NAC459.596. X-ray and electron therapy installations: Leakage radiation; beam-limiting devices.

     1. For existing equipment and new equipment manufactured or installed after February 28, 1980:

     (a) The leakage radiation, excluding neutrons, at a distance of 1 meter from the source must not exceed 0.1 percent of the useful beam dose rate at 1 meter from the source for any of its operating conditions.

     (b) Within 1 year after February 28, 1980, the registrant must determine or obtain from the manufacturer for each machine the leakage radiation of electrons, X rays or neutrons, existing at the points specified in paragraph (a) of this subsection, for specified operating conditions. Records on radiation leakage must be maintained at the installation.

     (c) The Division may by specific order impose upon any user of equipment from which neutron leakage may be a hazard such additional requirements as it deems appropriate or necessary to protect health or minimize danger to life or property.

     2. Adjustable or interchangeable beam-limiting devices must be provided.

     3. For existing equipment and new equipment manufactured or installed after February 28, 1980:

     (a) Adjustable or interchangeable beam-limiting devices must attenuate the radiation incident on the beam-limiting devices so that the dose equivalent in rems at any distance from the source does not exceed 2 percent of the maximum dose equivalent in the useful beam measured at an equal distance from the radiation source.

     (b) If the beam-limiting device does not meet the specifications in paragraph (a) of this subsection, the Division may accept auxiliary equipment or methods for accomplishing attenuation.

     4. Dose equivalent measurements may be averaged over an area up to but not exceeding 100 cm² at a distance of 1 meter from the target. In case of overlapping beam-limiting devices, the leakage through each set must be measured independently.

     [Bd. of Health, Radiation Control Reg. §§ 6.9.1-6.9.1.2.2, eff. 2-28-80]