Biological Shield and Personnel Dose
Beyond the magnet, a bulk biological shield protects people; access and dose planning shape how the breeder is operated and maintained.
Protecting people, not magnets
The inboard shield protects the coils; a separate bulk biological shield protects personnel and the environment during operation. It is the massive outer barrier that keeps radiation fields outside the machine within acceptable limits, and it defines where people can be and for how long during operation and after shutdown.
Access follows dose
Radiation fields govern maintenance planning. During operation the machine hall is inaccessible; after shutdown, residual activation sets a cooldown period before hands-on work near the machine is possible, and drives the use of remote handling for high-dose components. Dose planning is therefore inseparable from the maintenance schedule.
- Bulk shield keeps operational fields within limits for people.
- Residual activation sets post-shutdown cooldown times.
- High-dose components are handled remotely, not by hand.
- Dose planning shapes the whole maintenance sequence.
Part of the safety case
The biological shield, personnel dose planning, and remote handling together form the occupational-safety part of the breeder's design. As with activation and waste, this page treats dose as a physics-and-engineering fact, informing how the machine is built, operated, and maintained — with no economic content.
Skyshine and penetrations
Even a strong bulk shield must account for radiation that scatters through the atmosphere and back down, and for streaming through ducts and penetrations. The biological-shield design closes these paths with labyrinths and local shielding, so the protective boundary is continuous in practice and not just in the direct line of sight from the plasma.
This page documents a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. Figures are computed, reproducible targets, not measurements.