Temporary Enclosures

RADIOLOGICAL CONTROL

DOE-HDBK-1079-94

Tritium Primer

contamination, mainly by HTO. Heated monitor chambers are useful in minimizing

contamination by HTO.

The relative pressure of the glove box atmosphere is normally kept negative in order to

prevent the gloves from hanging outside the box where passersby may brush against them

and to prevent tritium from escaping into the room should a leak develop in the glove

box. However, outward permeation of HTO through the gloves and inward permeation

of room moisture are not affected by the pressure inside the glove box.

Temporary Enclosures

At times, maintenance or repair work is done on equipment that cannot be moved into a

glove box or fume hood and that has a high potential to release tritium. For these

activities a temporary box ("tent"), may be constructed over the equipment, and an

existing cleanup system installed to process the air. Alternatively, if the tritium at risk

is not significant, the enclosing atmosphere may be purged to the stack. If the enclosure

is small, gloves and glove ports may be fitted to the side of the enclosure. For larger

enclosures entry may be required. In such cases, personnel must work in air-supplied

suits inside the enclosure.

Protection by Local Ventilation

In spite of the greater protection afforded by glove boxes, fume hoods are commonly

used at tritium facilities for handling or storing material with low quantities of tritium or

with low-level contamination. Limits are generally imposed on the quantities used or

stored in these hoods.

Fume hoods are also used to protect personnel at the outside door of glove-box pass

boxes where materials are passed into and out of the boxes. Ideally, any tritium released

in a hood from outgassing or a leaky container, for instance, is routed to the hood's

exhaust duct. However, turbulence may occur at the hood entrance, resulting in

backwash and possible contamination of personnel if the face velocity is not adequate for

the design of the hood, the activities in the hood, or the local conditions (such as traffic

in front of the hood). No hood should be used that has not been thoroughly surveyed

and judged acceptable for tritium use.

For small operations local ventilation is commonly provided at the work site through a

flexible ventilation duct ("elephant trunk") directed to the room exhaust system. The

exhaust of these ducts is generally directed to the building ventilation exhaust system,

which of itself may be adequate to supply the needed air flow for the duct without help

from an additional in-line blower.

Tritium

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