At Forsmark nuclear power plant the rather old-fashioned software COPTA is used in containment safety analysis. There exists a desire within the organisation to introduce a more modern software with ability to more detailed modeling and increased usability.The goal of this thesis was to evaluate the software APROS in containment safety analysis. APROS models describing one of the containments at Forsmark NPP have been developed. Two simulations of typical containment incidents, one of them a large pipe break, have been made where containment safety parameters such as pressure and temperature are studied. Results are analyzed and verified against results from corresponding COPTA models.