Blanket and Breeding
The breeding blanket surrounds the plasma, captures 14 MeV neutrons, and converts them to tritium in lithium-bearing material.
Where breeding happens
The breeding blanket is the layer surrounding the plasma that captures fusion neutrons and breeds tritium. When a 14 MeV neutron is absorbed by lithium, it produces tritium and helium. The blanket is where the machine turns neutrons into product, and its design sets the achievable breeding ratio.
Design variables
- Lithium isotopics and lithium-bearing material choice
- Neutron multipliers to increase available neutrons for breeding
- Blanket thickness and coverage around the plasma
- Penetrations for heating, diagnostics, and maintenance that reduce coverage
The three-dimensional reality
A one-dimensional calculation of breeding ratio is optimistic. Real blankets have penetrations and structure that absorb neutrons and reduce net breeding. This is why TBR is treated as a lever across 1.1, 1.5, and 1.8, and why the reconciliation between design-level and net three-dimensional breeding is a tracked open question.
Maintainability
Blanket modules experience neutron damage and must be replaceable. The blanket is designed as modules for remote maintenance, which interacts with the assembly sequence and the neutron budget, replaceability requires penetrations, and penetrations cost breeding.
The blanket is a design for a machine not yet built. Its net breeding performance is measured at the fuel-loop gate G3, at first tritium, against the pre-registered prediction for the installed configuration.
