The RETRAN-02 and DYNODE-P thermal-hydraulic codes were compared against actual Prairie Island plant data from a steam generator tube break incident that occurred on October 2, 1979. The predictions from the code calculations compare well with actual plant behavior. The time of the break in the Prairie Island incident was found to be ∼260 s prior to scram with an initial break flow of 625 gal/min. Discharge coefficients are recommended for the calculations of critical flow from the break with extended Henry-Fauske and Moody critical flow models. In addition, a linear correlation was developed to predict the break flow with a given system depressurization rate for a Westinghouse two-loop plant.