SMR.INTEL
OKLOAurora+15MW.SMRSMRVOYGR+77MW.NuScaleNNENano Nuclear+Micro.ReactorLTBRLightbridge+Fuel.TechLEUCentrus+HALEU.ProdCCJCameco+Uranium.SupplyUECUranium Energy+U3O8.MiningCEGConstellation+TMI.RestartGEVGE Vernova+BWRX-300BWXBWXT+TRISO.FuelFUND.YTD2025-26$2.5B+.Raised

Nuclear & SMR Glossary

The definitive reference for nuclear and SMR terminology — reactor types, fuel, enrichment, regulatory, and deployment terminology.

50 terms defined · 8 categories
DeploymentEconomicsFuel-technologyNuclear-physicsPerformance-metricsReactor-componentsReactor-typesRegulatory
Deployment
Behind-the-Meter GenerationPower generation installed directly at a customer's facility and connected on the customer side of the utility meter, providing electricity without using the public transmission and distribution grid.→
DOME Test FacilityThe Demonstration of Microreactor Experiments facility at Idaho National Laboratory, a purpose-built test bed designed to host and evaluate prototype microreactors under controlled conditions with established safety approvals.→
Economics
Baseload PowerThe minimum level of electricity demand on a grid over a given time period, typically served by power plants that operate continuously at high capacity factors with low marginal generation costs.→
First of a Kind (FOAK)The first commercial unit of a new nuclear reactor design to be built, carrying the full burden of first-build costs including design finalization, regulatory licensing, supply chain development, and construction learning.→
Levelized Cost of EnergyThe average net present cost of electricity generation over a power plant's lifetime, expressed in dollars per megawatt-hour, accounting for capital costs, fuel, operations, maintenance, and decommissioning.→
Nth of a Kind (NOAK)A mature production unit of a nuclear reactor design that benefits from accumulated manufacturing learning, established supply chains, standardized construction procedures, and fleet deployment economics.→
Power Purchase AgreementA long-term contract between an electricity generator and a buyer (typically a utility or corporate offtaker) that establishes the price, volume, and terms for the sale of power over a defined period, providing revenue certainty for project financing.→
Fuel-technology
Dry Cask StorageA method for storing spent nuclear fuel in robust steel and concrete containers on a concrete pad at the reactor site, using passive air cooling without the need for water or active cooling systems.→
High-Assay Low-Enriched UraniumUranium enriched to between 5% and 20% U-235 concentration, required as fuel by most advanced reactor designs.→
LEU+ (5-10% Enrichment)Uranium enriched to between 5% and 10% U-235 concentration, occupying the gap between conventional LEU and the full HALEU range, and requiring less enrichment effort while enabling improved reactor performance.→
Low-Enriched UraniumUranium enriched to less than 5% uranium-235 concentration, the standard fuel form for conventional commercial nuclear power reactors and several SMR designs.→
Mixed Oxide FuelNuclear fuel composed of a blend of plutonium oxide and depleted or natural uranium oxide, enabling the use of plutonium recovered from spent fuel reprocessing or weapons dismantlement as reactor fuel.→
Separative Work UnitA unit of measurement for the effort required to separate uranium-235 from uranium-238 during the enrichment process, reflecting both the quantity of uranium processed and the degree of enrichment achieved.→
Spent Nuclear FuelIrradiated nuclear fuel that has been removed from a reactor after its fissile content has been depleted to the point where it can no longer efficiently sustain a chain reaction, remaining highly radioactive and requiring careful management.→
TRISO Fuel ParticlesTri-structural isotropic fuel particles consisting of a uranium kernel encased in multiple layers of ceramic and carbon coatings, providing exceptional fission product retention at extreme temperatures.→
Uranium EnrichmentThe industrial process of increasing the concentration of fissile uranium-235 isotope in natural uranium from its natural abundance of 0.7% to levels suitable for reactor fuel.→
Nuclear-physics
Breeding RatioThe ratio of new fissile material produced in a nuclear reactor to the fissile material consumed, where a ratio greater than 1.0 indicates the reactor produces more fuel than it burns (breeding).→
Decay HeatThe thermal energy produced by the radioactive decay of fission products and actinides in nuclear fuel after the fission chain reaction has been shut down, requiring continuous cooling to prevent fuel damage.→
Fast Neutron SpectrumA reactor operating regime in which the nuclear chain reaction is sustained by fast (high-energy) neutrons without the use of a moderator, enabling fuel breeding, waste transmutation, and higher fuel utilization.→
Fuel BurnupA measure of the total energy extracted from nuclear fuel, expressed in megawatt-days per metric ton of uranium (MWd/tU) or as a percentage of fissile atoms that have undergone fission.→
Neutron ModeratorA material used in thermal-spectrum nuclear reactors to slow fast neutrons produced by fission to thermal energies, where the probability of inducing further fission in fissile isotopes is dramatically higher.→
Nuclear CriticalityThe state in which a nuclear fission chain reaction is self-sustaining, with each generation of fission events producing exactly enough neutrons to maintain the reaction at a steady rate.→
Thermal Neutron SpectrumA reactor operating regime in which the nuclear chain reaction is sustained by thermalized (low-energy) neutrons that have been slowed by a moderator to energies in thermal equilibrium with their surroundings.→
Performance-metrics
Capacity FactorThe ratio of a power plant's actual electrical output over a given period to its maximum possible output if it operated at full nameplate capacity continuously, expressed as a percentage.→
