Threshold Test Ban Treaty
The Treaty on the Limitation of Underground Nuclear Weapon Tests (in short: Threshold Test Ban Treaty , abbreviation: TTBT ) is a treaty between the United States of America and the Union of Soviet Socialist Republics to limit nuclear weapon tests . It was signed at a summit meeting in Moscow in July 1974. The treaty prohibits underground nuclear weapon tests with an explosive force of more than 150 kT. It includes a protocol on the exchange of technical data and the limitation of tests to certain test areas. Both geographical and geological data were exchanged for these test areas in order to be able to check compliance with the contract. Furthermore, the contract forbids underground tests in which radioactively contaminated material could get across national borders.
The treaty was only sent to the United States Senate for review and ratification in 1976 , but was not subsequently ratified. Nevertheless, both states announced in 1976 that they would comply with the upper limit of 150 kT regardless of ratification. In November 1987, the US and USSR began negotiations on new protocols for verification rules to replace the original protocols of the treaty. On December 11, 1990, the treaty between the two states finally came into force.