Fusion Power Plant Balance-of-Plant Simulator

Plasma Controls

Temperature T 15.0 keV

Density n 1.00 ×10²⁰ m⁻³

Confinement time τ_E 3.0 s

Auxiliary heating P_aux 50 MW

Plasma State

Sub-ignition

nTτ_E triple productLawson criterion →

Fusion power

0 MW

Q (plasma)

0.0

Power Plant Balance

Fusion → thermal (×blanket)0 MW

Gross electric (turbine)0 MW

Recirculating power0 MW

Net electric to grid0 MW

Net electric

0 MW

Q (engineering)

0.0

How it works

A 0-D power-balance model of a D-T fusion power plant. The reaction rate uses the real Bosch-Hale parametrization of the D-T fusion reactivity ⟨σv⟩(T):

P_fusion = (n/2)² · ⟨σv⟩(T) · E_DT · V
E_DT = 17.6 MeV per reaction

20% of that energy is carried by alpha particles that stay in the plasma and help re-heat it; the plasma also loses energy through transport, at a rate set by the confinement time τ_E:

P_loss = (3·n·T·V) / τ_E
P_alpha = 0.2 · P_fusion
Q_plasma = P_fusion / P_aux

Ignition is reached when alpha self-heating alone covers the losses (P_alpha ≥ P_loss), equivalent to the classic Lawson triple-product threshold n·T·τ_E ≳ 3×10²¹ keV·s·m⁻³ shown on the bar above.

The remaining 80% of fusion energy — carried by neutrons — is absorbed in a lithium blanket that multiplies it slightly (breeding tritium and extra heat), then converted to electricity by a steam turbine. Some of that electricity has to be spent again on heating and running the plant, which is what actually decides whether the reactor is a net power source:

P_thermal = P_fusion · M_blanket        (M_blanket ≈ 1.15)
P_gross   = P_thermal · η_thermal        (η_thermal ≈ 0.40)
P_recirc  = P_aux/η_heat + P_house_load  (η_heat ≈ 0.50, house load ≈ 80 MW)
P_net     = P_gross − P_recirc
Q_eng     = P_gross / P_recirc

T, n, τ_E — the three levers that set the fusion power and whether the plasma can reach ignition.
P_aux — external heating injected into the plasma; needed until self-heating takes over.
Net electric power is the number that actually matters for a power plant: it can be negative even while Q_plasma > 1, because the house load and heating-system losses have to be paid first.

Cool plasma Hot / high fusion rate

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