Shielding Of Openings in Protective Barriers

General Requirements for Doors into Protected Areas

TM-1-1500-335-23 Nondestructive Inspection Methods Manual
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T.O. 33B-1-1 6-155 6.9.20.4 Shielding Of Openings in Protective Barriers. In the planning of an installation, careful consideration should be given to reducing the number and size of all perforations of protective barriers and openings into the protected areas. Protection for all such openings shall be provided by means of suitable protective baffles. a. Perforations. Provision should be made to ensure that nails, rivets, or screws which perforate lead barriers shall be covered to give protection equivalent to that of the unperforated barrier. b. Openings for Pipes, Ducts, Conduits, Louvers, etc. Holes in barriers for pipes, ducts, conduits, louvers, etc. shall be provided with baffles to insure that the overall protection afforded by the barrier is not impaired. These holes should be located outside the range of possible orientations of the useful beam. c. Doors and Observation Windows. The lead equivalent of doors and observation windows of exposure rooms, cubicles, and cabinets shall not be less than that required for the walls or barrier in which they are located. 6.9.20.5 General Requirements for Doors into Protected Areas. a. Location of Doors. Where practical, doors into exposure rooms should be so located, that the operator has control of access to the room. b. Interlock Switches for Doors. All door(s) and panel(s) opening into an X-ray exposure room or cabinet (except those that can be opened or removed only with tools) shall be provided with single interlocking switches preventing irradiation unless the door or panel is closed. Double doors shall have interlock switches that operate independently of each other. c. Resumption of Operation. If the operation of any radiation source has been interrupted by the opening of a door or panel to a Shielded, Protective or Enclosed Installation, it shall not be possible to resume operation by merely closing the door or panel in question. To resume operation, it must be necessary to re-energize the source at the console, and this procedure shall cause the time delay interlock system to be reinitiated. It shall NOT be possible to resume operation by merely re-engaging the interlock. d. Escape, or Interruption of Irradiation, from Inside Exposure Room. The exposure room shall include at least one means of exit that may be rapidly opened from the inside. Suitable means shall be provided to quickly interrupt irradiation from inside the room. The means of accomplishing this shall be explained to all personnel and a sign explaining its use shall be conspicuously posted inside the exposure room. Preferably, the beam should not be directed toward the door or interrupting device. e. Threshold Baffle for Door Sill. A door baffle or threshold will generally be required for radiography sources and for installations operating above 125 kVp, if the discontinuity can he struck by the useful beam. f. Lap of Door Jamb. The protective lead covering of any door leading to an exposure room or cabinet shall overlap that of the door jamb and lintel so as to reduce the radiation passing through clearance spaces to the allowable limit for the door itself. SECTION X 6.10 RT REFERENCES. 1. L.E. Bryant and P. McIntire, "Radiography and Radiation Testing" Vol.3, Nondestructive Testing Handbook, American Society for Nondestructive Testing, Columbus, OH, 1985.

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