Nevada National Security Site (NNSS)

The Nevada National Security Site is an expanse of federally controlled land and facilities in a remote region of southern Nevada. The approximate 1,375 square miles that make up the NNSS are surrounded by the Nellis Air Force Range and unpopulated land controlled by the U.S. Bureau of Land Management. Located 65 miles northwest of Las Vegas, the NNSS is one of the largest secure areas in the United States, due to buffer zones to the west, north, and east. More than 1,000 support buildings and other facilities are spread across the site.

History of the NNSS

In the Beginning: After the first nuclear test at the Trinity Site in New Mexico, the United States moved its nuclear weapons experimentation program to the Pacific. Security and logistical issues quickly illustrated the need for a continental test site. After consideration of many possible sites, an Atomic Energy Commission meeting on December 12, 1950, concluded that the Las Vegas Bombing and Gunnery Range in Nevada satisfied nearly all of the established criteria for a continental proving ground. As a result, President Harry Truman authorized a 680-square mile section of the Nellis Air Force Gunnery and Bombing Range in Southern Nevada as the Nevada Proving Grounds on December 18, 1950. In 1955, the name was changed to the Nevada Test Site (NTS).

One of 100 atmospheric tests conducted at the NNSS Atmospheric and Underground Testing: On January 27, 1951, the first atmospheric nuclear test was detonated at the NTS, code-named “Able.” A total of 100 atmospheric tests were conducted at the NTS until July 1962. All atmospheric testing was banned on August 5, 1963, when the Limited Test Ban Treaty was signed in Moscow, giving birth to the age of underground testing. The United States conducted 828 underground tests at the NTS. The last underground test, “Divider,” was conducted on September 23, 1992.

The End of Nuclear Testing and the Start of Subcritical Experiments: After conducting 928 nuclear tests, full-scale nuclear testing came to an end in 1992 when the United States entered into the Comprehensive Nuclear Test Ban with Russia and France. In order for the United States to maintain the safety and reliability of its nuclear stockpile without conducting full-scale tests, subcritical experiments were initiated at the NTS. An experiment is considered subcritical if no critical mass is formed and no self-sustaining nuclear reaction occurs. Subcritical experiments occur more than 900 feet below ground at the U1a tunnel complex.

From NTS to NNSS: In 2010, the name was changed to the NNSS to more accurately reflect the evolving mission of the site. Although the storied Nevada Test Site had a long history of supporting national security through full-scale atmospheric and underground nuclear testing, the last test occurred in 1992 following the signing of a nuclear weapons test ban treaty. Since that time, the nuclear weapons mission at the site has evolved to include subcritical experiments and other Stockpile Stewardship Programs designed to ensure the Nation’s remaining nuclear weapons remains safe, secure, and effective without full-scale nuclear testing. In addition, the emergence of global and homeland security threats has resulted in a further shift in the Site’s mission toward planning, experimentation and training to prevent and counter global and homeland security threats. Today, those activities comprise more than 50 percent of the site’s mission, providing ample justification for the name change.

Nuclear Testing Archive

DOE/NNSA Planning and Budget Information

• Nevada National Security Site FY2019 Congressional Budget Request Lab Table