Hitachi-GE developed a -class modular simplified and medium small reactor (DMS) between 2000 and 2004. It was designed to have merits over traditional nuclear power plants in areas of lower initial capital investment, flexibility, enhanced safety, and security. The balance of plant (BOP) system of the DMS was originally designed for supplying just electricity. In this study, the cogeneration DMS that supplies both electricity and heat is under investigation. The heat exchanger (HX) network, mainly consisting of the BOP heat exchanger, water pump, and the heat exchangers that deliver heat to the thermal utilization (TU) applications, must operate in an efficient way to keep the overall system costs low. In this paper, the configuration of a heat exchanger network that serves for various TU applications is investigated first. A numerical model for the heat exchanger network is built, and sensitivity studies are performed to estimate the energy efficiency and exergy efficiency of the whole heat exchanger network under different design and operating conditions (e.g., different water temperatures and flow rates). Important design and operating parameters, which significantly impact the performance of the network, are evaluated and presented.