[en] The Transient Reactor Analysis Code (TRAC) is being developed at the Los Alamos Scientific Laboratory (LASL) to provide an advanced best-estimate predictive capability for the analysis of postulated accidents in light water reactors. TRAC-P1A provides this analysis capability for pressurized water reactors and for a wide variety of thermal-hydraulic experimental facilities. It features a three-dimensional treatment of the pressure vessel and associated internals; two-phase nonequilibrium hydrodynamics models; flow-regime-dependent constitutive equation treatment; reflood tracking capability for both bottom flood and falling film quench fronts; and consistent treatment of entire accident sequences including the generation of consistent initial conditions. This report presents the results of initial developmental assessment calculations performed with TRAC-P1A prior to its public release. These calculations were performed with the same code version and include separate-effects experiments for the blowdown, refill, and reflood phases of a loss-of-coolant accident (LOCA); systems-effects experiments for the blowdown phase; and an integral-effects experiment for the blowdown/refill portion of a LOCA. Although the initial set of assessment calculations is not exhaustive, results obtained thus far are encouraging. Additional assessment of the code is in progress through predictions and analyses of other experiments