Underwater Nuclear Explosion Research Articles

Theoretical model and parameter sensitivity analysis of concrete slab vibration in concrete-face rockfill dams during underwater nuclear explosions

Large reservoir dams, which are carriers of energy and resources, have historically been the main targets of military conflict and terrorist attacks. A concrete-face rockfill dam (CFRD) is a competitive hydraulic structure widely used in large-scale water conservancy projects. However, the vibration response and damping paths of CFRDs under the influence of underwater explosion shock waves remains insufficiently understood. In this study, we created a theoretical model of slab vibration with four-sided free boundaries using Cole’s formula and the motion differential equation of a slab on an elastic foundation. Furthermore, a global sensitivity analysis of the vibration model parameters on the slab displacement was performed based on the Kriging surrogate model and Sobol method. The results showed that the antiseepage slabs experienced a void phenomenon, resulting in overall instability. The explosive distance and normal stiffness of the slab had the greatest influence on the void displacement of the slab, whereas the dam height and concrete density had insignificant effect. Moreover, increasing the dam height of the CFRD did not increase the risk of slab voids during underwater explosions, which was not the case under strong seismic loads. Therefore, the key factors for active and passive defense against blast resistance in CFRDs were identified, which can provide theoretical support for the blast-resistant design and research on CFRDs. In this study, the reliability of the theoretical model was verified by establishing a numerical analysis model.

Analysis of Nuclear Explosion Detection Capability of IMS Hydroacoustic Network

The Comprehensive Nuclear Test Ban Treaty (CTBT) organization has established a hydroacoustic network to ensure the effective detection of nuclear explosions in the vast ocean and in the atmosphere over it in order to effectively guarantee the implementation of the treaty. To assess its effectiveness, according to the reciprocity of underwater acoustic field, this study employs the hydrophone position as the central sound source and utilizes the parabolic equation, along with seabed topography and sound velocity profile data, to estimate the transmission loss. Background noise levels of station evaluation are conducted by using historical data so as to estimate the underwater nuclear explosion sound source level via a passive sonar equation. Utilizing the full ship shock trial (FSST) results of the “Ford” aircraft carrier on June 18, 2021, as a case study, the detection capability of the HA10 station for nuclear explosions is investigated. Subsequently, the network’s overall detection capability was evaluated using the source level at 20 Hz corresponding to a 1 kiloton nuclear explosion yield as a reference. Findings indicate the network’s proficiency in identifying long‐distance propagation signals, particularly those with high explosion source levels within the sound fixing and ranging (SOFAR) channel. The sensitivity analysis demonstrates the network’s ability to detect explosions smaller than 1 kg equivalent in close proximity to a station, and larger explosions exceeding 1 kg or 1 ton at greater distances. This evaluation underscores the network’s significance in detecting and monitoring underwater nuclear explosions across extensive oceanic regions.

The AtmoSOFAR Channel: First Direct Observations of an Elevated Acoustic Duct

AbstractThe Sound Fixing and Ranging (SOFAR) channel in the ocean allows for low frequency sound to travel thousands of kilometers, making it particularly useful for detecting underwater nuclear explosions. Suggestions that an elevated SOFAR‐like channel should exist in the stratosphere date back over half a century and imply that sources within this region can be reliably sensed at vast distances. However, this theory has not been supported with evidence of direct observations from sound within this channel. Here we show that an infrasound sensor on a solar hot air balloon recorded the first infrasound detection of a ground truth airborne source while within this acoustic channel, which we refer to as the AtmoSOFAR channel. Our results support the existence of the AtmoSOFAR channel, demonstrate that acoustic signals can be recorded within it, and provide insight into the characteristics of recorded signals. Results also show a lack of detections on ground‐based stations, highlighting the advantages of using balloon‐borne infrasound sensors to detect impulsive sources at altitude.

Numerical study on structural damage characteristics under long pulse width of underwater nuclear explosions

ABSTRACT In this paper, the loading characteristics of underwater nuclear explosions with low peak and long pulse widths are simulated using the difference in peak pressure and pulse width caused by different charge shapes. The flow field loading characteristics under four charge shapes are analyzed, and the plate failure response under contact and equal impact factors are discussed. The results show that the load characteristics of spherical and cylindrical charge are high peak pressure and narrow pulse width; The load characteristic of truncated cones charge is low peak pressure and long pulse width, which can reflect the long pulse width load characteristics of underwater nuclear explosions. In addition, it was found that the damage patterns of structures with different load characteristics under the same loading conditions differed significantly. This paper has important guiding significance for the study of underwater nuclear explosions and their damage to structures.

