US HB5951

Prohibits the United States from conducting explosive nuclear testing unless a foreign state first conducts an explosive nuclear test or there is a demonstrated technical need related to weapon safety, reliability, performance, or military effectiveness

Requires the President to submit notification to Congress at least 180 days before any proposed nuclear test, including a description of the testing, justification, cost estimates, and engagement with the Governor of the affected state

Mandates passage of a joint resolution of approval by Congress, with a two-thirds supermajority vote required in the Senate for both response-to-foreign-test scenarios and technical-need scenarios

Establishes expedited congressional procedures with 60-day committee reporting deadlines, 10 hours of Senate floor debate, and 24 hours of House debate for technical-need resolutions

Defines "explosive nuclear testing" as tests involving fissile material exceeding critical mass with nuclear energy release, explicitly excluding subcritical experiments and laser/inertial confinement fusion experiments