Steam interfacial condensation in a core makeup tank was simulated using the code RELAP5/MOD3 version 8.0 to predict the violent pressure oscillation phenomena in a core makeup tank. Six base cases were carried out to study the effects of back pressure and of vacuum conditions produced in the core makeup tank by rapid steam condensation. The effect of varying the liquid conduction thermal layer thickness was studied. In addition, the code's ability to predict condensation heat transfer was evaluated. Violent pressure oscillations were found in the early period of a transient. The violent pressure oscillations had no effect on the total amount of injection water from core makeup tank. The conduction thermal layer thickness was found to only effect the liquid temperature history. The current version of RELAP5/MOD3 was found to be incapable of dealing with the condensation heat transfer problem in which the volume liquid temperature is lower than the temperature of the heat structure which is connected to that hydraulic volume. / Graduation date: 1994

The purpose of this thesis is to design a robust test facility for a small space nuclear power system and model its physical behavior under different scenarios. The test facility will be used to simulate a 1-10kWe nuclear reactor, its electrical generation, and heat removal capabilities. This simulator will be used to explore, test and understand the steady-state and transient operation capabilities of small space nuclear power systems. Currently, the system is planned to operate on a variable, electrical heat source directly connected to heat pipes. The heat pipes are to be stainless steel with a water working fluid. These heat pipes will then be connected to a power conversion simulator or actual power conversion technologies. The power conversion simulator is connected to a radiator using a water based heat pipe network using fins and connecting plates in a cylindrical geometry. Modeling of the facility was performed using two different analysis programs, STELLA and SolidWorks. STELLA was used as a lumped sum heat transport code, and SolidWorks was used as a more accurate system to verify the validity of STELLA's results. Both programs were used to analyze startup, heat pipe failures, and loss of power conversion with the end goal of finding safe operational transient scenarios for the transient test facility. / Graduation date: 2013