The first of the Bikini events, Test Able, the explosion of a bomb
dropped from an aircraft over the target fleet, sank a number of major
vessels, left others sinking or crippled, contaminated many with
radiation, and laid a plume of fallout northward over the rim of the
atoll into the waters of the ocean. It was Test Baker, however, the
underwater explosion, that would make Bikini the subject of
radiobiological investigations for many years.
The Baker test was the first occasion in which nuclear debris was mixed
with water and ocean sludge and returned to the area of detonation. The
explosive device was of what later would be called nominal size, its
force equivalent to 20,000 tons of TNT. The test still is regarded as a
classic demonstration of the phenomena of shallow-water atomic
explosion.
[Illustration: _The Baker Test. A cauliflower-shaped cloud, after
dumping one million tons of water that had been sucked up by the
explosion, rises over the target warships, silhouetted in front of the
spreading base surge._]
At the moment of release, the surface water of the lagoon was first
lifted and then penetrated by a lighted bubble that vanished in seconds
in a hollow column of water of gigantic dimensions—a column 2000 feet in
diameter (its walls 300 feet thick) rising to a height of 6000 feet and
containing 1,000,000 tons of water. At the base of the column, foam was
churned upward for several hundred feet, and, moving out from the base,
as the column sank back into the lagoon, surged a monstrous wave
initially more than 80 feet high.
Radioactivity in the water was intense. The immediate total was
described as equal to “many hundred tons of radium”. Decay and dilution
of radioactive materials quickly reduced the total radioactivity. After
3 days, by which time water contamination had spread over an area of 50
square miles, the dose rate from the water was well within safe limits
for persons remaining for brief periods. Yet it was several more days
before inspection and scientific parties could spend useful time among
the surviving target vessels.
At the bottom of the lagoon, below the point of detonation, Navy divers
months later found that the explosion had scooped out thousands of tons
of mud and coral sediment, creating a shallow basin half a mile wide.
This basin, in the slow settling of returning sludge, became an area
from which long-lived radioactivity entered Bikini’s biological system.