The characteristics of risk important human events in the North Anna individual plant examination were analyzed based on the Risk Achievement Worth and the Fussell-Vesely importance.

Basic events, obtaining from CBR are inserted into FTA, which was not in FTA , thus fault field is expanded; On the other hand, degree of importance for minimum cut sets is getting from case library, which can find fault more accurately, the successful diagnosis case, which is obtained by FTA, is added in case library as a case.

Diagnosis approach based on failure mode importance of causality diagram;

Maintenance Manner Decision-Making for Equipment Based on Partitioning Importance;

Study on Diagnosis Approach Based on Basic Event Importance of Causality Diagram;

A simple method to determine the importance degree of ship machinery;

Study on impedance of gravitational mode based on importance degree;

The calculation of the probability of the top event is based on the inclusive-exclusive theorem, and the probability importance degree and key importance de.

The important degree and its analysis of the basic affairs in the trouble tree, the promotion function to safety management work were introduced mainly.

The fuzzy importance index of unit is one of simple and effective method to evaluate important degree of unit of equipment at short of the data.

It is emphasized that neural network model is used to evaluate the important degree of weapon system s development item.