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At least 1,657 records · Page 92
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

A Bottom-Up Cost Estimation Tool for Nuclear Microreactors

The rising interest in nuclear microreactors has highlighted the need for comprehensive technoeconomic assessments. However, the scarcity of publicly available designs and cost data has posed significant challenges. To address this issue, the Microreactor Optimization Using Simulation and Economics (MOUSE) tool is developed. MOUSE is a tool that integrates nuclear microreactor design with reactor economics. The design calculations encompass core simulations using the OpenMC Monte Carlo Particle Transport Code [romano2015], along with simplified balance of plant calculations. On the economic side, MOUSE provides detailed bottom-up cost estimates, calculating both the total capital cost and the levelized cost of energy for first-of-a-kind and nth-of-a-kind microreactors. The cost estimation correlations are developed using data from the MARVEL project and additional literature sources. MOUSE has released as an open-source tool on GitHub (MOUSE Tool). By combining design calculations with cost equations, MOUSE enables users to evaluate the impact of various technological consideration, advanced moderators, design changes, material/fuel changes, and geometry modifications—as well as economic parameters like interest rates and construction duration. This comprehensive framework can guide stakeholders towards technological solutions that enhance microreactor competitiveness. Additionally, powered by the WATTS toolkit [romano2022], MOUSE supports optimization studies, parametric analyses, and uncertainty calculations/propagation. Currently, preconceptual designs of three microreactor types are included in MOUSE: a liquid metal thermal microreactor (LTMR), gas cooled TRISO-fueled microreactor (GCMR) and heat-pipe TRISO fueled microreactor (HPMR). To showcase its ability, MOUSE was used to conduct detailed bottom-up cost estimates for the first of a kind (FOAK) and Nth of a kind (NOAK) of the following microreactors • A 20MWt LTMR that is built on the ongoing MARVEL demonstration at Idaho National Laboratory (INL) • A 15 MWt GCMR that was designed to be more representative of the typical commercial microreactor • A 7 MWt HPMR that was built on previous work (Choi 2024) The The reader should note that these three designs and corresponding cost estimates are examples to demonstrate the MOUSE capability. The designs are pre-conceptual, the reactor designs were not optimized, and the cost estimates were developed with incomplete information. Additionally, stakeholders might be interested in a variety of designs that may differ from the examples provided in this report. The MOUSE tool can also be used to study how design choices affect economics. To demonstrate its capability, MOUSE was used conduct parametric studies such as examining the economic impact of the reflector's material and thickness, the moderator's booster material and dimensions, fuel composition and enrichment, core size, and power level. Several insights were gained from these parametric studies.

Hanna, Botros↗
DOE OSTI2024

BlueCRAB Multiphysics in Support of the U.S.NRC

This presentation provides an overview of the nonLWR modeling and simulation project at INL. It includes a discussion of the various reference plant models developed since 2019 and a more detailed view at results from a monolith-based heat pipe cooled micro reactor.

21 - SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLAN↗
DOE OSTI2025

Integrated Molten Salt Reactor Modeling Capabilities in NEAMS Thermal Hydraulics Tools

The DOE neams program supports a full range of computational thermal fluids analysis capabilities and code developments for a broad range of advanced reactor concepts. The research and development approach under the thermal fluids technical area synergistically combines three length and time scales in a hierarchical multi-scale approach. To enable multi-scale thermal fluids capability using these codes, a key joint effort has been underway to develop an integrated system- and engineering-scale thermal fluids analysis capability, through integration of SAM and Pronghorn codes, both based on the MOOSE framework. This report summarizes recent advances in developing an integrated system- and engineering-scale modeling capability for the msr concept, which has gained significant interest in recent years. A consistent framework was established by coupling Pronghorn and SAM through the Saline interface, with thermophysical properties provided by the Molten Salt Thermal Property Database (MSTDB-TP). Further improvements were made to the coupling schemes and domain-overlapping strategies, enhancing the stability and robustness of multi-code simulations. Verification and validation efforts demonstrate the accuracy of this integration across a range of benchmark problems, including one-dimensional heated pipe flows, three-dimensional natural convection loops with evolving isotopic compositions, and \gls{msre} demonstration cases. Within Pronghorn, new capabilities were introduced to model corrosion and noble-metal plating phenomena, supported by an extended thermal-hydraulics framework and refined turbulence treatments. To capture two-phase flow behavior, a multiphase Euler–Euler model was implemented in Pronghorn, including advanced closure relations, high-resolution advection techniques, and capillary force reconstruction. Preliminary verification cases confirm the fidelity of the approach, while planned validation efforts target canonical multiphase benchmarks and application to msr components such as the msre pump bowl. Finally, updates to SAM’s msr mass transfer modeling were extended to consider noble gas migration into porous structures like graphite. The point kinetics model was updated to include reactivity feedback contributions from any defined species, such as xenon. The gas transport model was expanded for applicability to gas mixtures, bubble efflux phenomena, and species transport between liquid and gas phases. A selection of multi-scale Sherwood number correlations from MOSCATO/NekRS and multi-phase correlations from literature have been added for improved accuracy in calculating mass transfer coefficients. A companion effort on developing system-level redox corrosion has also been incorporated into SAM. Collectively, these enhancements strengthen the predictive capability of SAM and Pronghorn for simulating MSR thermal-hydraulics, corrosion, multiphase behavior, and fission-product transport, providing a more complete toolset for design, safety analysis, and licensing support of next-generation \gls{msr}s.

