NEVADA TEST SITE

Nuclear Weapons Testing

From the end of World War II until 1951, five US nuclear weapons tests were conducted at distant islands in the Pacific Ocean. When the decision to accelerate the development of nuclear weapons was made in the late 1940s, it became apparent that weapons development lead times would be reduced and considerably less expense incurred if nuclear weapons, especially the lower yield weapons, could be tested within the continental boundaries. An area within what is now the Nellis Air Force Range was selected to meet criteria for atmospheric tests. The Southern Nevada site was selected from a list of five possibilities which included Alamogordo/White Sands, New Mexico; Dugway Proving Ground, Utah; Pamilco Sound/Camp Lejuene, North Carolina; and a 50-mile-wide strip between Fallon and Eureka, Nevada. Public Land Order 805 dated 19 February 1952, identified 680 square miles (1,800 square kilometers) for nuclear testing purposes from an area used by the Air Force as a bombing and gunnery range; this area now comprises approximately the eastern half of the present Nevada Test Site.

When the Ranger Series ended in 1951, AEC initiated plans to expand the Test Site facilities. Construction began on utility and operational structures, including communications, a control point, and additional accommodations. As a safety measure, AEC decided to move the testing area from Frenchman Flat to Yucca Flat, where 12 areas were developed for air drops, tower, surface, tunnel and balloon tests. Additional land was added to the site in 1958, 1961, 1964, and 1967, thereby enlarging the site to its present size of about 1,350 square miles (3,500 square kilometers).

Nuclear testing at the NTS was conducted in two distinct eras: the atmospheric testing era (January 1951 through October 1958) and the underground testing era (1961 to 1992). On 31 October 1958, the United States and the Soviet Union entered into voluntary test moratoria which lasted until the USSR. resumed testing on 01 September 1961. The United States responded with renewed testing on 15 September 1961. A few surface, near surface, and cratering tests were conducted from 1961 to 1968, but all other nuclear weapons tests have been carried out underground since 1961. The United States and the Soviet Union signed the Limited Test Ban Treaty on 05 August 1963, which banned testing nuclear weapons in the atmosphere, in outer space and underwater. Six of the eight cratering tests conducted between 1962 and 1968 were part of a peaceful applications program.

The United States conducted 119 nuclear tests at the NTS from the start of testing in January 1951 through October 1958. Most of those nuclear tests were carried out in the atmosphere. Some tests were positioned for firing by airdrop, but metal towers were used for many Nevada tests at heights ranging from 100 to 700 feet (30-200 meters) above the ground surface. In 1957 and 1958, helium-filled balloons, tethered to precise heights and locations 340 to 1,500 feet (105 to 500 meters) above ground, provided a simpler, quicker, and less expensive method for the testing of many experimental devices. The tests of the atmospheric era took place in Yucca and Frenchman Flats. The 119 nuclear tests that were conducted at the NTS during the atmospheric testing era (1951-1958) consist of 97 nuclear tests conducted in the atmosphere, of two cratering tests, detonated at depths less than 100 feet (30 meters), and of 20 underground tests.

In 1962, before the onset of the Limited Test Ban Treaty, the United States conducted, in addition to its underground tests, two small surface tests, one tower test and two cratering tests as part of the nuclear weapons testing program. Six nuclear cratering tests were conducted from 1962 through 1968 as part of the peaceful applications (Plowshare) program. The overwhelming majority of the 809 tests that took place at the NTS from 1961 through September 1992 were conducted underground either in shafts or in tunnels that were designed for containment of the radioactive debris. Most underground tests were conducted under Yucca Flat but a few underg round and cratering tests took place under Buckboard, Pahute, and Rainier Mesas in the northern part of the Nevada Test Site.

When drilling of vertical shafts for underground tests at the NTS began in 1959, the biggest problem was the time it took to drill into the desert floor. A 36-inch diameter hole, 1,000 feet deep, could take up to 60 days. The initial method was to drill in three successive passes, each one larger. Eventually the tri-stage gave way to the flat bottom bit, with 12 to 24 cutters chewing up the rock as the entire unit rotated -- a process that could drill a 1,000-foot hole in 20 days. A normal hole is from 1 to 3 meters (m) (48 to 120 inches [in.]) diameter and from 213 to 762 meters (m) (600 to 2,500 feet [ft]) deep.

