Secondary Wall Design

DOE-HDBK-1129-99

tritium operations under this condition. Surveillance and/or preventive maintenance schedules

should be selected in order to maintain elastomer functionality.

5.3 Secondary Wall Design

5.3.1 High-Quality Secondary

The design requirements for a high-quality secondary wall are the same as the primary wall. If the

secondary wall is required to provide long-term containment of high concentrations of tritium, it

should meet the same requirements as the primary or first wall container.

5.3.2 Medium-Quality Secondary

If the secondary wall is a glovebox and only contains tritium that has been diluted by the glovebox

gases for a short duration (a few hours), e.g., while the glovebox is cleaned up by the tritium

removal system, then the requirements can be relaxed. Although the quantity of tritium contained

may be quite large, the low pressure and concentration of tritium will not result in material failure

due to tritium exposure.

5.3.3 Low-Quality Secondary

If the secondary wall is a room or building and only contains tritium that has been diluted by the air

contained in the room or building while the room or building is cleaned up by the tritium removal

system, then the construction requirements can be relaxed. Although the quantity of tritium

contained may be quite large, the low pressure and concentration of tritium will not result in

material failure.

5.4 Cleanup System Design

Most of the components of the tritium removal and cleanup system are only exposed to tritium at

low concentrations and pressure for short time periods. The only long-term exposure is in the

water collection system where the water is collected at low pressure on a molecular sieve. All

metal construction is recommended, but the materials of construction are not required to be

hydrogen-compatible materials. Where appropriate, elastomeric sealing materials have been used

successfully in these systems for many years without significant problems. When possible, metal

seals should be used because they are more durable and reliable and require less maintenance

than elastomeric seals.

To minimize the potential for the generation of mixed waste and to decrease radiation exposure of

the workers, oil-free pumps should be used where possible.

5.5 Storage System Design

Storage systems must consider the total cost of the storage cycle and the purpose for the storage.

Storage techniques that increase the complexity of the handling process without adding beneficial

features should not be used. The barrier concept discussed in Sections 4.1.1 through 4.1.3, in

addition to the wall design considerations discussed above, should be incorporated into all storage

system designs.