In the post-World War II years, nuclear weapons, which had first been used in anger to bring the conflict to a final conclusion, proliferated as the two superpowers, the United States and the Soviet Union, vied with one another for technological supremacy. With the bomb came the awful prospect of outright nuclear warfare.
It was, however, recognised that the devastating power released by a nuclear explosion did not always have to be used for destructive purposes. On 8 December, 1953, American President Dwight D Eisenhower, partly in an effort to allay fears of nuclear devastation, delivered a speech to the United Nations General Assembly entitled 'Atoms for Peace'. In this speech, he outlined proposals for a collaborative effort between nations to promote the use of atomic weapons for peaceful purposes. On the American side, a series of experiments named Project Plowshare proposed the use of nuclear explosions to create new canals and harbours, release natural gas from underground reservoirs, create underground aquifers and even widen the Panama Canal.
Project Gnome was the first of Operation Plowshare's experiments. Its primary purpose was to harness the heat of a nuclear explosion to produce steam that could be used to drive a generator and thereby generate electricity. Measurements of previous underground explosions indicated that temperatures of 1,100°C (2,000°F) would be produced — if the heat could be encapsulated underground long enough to be tapped off and used to power a turbine connected to a generator, a significant amount of electricity could be usefully created and diverted to the national supply. Further benefits thought to be possible from this experiment were the relatively easy recovery of radioisotopes for industrial and medical applications, and to carry out a number of experiments to further scientific knowledge useful in the development of nuclear reactors for the production of electricity. It was also envisaged that the shock wave produced by the explosion could be used for seismic experiments.
The test was designed by the Lawrence Radiation Laboratory, later to become the Lawrence Livermore National Laboratory, and carried out under the auspices of the United States Atomic Energy Commission. The most suitable medium for this purpose was thought to be a bed of rock salt laid down some 225 million years ago and subsequently covered by layers of clay and sandstone to a depth of over a thousand feet in the New Mexico desert, near the town of Carlsbad.
A shaft 370m (1,216ft) deep was drilled down to the salt layer and a 340m-long tunnel was taken off at that level to the southwest, at the end of which a chamber for the nuclear device was constructed. A U-shaped bend in the tunnel was provided to form a seal when the nuclear device was detonated. Ventilation shafts drilled vertically down into the chamber were to be used to introduce water and recover the superheated steam produced by the high internal temperatures.
At noon on 10 December, 1961, the device was detonated and yielded a 3.1 kiloton explosion, creating a chamber 52m (170ft) in diameter and 24m (80ft) high. Although the access tunnel had been plugged prior to the explosion, it had not fully sealed and within three minutes venting of radioactive smoke and steam began to issue from the shaft, from cracks in the surface layers and from the ventilation drillings above the chamber that should have been used to tap off the steam.
The flow rate continued to increase and for the next 40 minutes large quantities of steam continued to flow, creating a cloud which drifted northwest from the site. An hour after the detonation, high radiation levels were registered along Highway 128, five miles away, and contamination was recorded as far afield as Kansas some days later. The efflux of gas began to abate after 40 minutes but continued into the following day until depleted.
The surface radioactivity decayed rapidly, but high levels in the shaft opening delayed recovery operations for six days. The cavity was eventually entered on 17 May, 1962, to find residual temperatures of around 60°C (140°F) and the inner walls discoloured to hues of green and blue. However, the radioactivity had decayed to relatively safe levels.
Due to the loss of the initial product of the explosion, the experiment was not considered to have been successful. Only the seismic experiment had produced the desired results. Consequently, a second detonation at the same site was cancelled. Today, cattle graze around the surface area and a small plinth with a plaque marks the spot over the chamber denoting the position of the experiment. A second, smaller plaque forbids any drilling in the area. Eight miles away, the salt bed is currently used by the Waste Isolation Pilot Plant facility as an experimental long-term repository for low grade nuclear waste.