With the ongoing push to decarbonize energy use and especially greenhouse gas emissions across all sectors, there are incentives to investigate how nuclear reactors may be used to generate clean energy and be used in various energy economies beyond just the electrical grid. Two initial integrations, high temperature steam electrolysis (HTSE) and oil refineries, are investigated in this first DOE Integrated Energy Systems (IES) program detailed industrial integration design report. Increasingly detailed reports are anticipated both for the industries discussed in this report and for additional industries in the future of the program. This report is a robust starting point showing how integration thermodynamic analysis establishes the requirements on the reactor and methods by which those requirements can be evaluated for specific reactor designs. Two Advanced Reactor Demonstration Program awardees are selected as representative designs for their respective technologies: NuScale for light-water reactors (LWRs) and X-Energy for high temperature gas reactors (HTGRs). Other reactor technologies or specific reactor configurations would require specific analysis similar to what is done in this report, thus this report can be a reference point by which to extend this work to other nuclear plant designs. The first industrial technology integration studied is HTSE. The HTSE plant is sized such that the reactor is dedicated to the production of hydrogen and the net grid interaction should be zero at nominal conditions. All electricity is consumed in the generation of hydrogen, thus allowing the atomic energy within the nuclear system to be converted into transportable chemical energy in the form of hydrogen. This leads to modular systems sized such that the 200 MWth LWR produces 0.506 kg/s hydrogen while the 203 MWth HTGR produces 0.566 kg/s hydrogen. The reference oil refinery for integration is assumed to be a 100,000 barrel-per-day refinery. Due to the brownfield nature of the integration, the thermal integration of the nuclear systems is taken to be at the steam headers within the oil refinery. Replacing the hydrogen production of the refinery (nominally done via steam methane reforming) with nuclear power HTSE systems provides a significant opportunity for the introduction of nuclear energy into the refinery system. Three to four small modular reactors would be needed to supply the reference refinery. The heat and electricity balances are reported to detail the demands that the outside industries will place on the nuclear systems. How the systems will meet those balances is reported, as well as four preliminary process and instrumentation diagrams (P&ID), showing each of HTGR and LWR integrated with an HTSE plant and to an oil refinery. This report leverages work executed across the DOE IES program and will be the basis for additional cross-program efforts. This research provides reactor designers and possible energy consumers with preliminary designs and thermodynamic data for deploying advanced reactors in IES configurations. • System-wide thermodynamic and electrical balances are demonstrated for HTSE and refineries each with a reference HTGR and LWR configuration. • These balances are leveraged to demonstrate process and instrumentation diagrams along with initial proposed control schemes detailing the changes, especially on the nuclear side, that may be anticipated to nominal operation. • The system flows and diagrams establish component requirements that must be used to generate detailed engineering diagrams that include information such as piping size, valve types, heat exchanger materials, sizes, and types, pumps, etc. This information can be cataloged and leveraged for the applications within this report and then extended to additional applications. The designs detailed within this report will be used across projects within the IES program to identify research gaps, propose potential integrated systems, and be a basis for continued IES designs for additional energy consumers and reactor types.

This study reviews the integration of Brayton Cycle (BC) systems in nuclear power generation, emphasizing their potential to enhance thermal efficiency and operational flexibility over traditional Rankine Cycle (RC) systems. Key working fluids, such as helium (He), supercritical carbon dioxide (sCO₂), nitrogen (N₂), and air, are evaluated for their performance, efficiency, and compatibility with nuclear systems. He is recognized for its high thermal conductivity and inertness at elevated temperatures, while sCO₂ demonstrates advantages in compactness and efficiency in midrange temperatures. This article also highlights the importance of compressor designs in optimizing BC performance and reviews, available compressor technologies. Axial and centrifugal compressor designs enable efficient gas compression while managing the thermal and mechanical stresses associated with high-pressure operations in nuclear systems. Combined with variable geometry components and advanced materials, these technologies address the challenges posed by varying load conditions. Despite the promising features of BC systems, several challenges persist, including high leakage rates and material degradation under extreme conditions, which necessitate robust sealing technologies and thorough testing. The insights gained from operational experiences at facilities, such as the Oberhausen II plant and the High-Temperature He Test Facility (HHV), underscore the complexities involved in designing high-temperature gas turbines for nuclear applications. This review concludes that as the nuclear industry evolves, BC systems hold significant promise for contributing to a sustainable energy future, particularly in the context of small modular reactors (SMRs) and microreactors. Further exploration of combined cycle configurations that combine BCs with RCs may enhance overall efficiency and flexibility in power generation.

Nuclear microreactors are a potential technology to provide heat and electricity for remote microgrids. There is potential for the microgrid on the island of El Hierro to use a microreactor, within an integrated energy system (IES), to generate electricity and provide desalinated water. This work proposes a workflow for optimizing and analyzing IESs for microgrids. In this study, an IES incorporating a microreactor, thermal energy storage (TES) system, combined heat and power plant, and a thermal desalination plant was designed, optimized, and analyzed using Idaho National Laboratory’s Framework for Optimization of Resources and Economics (FORCE) toolset. The optimization tool, Holistic Energy Resource Optimization Network (HERON), was used to determine the optimal capacity sizes and dispatch for the reactor and thermal energy storage systems to meet demand. The optimized reactor and TES sizes were found to be 11.61 MW_th and 58.47 MWh_th, respectively, when optimizing the IES to replace 95% of the island’s existing diesel generation needs. A dynamic model of the system was created in the Modelica language, using models from the HYBRID repository, to analyze and verify the dispatch from the optimizer. The dynamic model was able to meet the ramp rates while maintaining reactor power with minimal control adjustments.