Development of automated operating procedure system using fuzzy colored petri nets for nuclear power plants

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Abstract

In this work, AuTomated Operating Procedure System (ATOPS) is developed. ATOPS is an automation system for emergency operation of a nuclear power plant (NPP) and it can monitor signals, diagnose statuses, and generate control actions according to corresponding operating procedures without any human operator’s help. Main functions of ATOPS are an anomaly detection function and a procedure execution function but only the procedure execution function is implemented in this work because this work is just the first step. In the procedure execution function, operating procedures of NPPs are analyzed and modeled using Fuzzy Colored Petri Nets (FCPN) and executed depending on decision making of the inference engine. In this work, ATOPS prototype is developed to demonstrate its feasibility and it is also validated using the FISA-2/WS simulator. The validation is performed for the cases of a loss of coolant accident (LOCA) and a steam generator tube rupture (SGTR). The simulation results show that ATOPS works correctly in the emergency situations.

Introduction

In large and complex machine systems, many operations have become more difficult for users, resulting in a greater potential for operation errors. Such mistakes may cause serious accidents, especially in aircraft industries and power plants. Hence, many machine systems have been automated through the introduction of modern computer and information technologies (Shimoda et al., 1999). A computerized procedure system is an example of such an automated system. Various computerized procedure systems have been developed during the past decade (Lee and Seong, 2001). They are operator supporting systems which supply necessary information to a human operator quickly and conveniently in order to reduce human errors through easy and accurate decisions. Owing to recent progress in computer control, information processing, and human interface devices, the design of instrumentation and control (I&C) systems for various plant systems is rapidly moving toward fully digital I&C systems with an increased proportion of automation (Kim et al., 2000, Sheridan, 1976).

In modern nuclear power plants (NPP), many computerized operating procedure systems such as computer based procedures (CBP), computer procedures (COMPRO), computer procedure systems (CPS), nuclear emergency operating support systems (NEOS), computerized control rooms (CR), emergency operating procedure tracking systems (EOPTS), and so on have been developed and some of them have been already installed in real plants. They convert text-based operating procedures to a procedure database in a computer and show the procedure database to human operators through a graphics or text-based display. They also support an operator’s interactions with the system, procedure maintenance, and configuration control.

There are also other researches which focus on an automation system. One of them is a “virtual collaborator,” an agent robot, which is realized in virtual reality (Shimoda et al., 1999). The virtual collaborator is a new type of human-machine interface, which works as an “intelligent interface agent” to help machine operators manipulate large scale machine systems such as a power plant. It is a kind of “virtual robot” that behaves like an intelligent agent robot in virtual reality space and communicates naturally with humans akin to the manner in which humans do with each other. It can behave like a plant operator in a simulated control room of a NPP in virtual reality space.

These systems appear to be similar to AuTomated Operating Procedure System (ATOPS) developed in this work, but they are very different in many aspects. The crucial difference is that they are only operator-supporting systems, whereas ATOPS is an automated system which does not need the help of a human operator.

In this work, operating procedures of a NPP are converted to a procedure database and they are used in ATOPS through Fuzzy Colored Petri Nets (FCPN). And an inference engine which consists of fuzzy functions, the time versus cognitive reliability (TCR) curve, and a knowledge database performs a decision making instead of human operators in the NPP. A prototype of ATOPS is developed and simulated using FISA-2/WS simulator. ATOPS is a prototype of a system that will help a NPP become fully automated for next generation NPP operation. Moreover, ATOPS is a very long-term research project. This study, in which the feasibility of ATOPS is verified, is just the first step for the full automation.

Section snippets

AuTomated Operating Procedure System (ATOPS)

ATOPS is a kind of automation system that operates a machine system according to prescribed procedures without any human operators’ help. Since ATOPS is not an operator supporting system but rather an automation system, a man-machine interface (MMI) is not considered. Operators in the main control rooms (MCR) of NPPs monitor signals, diagnose current status, and perform suitable actions according to corresponding operating procedures. ATOPS performs such actions as the operators do: It monitors

Implementation of the prototype ATOPS

In this work, the prototype ATOPS is implemented and validated. The prototype ATOPS is constructed by implementing the procedure execution function only. Validation of the prototype ATOPS is performed for the cases of LOCA and SGTR using accident mode-simulation of FISA-2/WS which is the simulator for the KORI 2 NPP unit and has a graphic user interface (GUI) as shown in Fig. 10. The prototype ATOPS converts the procedure database to FCPN, and shows the FCPN through a graphics-based display.

Conclusions

In this work, ATOPS is developed. ATOPS is an automation system to operate a NPP in emergency situations by monitoring signals, diagnosing statuses, and generating control actions according to corresponding operating procedures without any human operators’ help. Current operating procedures of NPP have some statements and information which are ambiguous and uncertain. In order to handle such statements and information, we modeled operating procedure database using FCPN. FCPN has more powerful

Acknowledgements

This work was supported by the Korean National Research Laboratory (NRL) Program.

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