Recommended Design Practices cont'd

DOE-HDBK-6004-99

In addition, the following materials for instruments, gaskets and seals of the primary confinement

system can contact tritium without detriment in the pressure and temperature ranges of most tritium

systems:

Copper,

Aluminum,

Nickel,

Silver,

Type 304 stainless steel,

Stellite, or Nitronic 60 (Titanium Corporation of America)

Vespel, and

Indium.

For cryogenic processes, Type 316L austenitic stainless steel is the recommended material of

construction.

The design should give particular attention to avoid conditions that could cause stress corrosion

cracking of austenitic stainless steels.

If the performance of a particular material in a hydrogen environment is not well known, the designer

should perform bench tests to establish performance in simulated operating and accident conditions.

Materials Not Recommended

The design should avoid use of the following materials of construction and materials of operation for

tritium primary confinement:

Metals that are susceptible to embrittlement and cracking upon exposure to hydrogen,3

Water

Hydrocarbons (oils)

Mercury,

Iron oxide contamination on either the tritium wetted surface or an outside surface as a

contaminant,

Precipitation hardened steels (e.g., 17-4 PH, 15-5 PH) are especially subject to embrittlement by

tritium and helium. Some metals including some type 300 stainless steels containing helium alone can crack

at elevated temperatures, including welding temperatures, by bubble agglomeration and creep crack growth.