|Fig. 1: A sculpture at the United Nations Headquarters in New York City (Source: Wikimedia Commons)|
In the latter half of the 20th century, both the US and Soviet Russia explored, through research and many real detonations, using nuclear explosions for non-military purposes. The U.S. executed these experiments through Operation Plowshare while the Soviet Union formed Program No. 7.
Operation Plowshare, established in summer of 1957 by the AEC, was a U.S. program organized to explore and implement civil uses of nuclear weapons.  The overarching history of the program has been covered by Powell.  The name is intended to evoke the following sentiment:
"And he shall judge among the nations, and shall rebuke many people: and they shall beat their swords into plowshares, and their spears into pruning hooks: nation shall not lift up sword against nation, neither shall they learn war any more." - Isaiah 2:3-5
The sculpture in the image at right represents this idea. The following paragraph summarizes the experiments conducted under plowshare:
The AEC conducted an initial underground nuclear explosion, Rainier, in 1957, which was followed by the establishment of the Plowshare program. Plowshare proceeded to sponsor 6 contained explosions underground and 6 cratering or nuclear excavation experiments. Of the 6 contained experiments, 3, namely Gnome in 1961, Handcar in 1964 and Marvel in 1967, were for scientific purposes. Among the purposes of these scientific experiments was to study the effects of nuclear explosions in different mediums, produce heavy elements, conduct experiments using the explosion's neutron flux, and study the flow of energy down a long cylindrical container. Considered industrial applications of contained underground explosions were rupturing of oil containing shale formations in Colorado, breaking copper ore, and making caverns in which to store oil and natural gas. However, only shale oil rupturing was actually tested with explosions - three tests were conducted between 1967 and 1973, namely Gasbuggy in 1967, Rullison in 1969, and Rio Blanco in 1973. Of the 6 nuclear excavation experiments, all were essentially to study cratering in different mediums with explosions from different depths. 
The Soviet Program No. 7 - Nuclear Explosions for the National Economy" was significantly larger than that of the US and involved 122 detonations to study 13 different possible applications.  These included "closure of runaway gas wells, disposal of toxic chemical wastes, block cave mining of under- ground minerals, productionof transplutonic elements,and the excavation of water reservoirs and canals."  Nearly all the nuclear explosions were between 2 and 20kt, though there are a few significant outliers. In 1966 and 1967 the Soviet program used nuclear detonations to close down two gas well fires, which spurred the young program onward.  While relevant to the initial development of the program, the closure of runaway gas wells did not become a significant use PNE because the Soviet capacity to close them through more conventional methods improved and rendered the PNE unnecessary.  Soviet Russia and the US held four discussions of peaceful nuclear explosions in the years 1969, 1970, 1971, and 1975. Minimal information about the program was then exposed from 1975 until the opening of the Soviet press starting in 1980. The program concluded definitively with the US-Soviet nuclear testing moratorium in 1989.The program ran from 1965 to 1989, thereby both beginning and ending several years later than the equivalent U.S. Plowshare program. 
The Soviet Program conducted a total of 10 cratering or nuclear excavation explosions in the pursuit of creating either a reservoir, canal and dam. Meanwhile it executed 112 contained explosions underground, primarily in the pursuit of creation of cavities for underground storage, seismic sounding of the earths crust and mantle, oil or gas stimulation, and heavy element production. Over half of all the contained detonations were for creating underground cavity or conducting seismic sounding. 17% of the detonations were for oil and gas stimulation. These numbers illustrate two significant differences between the Soviet and U.S. programs. Firstly, the Soviet program was conducted many more detonations overall. Secondly, the Soviet program placed a significantly greater emphasis on studying industrial applications, which yielded the 112 contained explosions. 
The first experiment was called Chagan and took place in 1965. The explosion was conducted in the center of a dry river bed during the winter in January. This way, the crater lip created a dam up river while the crater itself served as a reservoir. When snows melted in the springtime, the dam caused the formation of a reservoir up river of it, as well as down river in the crater. The experiment was thereby successful and the dam and reservoir remain in use today. In the same year the Soviets conducted a second cratering experiment dubbed Sary-Uzen with moderate success. A total of 5 detonations were carried out to study or implement reservoir construction. 3 explosions were executed in preparation for the nuclear excavation of a Kama-Pechora Canal - a project initiated in order to solve water shortages in the European USSR. [1,3] The program conducted two explosions in 1974, namely Crystal and Lazurite in order to create dams. The method for Crystal was to place the nuclear device at a depth roughly twice that of the Chagan experiment. The explosion then created a "dome-shaped mound"  with a peak height of 60 m in the center of the river. The Lazurite experiment employed a similar strategy, however, the device was placed into a 20 degree slope, such that the resulting mound of rock would slide down to fill the river bed below. The future use of these constructions is not well documented. Notably, the Lazurite experiment was the Soviets last attempt at nuclear excavation, though construction of the Kama-Pechora Canal, while never implemented, continued as a significant topic of interest for some time. 
The three most frequent applications of contained nuclear explosions were oil and gas stimulation, storage creation, and seismic sounding. A total of 7 projects were undertaken under Program No. 7 for oil and gas stimulation. 5 pursued oil stimulation while 2 pursued natural gas stimulation, but only the results of one natural gas stimulation experiment were published. The creation of underground cavities was also fairly successful.  Nuclear explosions in a salt medium form a standing dome instead of filling with rubble as in other mediums.  Three large scale implementations were able to successfully store liquid hydrocarbons at 140atm. There were, on the other hand, issues with many of the other cavity experiments. In particular roughly a quarter contained water leaks that allowed water to seep in, dissolve salt in the cavity walls and become radioactive, thereby potentially contaminating any stored substances. Deep seismic sounding (DSS) was probably the most ambitious and successful application of peaceful nuclear explosions.  The Soviets had a great deal of experience conducting seismic sounding using conventional explosives. However, the inhospitable environments within the Soviet Union made the mapping of many areas difficult due to inability to place necessary equipment. Therefore, the greater strength of a nuclear detonation underground and the correspondingly greater signal were hugely helpful to the Soviets. The stronger signal also yielded increased detail.  The Soviet Ministry of Geology used nuclear detonations to profile 200 km below the surface along immense DSS lines, which spanned thousands of kilometers. Nuclear devices were buried at 500-1000 m and set along DSS lines of 1,500- 4000 km. Each device was separated from the next by 500-900k. Also along these lines were seismometers to detect the results. A total of 15 DSS lines were explored. 
© Brad Hakes. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 M. D. Nordyke, "The Soviet Program for Peaceful Uses of Nuclear Explosions," Science and Global Security 7, 1 (1998).
 D Powell, "Operation Plowshare," Physics 241, Stanford University, Winter 2014.
 "The Soviet Program for Peaceful Uses of Nuclear Explosions" [Sanitized Version], U.S. Central Intelligence Agency, October 1981.
 J. F. Scheimer and I. Y. Borg, "Deep Seismic Sounding with Nuclear Explosives in the Soviet Union," Science 226, 787 (1984).