Operational experience with the Sizewell B integrated plant computer system

The Westinghouse Integrated System for Centralised Operation (WISCO) is the primary plant control system at the Sizewell B Power Station. It comprises three subsystems; the High Integrity Control System (HICS), the Process Control System (PCS) and the Distributed Computer system (DCS). The HICS performs the control and data acquisition of nuclear safety significant plant systems. The PCS uses redundant data processing unit pairs. The workstations and servers of the DCS communicate with each other over a standard ethernet. The maintenance requirements for every plant system are covered by a Maintenance Strategy Report. The breakdown of these reports is listed. The WISCO system has performed exceptionally well. Due to the diagnostic information presented by the HICS, problems could normally be resolved within 24 hours. There have been some 200 outstanding modifications to the system. The procedure of modification is briefly described. (A.K.)