Sedan (nuclear test)

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Storax Sedan
Storax Sedan nuke.jpg
Storax Sedan explosion.
CountryUnited States
Test seriesOperation Storax
Operation Plowshare
Test siteNevada Test Site
DateJuly 6, 1962
Test typeUnderground
Yield104 kt

Storax Sedan was a shallow underground nuclear test conducted in Area 10 of Yucca Flat at the Nevada National Security Site on July 6, 1962, as part of Operation Plowshare, a program to investigate the use of nuclear weapons for mining, cratering, and other civilian purposes.[1] The radioactive fallout from the test contaminated more US residents than any other nuclear test. The Sedan Crater is the largest human-made crater in the United States and is listed on the National Register of Historic Places.


Sedan was a thermonuclear device with a fission yield less than 30% and a fusion yield about 70%.[2][3] According to Carey Sublette, the design of the Sedan device was similar to that used in the Bluestone and Swanee tests of Operation Dominic conducted days and months prior to Sedan respectively, and was therefore not unlike the W56 high yield Minuteman I missile warhead.[4] The device had a diameter of 43 cm (17 in), length of 96.5 cm (38.0 in), and a weight of 212.2 kg (468 lb).[4]

The timing of the test put it within the Operation Storax fiscal year, but Sedan was functionally part of Operation Plowshare, and the test protocol was sponsored and conducted by Lawrence Livermore National Laboratory with minimal involvement by the United States Department of Defense. The explosive device was lowered into a shaft drilled into the desert alluvium 194 m (636 ft) deep.[3] The fusion-fission blast had a yield equivalent to 104 kilotons of TNT (435 terajoules) and lifted a dome of earth 90 m (300 ft) above the desert floor before it vented at three seconds after detonation, exploding upward and outward displacing more than 11,000,000 t (11,000,000 long tons; 12,000,000 short tons) of soil.[5] The resulting crater is 100 m (330 ft) deep with a diameter of about 390 m (1,280 ft). A circular area of the desert floor five miles across was obscured by fast-expanding dust clouds moving out horizontally from the base surge, akin to pyroclastic surge.[6] The blast caused seismic waves equivalent to an earthquake of 4.75 on the Richter scale.[1] The radiation level on the crater lip at 1 hour after burst was 500 R per hour (130 mC/(kg·h)),[7] but it dropped to 500 mR per hour after 27 days.[7]

Within 7 months (~210 days) of the excavation, the bottom of the crater could be safely walked upon with no protective clothing,[8] with radiation levels at 35 mR per hour after 167 days.[7]


US counties that measured the highest levels of radioactive fallout from both Sedan and "Small Boy" of Operation Sunbeam, detonated eight days later. Units are millisieverts.
The ten highest radiation exposures to residents from US continental nuclear testing

The explosion caused two plumes of radioactive cloud, rising to 3.0 km and 4.9 km (10,000 ft and 16,000 ft). The plumes headed northeast and then east in roughly parallel paths towards the Atlantic Ocean.[citation needed] Nuclear fallout was dropped through several counties.[3] Detected radioactivity was especially high in eight counties in Iowa and one county each in Nebraska, South Dakota and Illinois. The most heavily affected counties were Howard, Mitchell and Worth counties in Iowa as well as Washabaugh County in South Dakota, an area that has since been incorporated into Jackson County and is within the Pine Ridge Indian Reservation. These four counties measured maximum levels higher than 6,000 microcuries per square meter (220 MBq/m2).[9]

Of all the nuclear tests conducted in the United States, Sedan ranked highest in overall activity of radionuclides in fallout. The test released 880,000 curies (33 PBq) of radioactive iodine-131, an agent of thyroid disease, into the atmosphere.[10] Sedan ranked first in percentages of these particular radionuclides detected in fallout: 198Au, 199Au, 7Be, 99Mo, 147Nd, 203Pb, 181W, 185W and 188W. Sedan ranked second in these radionuclides in fallout: 57Co, 60Co and 54Mn. Sedan ranked third in the detected amount of 24Na in fallout. In countrywide deposition of radionuclides, Sedan was highest in the amount of 7Be, 54Mn, 106Ru and 242Cm, and second highest in the amount of deposited 127mTe.[9] While Sedan ranks highest in percentages of 198Au detected, it is not the most prolific generator or gold-heavy design that was tested by the US: due to the explosion being far more well contained, a larger quantity of gold, referred to as "a goldmine", was used extensively in the W71 warhead,[11] that was proof-tested in 1971 within a deep borehole in the Amchitka islands off Alaska.

