1. (a) Leakage radiation measurements. For operating conditions producing maximum leakage radiation in systems of 1 MeV or more, the absorbed dose in rads due to leakage radiation, including x-rays, electrons and neutrons, shall not exceed 0.1 percent of the maximum absorbed dose in rads of the unattenuated useful beam. For purposes of this subsection, the leakage absorbed dose is to be measured at any point in a circular plane of 2 meters radius centered on and perpendicular to the central axis of the beam at the isocenter or normal treatment distance and outside the maximum useful beam size; and the maximum absorbed dose shall be measured at the point of intersection of the central axis of the beam and the plane surface.

   1. (1) Measurements excluding those for neutrons shall be averaged over an area up to but not exceeding 100 square centimeters at the positions specified.
   2. (2) Measurements of the portion of the leakage radiation dose contributed by neutrons shall be averaged over an area up to but not exceeding 200 square centimeters.
2. (b) Specifications. Permittees must determine or obtain from the manufacturer the leakage radiation existing at the positions specified in subsection (a) of this section for specified operating conditions.

Added at 17 Ok Reg 1136, eff 6-1-00