A method allowing individual representation of a ruptured steam generator tube without including it explicitly in the RETRAN-02 nodalization was investigated. The resulting methodology allows accurate representation of flow through a single ruptured tube without incurring prohibitive computing costs. The study considered a wide variety of fluid conditions at the rupture ranging from subcooled liquid to two-phase fluid and from choked to unchoked rupture flow. Although only one tube rupture geometry was considered, this study provides the groundwork from which methods specific to other geometries can be easily developed. Portions of this method were compared with RELAP5 calculations and good agreement was shown. This methodology was incorporated in a RETRAN-03 analysis of a steam generator tube rupture event in a Westinghouse two-loop plant. This included a case with a tube rupture accompanied by loss of off-site power as well as a case incorporating procedures for operator actions during a tube rupture event. The results indicate both the impact and the necessity of appropriate operator actions in such an event. The RETRAN-03 computer code was found to perform satisfactorily when this tube rupture modeling technique was incorporated. Faster than “realtime” computational speed was demonstrated on a Cyber 176 computer when using a fairly detailed RETRAN plant model (54 volumes, 82 junctions).