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Sedan Crater

Sedan Crater

Sedan Crater

Sedan Crater is located at 37°10’36.5”N 116°02’47.0”W (37.176820, -116.046382) in Area 10 on the Nevada National Security Site (formerly the Nevada Test Site) near Mercury, Nye County, Nevada. It was added to the National Register of Historic Places (#94000183) on March 21, 1994.

Project Plowshare and the Sedan Experiment

The United States Atomic Energy Commission’s Project Plowshare was intended to develop techniques to use nuclear explosives for peaceful construction purposes. In the 1960s and 1970s, during the Cold War, the United States and the Soviet Union carried out a number of Peaceful Nuclear Explosions (PNE).

The PNEs were nuclear explosions conducted for non-military purposes, such as activities related to economic development, the creation of canals, rock blasting, stimulation of tight gas, chemical element manufacture (test shot Anacostia resulted in Curium-250m being discovered), unlocking some of the mysteries of the so-called “r-Process” of stellar nucleosynthesis, probing the composition of the Earth’s deep crust, creating reflection seismology data, and mining company prospecting.

There was significant public opposition to Project Plowshare’s 27 nuclear projects, which eventually led to the program’s termination in 1977. Some of the consequences of the program included the deposition of fallout from radioactive material being injected into the atmosphere and tritiated water (T2O, a radioactive form of water where the usual hydrogen atoms are replaced with tritium) which was projected to increase to a level of 2% of the then-maximum level for drinking water.

The Sedan Experiment was a part of Project Plowshare to take place at the Nevada Test Site consisted of detonating a 100-kiloton thermonuclear device 635 feet underground. The device was relatively clean as far as thermonuclear devices go—fission contributed less than 30% of the total yield. The device was buried in a 36-inch diameter cased hole that was back-filled with sand.

Predictions

The predicted crater diameter was 1,200–1,400 feet (366–427 meters) and the depth from about 170–300 feet (52–91 meters). About 95 per cent of the radioactivity produced by the explosion would be trapped underground. The heavier fallout would be confined to within about two miles upwind and crosswind, and four miles downwind of ground zero.

Detonation

On July 6, 1962 at 10:00 PDT (17:00:00 UT) the device was detonated. The detonation created a crater 1,200 feet (366 meters) across and 320 feet (98 meters) deep. About 7.5 million cubic yards (5.7 million cubic meters)—12 million US tons (10.9 million metric tons)—of earth and rock were removed. A 12,000-foot (3658-meter) dust cloud formed of some of the smaller earth particles. The lip of the crater (Hal in the diagram below) varied in height from about 20 feet (6 meters) to 100 feet (30 meters).

Nuclear Explosion Crater Cross Section
Nuclear Explosion Crater Cross Section [Glasstone and Dolan, 1977]

 

SZ surface zero 37°10’36.5”N 116°02’47.0”W
(37.176820, -116.046382)
DOB depth of burst 635 feet (194 meters)
Da apparent depth 320 feet (98 meters)
Dal depth from the lip crest 340–420 feet (104–128 meters)
Hal height of the lip crest from the original ground surface 20–100 feet (6–30 meters)
Average 33 feet (__ meters)
Ra apparent radius 1,200 feet (366 meters)
Ral radius to crater lip crest
Re radius of ejecta

 
The exact percentage of escaping radioactivity could not be obtained from the available preliminary data, but there was no major deviation from the prediction. The dust cloud carried the small amount of radioactivity which was not trapped underground or deposited close to the crater north at a speed of about 12 miles per hour. The fallout was in line predictions.

Photographs

Crater from the 1962 “Sedan” nuclear test as part of Operation Plowshare. The 104 kiloton blast displaced 12 million US tons (10.9 million metric tons) of earth and created a crater 320 feet (98 meters) deep and 1,200 feet (366 meters) wide. (Look to the size of the roads in the bottom-right of the picture, and the observation deck at the lower-right edge of the crater, for a sense of scale.)

Sedan Crater
Photo courtesy of National Nuclear Security Administration / Nevada Field Office.

Sedan Crater at Nevada Test Site with the information sign about the project. The image was created from a dozen smaller images and stitched together using Hugin software.

