Effect of Calculation Average Probability Failure on Common Cause Failure

In order to analyze the effect of common cause failure（CCF） on average probability of failure on demand（P_avg） calculation, fault tree models of a normal excitation 1oo2 system are established. The P_avg without regard to CCF and P_avg with regard to CCF（use β factor model） are both calculated. By comparing the calculation results, find that CCF has a great impact on P_avg calculation. Correlation analysis shows that when the system is safer（dangerous failure rate is lower, the detect rate of dangerous failure is higher）, the impact is greater.