PHISICS (Parallel and Highly Innovative Simulation for INL Code System) is a reactor physics package developed at the Idaho National Laboratory. It is composed of several modules: a nodal and semistructured transport core solver (INSTANT), a depletion module (MRTAU), a time-dependent solver (TimeIntegrator), a cross-section interpolation and manipulation framework (MIXER), a criticality search module (CRITICALITY), and a fuel management and shuffling component (SHUFFLE). The PHISICS code has been coupled to the RELAP5-3D thermal-hydraulics code. Flexibility in the coupling among the different modules and with RELAP5-3D allows for several new integrated computational schemes and improvements with respect to current available options using NESTLE/RELAP5-3D. These schemes will be described in this paper. Moreover, the whole PHISICS package is fully parallelized, using the Message Passing Interface protocol. This allows for reduced computational times, while providing the capability to solve very detailed problems.