Radiological Area Classification

Areas are zoned by radiation and contamination level, with access, monitoring, and protection scaled to each zone.

A working radiological safety program organizes the plant into zones by the radiation and contamination expected in each, and scales access, monitoring, and protection accordingly. For a fusion plant the zoning is driven by two things: the operational neutron field (present only while burning) and the tritium and activation present at other times.

Typical zoning

• Unrestricted areas: offices and support — no radiological controls.
• Supervised areas: low potential, routine monitoring.
• Controlled areas: tritium systems and activated-component handling — access controls and dosimetry.
• Exclusion during operation: the plasma vault — no access while the neutron field exists.

The neutron exclusion is enforced by interlocks: the machine cannot operate with vault access barriers open, and it cannot be entered while the field is present. When operation stops, the neutron field vanishes and access transitions to the activation-and-tritium regime, staged as short-lived activity decays — see post-shutdown fields.

Contamination control

Tritium's mobility means contamination control (surface and airborne) is as important as external-dose control. Controlled areas have monitoring, protective measures, and change-control at boundaries to keep contamination contained. All of it feeds the ALARA program. The burner's low activation and minimal tritium make its controlled areas smaller in scope.

Zoning turns a distributed hazard into a managed, bounded set of controls matched to real conditions.