[en] The US Nuclear Regulatory Commission adopted the Kemeny Commission recommendations that all nuclear plants have a plant specific simulator for operator training. In support of this requirement a project was initiated to examine the capabilities of the current generation of simulators using advanced thermal hydraulic systems codes such as RELAP5 and TRAC-B. As part of the project, RELAP5 models of Pressurized Water Reactor simulators at the US Nuclear Regulatory Commission's Technical Training Center have been developed and sets of transients performed for comparison with simulator predictions. One such model was for the Washington Nuclear Project Unit 1 Simulator. Thermal-hydraulic analyses of five hypothetical accident scenarios were performed with the RELAP5/MOD3 computer code, then the same scenarios performed on the simulator, prior to a scheduled upgrade with S3 Technology's RETACT simulator code. The five transients performed were: (1) Loss of AC power, (2) Small Break Loss of Coolant Accident with Loss of AC power, (3) Stuck open Pressurizer Safety Valve, (4) Main Steamline Break with Steam Generator Tube Rapture, and (5) Loss of main Feedwater with Delayed Scram. Comparison of code and simulator data was performed by reviewing each transient with a team of plant analysts and experienced reactor operators. The initial findings show that both the simulator and system codes' modeling need improvement. The conclusion drawn from this preliminary study is that simulator benchmarking is and should be a dynamic, iterative process with benefits for both simulator engineers and plant analysts