By 1963, various nuclear powers had conducted multiple tests of nuclear bombs in the atmosphere, on the ground and under water. The United States was conducting powerful thermonuclear devices during the 1950s and the Soviet Union exploded its first thermonuclear bomb in 1961. International concern over the effects of radioactive fallout out from these tests had been growing during the 1950s.
The United States, the United Kingdom and the Soviet Union had been negotiating on nuclear weapons under the auspices of the United Nations Disarmament Commission during the 1950s. Various offers were made by both sides on nuclear disarmament, nuclear testing restriction and conventional weapons. Around 1960, the U.S., the U.K. and the U.S.S.R. finally decided to detach the issue of nuclear testing from the general disarmament discussion.
A major topic of debate was how to verify compliance. Underground testing was a special problem. The blast created a shock wave which could be confused with the shockwave generated by an earthquake. The U.S. and the U.K. wanted to have inspectors at nuclear facilities in all three countries. The U.S.S.R. felt that seismographs outside each country should be able to detect underground tests without the need for onsite inspectors. Finally, in 1963, Premier Khrushchev agreed to a test ban that would not include underground tests. After a decade of debate the Partial Nuclear Test Ban Treaty was signed by the U.S., the U.K., and the U.S.S.R in August of 1963.
In 1965, the U.S.S.R was working on developing nuclear bombs for peaceful use such as creating artificial lakes, rerouting rivers and other big earthmoving projects. A shallow underground test was carried out with a one hundred and forty kiloton bomb. Most of the radioactive fallout that escaped above ground fell inside the U.S.S.R. but a small amount drifted east and was detected over Japan. The U.S. and other signatories complained because the Treaty stipulated that any radioactivity escaping from an underground test could not leave the territory of the country which conducted the test. The matter was ultimate dropped.
In 1970, the U.S. conducted a test of a ten kiloton atomic bomb at a depth of 900 feet at the Yucca Flat test range in Nevada. The explosion ruptured the soil in a way that had not been anticipated and a plume of radioactive dust and smoke escaped into the air. Radioactive fallout was carried over California, Idaho, Washington and Oregon and, ultimately, to Canada, the Gulf of Mexico and the Atlantic Ocean.
Following the drafting of the Treaty by the U.S., U.K. and the U.S.S.R., other countries signed the Treaty as time went by. One hundred and twenty three nations have signed the Treaty. Another ten nations have ratified the Treaty but have not official signed it. Three nations, France, China and North Korea, have exploded nuclear bombs but have not ratified or signed the Partial Nuclear Test Ban Treaty.
Signing of the Treaty from www.cbto.org:
