Low-Quality Secondary Containment Systems cont'd

DOE-HDBK-1132-99

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/ming.

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

high.

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.

I-119