[en] The boiling water reactor (BWR) Transient Reactor Analysis code (TRAC) is an advanced best-estimate computer code originally developed for the thermal-hydraulic analysis of BWR loss-of-coolant accidents (LOCAs). Recent and planned additions to the code also offer capabilities that are considered useful in the simulations of other severe accidents. The developmental work is being conducted at the Idaho National Engineering Laboratory (INEL) by EG and G Idaho, Inc. for the United States Nuclear Regulatory Commission (NRC). The code is structured to address single-and two-phase, nonequilibrium, multidimensional hydraulic conditions. An intermediate version of the code (TRAC-BD1/Version 12) underwent a limited release to interested agencies in April 1982. Then, from April 1982 to May 1983, a series of nine independent assessment studies, consisting of 14 test simulations, was performed at the INEL by EG and G Idaho. The major conclusions from these studies relate to code technology strengths and deficiencies, recommended modeling practice, and run statistics