Exchange with Hydrogen, Hydrogenated Compounds, and Hazardous Wastes

DOE-HDBK-6004-99

can crack at elevated temperatures, including welding temperatures, by bubble agglomeration and

creep crack growth.

Design should eliminate embrittlement as a design issue by considering in the choice of materials a

lifetime projection of pressures and temperatures and exposure to hydrogen isotopes.

Exchange with Hydrogen, Hydrogenated Compounds, and Hazardous Wastes

Tritium will readily exchange with a hydrogen atom in water, oils and almost all other hydrogenated

compounds. Tritiated water and some tritium hydrocarbon compounds are absorbed quickly into the

human body where the beta energy of tritium decay can cause biological damage. When tritiated,

mercury, oils and other hazardous wastes become mixed waste with a significant disposal cost.

The design should avoid use of water, moisture, mercury, hydrocarbons (oils), plastics, asbestos or

elastomeric gaskets and other hydrogenated compounds that could contact tritium. Gaskets and O-

rings in contact with tritium should not use elastomers or plastics or asbestos; tritium will degrade

them and cause premature failure. Ultra-high molecular weight polyethylene (UHMWPE) is an

exception to this rule; see "Recommended Design Practices" below.

Components of Primary Confinement System

Piping, pumps, valves and pressure relief devices should meet all pressure requirements and vacuum

requirements for the primary confinement, and should comply with applicable ANSI/ASME standards

(ASME 89d, ASME 93a, ASME 93b).

Welded joints are preferable to compression fittings which are preferable to threaded fittings. Welded

joints or mechanical joints are acceptable for piping enclosed in a secondary confinement glove box

or cabinet. But outside glove boxes or cabinets, piping should have all welded joints. Pumps should

comply with National Electrical Code requirements for explosion proof installation (NFPA 70), and

should not use organics, hydrocarbons or other volatiles for surfaces that will contact the tritium

process gas. Valves should meet prescribed leak requirements across the valve seat and from the

valve bonnet and body.

Recommended Design Practices

Materials of Construction for Primary Confinement

Recommended Materials

For the primary confinement system for tritium, the recommended materials of construction are

austenitic stainless steels:

Type 304-L,

Type 316, or

Type 316L.