The engineering specification, design and implementation of the Sizewell B reactor secondary protection system

The author describes the secondary protection system (SPS), which along with the primary protection system (PPS) constitutes the Sizewell B reactor protection system (RPS). The RPS provides automatic protection from unsafe states arising from faults within the station design basis. The two systems operate as two diverse and independent protection systems, each with its own set of plant sensors, logic equipment and reactor trip switchgear and reactor trip contactors. Each system also derives its own initiation signals for engineered safety safeguard plant items. The SPS system performs the functions of initiation a reactor trip. It also actuates engineered safety features (ESFs) plant as required, to mitigate the consequences of the fault