Nuclear testing at the Nevada Test Site

The U.S. Nuclear Weapons Cost Study Project was completed in August 1998 and resulted in the book Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940 edited by Stephen I. Schwartz. These project pages should be considered historical.

Preparing to lower a nuclear test canister and diagnostic cables into a test shaft

Before the United States halted underground nuclear testing in September 1992, more than 800 underground nuclear tests were conducted at the Nevada Test Site. Most of these tests took place in vertical shafts (3 to 12 feet [0.9 to 3.7 meters] wide), drilled into the desert floor to depths of 600 to 5,000 feet (183 to 1,524 meters). The test device was placed at the lower end of a long (up to 200 feet, 61 meters) cylindrical canister, which also contained many diagnostic instruments. Miles of electrical cables connected the cannister to firing and recording stations on the surface. After the canister was lowered down the shaft, the hole was closed by filling it with sand and gravel and sealing it with one to three coal tar expoxy plugs (this procedure failed to contain the radioactivity from tests about one-third of the time).

In preparation for an underground nuclear test at the Nevada Test Site, miles of cables connect the nuclear device to diagnostic and monitoring instruments in trailers located a safe distance away from the test shaft. In the instant after the device detonates—destroying itself and everything in the test shaft—the cables relay critical measurements back to weapons scientists, allowing them to ascertain the device's yield, efficiency, and other characteristics. Note the subsidence craters from previous tests in the vicinity.

Radioactive dust and gases venting after the Baneberry underground nuclear weapons test, December 18, 1970.

The Baneberry test involved a 10 kiloton nuclear device detonated 910 feet (277 meters) underneath Yucca Flat near the northern border of the Nevada Test Site. Shortly after the test, the plug sealing the test shaft from the surface failed and a large quantity of radioactive debris vented to the atmosphere, reaching a height of 10,000 feet (3,048 meters). Some 86 workers at the site were exposed to radioactivity, but according to the Department of Energy none received a dose exceeding site guidelines (radiation drifting offsite was similarly not considered to pose a hazard).

Aerial view of the north end of Yucca Flat at the Nevada Test Site

Underground nuclear tests leave subsidence craters of vary dimensions depending on the yield of the device detonated, the depth of emplacement, and the geological characteristics of the surrounding soil. Eight-hundred and twenty-eight underground nuclear tests, including 24 joint U.S.-United Kingdom tests, were conducted at the Nevada Test Site between 1951 and 1992.

Reporters from across the country wearing protective goggles gather at News Knob at the test site to witness the Charlie nuclear weapons test, involving a 31 kiloton bomb dropped from a B-50 bomber. This April 22, 1952, test was broadcast live on national television.

Credit: Department of Energy; Lawrence Livermore National Laboratory (courtesy Natural Resources Defense Council); National Archives