Estimation on the Underwater Explosion Equivalent Based on the Threshold Monitoring Technique

Underwater nuclear explosions can be monitored in near real-time by the hydroacoustic network of the International Monitoring System (IMS) established by the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which could also be used to monitor underground and atmospheric nuclear explosions. The equivalent is an important parameter for the nuclear explosions’ monitoring. The traditional equivalent estimation method is to calculate the bubble pulsation period, which is difficult to obtain satisfactory results under the current conditions. In this paper, based on the passive sonar equation and the conversion process of acoustic energy parameters in the hydroacoustic station, the threshold monitoring technique used for underwater explosion equivalent estimation was studied, which was not limited to the measurement conditions and calculation results of the bubble pulsation period. Through the analysis of practical monitoring data, estimation on the underwater explosion equivalent based on the threshold monitoring technique was verified to be able to reach the accuracy upper boundary of current methods and expand the measurement range to further ocean space, along with the real-time monitoring capability of IMS hydroacoustic stations which could be estimated by this method.

The detectability of the Wigwam underwater nuclear explosion by the radionuclide stations of the International Monitoring System

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions, including those detonated from an underwater nuclear explosion. To improve the understanding of the radionuclide signatures of such an event, and whether it would be detectable under the verification regime of the CTBT, the 1955 Wigwam underwater nuclear explosive test has been modelled. Inventory calculations and atmospheric transport modelling has been performed to estimate the activity at the radionuclide stations (RN) of the International Monitoring System (IMS). This has utilized reported release values (0.92%) and meteorological data from the event. The research shows that there is a high probability that Wigwam would have been detectable at U.S. IMS stations at Wake Island (RN77) at 8.4 d, Upi, Guam (RN80) at 10.7 d and Sand Point, AK (RN71) at 13.7 d. At these locations, the majority of IMS relevant radionuclides were fission products, such that additional radionuclides from the seawater activation had largely decayed before reaching the stations.

Radionuclide observables of underwater nuclear explosive tests

There remain technical challenges for an On-site Inspection (OSI) in the high seas environment, which gathers evidence of a violation of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). For terrestrial nuclear explosions, the radionuclide observables are well defined and States Parties have chosen 17 particulate radionuclides that allow discrimination from other nuclear events. However, an underwater nuclear explosion generates induced radionuclides from the neutron activation of seawater, which has the potential to interfere with the measurement of the radionuclide observables using gamma-spectrometry techniques. To understand these effects the inventory of OSI relevant (6.0 × 1016 Bq) and activation (1.6 × 1019 Bq) radionuclides has been calculated for a 1 kT underwater nuclear explosion. The activation products consist predominantly of 38Cl and 24Na, which decay to 5.56% and 0.0007% of their initial activity within 1 and 14 days. Monte Carlo techniques have been used to assess spectral interferences within this timeframe. It is demonstrated that during this period they do not interfere with the measurement of the existing radionuclide observables. Additionally, 24Na has been identified as useful for inspection purposes.

Risk Assessment Method and Protection Goals of High Concrete Gravity Dam Subjected to Far-Field Underwater Nuclear Explosion

The nucleus threat and hydraulic engineering's security problem are two focal point problems. At present, a new problem associated with the two problems has not systematically investigated and full understanding. This paper propose that the damage spectrum is used to predict the damage state of the concrete dam subject to far-field underwater nuclear explosion, and the environmental pollution factor is added in the risk assessment model. Finally, the protection design targets is mathematical described.

T-phase Perception: The August 2003, Mw 7.1, New Zealand Earthquake Felt in Sydney 1,800 km Away

The Mw 7.1 New Zealand earthquake in August 2003 was the largest earthquake in New Zealand in 60 years and occurred in the sparsely populated Fiordland of the South Island. The earthquake caused no deaths and only minor damage in the town of Te Anau, although it was felt throughout most of the South Island of New Zealand. Surprisingly, it was felt in Sydney, 1,800 km away, with some people evacuating buildings. Based on the timing of felt reports, I conclude that people in Sydney did not feel body or surface waves but felt the T phase from the event. Human perception of a T phase is rare; the 1977 Mw 8.1 Tonga event, which was felt in Tahiti 2,600 km away (Talandier and Okal, 1979), is one of the few well documented instances. T phases from the 1958 magnitude 7.7 Alaskan earthquake and the May 1955 Wigwam underwater nuclear explosion are also considered to have been felt in Hawaii (Talandier and Okal, 1979). The Sydney recording of the T phase, while larger than the body waves, would still be considered weak motion and not normally felt. I suggest that for someone to have felt this event required the coincidence of several factors which enhanced the resultant shaking. On 21 August 2003 at 12:12:50 UTC a large earthquake occurred off Fiordland near the southwest corner of New Zealand (-45.19 166.83 24 km). The earthquake measured ML 7.0 (GNS), Mw 7.1 (USGS), and Ms 7.4 (USGS). The USGS best double-couple solution is NP1: Strike 8° Dip 27° Slip 59; NP2: Strike 222° Dip 67° Slip 105. This is an almost pure thrust event with the strike of the nodal planes being parallel to the coast (Figure 1). New Zealand straddles the tectonic boundary between the …

Numerical Modeling of Marine Target Impacts

The principles of the numerical modeling of marine impacts of large cosmic bodies are described. Three underwater impact structures, MjOlnir, Lockne, and Eltanin, are considered with the aim of studying the characteristics of the crater formation at varying sea depths; the distinctions between the underwater and continental craters are discussed. The mechanisms for tsunami-wave generation are studied at different ratios of sea depth to impactor size. The calculation results are compared to the experimental data obtained during underwater nuclear explosions.

