Improvement Study Of Fault Tree Expert System

Fault Tree Expert System (abbreviated to FTES) developed by Institute of Nuclear and New Energy Technology of Tsinghua University is a computer-aided fault tree building software. This thesis is dedicated to making some improvement study on the basis of FTES Version1, and developing FTES Version2.FTES V2 inherits the form of expert system from FTES V1, which includes two main parts, one is the knowledge base structure with Knowledge Tree, and the other is the principle of deduction-synthesis united method for the reasoning machine. Three factors were thought about in improvement study. The first is the feedback of practical FT building experience. The second is the comparing study between FTES and KB3 which is advanced in this field. The third is the new demands in computer-aided FT building coming together with the development of PRA technology. Major improving directions are listed as following.Building Multi-Parameter and Multi-State reasoning mode. Sometimes, more than one parameters (such as flow, temperature or pressure) and more than one failed states of a parameter (such as loss of flow and half loss of flow) will be involved in building Fault tree. Multi-parameter and Multi-state reasoning mode has been built in FTES V2 based on the Single-parameter (flow) and Single-state (loss) reasoning mode in FTES V1, which makes the reasoning mode more perfect and integrity, and provides the precondition for application fields extending.Simplifying the fault tree model in modules. A new simplification method of constructing unit event based on component level is put forward. The thesis discusses the difficulties during modulization, brings forward the method of defining CCF (Common Cause Failure) based on Unit Event, creates the conception of dynamic modulization and describes the realizing steps in FTES V2. Fault tree models can be acquired rapidly via the modular method, which is an effective support for Living PRA.Increasing the flexibility of FTES by designing Fault Tree Editor. Six scenes that can make use of Fault Tree Editor are put forward: fault tree models, manual rules, top logic, node logic, knowledge tree and cut knowledge tree (fault tree) of component. Fault tree models can be browsed, edited and printed in Fault Tree Editor; furthermore, users can use Fault Tree Editor to customize reasoning rules manually, which makes the software more flexible.