Projects GNOME and SEDAN

The PLOWSHARE Program

Note: For information related to claims, call the Department of Veterans Affairs (VA) at 800-827-1000 or the 

Department of Justice (DOJ) at 800-729-7327. For all other information, call the Nuclear Test Personnel 

Review (NTPR) Program Helpline at 800-462-3683.

The U.S. Atomic Energy Commission (AEC) established the PLOWSHARE program in June 1957, under the 

technical direction of the Lawrence Radiation Laboratory (LRL). The program consisted of 27 nuclear 

detonations conducted at the Nevada Test Site (NTS) and other sites in Colorado and New Mexico from 1961 

to 1973. The nuclear tests, identified in the first of the accompanying tables, were all underground, either shaft 

or cratering shot, and they had yields of no more than 200 kilotons. The PLOWSHARE detonations were 

designed to evaluate nonmilitary applications of nuclear explosives. The primary potential use envisioned was 

in large-scale geographic engineering, in such projects as canal, harbor, and dam construction; the stimulation 

of oil and gas wells; and mining. Considering the peaceful objectives of PLOWSHARE, the AEC took the 

name of the program from the Bible: “And they shall beat their swords into plowshares” (Isaiah 2:4).

Historical Background

Projects GNOME and SEDAN, the first two detonations of the PLOWSHARE program, were selected for 

discussion because they were conducted during the period of U.S. atmospheric nuclear testing, had 

documented (although limited) Department of Defense (DOD) participation, and had sufficient documentation 

for a discussion of the detonations and associated activities. DOD did not conduct military exercises during 

PLOWSHARE and had limited involvement in the shots. The primary role of the military was to provide 

logistical support; technical participation was allowed, provided it did not interfere with AEC activities.

Project GNOME, a shaft detonation, was fired at noon Mountain Standard Time on December 10, 1961, at a 

site 40 kilometers southeast of Carlsbad, New Mexico. The first of the accompanying figures shows the site 

location. The device was buried 1,184 feet underground in bedded rock salt at the end of a 1,116-foot hooked 

and self-sealing tunnel. A shaft 1,216 feet in depth and 10 feet in diameter ended in a station room connected 

to the tunnel. The detonation, which had a yield of 3 kilotons, resulted in an underground dome-shaped 

chamber 60 to 80 feet high and 160 to 170 feet in diameter.

Although it had been planned as a contained explosion, GNOME vented to the atmosphere. A cloud of steam 

started to appear at the top of the shaft 2 to 3 minutes after the detonation. Gray smoke and steam, with 

associated radioactivity, emanated from the shaft opening for about 7 minutes after the detonation. 

Radioactive materials vented to the atmosphere about 340 meters southwest of ground zero. The highest 

measured onsite gamma intensity was 1 Roentgen per hour (R/h). This intensity was recorded 1,300 meters 

northwest of the shaft opening at 1938 hours on shot day. The highest offsite reading was 1.4 R/h, 

encountered 5.5 kilometers west of the Control Point on Highway 128 one hour after the detonation. 

Underground recovery operations were delayed, in part because of high radiation levels at the shaft opening 

(for example, 5 R/h at 9:08 a.m. on the day after the detonation). Six days after the shot, an initial radiological 
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and toxicological survey was conducted to the bottom of the shaft. After the survey was completed, 

underground recovery operations were permitted.

An extensive program of scientific and technical projects was conducted to obtain information on the 

characteristics of a nuclear detonation in an underground rock salt formation and to explore the feasibility of 

energy recovery, radioisotope recovery, and generated-neutron utilization. To emphasize the peaceful aims of 

Project GNOME, the AEC conducted an observer program involving, among others, Government officials, 

representatives of scientific and industrial groups, and news media personnel.

DOD personnel took part at GNOME in the VELA UNIFORM program, conducted by DOD to develop U.S. 

capabilities in detecting and identifying underground nuclear detonations. DOD’s Advanced Research Projects 

Agency administered the program, which consisted of 19 projects. The Air Force Technical Applications 

Center formulated technical requirements for the projects, and the Defense Atomic Support Agency developed 

and directed the activities. DOD personnel also conducted at least one other project (Design, Testing, and 

Field Pumping of Grout Mixtures). In addition, the Air Force Special Weapons Center (AFSWC) conducted 

photography, cloud-sampling, and cloud-tracking missions at the shot.

Project SEDAN, a nuclear cratering experiment, was detonated with a yield of 104 kilotons at 9 a.m. Pacific 

Standard Time on July 6, 1962. The shot was fired in Area 10 of the NTS, shown in the second of the 

accompanying figures. The device was buried 635 feet underground in desert alluvium, and the detonation 

resulted in a crater with a radius of 607 feet, a depth of 323 feet, and a volume of about 6.5 million cubic yards. 

The lip of the crater ranged in height from 18 to 95 feet above the pre-shot surface. Two and one-half hours 

after the detonation, the 10 R/h line extended 3.3 kilometers to the west and 3.1 kilometers to the south, and 

the 1 R/h line extended 3.5 kilometers to the west and 3.3 kilometers to the south. The radiation isointensity 

contours were not completely plotted to the north and east, the direction of the fallout. Two days later, 

intensities of 1 R/h were confined to within 3.2 kilometers of ground zero.

The purposes of Project SEDAN were to extend knowledge of cratering effects from detonations with yields of 

100 to 200 kilotons and to provide safety data related to nuclear cratering detonations. To collect information, 

the LRL conducted an extensive program of scientific and technical projects.

