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.
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.