Blankets & Tritium

In a D–T reactor the blanket is the single most multi-functional component. It surrounds the plasma and must do three jobs at once: slow down and absorb the 14.1 MeV neutrons so their kinetic energy becomes recoverable heat, shield the superconducting magnets and structures behind it, and breed tritium by capturing those neutrons in lithium. No fission plant has an equivalent system, which is why blanket engineering is often called the critical path to commercial fusion.

Tritium breeding rests on two reactions: neutrons captured in lithium-6 release tritium and helium plus energy, while faster neutrons on lithium-7 also breed tritium but consume a neutron. Because each fusion event supplies only one neutron and some are inevitably lost to structure and ports, blankets use neutron multipliers — beryllium or lead — to boost the count so the breeding ratio can exceed one. Solid lithium-ceramic pebble beds and flowing liquid lead-lithium are the two leading blanket families, each with different heat-transfer, tritium-extraction, and materials behaviour.

The tritium that is bred then has to be extracted from the breeder, kept from permeating through hot metal walls into coolant and environment, and inventoried precisely for safety and regulation. The ten topics — breeding ratio, lithium ceramics, liquid lead-lithium, beryllium multipliers, neutronics modelling, tritium extraction, permeation control, shielding, blanket modules, and inventory safety — are where fusion’s promise of a nearly limitless fuel is either closed into a working cycle or not.