Linear Accelerator Decommissioning

Radiation-activated materials

Unlike diagnostic imaging, linacs above 10 MV produce neutron-activated materials. Collimator, target, flattening filter + surrounding gantry parts may be slightly radioactive for weeks to years after shutdown.

Decommissioning protocol

1. Final treatment cessation + beam-off clearance.
2. Cool-down period — typically 6–12 months before major disassembly to allow activated materials to decay to release limits.
3. Survey — physicist surveys all potentially activated components.
4. Disassembly — high-activation parts (target, primary collimator, flattening filter) may be released only after extended cool-down or sent to low-level radioactive waste disposal.
5. Structural release — concrete vault surveyed for residual activation.
6. State license amendment — notify radiation authority.

NRC / state license

Facility license amended when therapy cessation is final.

Vendors

Specialist rad-onc decommissioning companies handle activation management. Varian / Elekta service arms sometimes partner with third parties.