Squib

A squib is a small explosive used to open a pathway (valve). By its nature, this a 1 time event used during emergency conditions.

The nuclear industry has a limited amount of experience with the use of squib valves. The available operating experience is typically from small squib valves in the standby liquid control system at boiling water reactor (BWR) nuclear power plants. The design, qualification, procurement, and in-service testing and inspection activities for squib valves to be used in new reactors represent a significant engineering challenge because of their risk and safety importance, large size range, and new design aspects.

A squib valve ensures zero leakage during normal operations by its sealed closure. Actuation occurs by a pyrotechnic process that is triggered by an electric control signal. Actuation of the squib valve results in the shearing of a pipe cap to allow fluid to flow through the valve. Squib valves can be used to depressurize plant systems, or to provide for coolant to flow to the reactor core or containment building. Actuation of a squib valve is a once-only sequence that requires refurbishment to return the valve to service.