Because the containment boundaries for systems are represented by the
floors, walls, ceilings, doors, and windows of the rooms or the building in
question, tritium leakage rates from containment systems cannot be stated
accurately. Like the intermediate-quality secondary containment systems
described above, the purpose of low-quality secondary containment systems is
to prevent the immediate release of tritium to the environment in the event of a
breach of the primary containment system.
Independent of the scale of the operation, the tritium removal systems used for
these types of containment systems must be capable of a very high rate of
throughput, and they should be examined with great care prior to selecting the
containment systems for use. For example, for a small building with a 100 m 3
volume, on the order of 20 × 18 × 10 feet, a 1-g tritium release into the
building will result in a volumetric air concentration of about 100 Ci/m 3. If the
building has a true leakage rate on the order of 100 cm 3/sec, the tritium
leakage rate out of the building will be about 0.6 Ci/min·g.
With the building ventilation system shut down, no benefits will be gained from
massive dilution factors, and the tritium will be released to the environment at
ground level through the walls, ceilings, doors, windows, etc., of the building.
Expanding on the details, the released tritium will convert quite quickly to HTO
(i.e., the more hazardous form of tritium); the tritium will thoroughly contaminate
the building, adjacent rooms in the building, and the areas immediately
surrounding the building. In addition, the tritium released to the environment
will be poorly mixed with the environment, and, as a consequence, exposures
to personnel living or working downwind could be expected to be relatively
In spite of their apparent drawbacks, it should be noted that low-quality
containment systems do have a place in the broader spectrum of tritium
containment strategies, particularly when used as an integral part of conversion
projects, retrofit projects, or add-on projects, and particularly when other
primary/secondary containment system combinations intended for use have a
very low probability of release.