The following additional considerations should be addressed in designing
Where practical, equipment not functionally required to operate directly
in the presence of radioactive materials should be located outside the
enclosure. Equipment that must be located within the enclosure should
be designed to allow for in-place maintenance and/or replacement.
The design and operation of support and protection systems, such as
fire protection, should not promote the failure of the enclosure system
integrity or the loss of confinement.
Noncombustible or fire-resistant, corrosion-resistant materials should be
used for enclosures and, to the maximum extent practicable, for any
required radiation shielding. In no case should the total combustible
loading located in a fire area exceed the fire resistance rating of the
structural envelope. (See National Fire Protection Association (NFPA)
Fire Protection Handbook for guidance on the relationship of
combustible loading versus fire resistance rating.)
In conjunction with their ventilation systems, enclosures should be
capable of maintaining confinement (i.e., negative pressure with respect
to the surrounding operating area).
To reduce migration of contamination, closure devices or permanent
seals should be provided on entrances to and exits from piping, ducts, or
conduits penetrating confinement barriers. Such closures or seals
should have an integrity equal to or greater than the barrier itself.
Where pertinent to safety, enclosure design should consider heat
generation in the enclosure. Such heat sources may be from processes,
lighting, chemical reactions, and the decay of radioactive material.
Consideration of radioactive material as a heat source is particularly
applicable to storage enclosures.