of inert or oxygen-deficient process glovebox lines. Allowable leakage
rates for ductwork systems should be taken into consideration.
The supply of air to primary confinement, such as enclosures that
confine the processing of plutonium and enriched uranium, should be
filtered by HEPA filters at the ventilation inlets to the enclosures and
area confinement barriers to prevent the transport of radioactive
contamination in the event of a flow reversal.
If room air is recirculated, the recirculation circuit should provide at least
one stage of HEPA filtration. The design should include redundant filter
banks and fans. If recirculation systems are used, contaminated process
enclosure air should be prevented from exhausting into the working area
rooms. Process enclosure air (from hoods, gloveboxes, etc.) should be
treated and exhausted without any potential for recirculation to occupied
The designer should specify and locate components in the exhaust
systems to remove radioactive materials and noxious chemicals before
the air is discharged to the environment. These components should be
capable of handling combustion products safely. Exhaust system design
should safely direct effluents through the appropriate ventilation ducts
and prevent spread beyond the physical boundary of the ventilation
system until treated.
HEPA filters should be installed at the interface between the enclosures
that confine the process and the exhaust ventilation system to minimize
the contamination of exhaust ductwork. Prefilters should be installed
ahead of HEPA filters to reduce HEPA filter loading. The filtration
system should be designed to allow reliable in-place testing of the HEPA
filter and to simplify filter replacement.
Separate exhaust ventilation system ductwork and the initial two stages
of filtration should be designed for exhaust air from enclosures that