[en] The potential effects of steam generator tube ruptures during large break loss-of-coolant accidents were investigated in the Semiscale Mod-1 system. As a result of testing, a relatively narrow band of secondary-to-primary mass flow rates with the potential for causing high core heater rod cladding temperatures in the Mod-1 system has been identified. The maximum cladding temperatures for tests which simulated tube rupture flows within this narrow band were below 1315 K. The system hydraulic phenomena which influenced the core thermal behavior during the period of secondary-to-primary flow have also been identified