Sunday, February 16, 2014

Bikini Atoll

Mushroom-shaped cloud and water column from the underwater Baker nuclear explosion of July 25, 1946. Photo taken from a tower on Bikini Island, 3.5 miles (5.6 km) away.
Country United States
Test site NE Lagoon, Bikini Atoll
Period 1946
Number of tests 2
Test type Free fall air drop, Underwater

Operation Crossroads was a series of two nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. They were the first nuclear weapon tests since Trinity in July 1945, and the first detonations of nuclear devices since the atomic bombing of Nagasaki on August 9, 1945. The purpose of the tests was to investigate the effect of nuclear weapons on warships.
The Crossroads tests were the first of many nuclear tests held in the Marshall Islands, and the first to be publicly announced beforehand and observed by an invited audience, including a large press corps. They were conducted by Joint Army/Navy Task Force One, headed by Vice Admiral William H. P. Blandy, rather than by the Manhattan Project, which had developed nuclear weapons during World War II. A fleet of 95 target ships was assembled in Bikini Lagoon and hit with two detonations of Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki, each with a yield of 23 kilotons of TNT (96 TJ).

The first test was Able. The bomb, named Gilda after Rita Hayworth's character in the 1946 eponymous film, was dropped from the B-29 Superfortress Dave's Dream of the 509th Bombardment Group on July 1, 1946, and detonated 520 feet (158 m) above the target fleet. It caused less than the expected amount of ship damage because it missed its aim point by 2,130 feet (649 m). The second test was Baker. The bomb, known as Helen of Bikini, was detonated 90 feet (27 m) underwater on July 25, 1946. Radioactive sea spray caused extensive contamination. A third deep water test, Charlie, planned for 1947, was canceled primarily because of the United States Navy's inability to decontaminate the target ships after the Baker test. Ultimately, only nine target ships were able to be scrapped rather than scuttled. Charlie was rescheduled as Operation Wigwam, a deep water shot conducted in 1955 off the California coast.
the photo colorized
Bikini's native residents agreed to evacuate the island, with most moving to the Rongerik Atoll. Later, in the 1950s, a series of large thermonuclear tests rendered Bikini unfit for subsistence farming and fishing. Because of radioactive contamination, Bikini remains uninhabited as of 2013, though it is occasionally visited by sport divers. Although planners attempted to protect participants in the Operation Crossroads tests against radiation sickness, one study showed that the life expectancy of participants was reduced by an average of three months. The Baker test's radioactive contamination of all the target ships was the first case of immediate, concentrated radioactive fallout from a nuclear explosion. Chemist Glenn T. Seaborg, the longest-serving chairman of the Atomic Energy Commission, called Baker "the world's first nuclear disaster."[1]