42 - ENGINEERING↗
DOE OSTI2025

A Microreactor Program Plan for The Department of Energy

The DOE Microreactor Program was established in FY 2019 to support research and development (R&D) of technologies related to the development, demonstration, and deployment of low-power, transportable reactors to provide power and heat for decentralized generation in civilian, industrial, and defense energy sectors. The program conducts both fundamental and applied R&D to de-risk technology performance and manufacturability readiness of microreactors. R&D projects and work packages are selected to support concept-neutral technology maturation. The intent is to ensure those concepts can be licensed and deployed by commercial entities to meet specific use case requirements. At the same time, the program will also support R&D specific to certain reactor technology groups (e.g., heat pipe reactors and gas-cooled reactors) to ensure relevancy and address the technology needs of commercial developers. The program will ensure coordination of work and activities across participating laboratories and universities, establish, and manage stakeholder interactions, and support program meetings. These stakeholders include, but are not limited to, industry developers, the U.S. Nuclear Regulatory Commission, the Department of Energy, policymakers, and end users. This document provides an overview of the overall Microreactor Program, including its vision, key technical objectives, and scope of the current and proposed R&D portfolio. It covers a 5-year rolling currently from Fiscal year 2025 through Fiscal year 2030. This document will be revised at least biennially to reflect changing priorities.

99 - GENERAL AND MISCELLANEOUS↗
DOE OSTI2026

The General Antiparticle Spectrometer (GAPS) Antarctic Balloon Payload

The General Antiparticle Spectrometer (GAPS) is an Antarctic stratospheric balloon mission designed to provide unmatched sensitivity to low-energy (<0.25 GeV/n) cosmic-ray antiprotons, antideuterons, and antihelium nuclei as signatures of dark matter. The distinctive GAPS particle identification technique relies on measuring the energy loss along the track of an incoming antinucleus as it slows down and is captured into an exotic atom, and then detecting the de-excitation X-rays and the nuclear annihilation products. This measurement is realized using a Tracker composed of more than 1000 custom silicon strip detectors and a plastic scintillator time-of-flight (TOF) system instrumenting more than 40m$^2$. Together, these subsystems provide the velocity and energy resolution, stopping power, particle tracking, and X-ray identification necessary to distinguish rare antinucleus signals from the abundant positive-nucleus backgrounds, all within the constraints of a high-altitude mission. A multi-loop capillary heat pipe system has been developed to maintain the tracker operating temperature with significant mass and power savings over a conventional pump-based system. The first GAPS science payload flew for 25 days during the 2025/26 NASA Antarctic balloon campaign. We detail the design, integration, and commissioning of the payload prior to flight.

Aoyama, Kazutaka [JAXA, Sagamihara]↗
NASA NTRSDate not supplied

Electric Aircraft Thermal Management Using a Two-Phase Heat Transport System with Solid-State Thermal Switching Capability

Advanced Cooling Technologies, Inc. (ACT) is collaborating with NASA Glenn Research Center (GRC) to develop a heat pipe-based thermal delivery system to efficiently manage the waste heat generated onboard an electric aircraft. The heat pipe system will interface with NASA GRC’s thermoacoustic heat pump in order to recycle waste heat by transporting thermal energy to various end users onboard the aircraft. This paper discusses the layout of theoretical heat pipe networks for a MW-class commercial electric aircraft. This is followed by a discussion of progress made on the development of a novel two-phase heat transport system with solid-state thermal switching and control capabilities.

