Effects of the underground nuclear explosions on the environment

When a camouflet explosion occurs under high temperature (over a million degrees Kelvin) and high pressure (order of several million atmospheres), evaporation and melting of rock occurs in the region where the charge was laid, resulting in a boiler chamber having a shape similar to a three­dimensional ellipsoid. The effective radius of this cavity is 10-40 m. The cavity wall thickness is several tens of centimeters, composed of sintered layers of rock. The mass of the melt reaches 400 m at 1 kiloton of explosive power. Behind the wall cavity, as a result of the shock wave, is crushed rock. At large distances behind the wall cavity, is a region of increased fracturing. A truncated cylinder shape is formed with the upper limit in the cleavage zone impacting the surface of the Earth above the boiler cavity zone where increased fracturing occurs (Israel, 1974).

Over time, gravity causes the melt to flow down from the top and side walls of the cavity to its lower part, forming a lens of melt. After a further decrease in temperature, the melt passes into a solid phase and is partially or completely embedded with fragments of rock up to a height of a few meters from the bottom of the cavity. In this case, the bottom layer of the fractured rock pile covers the lens of melt. The array of the rock above the boiler cavity has been destroyed and eventually starts to sink down to form a pillar collapse. This process partially reverses the expansion of soil and rock mechanical faults caused by the shock wave, but also lowers the gas pressure in the cavity that was formed. Since the diameter of the column collapses the diameter of the boiler cavity, the cave only partially fills the cavity, forming one or more hollow zones located closer to the surface. The pillar collapse has very high moisture and gas permeability. The associated, filtration coefficient is hundreds of meters per day, and the coefficient of loosening of pillar collapses, defined by the ratio of porosity before and after the explosion, reaches 0.73-0.85. At the same time, the lateral border pillar collapses and is clearly separated from the solid undisturbed rock. At the point of contact, the lateral border pillar collapses along with the adja­cent undisturbed rock to form a peeled zone with permeability greater than the permeability of the collapsed column. At the ground surface above the explosion zone epicenter cleavage phenomena were observed. These took the form of swelling or rock subsidence depending on the exact nature of the explosion. Often crushed rocks are observed on the rock — similar arrays in the cleavage zone.

Because of the complexity of nuclear processes, a range of radionuclides are released in the explosion, which are deposited mainly in the cavity of the explosion. High-melting products are concentrated mainly in the lens of the melt and are mostly fissile nuclides of uranium and plutonium, fission fragments and neutron-activated elements of the charger and breeder. In the column collapse and fracture zone, volatile compounds such as pluto­nium and polonium are concentrated, as well as the radionuclides stron­tium, cesium, lanthanum, etc. (Israel, 1974).

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