the districts of the republic bordering the area of emergency underground nuclear explosions can be considered as their long-term consequences due to additional dose loads, for example, from caesium during the entire time after the explosions, since the half-life of caesium is approximately 30 years. The results of this study can be considered as a basis for the development of recommendations, possible regulations that can be applied in the implementation of compliance with radiation safety standards during future similar tests and during mining, during which there may be emissions of natural radionuclides to the earth's surface.

Seismic Discrimination Between Nuclear Explosions and Natural Earthquakes using Multi-Machine Learning Techniques

AbstractIn the field of seismic signal analysis, it is of utmost importance to accurately differentiate between earthquakes and underground nuclear explosions. As a contribution for the verification regime of the Comprehensive Nuclear Test Ban Treaty (CTBT), Various methods have been employed for this purpose, including Complexity, Spectral ratio, mb—Ms (body wave and surface wave magnitudes), and corner frequency of P and S waves. These discrimination techniques have been examined to manually identify natural seismic events from nuclear explosions across different regions worldwide, such as China, India, Pakistan, North Korea, and the United States. To gather the necessary data, a comprehensive dataset comprising nuclear explosions and earthquakes of the same magnitude range (4 ≤ mb ≤ 6.5) of 35 seismic events from 1945 to 2017 has been compiled from the International Research Institute for Seismology (IRIS) using broadband and long period seismic stations. The objective of this study is to employ a range of linear and nonlinear Machine Learning (ML) models with the aim of automatically distinguishing between underground nuclear explosions and large earthquakes to enhance the accuracy of manual feature extraction. For this purpose, time domain waveforms and different classifier techniques focused on feature extraction have been used. The ML models employed include logistic regression, K-nearest neighbours classifier, decision tree classifier, random forest classifier, voting classifier, and Naive Bayes. The outcomes of the ROC and AUC analyses were employed to validate the validity of our proposed discrimination algorithm. The results show that the Random Forest Classifier is the most effective model, obtaining 100% accuracy in the case of feature extraction, while the best model for the time domain waveform classifier that achieved 75.5% accuracy is the voting classifier.

Bayesian Inversion of MDJ Seismograms for Source Parameters and Yields of DPRK Underground Nuclear Explosions 2 to 6

AbstractThe Democratic People’s Republic of Korea (DPRK) conducted six underground nuclear explosions at the Punggye-ri nuclear test site at Mount Mantap, a granite peak. Test 1 was separate from tests 2 to 6, which were within about 1 km of each other. Using seismograms recorded at Mudanjiang (MDJ) seismic station in China, I propose a new approach to obtain source parameters, source time functions and yields of events 2 to 6, assuming they share the same Green’s function from Punggye-ri to MDJ. Each source is modelled as a spherical cavity in a homogeneous isotropic elastic full space, with four independent parameters constrained by published data on the properties of granite and analysis of the recorded MDJ seismograms. The effect of the ground surface is included as a planar reflection that modifies the pressure at the cavity boundary. The Green’s function for each event is estimated by deconvolving the seismogram for the estimated source time function. Very fast simulated annealing (VFSA) is used to search the parameter space to minimise the root-mean square difference among the estimated Green’s functions and their mean. The estimated Green’s functions are similar and differ in amplitude by less than a factor of 2. Green’s functions from Punggye-ri to other seismic stations may be obtained by deconvolving the seismograms for the corresponding source time functions. Mapping the nonlinear zones surrounding each explosion indicates that this part of the site was destroyed by the underground nuclear tests before its official destruction on 24 May 2018.

Indirect effects of oil products on the environment

The article is focused on chemical and radioactive contamination of the environment during hydrocarbon production. The objective of the research is to present relatively unknown facts of indirect long-term environmental effects of hydrocarbon production. Traces of radioactive contamination of soils, ground- and surface water were studied, and also in drinking water in the Republic of Bashkortostan. The authors’ own field and laboratory studies were used. They were performed as part of the preparation of geochemical base map (GHO-1000) of 1:1000000 scale in the Republic of Bashkortostan and in the Ukhto-Izhemsky oil and gas bearing region. The methods applied for laboratory research were inductively coupled plasma mass spectrometry (ICP-MS) for soil and bottom sediment samples and atomic emission spectrometry (ICP-AMS) for ground- and surface waters. It has been determined that in the areas affected by oil production the chemical pollution aspects include deterioration of the groundwater quality caused by associated water and oil products ingress into aquifers due to violation of the oil and gas well drilling techniques, and soil salination caused by frequent equipment breaks during oil production. Aspects of radiation contamination of the environment during oil production include the intake of radionuclides with associated water, and sometimes with heavy hydrocarbon fractions, as well as the consequences of underground nuclear explosions. It is concluded that the territories of hydrocarbon exploration, production and storage should be classified as areas of potential risk for radioactive contamination and chemical pollution (by inorganic compounds, including heavy metal salts). Uranium concentration in drinking water was determined by the INAA method (instrumental neutron activation analysis).

