Confinement Devices - STD-1128-98master0320

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

shielding during the lifetime of the facility because of increased throughput or

higher radiation levels of the material being processed.

Concrete radiation shielding should be in accordance with ANSI N1O1.6-1972,

Concrete Radiation Shields (ANSI, 1972).

Straight-line penetration of shield walls should be avoided in order to prevent

radiation streaming.

Robotics and/or shielded operations performed remotely should be used as much as

practicable and should be used where it is anticipated that exposures to hands and

forearms would otherwise approach 10 rem/y. Also, robotics or other non-hand

contact methods should be used where contaminated puncture wounds could occur.

Shielding materials should be noncombustible or fire resistant, to the maximum

extent practicable.

C.4.3.5 Confinement Devices

Different devices may be used to confine and control radioactive material. The

selection of the appropriate device will depend on the quantity of material, its form,

and the operations to be performed. For specific operations, encapsulation may be

the confinement of choice. Sealed source containers should be designed to prevent

contact with and dispersion of the radioactive material under all normal conditions

and when inadvertently dropped. Sealed sources should be shielded as required to

ensure that personnel in routinely occupied areas do not receive more than 0.5

mrem/h.

Seismic protection should be provided to minimize movement of confinement

enclosures if ground movement occurs.

Fume hoods may be used for some operations with plutonium, depending on the

quantity and dispersibility of the material. In general, plutonium fume-hood

operations should be limited to wet chemistry processes and less than 100 mg of

plutonium. For some operations, such as metallography and x-ray analysis, larger

quantities may be handled. The location of each hood should be evaluated with

respect to ventilation supply and exhaust points, room entrances and exits, and

normal traffic patterns. Hood faces should not be located within 10 ft of the closest

air supply or room exhaust point, which might disturb airflow into the hood.

Hoods should not be located in or along normal traffic routes.

An open-faced hood should be designed and located to provide a constant air

velocity across the working face. A face velocity of greater than 125 linear ft/min

over the hood face area should be provided to ensure control of radioactive

materials. Much of the nuclear industry uses 150 linear ft/min as the criterion. If

room air currents might upset the uniform entrance of air, the hood-exhaust

requirements should be increased. Turbulence studies may be necessary to verify

adequate control of radioactive material. Physical stops should be provided to

ensure that the required hood face velocity is maintained.

C-14