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.

A novel method for simulating nuclear explosion with chemical explosion to form an approximate plane wave: Field test and numerical simulation

A nuclear explosion in the rock mass medium can produce strong shock waves,seismic shocks,and other destructive effects,which can cause extreme damage to the underground protection infrastructures.With the increase in nuclear explosion power,underground protection engineering enabled by explosion-proof impact theory and technology ushered in a new challenge.This paper proposes to simulate nuclear explosion tests with on-site chemical explosion tests in the form of multi-hole explosions.First,the mechanism of using multi-hole simultaneous blasting to simulate a nuclear explosion to generate approximate plane waves was analyzed.The plane pressure curve at the vault of the underground protective tunnel under the action of the multi-hole simultaneous blasting was then obtained using the impact test in the rock mass at the site.According to the peak pressure at the vault plane,it was divided into three regions:the stress superposition region,the superposition region after surface reflection,and the approximate plane stress wave zone.A numerical simulation approach was developed using PFC and FLAC to study the peak particle velocity in the surrounding rock of the underground protective cave under the action of multi-hole blasting.The time-history curves of pressure and peak pressure partition obtained by the on-site multi-hole simultaneous blasting test and numerical simulation were compared and analyzed,to verify the correctness and rationality of the formation of an approximate plane wave in the simulated nuclear explosion.This comparison and analysis also provided a theoretical foundation and some research ideas for the ensuing study on the impact of a nuclear explosion.

Effects of nuclear chimney on climate

In this paper, according to the data from several single nuclear explosion experiments of an equivalent to magnitude of million tons, and combined with meteorological data, their effects on the regional climate nave been analysed.

Concept of Application of Nuclear Explosive Devices in a Space-Rocket Complex to Protect the Earth against AsteroidaI-Cometary Danger

Herein an estimation is given to the efficiency of nuclear explosive devices in a space-rocket complex to withdraw Hazardous Space Objects （HS0）-asteroids and cometary nuclei from the trajectories leading to their dangerous entry to the atmosphere and falling to the Earth. A conceptual choice of parameters and schemes of application of nuclear explosive devices in impact modules of space-rocket complexes to ensure asteroidal-cometary safety was made.

Study on Horizontal Relative Diffusion in theTroposphere and Lower Stratosphere

The behaviour of relative diffusion theory and Gifford’s random-force theory for long-range atmospheric diffusion is examined. When a puff scale is smaller than the Lagrangian length scale, √2KTL, an accelerative relative diffusion region exists, i.e., σy∝ t 3/2. While the puff diffusion enters a two-dimensional turbulence region, in which the diffusion scale is larger than 500 km, or time scale is larger than 1 day, divergence and convergence are main cause of horizontal diffusion. Between the two above-mentioned regimes, diffusion deviation is given by σy = √2KT. The large-scale horizontal relative diffusion parameters were obtained by analyzing the data of radioactive cloud width collected in air nuclear tests. Key words Tropospheric and lower stratospheric diffusion - Relative diffusion - Large scale turbulence - Nuclear explosion clouds This work is sponsored by the National Natural Science Foundation of China under Grant No. 49505064.The author would like to thank Prof. Chen Jiayi Department of Geophysics of Peking University and Dr. Cai Xiaoming School of Geography and Environmental Sciences of Birmingham University for their helpful discussions.

My Research Connections with Russian Scientists over the Past Half Century

Over the past half century, I have maintained research connections with Russian scientists during investigations in seismology and mineral physics. These studies have focused on detection and discrimination of underground nuclear explosions and measurements of the physical properties of minerals at high pressures and temperatures. During this period, I have also visited many research laboratories in Russia, including Moscow, Chernogolovka, Novosibirsk and St. Petersburg. The objective of this paper is to relate this history.

Architecture and critical technologies of seismic information system in CTBT verifi-cation

Seismic monitoring is one of the most important approaches for ground-based nuclear explosion monitoring. In order to improve the monitoring capability for low magnitude seismic events, a seismic information system was developed by using the technologies of geographic information system and database. This paper describes the designing and critical technologies of the Seismic Information System in CTBT Verification developed based on ArcGIS and ORACLE platforms. It is a combination of the database storage framework, application programming interface and graphic application software for users to meet their monitoring objectives. Combining the ArcSDE Geodatabase, RDBMS ORACLE and ArcObjects developing technique on COM, not only the multi-sources data has been seamlessly integrated, but also the most functions of ORACLE, for example, consistency, concurrent access, security mechanism, etc, have been reserved. For easy access to the information system we develop two different mechanisms. The first is a menu-driven internal system that is run on NT platforms. The second access mechanism is based on LAN and easily accessible by any web browsers.

Ghana's experience in the establishment of a national data center

The government of Ghana in a bilateral agreement with the Preparatory Commission for the Comprehensive Nuclear Test-Ban Treaty Organization （CTBTO） has established a National Data Center in Ghana with the aim of monitoring the testing of nuclear explosions. Seismic, hydroacoustic, radionuclide and infrasound methods are used for the monitoring. The data center was commissioned on 3 February, 2010 at the Ghana Atomic Energy Commission. At present Ghana does not have any operational, centralised data （seismic, hydroacoustic, radionuclide and infrasound） acquisition system with the capability of accessing data from other international stations. Hence, the need of setting up the National Data Center which would enable us constantly monitor, manage and coordinate both natural and man-made seismic activities in the country and around the globe, upload data to the International Data Center （IDC） as well as receive and use International Monitoring System （IMS） data and IDC products for treaty verification and compliance. Apart from these, the center also accesses and analyzes seismic waveforms relevant to its needs from the International Data Center; makes data available to its stakeholder institutions for earthquake disaster mitigation; reports on all aspects of disasters related to earthquake to the relevant government agencies that deal with disasters; makes recommendations to the government of Ghana on earthquake safety measures; provides information to assist government institutions to develop appropriate land and building policies. The center in collaboration with stakeholder agencies periodically organises public lectures on earthquake disaster risk mitigation.

Nuclear Security Commitments

The Fourth Nuclear Security Summit—to be held in Washington,D.C.from March31 to April 1—will be of particular importance with regards to the Democratic People’s Republic of Korea’s recent announcement that it will conduct a nuclear warhead explosion test and the fifth anniversary of the Fukushima nuclear power plant accident in March.President Xi Jinping will attend the summit and elaborate on the global nuclear security situation and China’s nuclear security concept.