Hydromechanical characterization of gas transport amidst uncertainty for underground nuclear explosion detection

Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone, surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions (UNEs). However, the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved, including the generation of complex fracture networks, reactivation of natural fractures and faults, and thermo-hydro-mechanical-chemical (THMC) coupling of radionuclide gas transport in the subsurface. In this study, we provide an experimental investigation of hydro-mechanical (HM) coupling among gas flow, stress states, rock deformation, and rock damage using a unique multi-physics triaxial direct shear rock testing system. The testing system also features redundant gas pressure and flow rate measurements, well suited for parameter uncertainty quantification. Using porous tuff and tight granite samples that are relevant to historic UNE tests, we measured the Biot effective stress coefficient, rock matrix gas permeability, and fracture gas permeability at a range of pore pressure and stress conditions. The Biot effective stress coefficient varies from 0.69 to 1 for the tuff, whose porosity averages 35.3% ± 0.7%, while this coefficient varies from 0.51 to 0.78 for the tight granite (porosity <1%, perhaps an underestimate). Matrix gas permeability is strongly correlated to effective stress for the granite, but not for the porous tuff. Our experiments reveal the following key engineering implications on transport of radionuclide gases post a UNE event: (1) The porous tuff shows apparent fracture dilation or compression upon stress changes, which does not necessarily change the gas permeability; (2) The granite fracture permeability shows strong stress sensitivity and is positively related to shear displacement; and (3) Hydromechanical coupling among stress states, rock damage, and gas flow appears to be stronger in tight granite than in porous tuff.

Examining the potential for detecting simultaneous noble gas and aerosol samples in the international monitoring system radionuclide network

The purpose of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) is to establish a legally binding ban on nuclear weapon test explosions or any other nuclear explosions. The Preparatory Commission for the CTBT Organization (CTBTO PrepCom) is developing the International Monitoring System (IMS) that includes a global network of 80 stations to monitor for airborne radionuclides upon entry into force of the CTBT. All 80 radionuclide stations will monitor for particulate radionuclides and at least half of the stations will monitor for radioxenon. The airborne radionuclide monitoring is an important verification technology both for the detection of a radionuclide release and in the determination of whether the release event originates from a nuclear explosion as opposed to an industrial use of nuclear materials.Nuclear power plants and many medical isotope production facilities release radioxenon into the atmosphere. Low levels of a few particulate isotopes, such as iodine, may also be released. Detections of multiple isotopes are useful for screening the radionuclide samples for relevance to the Treaty. This paper examines the anticipated joint detections in the IMS of noble gas and particulate isotopes from underground nuclear explosions where breaches in the underground containment vents from low levels to up to 1% of the radionuclide inventory of the resulting fission products to the atmosphere. Detection probabilities are based on 844 simulated release events spaced out at 17 release locations and one year in time. Six different release (venting) scenarios, including two fractionated scenarios, were analyzed.When ranked by detection probability, 11 particulate isotopes and one noble gas isotope (133Xe) appear in the top 20 isotopes for all six release scenarios. Using the 11 particulate isotopes and the one noble gas isotope, the IMS has nearly the same detection probability as when 45 particulate and 4 noble gas isotopes are used. Thus, a limited list of relevant radionuclides may be sufficient for treaty verification purposes. The probability that at least one particulate and at least one radioxenon isotope would be detected in the IMS from the release events ranged from 0.15 to 0.86 depending on the release scenario.

On Magnitudes and Inferred Yields of the 39 Underground Nuclear Test Explosions at the Novaya Zemlya Test Site

ABSTRACT We review the previously compiled seismic magnitudes for underground nuclear explosions at the Union of the Soviet Socialist Republics Novaya Zemlya Test Site, and analyze these data in the context of published details about individual tests and official Russian reports of annual cumulative explosive energy release at the test site. We derive relationships between teleseismic body wave magnitude mb and explosive yield Y by predicting the yield of each test using mb and minimizing the difference between predicted and reported annual cumulative yield. A linear relationship between mb and logY with a slope of 0.82 provides a good fit to the annual total yield, with a root mean square (rms) misfit of 0.095 logY units. A spectral magnitude relationship based on the explosion source model of Mueller and Murphy (1971) with a single-free-parameter provides a slightly better fit. For the 10 tests for which individual yields can be directly deduced from the official reports, the rms misfit of reported yields is less than 0.1 logY units or about 25%. More complex relationships that differentiate between the northern and southern test areas, or take account of variations in the scaled depth of burial, do not provide substantially better fits to the reported yields.

