As part of I-NERI program, two US laboratories, INL and ANL, and one laboratory, KAERI, are involved in development of HyPEP, a hydrogen production plant efficiency calculation computer code. The Department of Energy envisions the next generation very high-temperature gascooled reactor (VHTR) as a single-purpose or dual-purpose facility that produces hydrogen and electricity. The Ministry of Science and Technology (MOST) of the Republic of Korea also selected VHTR for the Nuclear Hydrogen Development and Demonstration (NHDD) Project. This collaborative work will address the evaluation of hydrogen and electricity production cycle efficiencies for such systems as the VHTR and NHDD, and the optimization of system configurations. This project will select a reference design that deals with the primary coolant system, the secondary coolant system, the intermediate heat transfer loop, the hydrogen production plant and all requirements. Calculations are based on methods defined for the plant efficiency, HyPEP overall numerical schemes, partial load and operating constraints. Both thermochemical and HTE processes will be included in the complex system.