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Figure 9. Intermediate-quality secondary containment
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Design Considerations - index
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Low-Quality Secondary Containment Systems


DOE-HDBK-1132-99
Gloveboxes should, however, be designed in accordance with the
recommendations of the American Glovebox Society.
The purpose of intermediate-quality secondary containment systems, such as
gloveboxes, is to prevent the immediate release of tritium into the room or out
to the environment in the event of breach of the primary containment system.
Following a release into an intermediate-quality secondary containment
system, the tritium is generally recovered in the tritium removal sections of the
cleanup system (see below) and several hours can elapse during the recovery
process without a significant release of tritium to the room or the environment.
In a typical working environment, tritium gloveboxes are operated at a pressure
that is slightly negative with respect to the pressure in the room (i.e., on the
order of a few tenths of an inch of water column). This allows for greater
comfort for the worker while he or she is working through the gloves. part, This
is supposed to prevent the leakage of tritium from the box into the room.
Tritium levels in the box are usually several orders of magnitude greater than
the tritium levels in the room, and, due to the laws of partial pressures, the
movement of tritium due to permeation alone will always be from the box to the
room. To minimize the permeation of tritium from the box to the room,
gloveports should be covered and evacuated when they are not in use.
Because the true leakage rates of most tritium gloveboxes can generally be
certified to be no more than 10  -2 to 10-3 cm3/sec, the ingress of air into the box
environment is a problem that must constantly be addressed. For this reason,
most tritium gloveboxes are connected to cleanup systems designed to remove
undesired impurities from the glovebox gases and return clean gases back to
the box. Because one of the undesired impurities will always include tritium (as
T2, HT, and/or HTO), the cleanup systems must always remove free tritium
from the glovebox gases. In most cases, the cleanup systems will be designed
to remove free tritium down to the part-per-million to part-per-billion level.
Because this is still equivalent to tritium concentrations that range from 2.6
Ci/m3 down to 2.6 mCi/m3, the return gases from such cleanup systems will
never be completely devoid of free tritium. In addition, cleanup systems
I-117


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