Exergy↗
NASA NTRS1979

Thermal study of interface between the Orbiter cold plate and typical Shuttle spacecraft payload flight electronics

Spacelab provides a set of Freon line plumbing and cold plates for experiment equipments which are located in the Shuttle pallet and which need active thermal control. The reported study deals with the thermal problem of attaching a Command and Data Handling module with various electronic boxes whose combined footprints on the baseplate are much larger than the cold plate. A description of two modules and the cold plate assembly in the pallet is presented and a thermal model description is provided. The method employed in modeling heat pipes-honey-comb matrix is based upon an effective conductance between the heat pipe vapor and the walls of the heat pipe. The considered thermal models and a computer program are used to perform steady-state thermal analyses. The temperature gradients in the large module baseplate attached to the small cold plate are predicted as a function of the interface plate thickness.

Hwangbo, H.↗
NASA NTRS2019

Two-Phase Convection Heat Transfer Correlations for Liquid Hydrogen Pipe Chilldown

Recently, heat transfer correlations based on liquid nitrogen (LN2) and liquid hydrogen (LH2) pipe quenching data were developed to improve the predictive accuracy of lumped node codes like SINDA/FLUINT and the Generalized Fluid System Simulation Program (GFSSP). After implementing these correlations into both programs, updated model runs showed strong improvement in LN2 pipe chilldown modeling but only modest improvement in LH2 modeling. Due to large differences in thermal and fluid properties between the two fluids, results indicated a need to develop a separate set of LH2-only correlations to improve the accuracy of the simulations. This paper presents a new set of two-phase convection heat transfer correlations based on LH2 pipe quenching data. A correlation to predict the bulk vapor temperature was developed after analysis showed that high amounts of thermal nonequilibrium of the liquid and vapor phases occurred during film boiling of LH2. Implemented in a numerical model, the new correlations achieve a mean absolute error of 19.5 K in the predicted wall temperature when compared to recent LH2 pipe chilldown data, an improvement of 40% over recent GFSSP predictions. This correlation set can be implemented in simulations of the transient LH2 chilldown process. Such simulations are useful for predicting the chilldown time and boil-off mass of LH2 for applications such as the transfer of LH2 from a ground storage tank to the rocket vehicle propellant tank, or through a rocket engine feedline during engine startup.

critical heat flux↗
NASA NTRS1995

Numerical Prediction of Turbulent Oscillating Flow and Heat Transfer in Pipes with Various End Geometries

Unsteady flow is present in man, machine and nature. The flow of blood in arteries and capillaries in the human body is pulsatile-composed of a mean flow superposed with an oscillating component. The tides that wash in and out of rivers, harbors and estuaries are unsteady flows with very long periods of oscillation. Many engineering devices employ pulsatile and oscillating flow. Pulsating flow is defined here as a periodic flow with a net displacement of fluid over each flow cycle. Oscillating flow is defined as a period flow with a zero mean over each cycle. The subject of this thesis is oscillating flow and heat transfer in pipes which make up the heater and cooler sections of the NASA Space Power Research Engine (SPRE) currently under development. This engine uses the Stirling cycle as the thermal energy converter in a power plant for future space applications. The information presented in this thesis will of course be applicable to the design of many types of machinery which employ oscillating flow and heat transfer.

Oseid, Kirk Leroi↗
NASA NTRS1987

Hybrid honeycomb panel heat rejection system

The evolution of a hybrid honeycomb panel heat rejection system concept for future high-power spacecraft is described. Performance evaluation of this heat pipe-based hybrid radiator is based on data and prediction models from a developmental component hardware testing program. The concept integrates three high-performance components into an optimized radiator system. These components are the sideflow heat pipe transport leg, honeycomb panel evaporator, and light-weight high-efficiency heat pipe fins. A 3.05 m (10 ft.) long hybrid radiator was designed considering remnant hardware available from other Hughes programs. The key performance objective for the hybrid radiator was to demonstrate high thermal transport capacity, increased radiating fin lengths, improved thermal efficiency across structural boundaries, and reduced weight. Analysis showed that 9000 W can be transported over a 3.05 m radiator and that finlengths of up to 1 m are possible.

