Confinement Devices - doe-std-1128-98

DOE-STD-1128-98

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-15