Load-Following CapabilityThe ability of a power plant to adjust its electrical output in response to real-time changes in grid demand, essential for integration with variable renewable energy sources.→
Refueling OutageA scheduled reactor shutdown period during which spent fuel assemblies are removed from the core and replaced with fresh fuel, representing the primary planned downtime for nuclear power plants.→
Reactor-components
Containment StructureThe engineered barrier, typically a reinforced concrete and steel structure, designed to prevent the release of radioactive materials to the environment during normal operations and accident conditions.→
Defense-in-DepthA nuclear safety philosophy that employs multiple independent and redundant layers of protection, both physical barriers and administrative controls, to prevent accidents and mitigate their consequences.→
Passive Safety SystemsNuclear reactor safety systems that rely on natural physical phenomena such as gravity, natural convection, and thermal expansion rather than active mechanical components or operator intervention to maintain safe conditions.→
Reactor-types
Boiling Water ReactorA nuclear reactor in which ordinary water serves as both coolant and moderator, boiling directly in the reactor core to produce steam that drives the turbine-generator in a single-loop design.→
Fluoride Salt-Cooled High-Temperature ReactorA reactor design that combines fluoride molten salt coolant with solid TRISO fuel, achieving high temperatures and atmospheric-pressure operation without dissolving fuel in the coolant.→
Heat Pipe ReactorA nuclear reactor design that uses sealed heat pipes filled with a working fluid (typically sodium or potassium) to passively transport thermal energy from the reactor core to a heat exchanger, eliminating the need for coolant pumps and piping loops.→
High Temperature Gas-Cooled ReactorA nuclear reactor that uses helium gas as the primary coolant and graphite as the moderator, achieving outlet temperatures above 700 degrees Celsius for electricity generation and industrial process heat applications.→
Lead-Cooled Fast ReactorA nuclear reactor that uses liquid lead or lead-bismuth eutectic as the primary coolant, operating in the fast neutron spectrum at atmospheric pressure with inherent safety advantages from lead's high boiling point and chemical inertness.→
MicroreactorA nuclear reactor producing less than approximately 20 MWe of electrical output, designed for factory fabrication, truck transportability, rapid deployment, and operation in remote or distributed settings without traditional nuclear infrastructure.→
Molten Salt ReactorA class of nuclear reactor that uses molten fluoride or chloride salt as the primary coolant or as both the coolant and the fuel carrier, enabling high-temperature operation at atmospheric pressure.→
Pressurized Water ReactorA nuclear reactor that uses ordinary water under high pressure as both the coolant and neutron moderator, with a separate secondary steam loop to drive the turbine, representing the most widely deployed reactor type globally.→
Small Modular ReactorA nuclear reactor with electrical output less than 300 MWe, designed for factory fabrication and modular deployment.→
Sodium-Cooled Fast ReactorA nuclear reactor that uses liquid sodium metal as the primary coolant, operating in the fast neutron spectrum without a moderator, enabling efficient fuel utilization and the potential to breed fissile material or transmute nuclear waste.→
Regulatory
Advanced Reactor Demonstration ProgramA U.S. Department of Energy program providing multi-billion-dollar cost-sharing to accelerate the construction of first-of-a-kind advanced nuclear reactor demonstration projects.→
Canadian Nuclear Safety CommissionCanada's independent nuclear regulatory body responsible for licensing nuclear facilities, regulating nuclear substances and radiation devices, and ensuring compliance with international nuclear safeguards obligations.→
Combined License (COL)An NRC authorization under 10 CFR Part 52 that combines the construction permit and operating license into a single proceeding, allowing the holder to both build and operate a nuclear power plant upon completion of construction.→
Construction PermitAn NRC authorization under 10 CFR Part 50 that allows the holder to begin constructing a nuclear power plant at a specific site, subject to subsequent application for an operating license before fuel loading.→
Generic Design Assessment (UK)The UK Office for Nuclear Regulation's process for assessing new nuclear reactor designs against safety, security, and environmental standards before site-specific licensing, enabling regulatory pre-approval of reactor technologies.→
National Reactor Innovation CenterA DOE program at Idaho National Laboratory that provides physical infrastructure, testing capabilities, and regulatory pathway support to accelerate the demonstration and deployment of advanced nuclear reactor concepts.→
NRC Design CertificationAn NRC-issued rulemaking that approves a nuclear reactor design independent of a specific site, allowing the certified design to be referenced in applications for combined licenses to build and operate plants.→
NRC Part 50 LicensingThe traditional two-step NRC licensing process under 10 CFR Part 50, requiring separate approval of a Construction Permit and an Operating License for nuclear power plants.→
NRC Part 52 LicensingThe NRC's one-step licensing framework under 10 CFR Part 52, providing combined construction and operating authorization through Design Certifications, Early Site Permits, and Combined Licenses.→
NRC Part 53 FrameworkA new technology-inclusive, risk-informed, and performance-based regulatory framework being developed by the NRC for licensing advanced nuclear reactors, designed to accommodate non-light-water technologies more efficiently.→
Nuclear Regulatory CommissionThe independent U.S. federal agency responsible for regulating civilian nuclear power, nuclear materials, and radioactive waste to protect public health, safety, and the environment.→