Abstract: The method of analysing radiological consequences for design base accident by using alternative source term was described. The radiological consequences were analyzed by using integral safety analyse code for nuclear power plant of 900 MW in the case of large break loss of coolant accident, including dose computation of control room, exclusion area boundary and outer boundary of low population zone. The results were compared wih dose rule of Nuclear Regulary Committee (NRC) Regulary Guide 1.183 and met the dose criteria.