Abstract: Based on the scenarios of hypothetical accidents described in RG 1.183 “Alternative radiological source terms for evaluating design basis accidents at nuclear power reactors”, considering the design features of most of the current advanced small modular reactor (SMR) on &|under ground layouts, the calculation model of the source term of large pressurized water reactor was improved: based on the radioactive conservation equation in the containment, considering the obstacles and retention of the auxiliary building, the radioactive conservation equation in the auxiliary building was established. Taking an advanced small modular reactor nuclear power plant as an example, the radioactive release of the representative nuclides was calculated using the new model and compared with the existing model.

Key words: RG 1.183, small modular reactor (SMR), siting source term