Section 835.502 - High and very high radiation areas(a) The following measures shall be implemented for each entry into a high radiation area:(1) The area shall be monitored as necessary during access to determine the exposure rates to which the individuals are exposed; and(2) Each individual shall be monitored by a supplemental dosimetry device or other means capable of providing an immediate estimate of the individual's integrated equivalent dose to the whole body during the entry.(b)Physical controls. One or more of the following features shall be used for each entrance or access point to a high radiation area where radiation levels exist such that an individual could exceed an equivalent dose to the whole body of 1 rem (0.01 sievert) in any one hour at 30 centimeters from the source or from any surface that the radiation penetrates:(1) A control device that prevents entry to the area when high radiation levels exist or upon entry causes the radiation level to be reduced below that level defining a high radiation area;(2) A device that functions automatically to prevent use or operation of the radiation source or field while individuals are in the area;(3) A control device that energizes a conspicuous visible or audible alarm signal so that the individual entering the high radiation area and the supervisor of the activity are made aware of the entry;(4) Entryways that are locked. During periods when access to the area is required, positive control over each entry is maintained;(5) Continuous direct or electronic surveillance that is capable of preventing unauthorized entry;(6) A control device that will automatically generate audible and visual alarm signals to alert personnel in the area before use or operation of the radiation source and in sufficient time to permit evacuation of the area or activation of a secondary control device that will prevent use or operation of the source.(c)Very high radiation areas. In addition to the above requirements, additional measures shall be implemented to ensure individuals are not able to gain unauthorized or inadvertent access to very high radiation areas.(d) No control(s) shall be established in a high or very high radiation area that would prevent rapid evacuation of personnel.58 FR 65485, Dec. 14, 1993, as amended at 63 FR 59684, Nov. 4, 1998; 72 FR 31926 , June 8, 2007