Analysis of the Fallback Values of Digital Control Systems in Nuclear Power Plants

Abstract

A digital control system (DCS), based on the Mitsubishi MELTAC + HOLLIAS platform, has been developed in ACPR1000 nuclear power plants. To fully utilize the superiority of digitalized technology, an analysis of fallback value setting in a DCS was conducted. Fallback values, as the substitution of invalid signals when they are detected in a DCS, are in a uniquely dominant position to determine the system behavior and consequences of a nuclear power plant’s operation, as they participate in the control logic in place of invalid signals. After briefly introducing both the architecture of the ACPR1000 DCS and the invalidity management mechanism of signals, the failure mode of signals from sensors to DCS cabinets, the analysis range for fallback values, analysis principles a nd method, the implementation of modes for various signals, and engineering applications are summarized in this paper. This study is significant for enhancing the reliability of the instrument and control system itself and guaranteeing the safety level of nuclear power plants.

Keywords

• nuclear power plant
• digital control system
• fallback value
• reliability
• safety