Westinghouse (W) Reactor Protection System (RPS)

The Westinghouse RPS is a complex control system that provides the ability to produce an automatic or manual rapid shutdown of the nuclear reactor, known as a reactor trip or scram. In spite of its complexity, the Westinghouse RPS can be roughly divided into four segments-control rods, reactor trip breakers (RTBs), logic cabinet (containing the two trains of the RPS), and instrumentation rack.

When a bistable in the instrumentation rack trips, it actuates associated relays in both of the trains. The solid-state logic module, or universal card, for that trip parameter (one in each train) then determines whether sufficient relays have actuated. If so, a trip signal is sent to the undervoltage driver card (one in each train), which then opens the RTB associated with that train.

Train A of the RPS logic actuates RTB-A and train B of the logic actuates RTB-B. Opening of either RTB disconnects ac power from the rod control motor generator sets to the rod drive power cabinets, which results in the rods dropping into the reactor core and shutting down the nuclear reaction. An undervoltage driver card trip signal results in actuation of the undervoltage coil and energizing (through the auto shunt trip relay) of the shunt trip coil, either of which will open the RTB.

The initial system study is documented in "Reliability Study: Westinghouse Reactor Protection System, 1984-1995" (NUREG/CR-5500, Volume 2 ). The links below provide the current information for the study and latest results.

Current Results:

Supporting Information:

Historical Results:

Page Last Reviewed/Updated Monday, October 24, 2022