Why Uranium Beds?
Uranium beds are used successfully to pump, store and purify tritium gas. Uranium tritide not only has a high tritium capacity but also a low dissociation pressure at room temperature. Such tritides provide an attractive alternative to compressing and storing tritium in pressure containers. UT3 is dissociated by heating and tritium liberated from the solid phase. On cooling, the uranium metal quickly reabsorbs the tritium gas. This reversible liberation and re-uptake of tritium from uranium beds can be performed many times under appropriate conditions without loss of efficiency. These properties of uranium tritide make it an excellent tritium storage and pumping material.
The advantages of handling and storage of tritium as uranium tritide
- Large quantities of tritium can be stored in the smallest volume.
- High-purity tritium gas can be generated "in situ" for any experiment.
- Fast uptake of tritium even at low pressures is possible.
- Surplus tritium can easily be recovered at room temperature from the vacuum system and be reabsorbed back onto the tritium getter for later reuse. Discharges to the environment are reduced by orders of magnitude.
- The decay product He-3 which has accumulated during storage can simply be pumped off.
- In case of any air ingress or leakage of a container only small amounts of tritium will escape.
All structural materials, including bellows valves, which are used for the production of these traps, are of stainless steel series 316. This type of steel is particularly resistant to hydrogen embrittlement and ensures best diffusion properties for tritium in high pressure / temperature systems. Special loading of the depleted uranium provides a homogeneous distribution of the pyrophoric powder and prevents channelling of the gas through the bed. An integrated filter system prevents uranium dust from escaping from the system. The depleted uranium (mainly U-238) inside the bed presents no radiation hazard, due to the very low specific activity and the non-penetrating radiation. After assembling and welding, the finished uranium beds are He-leak tested and pre-activated to guarantee full absorption performance on receipt. Basically two types of uranium beds are available, which can be modified according to the customer's requirements.
One-valve uranium beds
One-valve uranium beds are used for storing and generating fresh, high-purity tritium "in situ" and for reabsorbing surplus tritium from an experiment.
Material: all SS316
Coupling: Swagelok VCR 1/4” male (with blind cap)
Valve: Swagelok Nupro SS-4H
|Micro „S“||up to 250 Ci||1.5 g||11 mm||160 mm||60 mm||~ 2 ml|
|Micro „L“||up to 750 Ci||2.5 g||11 mm||160 mm||60 mm||~ 3 ml|
|Standard 17||2’500 Ci||7.5-(15) g||17 mm||190 mm||80 mm||~ 12 ml|
|Standard 20||5’000 Ci||15 g||20 mm||220 mm||80 mm||~ 12 ml|
|Standard 30S||2'500 Ci||7.5 g||30 mm||160 mm||35 mm||~ 12 ml|
Flow-through uranium beds
Flow-through uranium beds are used to accelerate complete recovery of surplus tritium, especially if it contains larger amounts of He-3 or other noble gas impurities. These impurities strongly reduce the tritium absorption speed in one-valve beds by blanketing the surface of the uranium. These flow-through beds are used in combination with circulation pumps.