The Peaceful Nuclear Explosions Treaty (PNET), designed in preparation for the Threshold Test Ban Treaty (TTBT), governs nuclear explosions that are carried out outside test sites, as established under the Threshold Test Ban Treaty. The United States and the Soviet Union agreed to not carry out explosions exceeding 150 kilotons and group explosions unless the yield of individual explosions in the group could be verified. The Treaty does not ban against peaceful nuclear explosions in the territory of another state, but these explosions have to comply with yield limitations and be in accord with the nuclear Nonproliferation Treaty. The PNET and TTBT were established under a comprehensive system of regulations with neither state able to withdraw from the treaty until the TTBT finished its duration of five years.
Opened for Signature: 28 May 1976
Entry into force: 11 December 1990
Official Text: http://www.state.gov/t/isn/5182.htm#treaty
Status and Signatories: http://www.state.gov/t/isn/5182.htm#narrative
ACA Backgrounder: https://www.armscontrol.org/factsheets/Nuclear-Testing-and-Comprehensive-Test-Ban-Treaty-CTBT-Timeline