Induced radioactive nuclides of 10-MeV radiotherapy accelerators detected by using a portable HP-Ge survey meter

The radioactivation of linear accelerator components for radiation therapy is interest for radiation protection in general, and particularly, when decommissioning these structures. The energy spectra of gamma rays emitted from the heads of two accelerator models, EXL-15SP and Clinac iX, after 10-MeV X-ray irradiation, were measured using a high-purity germanium semiconductor survey meter. After spectrum analyses, activities of ²⁴Na, ²⁸Al, ⁵⁴Mn, ⁵⁶Mn, ⁵⁷Ni, ⁵⁸Co, ⁶⁰Co, ⁶⁴Cu, ⁶⁵Zn, ¹²²Sb, ¹²⁴Sb, ¹⁸¹W, ¹⁸⁷W, ¹⁹⁶Au, and ¹⁹⁸Au were detected. One centimetre deep dose-equivalent rate of the heads of the linear accelerator was measured using the survey meter. The dose rate decreased to ~10 % of its initial rate after 1 week. Long-term activations were few, the radioactivity level was low, and a cooling time of several days was effective for reducing dose rate to an acceptable level for decommissioning.