Sedan's fallout contamination contributed a little under 7% to the total amount of radiation which fell on the US population during all of the nuclear tests at NTS. Sedan's effects were similar to shot "George" of Operation Tumbler–Snapper, detonated on June 1, 1952, which also contributed about 7% to the total radioactive fallout. Uncertainty regarding exact amounts of exposure prevents knowing which of the two nuclear tests caused the most; George is listed as being the highest exposure and Sedan second highest by the United States Department of Health and Human Services, Centers for Disease Control and Prevention, and the National Cancer Institute.[12][13]

Had this test been conducted after 1965 when improvements in device design were realized, achieving a 100-fold reduction in radiation release is considered feasible.[14]


The Plowshare project developed the Sedan test in order to determine the feasibility of using nuclear detonations to quickly and economically excavate large amounts of earth and rock. Proposed applications included the creation of harbors, canals, open pit mines, railroad and highway cuts through mountainous terrain and the construction of dams. Assessment of the full effects of the Sedan shot showed that the radioactive fallout from such uses would be extensive. Public concerns about the health effects and a lack of political support eventually led to abandonment of the concept.[15] No such nuclear excavation has since been undertaken by the United States,[16] though the Soviet Union continued to pursue the concept through their program Nuclear Explosions for the National Economy, particularly with their 140 kiloton Chagan (nuclear test), which created an artificial lake reservoir (see Lake Chagan).

Diplomatic issue with Sudan[edit]

On March 2, 2005, Ellen Tauscher, a Democratic member of the U.S. House of Representatives from California, used Sedan as an example of a test which produced a considerable amount of radioactive fallout while giving congressional testimony on the containment of debris from nuclear testing. However, the name "Sedan" was incorrectly transcribed as "Sudan" in the Congressional Record.

Within days of the error, the international community took notice. Sudanese officials responded by stating that "the Sudanese government takes this issue seriously and with extreme importance". The Chinese Xinhua General News Service published an article claiming that the Sudanese government blamed the U.S. for raising cancer rates among the Sudanese people.[17] Despite the U.S. embassy in Khartoum issuing a statement clarifying that it was a typographic error, Mustafa Osman Ismail, the Sudanese Foreign Minister, stated his government would continue investigating the claims.[18]

See also[edit]


  1. ^ a b "NTS 50th Anniversary Newsletter—Sedan Tested Use of Nuclear Explosives to Move Earth". US Department of Energy Nevada Site Office. Archived from the original on 1 October 2011. Retrieved 25 September 2011.
  2. ^ Information sign at the crater: Nevada Test Site - Sedan Crater - 4.JPG
  3. ^ a b c United States Nuclear Tests; July 1945 through September 1992, DOE/NV--209-REV 15 December 2000, p. xv."Archived copy" (PDF). Archived from the original (PDF) on 2006-10-12. Retrieved 2013-12-18.{{cite web}}: CS1 maint: archived copy as title (link)
  4. ^ a b "Operation Storax". Archived from the original on 17 May 2008. Retrieved 4 August 2017.
  5. ^ "Operation Storax, Sun Beam, and Roller Coaster". Nuclear Weapons Archive. 20 September 1997. Archived from the original on 17 May 2008. Retrieved 2008-07-14.
  6. ^ Nevada Test Site Office. Library. Films. Historical Test Films Archived 2008-07-21 at the Wayback Machine
  7. ^ a b c Information sign at the crater: Nevada Test Site - Sedan Crater - 1.JPG
  8. ^ "Possibilities for peaceful nuclear explosions. An IAEA review of the 1968 book: The constructive uses of nuclear explosions by Edward Teller" (PDF). Archived from the original (PDF) on 2015-03-20.
  9. ^ a b Miller, Richard L. (2002). U.S. Atlas of Nuclear Fallout, 1951–1970. Vol. 1 (Abridged General Reader ed.). Two Sixty Press. p. 340. ISBN 1-881043-13-4. Retrieved 2008-07-19.
  10. ^ "National Cancer Institute. National Institute of Health. History of the Nevada Test Site and Nuclear Testing Background" (PDF). Archived from the original (PDF) on 2010-12-21. Retrieved 2008-07-22.
  11. ^ Schwartz, Stephen (2011). Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940. Brookings Institution. p. 332. ISBN 9780815722946.
  12. ^ "Report on the Feasibility of a Study of the Health Consequences to the American Population from Nuclear Weapons Tests Conducted by the United States and Other Nations, Vol 1. Technical Report" (PDF). Department of Health and Human Services, Centers for Disease Control and Prevention, and the National Cancer Institute. May 2005. Retrieved 4 August 2017.
  13. ^ "Appendix E, 'External Dose Estimates from NTS Fallout' – Radioactive Decay – Gamma Ray". Scribd. Retrieved 4 August 2017.
  14. ^ talkingsticktv (7 November 2007). "Declassified U.S. Nuclear Test Film #35". Archived from the original on 2021-12-12. Retrieved 4 August 2017 – via YouTube.
  15. ^ Center for Digital Discourse and Culture, Virginia Tech. U.S. Nuclear Testing from Project Trinity to the Plowshare Program Abby A. Johnson. (1986) Archived 2008-12-06 at the Wayback Machine
  16. ^ Nevada Test Site Office. Library. Factsheets. Plowshare Program Archived 2008-10-31 at the Wayback Machine
  17. ^ "Roundup of 2005 news articles and congressional testimony related to the Sedan/Sudan mixup". Federation of American Scientists. March 2005. Retrieved 2008-07-14.
  18. ^ "Typing error causes nuclear scare". BBC. 11 March 2005. Retrieved 2008-07-14.

External links[edit]

Coordinates: 37°10′37″N 116°2′46″W / 37.17694°N 116.04611°W / 37.17694; -116.04611