Fusion Power Plant & Tritium Lab

Explore magnetic confinement D-T fusion physics, high-temperature superconducting (HTS) $B^4$ power scaling, Lawson triple products, tritium breeding ratio (TBR), and 30-year LCOE.

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Reactor Archetypes:
D-T Fusion Power
- MW
Core reaction output
Thermal Power (BoP)
- MWth
Alpha + blanket multiplication
Net Electric Export
- MWe
Grid power delivery
Recirculating Fraction
- %
Auxiliary heating & cryo
Levelized Cost (LCOE)
$- /MWh
30-year lifecycle cost
Project NPV (30-Yr)
$- M
Net present value
Internal Rate of Return
- %
Project IRR
Tritium Breeding (TBR)
-
Fuel self-sufficiency
Reactor Physics & Economic Inputs
1. Plasma Geometry & Magnetic Field
3.3 m
Center-to-torus axis distance.
1.1 m
Plasma cross-section radius (defines aspect ratio R₀/a).
9.2 T
REBCO / HTS magnetic field. Fusion power scales as B₀⁴!
15.0
Ratio of fusion power to external auxiliary heating input (P_fus / P_aux).
2. Blanket & Power Conversion
42.0%
Supercritical CO₂ Brayton or advanced steam Rankine power cycle.
1.18x
Exothermic neutron-lithium capture thermal multiplication.
1.12
Must be ≥ 1.05 to account for decay and processing losses.
3. Commercial Project Finance
$5,400/kWe
Installed plant capital cost including magnets, cryostat, and BoP.
85%
Steady-state non-inductive operations and scheduled maintenance.
7.0%
$95/MWh
Tokamak Cross-Section & Energetics
HTS Confinement
CENTRAL SOLENOID Cryostat Envelope HTS Coil (REBCO) Li Breeding Blanket (TBR > 1.05) Tungsten Divertor 500 MWth Fusion 9.2 T (HTS Toroidal) TBR: 1.12 (Self-Sustaining)
Reactor Physics & Financial Breakdown
Plasma Volume / Aspect Ratio
- m³ / -
Aux Heating Power (P_aux)
- MWth
Alpha Self-Heating (20%)
- MWth
Fast 14.1 MeV Neutrons (80%)
- MWth
Gross Electrical Power
- MWe
Parasitic Aux / Cryo Load
- MWe
Annual Net Generation
- GWh/yr
Total Overnight CapEx
$- M
Annual O&M & Divertor Replacement
$- M/yr
Annual Net Operational Cash Flow
$- M/yr
Simple Payback Period
- yrs
5x5 Sensitivity Matrix: Magnetic Field (B₀) vs Plasma Gain (Q)

Explore how the on-axis toroidal magnetic field ($B_0$, 6.0 to 12.5 Tesla) and the plasma energy gain factor ($Q = P_{fus}/P_{aux}$, 10 to 45) impact the 30-year Levelized Cost of Electricity ($/MWh) and net electric generation (MWe). Higher magnetic fields exponentially shrink plant footprint and levelized costs via $B^4$ power scaling.

Fusion Energy Mastery Assessment
1. Why does magnetic confinement fusion power density scale with the fourth power of the magnetic field ($B^4$)?
2. Why must a commercial D-T fusion power plant achieve a Tritium Breeding Ratio (TBR) ≥ 1.05?
3. What is the fundamental definition of the Lawson criterion triple product ($n \cdot T \cdot \tau_E$)?
4. What constitutes the largest internal recirculating parasitic power consumer in a tokamak plant?
Engineering Deep-Dive: First-Principles Fusion Power
1. D-T Fusion Plasma Energetics & Partitioning

The most accessible terrestrial thermonuclear reaction fuses deuterium ($^2\text{H}$ or D) and tritium ($^3\text{H}$ or T) under temperatures exceeding 100 million Kelvin ($>10\text{ keV}$):

²H + ³H → ⁴He (3.52 MeV) + n (14.06 MeV) + 17.58 MeV Total

The 3.52 MeV positively charged alpha particle ($^4\text{He}$) remains magnetically confined within the plasma, transferring its kinetic energy directly to background ions via Coulomb collisions (plasma self-heating). The uncharged 14.06 MeV fast neutron escapes magnetic confinement immediately, carrying 80% of total reaction power across the first wall into the surrounding lithium blanket, where its kinetic energy is thermalized and transferred to a coolant loop.

2. The High-Temperature Superconductor (HTS) Revolution & $B^4$ Power Scaling

Historical tokamaks (such as JET and ITER) were constrained to magnetic fields of 5.3 Tesla by low-temperature superconductors ($\text{Nb}_3\text{Sn}$ / NbTi) operating at 4 Kelvin. The commercial emergence of Rare-Earth Barium Copper Oxide (REBCO) high-temperature superconducting tapes allows on-axis fields of 9 to 12+ Tesla at 20 Kelvin.

