Background: A flaw is discovered by ultrasonic test at reactor pressure vessel during the service.Purpose: In order to insure the structural integrality of RPV

it is necessary to perform the fracture analysis for RPV flaw.Methods: According to ASME rule

fracture analysis is performed

which the flaw is assumed as a circumferential surface crack and crack depth is 10.1 mm.The analysis work contains the calculation of fatigue crack growth and the assessment of stress intensity factor under several category conditions.The loads are the temperature fluctuation

pressure and weld residual stress.The concerned category conditions include normal and upset conditions

emergency conditions

and faulted conditions.Results: The analysis results show that normal and upset conditions transient loading has little effect on the fatigue crack growth of low inner surface crack.The fatigue crack growth is about 0.228 mm at the end of 40 years service life.Conclusions: The stress intensity factor results of all conditions satisfy the requirement of ASME Rule.The RPV with flaw can continue service without repair.