The Oregon State University (OSU) Radiation Center (RC) is the location of a one quarter scale model of the Westinghouse Electric Corporation advanced light-water nuclear reactor design called the AP-600. The full scale AP-600 is a 600 megawatt electric nuclear power plant that incorporates unique passive systems to perform the safety functions currently required of all existing nuclear power plants. Passive safety refers to a system's ability to perform its desired function using natural forces such as gravity and natural circulation. This reduces the reliance on active systems to assure plant safety. The Advanced Plant Experiment (APEX) at the OSU RC is an electrically heated simulation of the AP-600 that includes the Nuclear Steam Supply System (NSSS) and all of the passive safety systems. The APEX facility was funded by the United States Department of Energy and the Westinghouse Electric Corporation. The facility was built to perform the long term cooling tests necessary for design certification of the AP-600. The data taken will be used to benchmark the thermal hydraulic computer codes applied in the design certification process and to better understand the phenomena involved in the full scale AP-600. This paper presents the analysis of the Passive Residual Heat Removal System (PRHR) and in particular the PRHR's "c"-shaped heat exchanger (PRHR Hx). This paper includes analysis and modeling of the PRHR Hx including: hydraulic flow parameters, heat rejection capability, an empirical correlation for determining pressure drop, and an examination of the flow phenomena that occurs in the tank in which the heat exchanger is installed. / Graduation date: 1997