Access Controls and Shielding from Radioactive Hazards - Continued

DOE-STD-6003-96

The design of shielding and work spaces should permit the later installation of additional

temporary or permanent shielding to accommodate anticipated increases in workload or pro-

duction of hot spots by activation or the accumulation of radioactivity. This includes considera-

tion of size and weight of shielding and of such provisions as rigging fixtures, racks, portable

shielding carts, and the like. The design of shielding should also include consideration of even-

tual decommissioning of the facility.

The need to protect equipment and materials from radiation that may damage them or

cause them to become unduly activated should be considered in shielding design. The provision

of shielding should be balanced against the alternate choices of moving the equipment or mate-

rials, selecting other types of equipment or materials, and replacing the equipment or materials

more frequently.

Local shielding or portable (temporary) shielding should be considered, where appropri-

ate, such as for the removal of hot equipment, the protection of personnel doing contact mainte-

nance, and the protection of sensitive equipment. Modular construction and mobility of shielding

should also be considered. Fortuitous shielding by structural materials and equipment (i.e.,

shielding by items not designed for that purpose) should be employed where appropriate; how-

ever, such shielding should be fixed, in general.

Removable shielding should be provided for large, infrequently moved pieces of equip-

ment. In general, removable block may be used if access is required less than once a year. If

access is required at more frequent intervals, steel doors, removable concrete panels, or the like

should be considered. Blocks in removable block walls should be staggered both horizontally

and vertically. Grout used for block walls should be of a type, density, and application thickness

appropriate for the radiation type and strength of the source to be shielded.

Shielding should be provided for appropriate areas to allow personnel entry after off-

normal events. Shielding should be provided as needed to reduce doses to equipment required

to function following off-normal events.

In general, piping should not be embedded in shielding (e.g., concrete floors, walls,

columns, or earthen foundations); however, embedment of pipe sleeves in concrete, from which

the piping could be removed, may be acceptable.

The use of labyrinths should be considered for entryways to areas or cubicles containing

a source producing a potentially high dose rate. Labyrinths should generally be double where

there may be a high scatter fraction of the incident radiation and single where there is not; how-

ever, the choice also depends on the magnitude of the potential dose rate. If the labyrinth top is

lower than the height of the ceiling in the room served, the labyrinth should generally be sup-

plied with its own roof. Entrances with shield doors generally do not require a labyrinth.

An access hole for inserting a telescoping detector through a shield plug should generally

be provided in the plug; it should have a shielding subplug or cap to cover it when not in use.

Similarly, such an access hole should be considered for the roofs or labyrinth walls of cubicles

containing equipment producing high dose rates.

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