NuScale Power has designed a small modular reactor using natural circulation cooling dependent systems for both steady-state and transient operations. The NuScale Integral Test System (NIST-1) facility was built to supply test data to NuScale Power to verify and validate computer codes for the NuScale Power Mod- ule (NPM) with the goal to satisfy the Nuclear Regulatory Commission’s nuclear power plant certification criteria. The safety systems tested in NIST-1 heavily rely on the characterization of the heat transfer between the Containment Vessel (CNV) and Cooling Pool Vessel (CPV) via the Heat Transfer Plate (HTP) since the CNV acts as the cavity to contain steam leakage during an accident in the actual NPM. To ensure the heat loss in the CNV via insulation is small enough to be negligible and not affect test data, Computational Fluid Dynamics (CFD) program STAR CCM+ was used to simulate the test data from High Pressure Test (HP) 16b to analyze the heat loss. Grid convergence was achieved and results show good agreement with the HP-16b’s test data concluding the CNV heat loss to be minimal and negligible.