In addition to the requirements in § 336.317 of this title (relating to Control of Access to High Radiation Areas), the licensee shall institute measures to ensure that an individual is not able to gain unauthorized or inadvertent access to areas in which radiation levels could be encountered at 500 rads (5 grays) or more in one hour at 1 meter from a source of radiation or any surface through which the radiation penetrates.
30 Tex. Admin. Code § 336.318