Answer to Question #11137 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
Is there ever any radiation present in the lead that is used to shield x-ray rooms, computerized tomography (CT) scan rooms, and even radiation therapy rooms (linear accelerators)? Our company provides lead shielding materials for these types of applications, and we have always understood that radiation does not remain in the lead EVER. Can you please offer the definitive answer on this for us?
The radiation in rooms used with high-energy radiotherapy accelerators (above 8 MV) can cause some materials to become radioactive. The reference below gives quite a lot of information on that. Lead is not a material that becomes activated significantly in normal usage, even with the high-energy beams; however, some materials that might be in an alloy with the lead can be activated: tungsten, iron, aluminum, and antimony. Aluminum in concrete walls can also become activated. For the most part, the induced radioactivity in shielding from photon beams, the most common type of radiation used in radiotherapy, quickly decays and presents little danger to personnel or patients. When removing lead shielding from the wall of a radiotherapy room used with beams of 8 MV or greater, if the lead is alloyed with antimony, it might be prudent to have a health physicist check the lead for radioactivity before doing the deconstruction.
In rooms for radiotherapy that uses only photon beams below 8 MV, in diagnostic x-ray rooms, or in CT rooms, the lead, alloyed or not, cannot become radioactive, and the lead shielding is completely safe with respect to radiation.
Bruce Thomadsen, CHP
Thomadsen B, Nath R, Bateman FB, Farr J, Glisson C, Islam Mohammad K, LaFrance T, Moore ME, George XX, Yudelev M. Potential hazard due to induced radioactivity secondary to radiotherapy: the report of task group 136 of the American Association of Physicists in Medicine. Health Phys 107(5):442–460; 2014.