Because maximum stable plasma pressure scales as $p \propto B^2$, and fusion power density scales quadratically with pressure ($P_{fus} \propto p^2 \propto B^4$), increasing on-axis field from 5.3 T to 10.6 T increases fusion power density by a factor of 16. A commercial reactor producing 500 MW of fusion power can thus be built with a major radius of only 3.3 meters (ARC class) instead of ITER's 6.2 meters, reducing plant structural mass and capital costs by over 70%.

3. The Tritium Fuel Cycle & Self-Sufficiency

Unlike deuterium, which is abundant in ocean water ($\sim 33\text{ g/m}^3$), global commercial tritium inventory is limited to roughly 30 kg, primarily produced in Canadian CANDU reactors and decaying at 5.5% annually. Commercial fusion self-sufficiency requires in-situ breeding via neutron capture in lithium:

⁶Li + n → ⁴He + ³H + 4.78 MeV (Thermal Neutron Capture)
⁷Li + n → ⁴He + ³H + n' - 2.47 MeV (Fast Neutron Inelastic Scatter)

By pairing lithium-lead ($\text{Pb}_{83}\text{Li}_{17}$) or molten fluoride salt (FLiBe) with beryllium or lead neutron multipliers ($n, 2n$ reactions), reactors achieve Tritium Breeding Ratios (TBR) between 1.08 and 1.18, ensuring complete fuel autonomy.

Frequently Asked Questions

In magnetic confinement fusion, stable plasma pressure is fundamentally constrained by magnetohydrodynamic stability, governed by the Troyon beta limit (beta = 2 * mu_0 * p / B^2). Because maximum permissible plasma pressure scales quadratically with magnetic field (p ~ B^2), and D-T fusion reaction rate scales quadratically with plasma pressure/density (P_fus ~ p^2), the resulting fusion power density scales as the fourth power of the magnetic field (P_fus ~ B^4). Doubling the magnetic field from 5 Tesla to 10 Tesla yields a 16-fold increase in fusion power density, allowing compact commercial reactors.

Tritium is an extremely scarce radioactive isotope of hydrogen with a half-life of 12.32 years, with virtually no commercial global supply outside dwindling CANDU stockpiles. A commercial D-T fusion reactor must breed its own tritium by capturing fast 14.1 MeV fusion neutrons in a lithium-bearing blanket (via 6Li + n -> 4He + T and 7Li + n -> 4He + T + n'). The Tritium Breeding Ratio (TBR) is the ratio of tritium bred to tritium consumed. To compensate for radioactive decay, unrecovered tritium trapped in structural materials, and processing inefficiencies, a commercial plant requires TBR >= 1.05 to 1.15 to achieve self-sufficiency.

The Lawson criterion defines the minimum threshold where fusion energy production exceeds internal thermal conduction and radiation losses. Expressed as the plasma triple product of ion density (n), ion temperature (T ~ 10-20 keV or 100-200 million Celsius), and energy confinement time (tau_E), the condition requires n * T * tau_E >= 3 x 10^21 keV s/m^3. Ignition is achieved when alpha particle self-heating (20% of fusion energy) is sufficient to maintain plasma temperature without external auxiliary heating, corresponding to an infinite plasma gain factor (Q -> infinity).

A fusion plant requires substantial parasitic electrical power to sustain steady-state operations. Major auxiliary loads include: (1) external plasma heating and current drive systems (neutral beam injectors, gyrotrons, ion cyclotron antennas) operating at ~40-50% electrical efficiency; (2) cryogenic refrigeration plants maintaining superconducting magnet coils at 4 K (low-temperature superconductors) or 20-50 K (high-temperature REBCO superconductors); and (3) primary coolant pumps, liquid lithium-lead circulation loops, and vacuum pumping systems. The recirculating power fraction must be kept below 15-20% for economic grid export.

Commercial fusion LCOE is primarily driven by: (1) overnight capital costs ($4,500 to $7,000/kWe for Nth-of-a-kind plants), dominated by superconducting magnet tapes (REBCO), vacuum vessels, and cryostats; (2) the replacement lifecycle of the plasma-facing first wall and divertor cassettes every 3 to 5 years due to neutron displacement damage (dpa); and (3) thermal-to-electric conversion efficiency (40% to 45% via supercritical CO2 Brayton cycles). High-field compact reactors minimize material volumes, enabling competitive baseload LCOEs between $65 and $95/MWh.
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