Breeding Ratio 1.5 — Comfortable Margin

A breeding ratio of 1.5 gives a substantial fuel surplus, enough to absorb losses comfortably and to help start additional machines.

What 1.5 provides

At a tritium breeding ratio of 1.5, the plant produces half again as much tritium as it burns. This surplus comfortably covers recovery and retention losses and leaves meaningful spare fuel. It is the middle point of the breeder's design sweep, balancing achievability against the ability to grow a fleet.

Why the middle point is attractive

A 1.5 ratio is demanding enough to require good neutron management — multipliers, lithium enrichment, and full blanket coverage — but not so aggressive that it dominates the design. The surplus it generates can provide the initial tritium charge for a next machine on a reasonable timescale, or accumulate as helium-3.

• Fifty percent margin over consumption
• Comfortably absorbs recovery and retention losses
• Provides startup fuel for additional plants
• Balances achievability against growth

Honest gate

The 1.5 value is a design-sweep point, not a demonstrated blanket result; net breeding after losses is the figure that matters. See the 1.1 case and the 1.8 case.

Achievability and growth in balance

The 1.5 case is attractive because it asks for competent but not extreme neutron management while still generating enough surplus to seed additional machines on a sensible timescale. It sits where the trade between engineering difficulty and fleet-growth potential is most balanced. For that reason it often serves as the reference point when reasoning about how a fleet could bootstrap itself from internally bred fuel.