Tanzer, H. J.↗
DOE OSTI2023

Development of a BlueCRAB/MELCOR Framework for Supporting Realistic Mechanistic Source Term Calculations in Microreactors

Efforts are currently underway to deploy microreactor modeling and simulation tools to better support vendors and regulatory authorities in submitting and reviewing licensing applications. In particular, the Nuclear Regulatory Commission is expected to rely on the Comprehensive Reactor Analysis Bundle (BlueCRAB) multiphysics toolset in performing design- and beyond-design-basis accident analyses. In addition, the Nuclear Regulatory Commission has been using the MELCOR code to estimate mechanistic source terms during accidents. As MELCOR relies on isotopic inventory and reactor temperature/power evolution profiles during accident conditions—all of which can theoretically be obtained from BlueCRAB—the ultimate goal of this activity is to establish a common BlueCRAB-MELCOR framework. However, prior to the present research, BlueCRAB had never been used to calculate such quantities of interest at the full-core level. While there are many Monte Carlo (MC) codes capable of computing such quantities of interest, they are unable to readily account for multiphysics feedback. BlueCRAB allows for the coupling of different physics codes together to perform multiphysics-informed calculations. Therefore, the purpose of this fiscal year 2023 work is to investigate the feasibility and challenges of performing such calculations within BlueCRAB so as to generate the data that MELCOR relies on. To demonstrate the methodology, the proposed workflow was applied to a prototypical heat pipe-cooled microreactor model. To predict isotopic concentrations (taking into account the ac- cumulation of fission products during operation), the necessary microscopic cross sections were generated via OpenMC and tabulated with respect to temperature and burnup. Next, a recently developed capability in Griffin (the reactor physics application in BlueCRAB) was used to convert the OpenMC output format into the ISOXML format used by Griffin. A multiphysics microscopic depletion calculation that involved performing a coupled full-core, heterogeneous neutron trans- port and thermal calculation at each depletion step was conducted to deplete the core to end of life (EOL) conditions so as to provide both isotopics and the initial condition for the transient calculation. Following a brief null-transient to verify that the initial condition had been properly restarted and was indeed in thermal equilibrium, a heat pipe failure transient was simulated. Thus, the entire workflow of using BlueCRAB to generate MELCOR inputs, from cross-section generation to producing isotopic inventory and power/temperature evolution profiles during transients, is demonstrated. This report also details the identified gaps in the workflow and how they were (for the most part) addressed. Future work should focus on directly including MEL- COR into the workflow by performing a MELCOR calculation using the BlueCRAB-generated input data. In addition, the heat pipe reactor design should be improved so as to reflect more prototypical burnup characteristics at EOL.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1993

Low Reynolds number kappa-epsilon and empirical transition models for oscillatory pipe flow and heat transfer

Stirling engine heat exchangers are shell-and-tube type with oscillatory flow (zero-mean velocity) for the inner fluid. This heat transfer process involves laminar-transition turbulent flow motions under oscillatory flow conditions. A low Reynolds number kappa-epsilon model, (Lam-Bremhorst form), was utilized in the present study to simulate fluid flow and heat transfer in a circular tube. An empirical transition model was used to activate the low Reynolds number k-e model at the appropriate time within the cycle for a given axial location within the tube. The computational results were compared with experimental flow and heat transfer data for: (1) velocity profiles, (2) kinetic energy of turbulence, (3) skin friction factor, (4) temperature profiles, and (5) wall heat flux. The experimental data were obtained for flow in a tube (38 mm diameter and 60 diameter long), with the maximum Reynolds number based on velocity being Re(sub max) = 11840, a dimensionless frequency (Valensi number) of Va = 80.2, at three axial locations X/D = 16, 30 and 44. The agreement between the computations and the experiment is excellent in the laminar portion of the cycle and good in the turbulent portion. Moreover, the location of transition was predicted accurately. The Low Reynolds Number kappa-epsilon model, together with an empirical transition model, is proposed herein to generate the wall heat flux values at different operating parameters than the experimental conditions. Those computational data can be used for testing the much simpler and less accurate one dimensional models utilized in 1-D Stirling Engine design codes.

Bauer, Christopher↗
NASA NTRS2023

Universal Two-Phase Convection Heat Transfer Correlations for Cryogenic Pipe Chilldown

This paper presents a set of universal two-phase convection heat transfer correlations for modeling boiling heat transfer during pipe chilldown fit over the widest available range of cryogenic fluids and thermodynamic conditions. The correlations improve upon prior correlations that were developed separately for liquid nitrogen (LN2) and liquid hydrogen (LH2) pipe quenching datasets. The new correlations include equations to calculate the single-phase vapor heat transfer, film boiling heat transfer, transition boiling heat transfer, nucleate boiling heat transfer, single-phase liquid heat transfer, bulk vapor temperature during high quality film boiling, Leidenfrost temperature, critical heat flux, critical heat flux temperature, and the onset of nucleate boiling temperature. The correlations were validated against LH2, LN2, liquid methane, liquid oxygen, and liquid argon pipe quenching datasets. The eight datasets cover the following parameter ranges: pipe lengths of 0.1 to 6.5m; outer pipe diameters of 12.7 to 25.4 mm; pipe wall thicknesses from 0.51 to 1.64 mm; flow directions of upward, downward, and horizontal; gravity levels of 1g and 0g±0.01g. A numerical model assumes homogeneous mixing between the vapor and liquid and implicitly integrates the coupled energy equations for the pipe and fluid, as well as continuity for the fluid. The model was used to estimate the equilibrium quality and fluid mass accumulation along the pipes during chilldown from estimates of the fluid-pipe heat transfer extracted from temperature measurements. The correlations can be implemented in lumped parameter codes such as SINDA/FLUINT and the Generalized Fluid System Simulation Program (GFSSP) to improve the accuracy of chilldown time and chilldown boiloff mass predictions. Such predictions are useful for designing ground or in-space cryogenic liquid transfer systems.

Universal Correlations↗
DOE OSTI2025

Thermo-hydraulic steam pipe models for district heating simulations: Simplifications to balance accuracy and simulation speed

Steam piping networks are essential for optimizing performance in industrial processes and district heating systems. However, dynamic models that balance thermo-hydraulic accuracy with computational efficiency remain limited. In response, this paper presents a new discretized steam pipe model based on the plug flow approach, capturing key thermo-hydraulic behaviors while simplifying steam phase change processes. Implemented in Modelica, the model accurately calculates temperature and pressure distributions along steam pipelines. To improve computational efficiency for district-scale simulations, five model simplifications are introduced: lumped thermo-hydraulic functions, empirical correlations, fluid state approximations, steady-state dynamics and inclusion of flow derivatives. These simplified models achieve 85%-98% accuracy in predicting pressure drop and condensation losses, including dynamic condensate behavior during pipe warm-up—a factor often overlooked in existing models. The models support diverse network configurations, scaling effectively to systems with multiple distribution pipes and connected building loads. Discrete models provide detailed insights but exhibit a cubic increase in simulation time as the network scales by N connected building O(N 2.42 ). In contrast, lumped models simulate 10–28 times faster than discrete, offering quadratic scaling of simulation time O(N 1.73 ). However, they still require 6 times more computation time than a lossless network, highlighting the inherent computational challenges of modeling compressible fluid flow. In conclusion, the steady-state lumped variant, with its near-linear scalability in computational time O(N 1.01 ), emerges as an efficient solution for preliminary design evaluations and extensive parametric studies.

15 GEOTHERMAL ENERGY↗
DOE OSTI2025

Spatially and temporally resolved plasma parameter estimations of laser heated MagLIF relevant gas pipes at NIF

The ability to control laser pre-heat is an integral part of the inertial confinement fusion concept known as Magnetized Liner Inertial Fusion. This process is studied at the National Ignition Facility (NIF) where 4 of the 192 laser beams are propagated through a 1-cm long gas cell where they deposit >20 kJ of energy into the gaseous fuel via inverse bremsstrahlung absorption. This process ionizes the gas, producing a plasma that follows behind the laser front and expands over the radius of the cell. Emission from this plasma, as viewed by a gated x-ray detector, can be used to build spatially and temporally resolved estimations of the pre-heat plasma's density and temperature profiles. This can then be used to estimate the plasma pressure, internal energy, and radiation losses. Estimations show the evolution of the plasma in magnetized and unmagnetized gas cells filled with ambient temperature neopentane (C5H12) +1% Ar, as well as unmagnetized cryogenically cooled (32 K) deuterium +1% Ne filled targets. This analysis shows the effects of initial gas-fill density, composition, and axial magnetization on the time-dependent plasma parameters. Previously, these parameters at the NIF had not been experimentally characterized, and these estimations provided a potential new means of testing radiation magneto-hydrodynamic predictive capability models. Results in unmagnetized targets have strong agreement with simulations. However, in targets with a 19 T applied axial magnetic field, this method yields electron temperatures up to 100% hotter than those predicted by HYDRA codes.

Bremsstrahlung↗