Short-Term Storage

DOE-HDBK-1129-99

5.5.1 Short-Term Storage

Tritium used to support the day-to-day activities in a facility must be readily available to the facility

customers. If the facility uses tritium in gaseous form and its decay to helium does not impact the

process, then, to simplify the operation and the equipment, the tritium can be stored in gaseous

form. The storage container should be fabricated of all metal, hydrogen-compatible materials

including valves, valve seats, and seals.

5.5.2 Medium-Term Storage

If tritium is only used in periods of two years or less, the requirements do not change significantly

from those of short-term storage. Experience has shown that tritium can be stored safely at near

atmospheric pressure for long periods of time. If the buildup of helium in the supply does not

impact the use, then storage as a gas is an acceptable alternative. There are, however,

advantages of tritide bed storage for medium-term use. Impurities such as nitrogen and oxygen

form uranium nitride and uranium oxide and are removed from the gas stream as the bed is heated

and cooled. Helium, which accumulates due to the decay of tritium, and any other impurities

remain in the overpressure gas above the bed and may be pumped off after the bed had been

cooled down and the tritium has been gettered by the uranium. As a result, the uranium bed not

only provides for tritium storage but also provides a means of maintaining a reasonably pure and

stable tritium supply.

5.5.3 Long-Term Storage

Due to the half-life, storage of tritium for several years implies that it is not readily needed. It

should be placed in a safe and stable condition while the tritium decays.

5.5.3.a Storage as a Gas

Compared to the fabrication and preparation of metallic storage beds, regardless of what metal is

used, the cost of storage of tritium as a gas at near atmospheric pressure is economical. ASME-

code-designed stainless steel tanks are available or can be designed and fabricated at a

reasonable cost. A tank at atmospheric pressure would end with a final of 15 pounds per square

inch gauge (psig) pressure after all of the tritium had decayed, so embrittlement is not an issue.

The long-term storage of hydrogen and tritium in containers is well understood in comparison to

the understanding of long-term storage of metal tritides.

5.5.3.b Storage as a Metal Tritide

Uranium beds designed at Sandia in the late 1970s for laboratory use were about the size of two

one-gallon paint cans. This included the secondary containment system and electric heaters used

to drive the tritium off during tritium removal. These beds were designed to store 50 grams of

tritium as uranium tritide that was easily recoverable in a matter of less than an hour. Long-term

storage in this type of container is expensive, but the tritium can be easily and quickly recovered

for use. Additionally, large uranium beds capable of storing kilogram quantities are possible, and

would significantly decrease the volume required to store large quantities of tritium. Also,

impurities such as nitrogen and oxygen form uranium tritide and uranium oxide, and are removed