70 Years Ago: A-Bombs Tested on Ships at Bikini Atoll

By Paul Benecki 2016-07-26 13:18:20

To commemorate the seventieth anniversary of the first Bikini Atoll nuclear tests, the nonprofit National Security Archive has published declassified footage of the Able and Baker "shots" in the summer of 1946. 

The tests were intended to determine the effect of nuclear blasts on Navy vessels – and the results came as a surprise. The relatively small explosions (by nuclear standards) sank 15 out of 95 ships deployed, severely damaged many of the rest, and so thoroughly contaminated others with radioactive fallout that they had to be scuttled rather than scrapped. The tests are credited with bringing the problem of contamination from nuclear weapons to widespread public attention for the first time. 

The first test, Able, was an air burst conducted well above ground level to keep local fallout to a minimum. It sank two transports, a cruiser and two destroyer, and the shock wave badly damaged 14 other vessels. Even vessels which were far enough away to survive the blast without damage would have suffered loss of life from the initial burst of radiation if they had been manned – but next test revealed an entirely different and more frightening possibility. 

Test Baker was set off beneath the surface, with the bomb suspended from a landing craft. Its shock wave and the following tsunami sank ten ships, including two battleships and an aircraft carrier, and damaged many more (including three that would have sank if they had not been beached). It also threw two million tons of radioactive water into the air, which fell back and created a 900-foot-tall rolling wave of mist, contaminating all remaining vessels within range. 

Test animals were on board the target vessels for both tests. Survival in Able was good, at about two thirds. None of the hundreds of pigs placed on the range survived Baker.

Decontamination efforts in the days following showed that none of the ways the Navy thought to clean off radioactive fallout were effective. Plutonium is toxic in microgram amounts, and tests showed that after cleaning, incredibly miniscule but still deadly quantities remained, more than enough to pose a threat to human health. The workers cleaning the vessels even contaminated their own living quarters when they returned to the support ships. After days of trying to warn the Navy command, Colonel Stafford Warren, the Army officer in charge of radiation safety, famously convinced the deputy chief of naval operations to halt the cleaning and any further tests by showing him an x-ray of a fish from the atoll's lagoon – a self-x-ray, as the radiation from the fish was enough to create an image on film.

The majority of the surviving target ships were too radioactive to clean off and were scuttled. In a top secret report which was kept classified for the next 30 years, the Navy concluded that contamination of the type produced by Baker could not be remediated, and, further, could even be used to "depopulate vast areas of the earth's surface, leaving only vestigial remnants of man's material works.” 

As for the atoll itself, it would remain quiet until 1954, when the “Castle Bravo” hydrogen bomb test – which had roughly 650 times the yield of Baker – sent traces of radioactive material around the world and contaminated seawater as far away as Japan. 

study released in June found that even so many years after the end of nuclear testing, radiation levels in some parts of Bikini Atoll remain at about six times the maximum safe limit. The 5,000-plus descendents of the atoll’s former inhabitants have not returned; they still elect a mayor, but they live scattered amongst the other Marshall Islands and abroad. Four to six caretakers are on the atoll for part of the year, and one dive tour operation makes two-week trips; it is otherwise uninhabited. 

Diving the USS Saratoga today: