Open-source nuclear microreactor economics
MOUSE (Microreactor Optimization Using Simulation and Economics) is a framework connecting early-stage microreactor design choices to bottom-up technoeconomic outcomes. By coupling physics-based core simulations with detailed cost estimation, it helps engineers, investors, and policy makers see how geometry, fuel, enrichment, and operating assumptions drive capital cost and LCOE before major decisions are locked in.
Motivation
Nuclear microreactors are being developed for transportable, rapidly deployable, resilient power in remote or infrastructure-limited locations. Their small size and modularity can also amplify diseconomies of scale: first-of-a-kind costs may be driven by fuel fabrication, specialty materials, indirect costs, and other accounts that do not shrink proportionally with power.
Historically, reactor development has treated physics and engineering as the primary design drivers, with economics arriving later. For microreactors, that sequencing is risky because fuel loading mass, enrichment, core geometry, materials, and balance-of-plant complexity can be largely fixed by the end of core design.
MOUSE makes economics a first-class input to design by building costs from first principles rather than scaling down large reactor estimates. It helps teams test whether choices such as exotic fuel forms, reflector changes, longer fuel lifetime, or material substitutions actually improve levelized cost of electricity.
What MOUSE Does
MOUSE integrates OpenMC Monte Carlo neutron transport, simplified balance-of-plant calculations, and a bottom-up cost engine built from MARVEL project data and open literature. It produces FOAK and NOAK projections for liquid-metal thermal, gas-cooled, and heat-pipe microreactor concepts, connecting design choices to cost, fuel cycle, neutronics, thermal, and transportability outcomes.
Estimate overnight capital cost, total capital investment, LCOE, levelized cost of heat, fuel lifetime, burnup, enrichment needs, and first-order thermal hydraulic sizing.
Compare LTMR, GCMR, and HPMR designs while checking geometry, materials, fuel enrichment, financing assumptions, IRA credits, market conditions, and transport limits for truck, rail, and sea containers.
Run custom OpenMC and WATTS workflows in Python for parametric studies, sensitivities, and uncertainty propagation, or use the Streamlit app's precomputed nearest-neighbor results for second-scale estimates.
The MOUSE Python package is published by the Idaho National Laboratory GitHub organization for users who need full control over their analysis. It exposes the complete OpenMC Monte Carlo neutron transport workflow, WATTS-powered parametric and sensitivity studies, custom geometry and materials, modifiable balance-of-plant assumptions, and the full bottom-up cost engine.
Define custom geometries, materials, reactor types, enrichment levels, core layouts, and balance-of-plant assumptions for deeper studies than the curated web app exposes.
Access bottom-up cost accounts for capital, fuel cycle, financing, operations and maintenance, replacements, decommissioning, FOAK learning, and NOAK deployment cases.
Connect reactor design, balance-of-plant sizing, uncertainty ranges, Code of Accounts results, cost-driver rankings, LCOE, LCOH, and market benchmarks in one reproducible workflow.
These studies show why coupling physics and economics matters: choices that extend fuel lifetime or shrink the core can still lose economically once material cost, fuel loading, and deployment assumptions are included.
The hosted app makes MOUSE accessible to engineers, investors, and policy makers without any simulation environment or code setup. Instead of running full Monte Carlo and depletion calculations at runtime, it serves precomputed parametric results through fast nearest-neighbor interpolation, returning updated cost estimates within seconds as users adjust inputs for LTMR, GCMR, and HPMR designs. The app organizes results into design and cost summaries, transportability checks, scoping metrics, cost decomposition, and market and geographic competitiveness views for scoping, comparison, and stakeholder communication.
Reactor Concepts
The repository includes reference models for liquid-metal, gas-cooled, and heat-pipe microreactor concepts. These are pre-conceptual designs intended for transparent technoeconomic assessment.
Liquid-metal thermal microreactor reference concept.
Gas-cooled TRISO-fueled microreactor reference concept.
Heat-pipe microreactor reference concept.
Research Basis
MOUSE builds on open-source reactor modeling, bottom-up nuclear cost estimation, and published microreactor technoeconomic analysis.
Launch the hosted app to compare reactor inputs, uncertainty ranges, FOAK and NOAK costs, LCOE, fuel cycle metrics, and cost drivers.