Experimental and Monte Carlo analysis of activation in a medical cyclotron target assembly

Radiological characterization of activated materials is a crucial step in the decommissioning and waste classification of medical cyclotron. This work combines on-site HPGe γ-spectrometry with FLUKA Monte Carlo simulations to characterize activation in the major components of a commercial ¹⁸F target assembly, namely the HAVAR foil, titanium window, niobium insert, and aluminum/stainless-steel structures. The measured and simulated results showed consistent radionuclide inventories, confirming that activation is initially dominated by short-lived nuclides, while long-lived isotopes such as ⁶⁰Co, ⁵⁸Co, ⁵⁴Mn, ⁶⁵Zn, ⁴⁶Sc, and ²²Na govern the residual dose rate after extended cooling. Among these, ⁶⁰Co in HAVAR and stainless steel, ⁴⁶Sc in titanium, and ²²Na in aluminum were identified as the key radionuclides determining clearance timeframes. Furthermore, this work established correlation between residual dose rates and the clearance levels of dominant radionuclides demonstrates that dose-rate measurements can serve as practical indicators for determining whether activated components meet clearance criteria after sufficient cooling. This study provides a quantitative basis for waste management of medical accelerators.