Summary - hdbk11290026

DOE-HDBK-1129-99

2.5.3 Summary

2.5.3.a Best for Storage Conditions

The decision on storage media is a function of the storage length and frequency of unloadings.

Media range from gas (short time frame, many movements) to titanium (long time frame, few or no

movements) with other media (e.g., uranium) in between. Although the preferred form for storage

is a metal tritide and the least desirable form is a liquid, there are always exceptions to this rule.

Factors to be considered include:

Solid (Metal Tritides): Unless already in solid form, tritium is not readily available as a solid metal

tritide and requires conversion before storage. Metal tritides can store large quantities of tritium

without occupying large volumes, but the storage containers are more complex than gaseous

storage containers. Depending upon the metallic tritide chosen for storage, there are both

advantages and disadvantages. Titanium tritide is very stable, even when exposed to air, but it is

more difficult to recover tritium from the titanium than from other metals. Stored as uranium tritide,

the tritium can be easily and quickly recovered and provides for the removal of most impurities that

might accumulate during storage. However, uranium powder is also pyrophoric, and starts

releasing 3He after a few months.

Liquid (T2O): Tritium is not readily available in water form and requires conversion before storage.

It is up to 25,000 times more hazardous in oxide form than in elemental form. It takes very little

space, but is difficult to store due to the corrosivity of the water. The tritiated liquid can be

solidified on clay, molecular sieves, or polymers prior to disposal. It may also be converted to its

gaseous form for storage purposes. In either case, the final decision should be based on the

quantity of tritium and the tritium concentration of the water to be stored.

Gas (T2): Tritium is readily available in gaseous form. A great deal of experience already exists on

the design of gaseous tritium storage systems. As a gas it takes up more volume than as a liquid

or solid, and can be easily released to the environment if the tritium container is breached. Gas

also presents a flammability vulnerability.

2.5.3.b Best for Operations/Process

Solid (Metal Tritides): When used as a gas in research where tritium is issued and returned as a

gas, there are advantages to the use of uranium beds for storage. The heating/cooling cycle used

to store and recover tritium from the bed results in routine removal of the 3He and other impurities

from the tritium supply. It can be reused in other processes at reasonably high purity. Additionally,

storage as a metal tritide allows the bed to be used as a pressure generator and, in some cases,

eliminates the need for mechanical pumps.

Liquid (T2O): Unless the process itself uses tritium in the form of water, there are no advantages to

storage of tritium in liquid form for operations.

Gas (T2): Tritium is primarily used in gaseous form, purified in gaseous form, assayed in gaseous

form, and is more useful in this form than any other form. As a result, storage in gaseous form for

operations is appropriate.