Metal Tritides

DOE-HDBK-1129-99

He. This pressure increase, at most, would only be double the initial pressure. This factor should

be considered during the initial design of the vessel so it does not become an issue.

Gaseous tritium at high pressure takes up less space but is more difficult to contain in part due to

the potential for tritium and helium embrittlement of the vessel materials. This embrittlement

increases the probability of a tritium leak or catastrophic container failure. Unloading high-

pressure gas requires specifically designed systems and experienced, skilled operators.

2.5.1.b Metal Tritides

Metal tritides reduce the overall volume of the stored tritium, but some of the finely divided metals

used are pyrophoric. Some metals form low melting point alloys with the materials used in the

construction of the metal tritide containers. Others require extremely high temperatures in order to

recover tritium from the material.

2.5.1.c Tritiated Water

Tritium in the form of T2O may be difficult to store for long periods due to its corrosive properties.

Classified experiments with T2O indicate that pure T2O is corrosive. This corrosiveness is likely

due to tritium oxide generating free radicals (OH-) from radiolytic decomposition of water in addition

to extra energy from beta decay impinging on surrounding molecules. Additionally, pure T2O, like

distilled H2O, will dissolve many materials. No data currently exist that quantify the degree of

corrosiveness; therefore, there is no basis to definitively state that the U. S. Environmental

Protection Agency (EPA) threshold of corrosivity (i.e., a characteristic of hazardous waste), defined

in Code of Federal Regulations 40 CFR 261.22, is not exceeded. The authors believe, however,

that only a high-purity product, and not waste, would have a reasonable chance of exceeding this

threshold. A broader discussion of the relationship between tritiated water and hazardous wastes

is contained in Section 3.1.3.

Dilute tritiated water recovered from tritium removal systems has also proven to be corrosive and

difficult to contain. In a severe case, storage of tritiated water recovered from tritium removal

systems in liquid form at concentrations as low as a few curies per milliliter has corroded through

the weld area of stainless steel vessels after only a few days of exposure. In this specific example,

it is probable that the extreme corrosive nature of this dilute tritiated water was due, in large

measure, to chlorine contamination of the catalyst in the tritium removal system. This corrosion is

evidently inhibited by absorption of the tritiated water on clay or in molecular sieve material.

Figure 2-3 provides a comparison of the various concentrations of tritiated water found throughout

the nuclear industry.