The Special Power Excursion Reactor Test III (SPERT III) was a series of reactivity insertion experiments conducted in the 1950s. This paper describes the validation of the U.S. NRC coupled code system TRITON/PARCS/TRACE to simulate reactivity insertion accidents (RIA) using several of the SPERT III tests. The NRC coupled code system was used to perform the SPERT III E-Core configuration tests in which the RIA was initiated by the rapid ejection of a central cruciform control rod. The resulting superprompt reactivity excursion and negative Doppler reactivity feedback produced the familiar bell-shaped power increase and decrease. The energy deposition during such a power excursion has important safety consequences, and the SPERT III tests provide a validation basis for the NRC coupled multiphysics codes. The models were developed using the original experiment documentation, and the results of five separate tests were used to validate the TRITON/PARCS/TRACE coupled code system.