DOD personnel took part in four projects studying peaceful uses of nuclear detonations. In addition, they 

participated in five VELA UNIFORM projects. Participating DOD agencies were:

• Defense Atomic Support Agency

• Army Engineer Nuclear Cratering Group

• Army Engineer Waterways Experiment Station

• Naval Radiological Defense Laboratory

• Air Force Technical Applications Center

AFSWC and other Air Force personnel conducted cloud-sampling, cloud-tracking, and support missions at the 

shot.

Radiation Protection Standards

To minimize the exposures of PLOWSHARE personnel to ionizing radiation, the AEC established an individual 

exposure limit of 3 rem∗ of gamma and neutron radiation per calendar quarter and not more than 5 rem 

 ∗ A rem is a radiation protection unit of measure that quantifies the risk of biological effects resulting from exposure to 

ionizing radiation. Ionizing radiation is any radiation (gamma, x-ray, beta, neutron, or alpha) capable of displacing 

electrons from atoms or molecules, thereby producing ions. According to the National Council on Radiation Protection 

and Measurements (NCRP, Report No. 160, Table 1.1), the general U.S. population receives about 0.62 rem per year 

from natural background radiation sources (radon, cosmic rays, and rocks) and man-made radiation sources (medical 
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annually. The radiological safety programs for Projects GNOME and SEDAN operated within these exposure 

guidelines. The AEC provided onsite radiological support, which included:

• Issuing anti-contamination clothing and equipment to personnel entering radiation areas

• Monitoring radiation areas and controlling access into these areas

• Plotting isointensity contour maps of radiation areas and providing radiation information to personnel 

entering radiation areas

• Decontaminating personnel, vehicles, and equipment

• Maintaining film badge and exposure records to determine the exposure of each participant to gamma 

radiation.

Neutron exposures were to be assessed on a case-by-case basis. Such exposures would occur, however, 

only if personnel were positioned close-in at shot time. Personnel were not permitted into areas of 10 R/h or 

greater unless they had special permission from the AEC.

U.S. Public Health Service (USPHS) personnel conducted offsite monitoring. Their activities involved:

• Monitoring for offsite radiation

• Conducting environmental monitoring of air, water, and milk

• Collecting data on fallout patterns.

USPHS personnel prepared reports, maps, and records describing results of the monitoring and data 

collection.

Radiation Doses at Projects GNOME and SEDAN

Dosimetry records indicate that radiation doses for two DOD participants in GNOME and SEDAN exceeded the 

3-rem limit. Both were Air Force officers who received about 4 rem after SEDAN. Of the 150 military 

participants, all 35 who received more than 0.1 rem were from the Air Force. Fourteen of these received more 

than 0.5 rem, including eight over 1 rem and four over 2 rem.

For more information, see the report “Projects GNOME and SEDAN, The PLOWSHARE Program” 

(DNA 6029F), available online at https://www.dtra.mil/DTRA-Mission/Reference-Documents/NTPR-Info/.

September 2021

 

diagnostic x-rays and consumer products). As a basis of comparison, a standard diagnostic chest x-ray delivers a 

radiation dose of about 0.02 rem.
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Summary of PLOWSHARE Nuclear Weapons Testsa

Shot Date Location Type Yield (kilotons)b

GNOME Dec 10, 1961 Carlsbad, NM Shaft 3

SEDAN Jul 6, 1962 NTS Crater 104

ANACOSTIA Nov 27, 1962 NTS Shaft 5.2

KAWEAH Feb 21, 1963 NTS Shaft 3

TORNILLO Oct 11, 1963 NTS Shaft 0.38

KLICKITAT Feb 20, 1964 NTS Shaft 70

ACE Jun 11, 1964 NTS Shaft 3

DUB Jun 30, 1964 NTS Shaft 11.7

PAR Oct 9, 1964 NTS Shaft 38

HANDCAR Nov 5, 1964 NTS Shaft 12

SULKY Dec 18, 1964 NTS Shaft 0.092

PALANQUIN Apr 14, 1965 NTS Crater 4.3

TEMPLAR Mar 24, 1966 NTS Shaft 0.37

VULCAN Jun 25, 1966 NTS Shaft 25

SAXON Jul 28, 1966 NTS Shaft 1.2

SIMMS Nov 5, 1966 NTS Shaft 2.3

SWITCH Jun 22, 1967 NTS Shaft 3.1

MARVEL Sep 21, 1967 NTS Shaft 2.2

GASBUGGY Dec 10, 1967 Farmington, NM Shaft 29

CABRIOLET Jan 26, 1968 NTS Crater 2.3

BUGGY Mar 12, 1968 NTS Crater 1.08 (for each of five

devices)

STODDARD Sep 17, 1968 NTS Shaft 31

SCHOONER Dec 8, 1968 NTS Crater 30

RULISON Sep 10, 1969 Grand Valley, CO Shaft 40

FLASK May 26, 1970 NTS Shaft 105, 0.09, 0.035 (for 

each of three devices)

MINIATA Jul 8, 1971 NTS Shaft 83

RIO BLANCO May 17, 1973 Rifle, CO Shaft 33 (for each of three

devices)

a Source: United States Nuclear Tests, July 1945 through September 1992, DOE/NV-209 (Rev. 15), Dec 2000. 

b One kiloton equals the approximate energy release of one thousand tons of TNT.
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