State Token petri net modeling method for formal verification of computerized procedure execution flow

Abstract

The Computerized Procedure System (CPS) is one of the primary operating support systems in the digital Main Control Room. CPS displays procedure on the computer screen in the form of a flow chart and displays plant operating information along with procedure in-structions. It also supports operator decision making by providing a system decision. A pro-cedure flow should be correct and reliable, as an error would lead to operator misjudgment and inadequate control. In this paper we present a modeling for CPS that enables formal veri-fication based on Petri nets. The proposed State Token Petri Net(STPN) also support model-ing of a procedure flow that has various interruptions by the operator according to the plant condition. STPN modeling is compared with Coloured Petri net when they are applied to Emergency Operating Computerized Procedure. A converting program for Computerized Procedure (CP) to STPN has been also developed. The formal verification and validation method of CP with STPN increase the safety of nuclear power plant and provide digital quali-ty assurance means that is needed when the role and function of CPS is increasing.