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Investigations of the parameters of the seismic waves in the closest (up to 2.3 km), medium (7.5 to 45 km) and far out (up to 270 km) zones and the computations made lead to the conclusion that the seismic effect upon structures in the closest zone was equal to the destruction force of a 6-7 point earthquake.

No ejection of radioactive products into the atmosphere was observed during the explosion.

After the explosion, at H-hour plus 12 min, H-hour plus 24 hours and H-hour plus 35 hours, a yield of noble radioactive gases through the investigation wells was observed. The amount did not exceed 1 percent of the total formed during the explosion.

Radioactive products penetrated along the fissures into the depth of the salt-bearing mass. Strontium-89 and cesium-137 spread the farthest away from the cavity; closer to the cavity were strontium-90, yttrium-91, and antimony. In the zone bordering the cavity, a concentration of zirconium-95, cerium-144, and ruthenium-106 isotopes was found.

Investigations confirmed the expediency of using nuclear explosions for the building of underground storage areas in salt rock masses and complemented to a considerable extent the information on the effects of explosions in this medium.

Chapter VI

BUILDING OF UNDERGROUND STORAGE FOR NATURAL
GAS, GAS CONDENSATE AND PETROLEUM PRODUCTS

The rate of development of petroleum recovery and gas industries is closely connected with the building of storage space.

Conventional methods of building underground storage space are either labor-consuming-as the mining method or not sufficiently universal--such as the method of washing of rock salt. The latter requires large salt deposits, an enormous supply of fresh water, and natural cavities for the storing of brine.

This situation stipulated the necessity of finding new improved methods of building underground storage space. Theoretical investigations, results of model-testing and an analysis of the mechanical effect of underground nuclear explosions conducted in various mining-geological areas showed that they may be used for the building of underground storage areas.

Preliminary technical-economic computations show that the cost of gas storage will be 6 times less if the gas is stored in reservoirs built by means of nuclear explosions than when it is stored in surface reservoirs with preliminary liquefaction, and 3 times less when compared to storage in chambers built by washouts, and the same under certain conditions such as the cost of storing in flooded natural collectors.

Three areas for the application of nuclear explosions in building of underground storage spaces were established as a result of the investigations: The creation of cavities in rock salt deposits and in dry clay; the creation of storage capacity in broken rock from the void space in the collapsed cavity and in crushed or fractured zones; and improving the filtering properties in natural collectors.

Two examples are presented below which characterize the technology of the building of underground storage areas as worked out for a scientific and technical report.

A storage space must be built for gas-condensate with a volume of 300,000 m3 at a site where the geological cross-section is represented by a thick layer of rock salt (Fig. 11) stratified under sandstone.

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(Ed. Note: The text and the symbols in this figure both indicate that the medium is actually salt rather than tuff.)

Keeping in mind the requirements of seismic safety for surface buildings and structures, the maximum explosion capacity has been established at 35 kilotons. The volume of the cavity obtained as a result of an explosion of the given capacity will attain 152,000 m3.

Two successive explosions must be made in order to achieve a storage space of the required volume. The depth of the charge is 810 m. The minimum distance between the charges (which guarantees the protection of the cavity against the effect of the compression wave) is 528 m. The cavities will be opened by means of drilled exploitation wells one month after the explosion.

At the second site, with a geological cross-section represented by tufflava rock of the Permian-Triassic eras, under a layer of permafrost 190 m thick, a cavity for the storage of 70 million m3 of natural gas is required (Fig. 12). The maximum allowable explosion force in the given area is 40 kilotons. The depth of the charge with such a capacity is 710 m. The volume of the cavities created by the explosion will attain 360,000 m3. The pressure, at which the gas storage may be achieved is 70 atm (7 × 106 neutrons/m2). The necessary total volume of the storage space guaranteeing the storing of 70 million m3 of gas equals 1 million m3.

In order to build a storage space with the required volume it is necessary to explode three charges of 40 kilotons each. The distance between the charges is 200 m.

As of today we still ignore the optimal operational conditions of such storage spaces, built by means of nuclear explosions, which provide a minimum pollution of the stored substance by radioactive products. Experimental studies indicated that gas, located since the moment of explosion in the cavity, when tapped 120 days after the explosion, had no traces of radioactivity. The length of this waiting period may be substantially reduced. This problem will be thoroughly studied after the next experimental-industrial explosion.

The opening of the explosion cavities is achieved, as a rule, by drilling additional wells. At present, measures are being worked out to use wells drilled for the lowering of the charges for the opening of cavities.

Chapter VII

UNDERGROUND MINING OF ORE DEPOSITS

As a result of experimental underground explosions in granite rock the following has been established: (1) The quantity of the granite rock broken by the explosion of a 1 kiloton charge, totally underground, is estimated to be 400,000 tons. (2) Under the effect of the seismic waves of an explosion, underground mine workings (depending upon the properties of the rock) completely collapse at a distance of 30 to 80 m, while falling rock is observed at distances of 60 to 150 m. (3) Dimensions of the zones of fractured rock: (a) primary cavity R。 = (10-15) Q, m; (b) zone of crushing Rer = (20-35) Q, m; and (c) zone of fracturing Rf = (50-70) Q, m; where Q is the charge capacity in a TNT equivalent, kilotons.

The results obtained lead us to the conclusion that an efficient use of underground nuclear explosions for the purpose of crushing ore in mine systems with massive caving is quite possible.

Nuclear charges permit crushing large ore deposits even at considerable distances between the charges. The use of this property will permit us to change in a fundamental manner the technology of underground mining of ore deposits: To reduce, many times, the volume of shaft building and drilling work; to concentrate the front of mine work at the expense of simultaneous crushing and caving of large supply of ores; to substantially simplify the design of the

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Fig. 12 BUILDING GAS STORAGE SPACES IN TUFFACEOUS ROCK

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