Metal Hydride Technology

DOE-HDBK-6004-99

Metal Hydride Technology

Metal hydridemetal hydride beds technology is multipurpose and has replaced several older

technologies for tritium storage, pumping and hydrogen isotope separation. Hydride beds require less

process space than does conventional equipment.

Hydride beds are metal containers filled with other granular alloys or metals that can absorb hydrogen

isotopes when the beds are cold and desorb the isotopes when the beds are heated. Electrical, gas

or other heating and cooling systems are satisfactory. The following sketch shows nitrogen gas to

heat and cool the hydride beds via shell and tube heat exchangers.

Several types of hydride metals have been successfully used in past applications:

- LANA (lanthanum, nickel, aluminum) for pumping and storage,

- Mischmetal (calcium, mixed rare earth metals, and nickel) for compression,

- Pd/K (palladium-coated kieselguhr) for purification and separation, and

- Uranium for storage.

Tritium Storage Process

Past practices have stored tritium in conventional tankage and on metal hydride beds. Metal hydride

beds provide significant safety advantages because they are low pressure devices and, if maintained

below desorption temperature, will not release tritium should the bed wall rupture. Also, hydride

beds require less process space with no significant sacrifice of storage capacity and are the preferred

storage option for most modern applications.

Purification Process

The purification process removes hydrogen isotopes from other waste gases and then separates the

hydrogen isotopes. A palladium diffuser bed removes hydrogen isotopes from helium and other waste

gases. To separate the hydrogen isotopes from each other, past practices have used four processes:

1. Thermal Diffusion Columns,

2. Chromatograph Columns,

3. Cryogenic Distillation Stills, and

4. Thermal Cycling Absorption Process (TCAP).