Evaluation of soil radioactivity in the areas of underground nuclear explosions at the Pomuk gas field site in Uzbekistan.

This study investigates soil radioactivity at the Pomuk gas field in Uzbekistan, a region with history of underground nuclear activity. Using a NaI (Tl) scintillation gamma spectrometer, soil samples were analyzed for concentrations of 232Th, 226Ra, 40K, and 137Cs. Concentrations were found to be in the range of 19.0-31.0 Bq/kg for 232Th, 12.0-32.0 Bq/kg for 226Ra, 450.0-634.0 Bq/kg for 40K, and 2.4-11.0 Bq/kg for 137Cs. Surface radon flux density was measured using a coal sorbent-based passive method, with values ranging from 26.1 to 79.0 mBq/m2s. Mean activity values for radium equivalent (Raeq) and gamma representative level index (Iγ) were calculated to be 75.2-96.5 Bq/kg and 0.3-0.4 Bq/kg, respectively. The absorbed airborne gamma dose rates (GDR) varied between 41.0 and 52.0 nGy/h, while annual effective dose rates (AEDR) were 0.3-0.4 μSv/year. The radiological risk assessment indicates the area is within safe limits for the population and environment, providing a foundation for future radiological monitoring programs.

Modern Radioecological Situation at the Site of the Peaceful Underground Nuclear Explosion “Crystal” and Radionuclides in the Surface Waters of the Adjacent Territory (Western Yakutia)

Modern Radioecological Situation at the Site of the Peaceful Underground Nuclear Explosion “Crystal” and Radionuclides in the Surface Waters of the Adjacent Territory (Western Yakutia)

A plastic scintillator and HPGe [formula omitted] coincidence detection system

A network of specialist laboratories support the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) with re-measurements of radionuclide samples, including xenon gas. The measurement of four xenon fission product radionuclides (133Xe, 135Xe, 131mXe and 133mXe) can be used to detect an underground nuclear explosion. Laboratories use a range of techniques to measure the radionuclides, including beta-gamma (β−γ) coincidence spectrometry. These highly-sensitive measurements are capable of detecting concentrations of down to 500 atoms of 133Xe in a few cm3 of xenon. In some detector systems, detection of the metastable isomers (131mXe and 133mXe) can be more challenging due to interferences between the signatures of different radionuclides. Recent work has shown that using high-purity Germanium (HPGe) high-resolution gamma detectors, these interferences can be reduced, lowering the dependence of the detection limits on radionuclide sample isotopic composition. One downside of these detectors is the reduction in detection efficiency, which impacts the overall detection sensitivity; so assessing different detector systems is a priority for radionuclide laboratories. This work presents a coincidence detector system comprising of a plastic scintillator gas cell and a large-crystal high-purity germanium detector. The energy resolution, coincidence detection efficiency, MDA and interference factors are determined from measurements of synthetic radioxenon gas samples.

Global Nuclear Explosion Discrimination Using a Convolutional Neural Network

AbstractUsing P‐wave seismograms, we trained a seismic source classifier using a Convolutional Neural Network. We trained for three classes: earthquake P‐wave, underground nuclear explosion (UNE) P‐wave, and noise. With the current absence of nuclear testing by countries that have signed the Comprehensive Test Ban Treaty, high quality seismic data from UNEs is limited. Even with limited training data, our model can accurately characterize most events recorded at regional and teleseismic distances, finding over 95% signals in the validation set. We applied the model on holdout datasets of the North Korean test explosions to evaluate the performance on unique region and station‐source pairs, with promising results. Additionally, we tested on the Source Physics Experiment events to investigate the potential for chemical explosions to act as a surrogate for nuclear explosions. We anticipate that machine‐learning models like our classifier system can have broad application for other seismic signals including volcanic and non‐volcanic tremor, anomalous earthquakes, ice‐quakes or landslide‐quakes.

