World's first thermonuclear explosion: U.S. 'George' test
on 9 May 1951, Eniwetok Atoll, Pacific Ocean

9 May 1951 - George

On 9 May 1951, the United States conducted its first experimental thermonuclear explosion, known as ‘Test George’. At the time, this test established a sad record with a yield of 225 kilotons, over 10 times more powerful than the bomb dropped over Hiroshima at the end of the World War Two. This record was to be broken only 17 months later by the U.S. ‘Ivy Mike’ test with over 10 megatons.

George was part of the ‘Operation Greenhouse’ testing series at the Eniwetok Atoll in the Pacific Ocean, where the U.S. conducted 43 mostly atmospheric nuclear tests. The test was a stepping stone towards the thermonuclear weapon, magnitudes more destructive than initial nuclear weapon designs. The technical novelty in this particular test was the use of deuterium and tritium to spark a fusion reaction.


Historical film by the U.S. Department of Energy on the Operation Greenhouse testing series:

In an effort to decontaminate the atoll, contaminated soil and debris were filled into one of the blast craters and covered with concrete.

The radioactive fallout generated by ‘George’, but also by other tests conducted in the Pacific Islands has gravely affected the local population and the environment and raised concerns about the effects of nuclear testing. It was only in the 1970s when the U.S. government started efforts to decontaminate the area.  In 2000, the Marshall Islands Nuclear Claims Tribunal recognized the population’s right to receive compensation for the harm inflicted by the nuclear tests.

The locations where over 1,500 underground nuclear tests were carried out worldwide are highly contaminated and have had to be completely fenced off to limit the danger to humans. The cumulative effects of the hundreds of atmospheric nuclear tests in the 1950s and 1960s released such vast amounts of radioactivity in the Earth's atmosphere that radioactive isotopes could be traced in baby teeth of children born even at great distances from the test sites in these decades.

Radioactivity in the atmosphere over Europe during the Cold War (source: WDR-Quarks & Co)

In this period of the Cold War, the the overall level of radioactivity in the Earth's atmosphere increased to levels that even dwarfed the Chernobyl disaster (see right). Public outrage over these consequences eventually led to the adoption of the 1963 Partial Test Ban Treaty (PTBT), which prohibits nuclear testing in the atmosphere, above ground, underwater and in outer space, but not underground. Only the 1996 Comprehensive Nuclear-Test-Ban Treaty bans all forms of nuclear explosions.