Sedan Crater Panorama
Photo courtesy of Jarek Tuszynski / Creative Commons Attribution-Share Alike 4.0 International license.

Sedan Crater aerial view.

Sedan Crater Aerial View
Original image source unknown.

Sedan Crater aerial view.

Sedan Crater Aerial View
Original image source unknown.

Statistics about Sedan Crater and other nearby craters are described in the image.

Sedan Crater and Nearby Craters Annotated
Original image source unknown.

Sedan Crater is marked on this satellite image. Many other craters are visible in the image.

Sedan Crater on Google Maps Satellite View
Based on image courtesy of Google Maps Satellite View.

Taking a Tour of the Sedan Crater

Yes! You can take a tour of the Sedan Crater and the rest of the Nevada National Security Site. The National Nuclear Security Administration’s Nevada Field Office provides free general interest tours of the Nevada National Security Site on a monthly basis.

Most tours depart from the National Atomic Testing Museum at 755 E. Flamingo Road, Las Vegas, Nevada. Tours depart at approximately 7:30 a.m. and return at 4:00 p.m. Provided transportation is usually a chartered bus equipped with a restroom.

The Nevada National Security Site is located 65 miles northwest of Las Vegas, Nevada. Each tour usually covers about 250 miles. Tour participants should bring their own food and drinks, but no alcoholic beverages. There are no lunch stops. Casual clothing is recommended, and sturdy shoes are required for the rugged terrain. No shorts or sandals are permitted. Visitors to the Nevada National Security Site must be at least 14 years old. Pregnant women are discouraged from participating in Nevada National Security Site tours because of the long bus ride and uneven terrain.

Points of interest on the tour include:

  • Mercury, Nevada — Mercury is a closed city 65 miles (105 km) northwest of Las Vegas. It is situated within the Nevada Test Site and was constructed by the Atomic Energy Commission to house and service the staff of the test site.
  • Frenchman Flat — On January 27, 1951, the first atmospheric nuclear test, Able, took place on the Nevada National Security Site.
  • Nonproliferation Test and Evaluation Complex (NPTEC) — The NPTEC is the world’s largest facility for open-air testing of hazardous materials and biological simulants.
  • Low-Level Radioactive Waste Management Site — There is a low-level waste storage pit at the Nevada National Security Site.
  • Sedan Crater
  • T-1 Training Area — The soil emits low levels of radiation, simulating widespread radiological contamination from Improvised Nuclear Devices (INDs) or multiple Radiological Dispersal Devices (RDDs or “dirty bombs”), yet posing minimal risk to participants.
  • Apple II Houses — In an effort to determine the seismic effects of low yield atomic tests, three “typical American homes” were built down range from the May 5, 1955 Apple II test of 29 kilotons.

Contact the Department of Energy’s Office of Public Affairs to find out the date of the next tour. (All 2016 tours have been filled.) Reservations are required for all tours. Space is limited and seats fill quickly. Groups, civic or technical organizations, and private clubs may request specially-arranged tours (minimum of 25 people) by calling 702-295-0944.

References

Furlow, Robert C. “Sedan Crater” PDF. National Register of Historic Places Registration Form. National Park Service. October 5, 1993. Retrieved 2009-05-25.

Glasstone, Samuel and Dolan, Thomas. 1977. The Effects of Nuclear Weapons. USGPO.

Reynolds Electrical and Engineering Co., Inc. “Project Sedan On-Site Radiological Safety Report”. PDF. United States Atomic Energy Commission. April 29, 1963.

Sublette, Carey.“The Effects of Underground Explosions”. Nuclear Weapon Archive. March 30, 2001.

United States Department of Energy, National Nuclear Security Administration, Nevada Field Office. Image NF-12187.

United States Department of Energy, National Nuclear Security Administration, Nevada Field Office. “Public Tours of the Nevada National Security Site”. August 2013. Accessed April 14, 2016.

United States Environmental Protection Agency. “Environmental Monitoring Report For The Nevada Test Site And Other Test Areas Used For Underground Nuclear Detonations”. PDF. U.S. Energy Research and Development Administration. May 1976.

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