Characterization of a [formula omitted]-[formula omitted] coincidence system comprising a plastic scintillator and HPGe detector for radioxenon measurements under the CTBT

Measurement of the four relevant radioxenon isotopes, namely 131mXe, 133mXe, 133Xe, and 135Xe, play a key role in underground nuclear explosion monitoring for ensuring compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). A β-γ coincidence system that employs a plastic scintillator detector and a HPGe detector was developed in Beijing Radionuclide Laboratory. The Minimum Detectable Activity (MDA) in a 24-h measurement of the system for 131mXe, 133mXe, 133Xe and 135Xe can achieve 1.8 mBq, 1.4 mBq, 3.4 mBq and 4.1 mBq, respectively.

Detection of anomalous radioxenon concentrations: A distribution‐free approach

AbstractThe detection of anomalous atmospheric radioxenon concentrations plays a key role in detecting both underground nuclear explosions and radioactive emissions from nuclear power plants and medical isotope production facilities. For this purpose, the CTBTO's International Data Centre uses a procedure based on descriptive thresholds. In order to supplement this procedure with a statistical inference‐based method, we compared several non‐parametric change‐point control charts for detecting shifts above the natural radioxenon background. The results indicate that the proposed methods can provide valuable tools for the institutions responsible for the verification and classification of anomalous radioxenon concentrations.

Characterization of CTBT-Relevant Radioxenon Detections at IMS Stations Using Isotopic Activity Ratio Analysis

Radioxenon isotopes measured at radionuclide stations of the Comprehensive Nuclear-Test-Ban Treaty’s (CTBT) International Monitoring System (IMS) may indicate releases from underground nuclear explosions (UNEs) but are often caused by emissions from nuclear facilities. Characterization of CTBT-relevant nuclear events may use the evolution of isotopic activity ratios over time, which goes from the release of an assumed UNE, through atmospheric transport, to sample collections and measurements. A mathematical approach is presented to discuss the characterization of the spatial and temporal relationships between a nuclear explosion and radioxenon measurements. On the one hand, activity concentrations at an IMS station are estimated by using the assumed release scenario regarding a UNE and atmospheric transport modelling. On the other hand, the activities collected in the samples are determined by spectral analysis first and the activity concentrations in the air passing over the IMS station are estimated under an assumption of constant concentration during sampling. The isotopic ratios of activities released from the UNE are related to the isotopic ratios of activity concentrations in the plume of air crossing the IMS station, resulting in a function of the isotopic activity ratio over the time from detonation to sample measurement. The latter is used for discrimination of a nuclear test and estimation of the time of detonation, such as a four radioxenon plot of the activity ratio relationship of 135Xe/133Xe versus 133mXe/131mXe.

SAUNA III - The next generation noble gas system for verification of nuclear explosions

The SAUNA III represent the next generation of the SAUNA systems designed for detection of low levels of radioactive xenon in the atmosphere, with the main purpose of detecting underground nuclear explosions. The system automatically collects, processes and measures 40 m3 atmospheric samples every 6 h, increasing both the sensitivity and time resolution as compared the systems currently in use. The higher sensitive increases the number of detections, especially for samples were more than one isotope of xenon are detected. This improves the understanding of the background and the possibility to screen out signal from civilian sources. The increased time resolution of the new system also provides a more detailed picture of the plumes, especially important for near-by sources. The design of the system as well as data from the first two years of operation are presented.

Source Characterization of the Declared North Korean Nuclear Tests From Regional Distance Coda Wave Spectral Ratios

AbstractSeismic observations of underground nuclear explosions provide crucial data on source yield and depth that cannot easily be estimated from other geophysical methods. However, it is difficult to obtain reliable yield estimates for test sites for which we do not have direct seismic calibration experiments. To obtain source information from uncalibrated sites and paths, local and regional seismic records of six, proximal, declared underground nuclear explosions in North Korea are used to compute spectral ratios of narrow‐band waveform envelopes of body‐wave coda that remove path and site effects to reveal precise, relative source moment. The yields of these explosions are obtained from the observed source ratios by simultaneously fitting the classical source model of Mueller and Murphy (1971), https://doi.org/10.1785/bssa0610061675 to all event pairs. The source model provides an impressive fit to the observations considering that the P phase coda derived source spectral ratios did not require a prior knowledge of the source or regionally calibrated corrections to be applied to the data. However, the observed corner frequencies from S wave coda spectral ratios are lower than the source model predictions, but are well fit by models calculated using the corner frequency consistent with the Fisk conjecture. The results presented here provide novel constraints on the spectral distributions of the energy radiated by the sources of the DPRK test series, and allows for an independent evaluation of existing estimated source model parameters.

