vestibules may be used to minimize the impact of open doors or hatches on the
ventilation system and to prevent the spread of airborne contamination within
typically used to limit the release of radioactive or other hazardous material to
the environment and to minimize the spread of contamination within the facility.
To the extent practical, discrete processing steps should be performed in
individual process confinements to reduce the amount of hazardous material
that can be released by a single or local failure of the confinement system. The
following general cleanup system features should be considered, as
appropriate, for ventilation system design:
The level of radioactive material in confinement exhaust systems should
be continuously monitored. Alarms should annunciate when activity
levels above specified limits are detected in the exhaust stream.
Appropriate manual or automatic protective features that prevent an
uncontrolled release of radioactive material to the environment or
workplace should be provided.
Elevated confinement exhaust discharge locations can limit onsite doses
and reduce offsite doses by enhancing atmospheric dispersion. An
elevated stack should be used for confinement of exhaust discharge.
Provisions should be made to provide an adequate ventilation exhaust
discharge path in the event of stack failure. The stack should be located
so that it cannot fall on the facility or an adjacent facility. Alternatively,
the stack may be constructed to remain functional following accidents,
including those caused by severe natural phenomena and man-made
external events. Stack location and height should also consider intakes
on the facility and adjacent facilities to preclude uptake.
Guidance for air sampling locations is provided in ACGIH/ASHRAE
criteria. Sample collecting devices should be located as close to the