Department of Defense Underground Nuclear Test Program (1962-1992)

Historical Background

Between 1945 and 1992, the United States conducted 1,054 nuclear weapons tests, 839 of them underground. 

The U.S. nuclear testing program moved exclusively underground as a result of the Limited Test Ban Treaty 

(LTBT), which was developed in part to reduce excessive release of nuclear fallout into the planet’s 

atmosphere. The LTBT, signed by President Kennedy on August 5, 1963, prohibited testing nuclear weapons 

in the atmosphere, underwater and in outer space. The nation’s underground nuclear test (UGT) program 

concluded on September 23, 1992. On September 24, 1996, President Clinton signed the Comprehensive 

Nuclear Test Ban Treaty, which prohibits any nuclear weapons test explosion by any State Party.

More than 98% of all U.S. UGTs (828 of 839) were conducted at the Nevada Test Site (NTS), including all but 

one Department of Defense (DOD) sponsored test, which took place in Alaska (“Long Shot”). The DOD

sponsored 58 these UGTs, the first of which was “Hard Hat” on February 15, 1962, at the NTS. The remaining 

UGTs were sponsored by the Atomic Energy Commission (AEC) (now the Department of Energy [DOE]); 

however, some AEC/DOE tests still had significant DOD involvement. In general, the purposes of the UGTs 

are listed as: Joint US-UK, Plowshare, Safety Experiments, Vela Uniform, Weapons Effects, and Weapons 

Related. While most tests were engineered to completely contain the release of radiation from underground,

some releases did occur that resulted in measurable personnel exposure. 

On January 2, 1980, the Director of the Defense Nuclear Agency (now the Defense Threat Reduction Agency 

[DTRA]) expanded the Nuclear Test Personnel Review (NTPR) Program to include the UGT participants. This 

was done in response to the public’s growing concern over the biological effects of personnel exposure to 

radiation during atmospheric nuclear testing. Currently, in support of the NTPR Program, the DOE and DTRA 

maintain a database of personnel exposures from the U.S. nuclear weapons test program.

Radiation Safety Standards

The DOD UGT program, which started more than a decade into the AEC nuclear testing program, had the 

benefit of using the lessons learned and technology advances in radiation safety developed during the AEC’s

program. Comprehensive radiation safety standards were established to limit the exposure of participants to 

the radiological effects of nuclear detonations while, at the same time, allowing them to receive the 

unavoidable small doses of radiation as they performed their missions. 

The maintenance of conservative radiation safety standards was a top priority during UGTs, which included 

stringent engineered, supervisory, and administrative controls. Engineered and supervisory controls included 

details such as: the design and construction of underground containments, placement of radiation monitoring 

devices to track any radioactive releases, and individually assigned oversight responsibilities to maintain 

personnel and equipment accountability and safe operations. Administrative standards included details like:

site-specific test and radiological procedures, area re-entry limits, exclusion areas, and exposure limits. All 
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personnel involved in UGTs were required to wear personal dosimetry, be vigilant while at the test site, report 

anomalies, and maintain exposure as low as reasonably achievable while conducting their official duties.

Radiation Doses from the UGT Program

The UGT program lasted more than 30 years, during which approximately 54,500 DOD-affiliated participants

(military, DOD civilian employees, and DOD contractor personnel) were exposed to ionizing radiation attributed 

to the tests. As technology improved and regulatory requirements evolved, state-of-the-art radiation detection 

devices were adopted to account for exposure to the low radiation levels present in manned areas during and 

after testing. All personnel involved with on-site UGTs were monitored for radiation exposure with personal 

dosimetry devices in addition to the radiation detection devices placed throughout the test site. In general, 

personal exposure was obtained with film badges (1962-1986) and then solid state dosimeters (1987-1992), 

supplemented as necessary by extremity, neutron, beta, and real-time indicating dosimeters.

Radiation doses from the DOD UGT program were closely monitored, assessed, and permanently documented 

for each participant in a comprehensive personnel exposure database. Table 1 gives an overview of the 

simple average annual occupational radiation exposure received by DOD-affiliated personnel, as well as the 

single maximum exposure received by an individual each year. In fact, less than 5 percent of participants 

received measurable radiation exposure. During testing, two personnel exceeded the annual administrative 

dose limit of 5 rem/year, and six personnel exceeded the quarterly administrative dose limit of 3 rem/quarter. 

Additionally, due to the potential release of gaseous and particulate radioactivity from UGTs, internal 

monitoring and bioassay were performed periodically on all personnel with a reasonable potential of ingesting 

radioactive contamination. All internal monitoring and bioassay results from DOD UGTs were within annual 

administrative radionuclide intake limits; only four results were recorded above minimum detectable activity.

Table 1. DOD-Affiliated UGT Participant Radiation Exposure by Year

YEAR Number of 

Participants

Avg. Max.

YEAR Number of 

Participants

Avg. Max.

Exposure (mR) Exposure (mR)

1962* 3,953 136 5,790 1967 2,165 21 4,320

1963 1,132 32 3,780 1968 1,983 28 2,215

1964 1,514 9 2,575 1969 1,224 9 1,960

1965 1,826 37 5,300 1970 1,185 29 1,600

1966 2,131 43 4,290 1971 -

1992 47,957 (total) <10 per year

<1,000

per year

*The 1962 data include DOD personnel exposure from four AEC atmospheric tests.

For more information concerning this program, please call the NTPR Program Helpline at 1-800-462-3683.

May 2015