Class II Nuclear Facilities and Prescribed Equipment Regulations
17 Every licensee shall, after changing a sealed source in a teletherapy machine or altering the shielding of a Class II nuclear facility containing a teletherapy machine, at all accessible locations within the nuclear facility and in the following manner, take measurements of the radiation dose rates while the teletherapy machine is in the irradiation mode:
(a) at locations that are in line with the direct beam, with the beam in its most adverse orientation in respect of each wall and ceiling, at its maximum energy, dose rate and field size, and not directed at a phantom; and
(b) at locations that are not in line with the direct beam, during irradiation of a tissue-equivalent phantom at the normal treatment distance.
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