Peaceful Nuclear Explosions Treaty

The Peaceful Nuclear Explosions Treaty (PNET) is a bilateral agreement between the United States and the Soviet Union signed on 28 May 1976 and entered into force on 11 December 1990, after extended negotiation over verification arrangements. It complements the Threshold Test Ban Treaty (TTBT) of 1974, which capped underground weapons tests at 150 kilotons. Without PNET, either side could in principle have circumvented the TTBT by labeling a high-yield detonation as a "peaceful" civil engineering or resource-extraction blast.

PNET applies to any nuclear explosion carried out at a location outside the parties' declared weapons test sites. Its core provisions:

• A 150-kiloton yield limit for any individual peaceful nuclear explosion.
• An aggregate yield limit of 1,500 kilotons for group explosions (multiple devices fired together), with each individual device in a group still subject to verification.
• A prohibition on using peaceful explosions to obtain information relevant to weapons design that could not be obtained under the TTBT.
• On-site verification rights, including the option for observers and, for higher-yield shots, hydrodynamic yield measurement — a notable concession in Cold War arms control because it allowed inspectors onto the territory of the other party.

The treaty grew out of 1960s–70s programs such as the US Plowshare project and the Soviet "Nuclear Explosions for the National Economy" program, which envisioned using nuclear devices for canal excavation, gas-field stimulation, and mining. By the time PNET entered into force these programs had largely been abandoned on safety, environmental, and economic grounds. The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT), which bans all nuclear explosions regardless of purpose, has effectively superseded PNET, though PNET formally remains in force between the United States and the Russian Federation as the Soviet successor state.