Physics / operating evidence
Quality and relevance of demonstrated reactor or plasma operation.
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Ten-Phase Reactor Program · Phase 4
Compare the evidence before choosing the machine
Twenty-three fission and fusion families are evaluated against the same eight public-safe evidence criteria. The score measures evidence readiness—not beauty, promise, theoretical elegance, or commercial destiny.
23 evaluated candidates8 weighted criteria100-point evidence indexPhase 3 lifecycle work pending
Evidence Readiness Index
Cross-family comparison matrix
Scores run from 0 to 5 for each criterion and are weight-normalized to 100. Unknown or unproven performance is not credited.
| Candidate | Branch | Maturity | Evidence score | Decision lane | Next evidence gate |
|---|---|---|---|---|---|
| Boiling Water ReactorFIS-BWR · Light-water | Fission | Established commercial fleet | 92 |
Established reference | Retain as a fleet reference for direct-cycle light-water architecture and operating evidence. |
| Pressurized Water ReactorFIS-PWR · Light-water | Fission | Established commercial fleet | 92 |
Established reference | Retain as the principal fleet and licensing reference; new deployment remains project- and jurisdiction-specific. |
| Marine ReactorFIS-MARINE · Marine propulsion / power | Fission | Extensive naval heritage; limited civilian deployment | 82 |
Mission-specific established reference | Do not transfer naval evidence directly to civilian use; port, shipyard, liability, safeguards, decommissioning, and public licensing remain separate gates. |
| Gas-Cooled ReactorFIS-GAS · Gas-cooled | Fission | Commercial heritage plus advanced variants | 80 |
Established / development reference | Separate established carbon-dioxide-cooled fleets from helium and advanced modular concepts before selection. |
| Pulsed Research ReactorFIS-PULSE · Research facility | Fission | Established specialized research role | 76 |
Mission-specific established reference | Retain as a research-facility class, not as a steady grid-generation candidate. |
| Small Modular ReactorFIS-SMR · Deployment format | Fission | Licensing, first deployment, and active development | 76 |
Conditional deployment track | Score the underlying reactor and fuel cycle; SMR is not one technology and does not automatically reduce cost or waste. |
| Pebble-Bed ReactorFIS-PEBBLE · High-temperature gas-cooled | Fission | Limited deployment plus continuing development | 70 |
Conditional development track | Advance where coated-particle fuel quality, graphite lifecycle, fuel handling, heat conversion, and licensing evidence close together. |
| Sodium-Cooled Fast ReactorFIS-SFR · Fast-spectrum liquid metal | Fission | Demonstration and limited-deployment heritage | 68 |
Strategic development track | Advance as a coupled reactor-plus-fuel-cycle program; fast spectrum can improve uranium use but does not eliminate fission products or repositories. |
| Space ReactorFIS-SPACE · Space power / propulsion | Fission | Flight heritage at small scale and active development | 62 |
Mission-specific conditional track | Advance only against a defined mission with launch approval, re-entry safety, shielding, reliability, retrieval, and disposal architecture. |
| TRISO-Fueled MicroreactorFIS-TRISO-MICRO · Microreactor / coated-particle fuel | Fission | Advanced development and demonstrations | 56 |
Conditional deployment track | Advance only with representative integral testing, qualified fuel supply, transport/security plan, maintainability, and return/disposal pathway. |
| Transportable / Mobile ReactorFIS-MOBILE · Deployment format | Fission | Demonstration and active development | 56 |
Mission-specific conditional track | Select the underlying reactor first, then close transport, security, return logistics, site restoration, and end-of-life obligations. |
| Lead-Cooled Fast ReactorFIS-LFR · Fast-spectrum heavy liquid metal | Fission | Special-application heritage and civilian development | 42 |
Advanced-reactor research reserve | Require corrosion, erosion, coolant chemistry, activation, inspection, repair, fuel-cycle, and civilian licensing evidence. |
| Molten Salt ReactorFIS-MSR · Salt-cooled or salt-fueled | Fission | Historical experiments and active development | 42 |
Advanced-reactor research reserve | Do not treat all MSRs alike; require salt chemistry, corrosion, cleanup, safeguards, off-gas, maintenance, and final-waste evidence for the exact design. |
| Tokamak FusionFUS-TOK · Magnetic confinement | Fusion | Major experimental programs; no commercial electricity fleet | 40 |
Primary fusion baseline | Advance through burning-plasma, heat-exhaust, blanket, tritium, materials, remote-maintenance, availability, and net-electric gates. |
| Stellarator FusionFUS-STE · Magnetic confinement | Fusion | Established experimental family with active optimization | 36 |
Primary fusion baseline | Advance beside tokamak work until optimized confinement, coil manufacture, exhaust, blanket, neutron access, and maintainability are demonstrated together. |
| Fusion Power-Plant IntegrationFUS-PLANT · Cross-cutting enabling architecture | Fusion | Subsystem research; no integrated fusion-electric plant | 26 |
Cross-cutting evidence gate | This is not a confinement candidate. Every fusion line must close breeding or external fuel supply, neutron materials, heat exhaust, remote maintenance, availability, licensing, waste, and net-electric balance here. |
| Supercritical Water ReactorFIS-SCWR · Generation-IV water-cooled | Fission | Conceptual and research development | 24 |
Long-range research reserve | Hold until representative fuel, cladding, chemistry, pressure-boundary, transient, maintenance, and integral-system evidence exists. |
