Evaluation of Next Generation Nuclear Power Plant (NGNP) Intermediate Heat Exchanger (IHX) Operating Conditions

Abstract

This report summarizes results of a preliminary evaluation to determine the operating conditions for the Next Generation Nuclear Plant (NGNP) Intermediate Heat Exchanger (IHX) that will transfer heat from the reactor primary system to the demonstration hydrogen production plant(s). The Department of Energy is currently investigating two primary options for the production of hydrogen using a high temperature reactor as the power source. These options are the High Temperature Electrolysis (HTE) and Sulfur-Iodine (SI) thermochemical hydrogen production processes. However, since the SI process relies entirely on process heat from the reactor, while the HTE process relies primarily on electrical energy with only a small amount of process heat required, the design of the IHX is dictated by the SI process heat requirements. Therefore, the IHX operating conditions were defined assuming 50 MWt is available for the production of hydrogen using the SI process. Three configurations for the intermediate loop were evaluated, including configurations for both direct and indirect power conversion systems. The HYSYS process analysis software was used to perform sensitivity studies to determine the influence of reactor outlet temperatures, intermediate loop working fluids (helium and molten salt), intermediate loop pressures, and intermediate loop piping lengths on NGNP performance andmore » IHX operating conditions. The evaluation of NGNP performance included assessments of overall electric power conversion efficiency and estimated hydrogen production efficiency. Based on these evaluations, recommended IHX operating conditions are defined.« less