Thermodynamic determination of condensation behavior for the precursory elements of radioxenon following an underground nuclear explosion

The measurement of radioactive xenon isotopes (radioxenon) in the atmosphere is a tool used to detect underground nuclear explosions, provided that some radioxenon escaped containment and that fractionation leading to the alteration of the relative proportions of these isotopes, is accounted for. After the explosion, volatilization followed by melting of the surrounding rocks produces a magma where the more refractory radioactive species get dissolved while the more volatile ones contribute to the gas phase that might escape. Indium, tin, antimony, tellurium and iodine are the main fission products involved in the decay chains leading to radioxenon. In this study, condensation as a function of temperature for these precursors of radioxenon were determined using thermodynamic calculations for systems with complex chemical composition corresponding to major environments of known underground nuclear explosions and for a range of pressure values representative of the cavity evolution. Our results illustrate a large difference between the relevant condensation temperatures for the radioxenon precursors and the tabulated boiling temperatures of the pure compounds often used as indicators of their volatility. For some precursory elements such as tin, the often-considered Heaviside function represents an oversimplification of the concept of condensation temperature, as condensation occurs over a temperature range as large as 2000 K. This results from the speciation of the elements in the gas phase mainly driven by the formation of oxides. Condensation also strongly depends on pressure while it moderately depends on the bulk chemical composition of the system. This study shows the importance and complexity of the condensation process following underground nuclear explosions. It also shows how thermodynamic computations allow the prediction of the quantity and the relative proportions of radioactive xenon isotopes in the gas phase in the presence of magma, before their potential emission to the atmosphere. Better detection, discrimination and understanding of underground nuclear explosions should arise by taking into account the fractionation resulting from the condensation of the radionuclides producing radioxenon in nuclear cavities.

Radiation situation at the “Pirit” peaceful underground nuclear explosion site

The aim of this study was to evaluate radiation situation at the “ Pirit ” peaceful underground nuclear explosion site . The peaceful underground nuclear explosion “ Pirit ” with the capacity of 37.6 kt оf TNT equivalent was carried out on May 25, 1981 on the territory of the Kumzhinskoye gas condensate field at a depth of 1.5 km . The field is located near the northern coast of the European part of Russia in the delta of the Pechora River ( Nenets Autonomous District ). The peaceful underground nuclear explosion “ Pirit ” was carried out with the aim to stop the uncontrolled gas gushing . Radiation situation is assessed according to the main indicators : dose rate values and content of technogenic radionuclides in soil and water . The radiation survey included d etermining g eographic c oordinates o f s pecific l andscape e lements , m easurement a nd s ampling p oints u sing s atellite n avigators , m easurement o f a mbient d ose e quivalent r ate , i dentification o f g amma-emitting r adionuclides i n s itu b y f ield g amma s pectrometry , s ampling o f w ater , p hoto a nd v ideo s hooting . On t he s ite o f t he u nderground n uclear e xplosion “ P irit ” t he v alues o f t he a mbient d ose e quivalent r ate w ere i n t he r ange o f 0.050–0.089 μ Sv / h, w hich c orresponds t o t he l evels o f t he n atural r adiation b ackground . No s ites o f l ocal r adioactive c ontamination o f s oil b y 137Cs w ere d etected . The t ritium c ontent ( l ess t han 5 B q / k g ) i n w ater b odies d oes n ot e xceed t he l evels o f f luctuations o f t his i ndicator i n o ther r egions o f t he European t erritory o f Russia. The e stimated v alue o f t he e ffective d ose d ue t o i ngestion o f t ritium i n d rinking w ater i n l ocal s ettlements w as 0.044 μ Sv / y ear . The r adiation s ituation o n t he t erritory o f t he p eaceful n uclear e xplosion “ P irit ” m eets t he r equirements o f t he Russian S anitary R egulations a nd Standards 2.6.1.2819-10 “ E nsuring t he r adiation s afety o f t he p opulation l iving i n t he r egions o f n uclear e xplosions f or p eaceful p urposes (1965–1988)” a nd c urrently d oes n ot p ose a t hreat t o p ublic h ealth . D ue t o t he p otential d anger o f t echnogenic r adionuclides c oming f rom t he e picenter o f t he e xplosion t o t he s urface f or l ong-term r adiation s afety , i t i s n ecessary t o o rganize r adiation m onitoring o f t he t erritory a djacent t o t he e xplosion s ite , d etermine t he b oundaries o f t he p rotected z one a nd s et a ppropriate i nformation s igns w arning o f r adiation d anger .

Possible effects of underground nuclear explosions (UNE) for peaceful purposes on the ecological and hydrogeological situation

Possible effects of underground nuclear explosions (UNE) for peaceful purposes on the ecological and hydrogeological situation

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.