| Inertial-Confinement FusionFUS-ICF · Driver-compressed targets | Fusion | Laboratory ignition; repetitive power plant unproven | 20 |
Fusion research reserve | Require efficient repetitive drivers, inexpensive targets, chamber clearing, durable optics, thermal capture, tritium, maintenance, and net-electric evidence. |
| Field-Reversed Configuration / SpheromakFUS-FRC · Compact toroid | Fusion | Frontier laboratory research | 18 |
Fusion research reserve | Require formation repeatability, sustainment, confinement, impurity control, neutron system, heat removal, fuel cycle, and integrated plant evidence. |
| Magnetic-Mirror FusionFUS-MIR · Open-ended magnetic confinement | Fusion | Historical and renewed laboratory research | 18 |
Fusion research reserve | Require end-loss control, stable confinement, collector performance, neutron and blanket integration, fuel-specific conversion, and closed plant balance. |
| Magneto-Inertial FusionFUS-MIF · Hybrid pulsed confinement | Fusion | Laboratory and demonstration research | 18 |
Fusion research reserve | Require repeatable plasma formation, efficient compression, chamber or liner lifetime, heat recovery, cadence, maintenance, and closed plant balance. |
| Aviation ReactorFIS-AVIATION · Historical propulsion research | Fission | Historical research; no deployed civilian system | 16 |
Historical / no civilian down-select | Retain for historical classification only; shielding mass, crash consequence, handling, maintenance, and licensing block a credible civil path. |
| Z-Pinch and Pulsed FusionFUS-ZP · Current-driven compression | Fusion | Established research tools; energy plant is frontier research | 16 |
Fusion research reserve | Require stability, reusable hardware, repetition, driver efficiency, chamber survival, heat capture, and credible availability evidence. |
Interpretation boundary: The index is a transparent screening tool, not a safety finding, economic forecast, construction recommendation, investment rating, or licensing decision.
Weighted Criteria
What earns evidence credit
Integrated plant evidence
Evidence for a complete energy plant rather than an isolated core, pulse, or plasma.
Fuel / resource readiness
Credible supply, fabrication, accountancy, recovery, and stewardship pathway.
Materials readiness
Representative irradiation, corrosion, temperature, fatigue, joining, and lifetime evidence.
Availability / maintenance
Inspection, repair, replacement, outage, logistics, and remote-maintenance evidence.
Safety / licensing evidence
Applicable standards, regulator experience, safety case, safeguards, and emergency-planning maturity.
Deployment / modular fit
Ability to serve the stated mission with credible construction, transport, siting, and interface architecture.
Waste / end-of-life pathway
Defined spent-fuel or activation-waste, decommissioning, recycling, storage, transport, and disposal pathway.
A high field, small plasma, long pulse, ignition shot, passive feature, modular label, or advanced material can strengthen one criterion. None of those facts closes the complete plant by itself.
Controlled Portfolio Result
Phase 4 down-selection lanes
Fleet and licensing reference
Pressurized-water and boiling-water reactors
They provide the deepest commercial operating, maintenance, supply-chain, regulatory, and lifecycle evidence. This is an evidence reference, not an automatic instruction to build another large plant.
Modular and distributed deployment
Design-specific SMR plus TRISO microreactor pathways
Retain both, but never score the word modular by itself. The underlying coolant, spectrum, fuel, conversion, transport, security, maintenance, and waste system must close.
High-temperature industrial heat
Gas-cooled and pebble-bed pathways
These retain meaningful operating and fuel evidence while still requiring design-specific qualification, graphite lifecycle, conversion, and licensing closure.
Resource utilization and actinide research
Sodium-cooled fast reactor pathway
It has the strongest fast-reactor evidence base in this portfolio, but only as a coupled reactor and fuel-cycle program. It does not eliminate fission products or repositories.
Advanced fission reserve
Molten-salt, lead-cooled, and supercritical-water pathways
Maintain research portfolios until chemistry, materials, inspection, fuel-cycle, integral-system, availability, and licensing gates are met.
Primary fusion physics lines
Tokamak and optimized stellarator in parallel
Tokamaks lead in integrated burning-plasma preparation; optimized stellarators preserve a credible steady-state line. Neither has closed the complete net-electric plant.
Fusion research reserve
Inertial, magneto-inertial, Z-pinch, compact-toroid, and mirror pathways
Preserve competition and learning, but do not promote them to plant candidates before representative repetition, materials, fuel, heat, maintenance, and energy-balance evidence.
23rd-century concepts
Unscored architecture reserve
Future Aurora concepts remain explicitly speculative and cannot outrank real machines using imagined performance.
Program Discipline
Phase 3 remains pending
Fuel resources, spent fuel, activation waste, recycling, decommissioning, and final disposal already influence this screen, but the dedicated Phase 3 lifecycle authority has not been completed. Phase 4 does not silently close that gap.
Authoritative Public Evidence
Reference basis
IAEA PRIS — official operating reactor data ↗IAEA ARIS — advanced reactor information ↗IAEA Fast Reactors ↗IAEA Small Modular Reactors ↗IAEA Nuclear Power Reactors ↗DOE Fusion Energy Strategy 2024 ↗ITER — Making Fusion Work ↗LLNL NIF — Achieving Fusion Ignition ↗Max Planck IPP — Wendelstein 7-X ↗Chinese Academy of Sciences — EAST 1,066-second milestone ↗NRC — Radioactive Waste Background ↗NEA/IAEA — Uranium 2024 ↗