Tests in vertical drill holes are of two types: smaller-yield devices in relatively shallow holes in the Yucca Flat area (Areas 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10) and higher-yield devices in deeper holes on Pahute Mesa (Areas 18, 19, and 20). Tests at the Yucca Flat and Pahute Mesa event sites have the same general requirements, but differ in the magnitude of the operations. Deeper-hole operations disturb a larger area, require more on-site equipment, and have a higher requirement for electrical power and utilities. The distance from the core of the infrastructure is also a factor; Pahute Mesa operations are 48 to 81 kilometers (km) (30 to 50 miles [mi]) farther away than Yucca Flat.

Tests have been conducted in 16 different tunnels in Rainier Mesa on the Nevada Test Site. The first test was conducted on 10 August 1957, when a zero-yield safety experiment named "Saturn" was detonated in C-Tunnel. By the early 1990s there was only one active tunnel in use by the Defense Nuclear Agency (DNA). The DNA evaluated the effects of nuclear weapons explosions, thermal radiation, blast, shock, x-rays and gamma rays, on military hardware, such as communication equipment, rocket nosecones, and satellites. The typical Horizontal Line of Site (HLOS) test was primarily for radiation effects research. Researchers attempted to minimize blast and shock effects from the experiments. A large tunnel complex mined under the mesa contained the HLOS pipe. The HLOS pipe is 1,500 to 1,800 feet long and tapers from up to 30 feet in diameter at the test chamber to several inches at the working point. Experiments were placed in the HLOS pipe test chambers. At zero time the nuclear device is fired, and radiation instantaneously flows down the pipe, creating the necessary radiation environment. To prevent bomb debris and blast from reaching and damaging the experiments, three mechanisms were used to close the pipe. The first is the Fast Acting Closure which is slammed shut by high explosives in about one millisecond; the other two closures follow within 30 and 300 milliseconds.

As many as 38 underground events detonated through September 1992 released volatile radioactive materials (particulate or gaseous), which resulted in detection off-site. The remainder of the 809 tests that took place at the NTS between 1961 and 1992 were either completely contained underground or resulted in releases of radioactive materials that were only detected onsite. A total of 299 events resulted in releases of radioactive materials that were detected onsite only.

The total number of nuclear weapons tests that were conducted at the Nevada Test Site up to September 1992 is 928 --- 100 which were atmospheric, and the other 828 underground. On 02 October 1992, the United States entered into another unilateral moratorium on nuclear weapons testing announced by President Bush. President Clinton extended this moratorium in July 1993, and again in March 1994.

President Clinton directed the Department to maintain a basic capability to resume nuclear testing activities at the NTS should the United States deem it necessary. One way DOE proposes to retain this capability is to conduct a series of subcritical experiments with nuclear materials at the NTS. Subcritical experiments use high explosives to create some of the physical conditions, such as pressure and temperature, that nuclear materials undergo in a nuclear weapon before reaching the critical stage. A final decision on these tests will be made following completion of the NTS environmental impact statement.

The nuclear safety program involves special nuclear material (SNM) in test device assembly. Due to the moratorium, no specific tests requiring device assembly are scheduled, and there is no SNM on site at this time. Also, NV is the lead DOE site for nuclear explosive safety and is developing a study guide for this functional area.

As a result of changing mission priorities, DOE has a need to focus on new national security, energy, and environmental issues and to redefine the role of the NTS within the DOE complex. NV went through one of the most dramatic and far-reaching changes in its history when BN took over as the performance-based contractor for the NTS. The switch to BN began October 26, 1995, when DOE announced its selection of the company to assume a five-year, $1.5 billion contract encompassing the work previously done by Reynolds Electric and Engineering Company, Inc.; Raytheon Services Nevada; and EG&G Energy Measurements, Inc.

NV distributed the final environmental impact statement (EIS) for NTS and offsite locations in the State of Nevada, DOE/EIS-0243, dated August 1996, in October 1996. The record of decision on this EIS was issued on 09 December 1996. The DOE preferred alternative published in the final EIS represents a continuation of the multi-purpose, mutli-program use of the site to pursue a further diversification of interagency and private industry uses, and to initiate certain public education activities.