Project Rio Blanco was an underground nuclear test that took place on May 17, 1973 in Rio Blanco County, Colorado, approximately 36 miles (58 km) northwest of Rifle.[2]
Three 33-kiloton nuclear devices were detonated nearly simultaneously in a single emplacement well at depths of 5,838, 6,230, and 6,689 feet (1,779, 1,899, and 2,039 m) below ground level. The tests were conducted in fine-grain, low-permeability sandstone lenses at the base of the Fort Union Formation and the upper portion of the Mesaverde Formation.
This was the third and final natural-gas-reservoir stimulation test in the Plowshare program, which was designed to develop peaceful uses for nuclear explosives. The two previous tests were Project Gasbuggy in New Mexico and Project Rulison in Colorado.
A placard, erected in 1976, now marks the site where the test was conducted. The site is accessible via a dirt road, Rio Blanco County Route 29.
Devices
As the creation of tritium was of greatest concern, the three devices used were specially designed to reduce tritium production, creating less than 0.2 grams (0.0071 oz) tritium each, primarily from the medium surrounding the devices. To reduce emplacement costs, the devices were very narrow in diameter, less than 200 millimetres (7.9 in) wide.[3]
^M. D. Nordyke (July 26, 2000). The Soviet Program for Peaceful Uses of Nuclear Explosions (Report). Lawrence Livermore National Lab. p. 8. OSTI793554. UCRL-ID-124410-Rev-2. The most significant radiological concern was the incorporation of tritium produced by the nuclear explosive into the gas produced from the stimulated region. To reduce emplacement costs and tritium levels to the lowest possible levels, the Plowshare Program developed a special nuclear explosive less than 200 mm (7.8 in.) in diameter that produced an extremely small amount of tritium (<0.2 g), primarily from the medium surrounding the explosive. Three of these special explosives were used in the same hole for the Rio Blanco event, one above the other spaced about 130 m apart.