Identification of presumed shallow underwater chemical explosions using land-based regional arrays

Abstract Seismic events located in the Gulf of Bothnia, the Baltic Sea, and the North Sea, recorded at the regional seismic arrays NORESS and FINESA, have characteristics of underwater blasts observed hydroacoustically. Spectral analysis of regional phases associated with the events reveals strong time-independent spectral scalloping indicating that the waveforms are made up of correlated “pulse-echo” type signals. Cepstral analysis gives consistent delay times between the pulse-echo pairs with the most common delays between 400 and 600 msec. Some cepstra also have negative peaks at quefrencies between 150 and 350 msec. The cepstral peaks are observed in all phases associated with the event, and events recorded at both arrays have the same delay times. The higher time delays are consistent with bubble-pulse delays commonly observed in underwater blasts recorded hydroacoustically. The lower-quefrency negative peaks are caused by echoes with reversed polarities relative to the primary pulse and are consistent with reflections from the top of the water column. Generally, these events have large Pn/Lg amplitude ratios similar to those observed from quarry blasts. Somewhat smaller high-frequency Pn/Lg ratios are observed for Baltic Sea events compared with the North Sea events, which may be due to differences in the water-bottom geologies of the two regions. Simple source models of underwater blasts explain many of the features of the observed cepstra and indicate that the shot depths had to be shallow (around 40 to 80 m) for shot sizes between 75 and 150 kg. This study shows that the seismic sensor network, called for by the Comprehensive Test Ban Treaty (CTBT), can augment the smaller network of hydroacoustic stations for the detection and identification of clandestine under-water nuclear-explosion tests in the near offshore environment.

Arsenic, trace metals, and organic micro contaminants in sediments from the Pechora Sea, Russia

Grain size material < 63 μm, TOC, TN, PAHs and organochlorines, and the major (Al and Fe) and trace (As, Cd, Cr, Cu, Hg, Li, Mn, Ni, Pb, V and Zn) elements have been determined for grab and core samples from the southeast part of the Barents Sea known as the Pechora Sea, Russia. Most of the organic matter appears to be of marine origin, but a terrestrial origin for OM is indicated for the coastal areas in the vicinity of the Pechora estuary. All organic micro contaminant concentrations, except lindane, were low. Lithium normalization of Cd, Cr, Cu, Hg, Ni, Pb, V, and Zn concentrations indicates that they are at or near natural levels as a result of natural granular and mineralogical variability in the sediments. High levels of arsenic, however, occur in fine grained surface and subsurface sediments. The As enrichment is most likely due to the deposition and post-depositional modification of As-rich radioactive particulate material dispersed into the Pechora Sea by underwater nuclear explosions in Guba Chernaya on the southwest coast of Novaya Zemlya during the 1950s and 1960s.

MODEL STUDIES OF IMPULSIVELY-GENERATED WATER WAVES

The wave action due to a sudden impulse in a body of water was studied in a wave basin with beach in the laboratory. Waves were impulsively generated in the 90 ft. tank of water, 3 ft. deep, by the impact or sudden withdrawal of a paraboloidal plunger 14 ft. in diameter. The waves had a dominant height of 2 inches and period of 3 seconds, respectively, at a distance of 50 ft. from the plunger. Such waves are scale representations of those generated by sudden impulses in the ocean, such as an underwater nuclear explosion, a sudden change in the ocean bed due to earthquakes, or the impact of a land slide. The waves produced by a downward impulse, or by an underwater explosion, form a dispersive system: whose properties are not constant as in a uniform progressive wave train. Wave periodicities, celerities and wave lengths increase with time of travel and wave heights decrease with travel distance. Theory has already been developed to predict the wave properties at a given travel time and distance for given source energy, displacement and travel path depth profile (Jordaan 1965). Measurements agree fairly well with predictions.

Rectification of Oblique Photographs to Obtain Base-Surge Contours

Rectification of oblique aerial photographs is one means used to obtain contours of the base surge formed by an underwater nuclear explosion. An analytic photogrammetric method of rectification, based on the visible horizon and altitude of the photo aircraft, is described. This method gives the position of any point on the photograph in terms of its coordinates in a rectangular grid system on the water surface. The supplemental information needed to rectify an oblique photograph also is discussed.