The US Department of Energy is investigating the use of high-temperature gas-cooled reactors (HTGR) to produce electricity and hydrogen. Although hydrogen production using nuclear energy is in an early stage of development, coupling a hydrogen plant to a HTGR requires both efficient heat transfer and adequate separation of the facilities to asure that off-normal events in the production facility do not impact the nuclear plant.

In anticipation of the design, development and procurement of an advanced power conversion system for HTGR, this study was initiated to identify the major design and technology options and their tradeoffs in the evaluation of power conversion systems (PCS) coupled to a hydogen plant. In this study, we investigated a number of design configurations and performed thermal hydraulic analyses using various working fluids and various conditions. Also using the high temperature steam electrolysis process (HTSE), we calculated the energy requirement for the operation of the HTSE. The balance of plant of the HTSE was developed and the HTGR was coupled with the HTSE. This paper includes design options and some results based on an indirect cycle for the power conversion unit (PCU) and a parallel intermediate heat exchanger (IHX) configuration option.