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1、187WSRC-MS-2000-00061Hydrides for Processing and Storing TritiumTheodore MotykaAbstractThe Savannah River Site (SRS) has 50 years of experience in handling and processing tritium for defense and other special applications. During the past 20 years, a new technology, metal hy- dride technology, was i
2、ntroduced to the tritium facilities. This technology dramatically changed the way tritium and the other hydrogen isotopes were handled and processed at SRS. Metal hydrides allowed tritium to be stored much more compactly and at much lower pressures, thereby minimizing accidental release and enhancin
3、g operational safety. The use of metal hy- drides also simplified many of the processes, resulting in smaller and more efficient operations, which led to significant cost savings.Multimillion-dollar cost savings have been realized in the existing tritium facilities at SRS by using metal hydride tech
4、nology. Similar cost savings are expected in several of the new tritium projects. New tritium applications continue to be developed at SRS to ensure the reliability of our nations tritium reserves and to support our nations commitment to a strong defense.In recent years, the Department of Energy and
5、 SRS have supported the development of “dual- use” metal hydride technology, which provides benefits not only for defense but also for future energy applications. SRS has collaborated on international energy programs aimed at demon- strating nuclear fusion as a potential, clean, and plentiful source
6、 of future energy. SRS has also partnered with government, industrial, and academic institutions to apply its expertise on metal hydrides to clean, non-polluting, hydrogen-powered energy systems. Benefits from these dual- use activities have allowed SRS to maintain its expertise in metal hydrides an
7、d have led to substantial cost savings for SRS facilities.IntroductionWhat are metal hydrides?While almost all metals can be made to react with hydrogen under some conditions, only a few metals do so “reversibly” at room tempera- ture and near atmospheric pressures. These materials are generally ref
8、erred to as “revers- ible” metal hydrides. Reversible metal hydrides have the ability to absorb and release hydrogen like a solid sponge (Sandrock and Huston 1981). They can do this over and over again. An analogy is that of a household sponge, which can absorb and release water as needed. Revers- i
9、ble metal hydrides can be either pure metal such as palladium, titanium, or zirconium. They can also be intermetallic compounds or alloys made up of two or more metals such as iron- titanium or lanthanum-nickel.Reversible metal hydrides offer a number of advantages in storing hydrogen versus com- pr
10、essed gas or a cryogenic liquid. Hydrides have an extremely high volumetric density for hydrogen. That means that a lot of hydrogen can be packed in a very small compact space. In fact, most metal hydrides can store hydrogen several times more compactly than high- pressure gas and often more compact
11、ly even than liquid hydrogen. This is because the hydrogen atoms in a hydride are bound to metal atoms more closely than they can bind to themselves either as a gas or a liquid. Hydrides can store hydrogen at very low pressure, which affords a higher level of safety. Hydrides often react only with h
12、ydrogen, which makes them ideal for use in many separation processes. The disadvantage of hydrides is their relatively high cost and weight.188Theodore MotykaWSRC-MS-2000-00061History of Metal HydridesWhile the ability of some pure metals to absorb hydrogen has been well known for over a 100 years,
13、the discovery of a new class of interme- tallic alloys that reversibly absorb and release hydrogen did not come about until the late 1960s. One of the first intermetallic alloys to be “hydrided” was iron-titanium. Brookhaven National Laboratory reported this in 1969 (Sandrock and Huston 1981). Iron-
14、titanium was one of the first practical metal hydrides. It readily absorbs hydrogen at room temperature and is relatively inexpensive. However, iron- titanium also has some disadvantages. It can be easily poisoned by small amounts of oxygen, and substantial heating of the material is required the fi
15、rst time that it is exposed to hydrogen. The initial conditions, required of a metal hydride, to first absorb hydrogen are normally referred to as its “activation” condi- tions.Around the same time that iron-titanium was being explored as a practical metal hydride, another important hydride material
16、, lantha- num-nickel, was discovered. The hydride properties of this material were discovered entirely by accident (Sandrock and Huston 1981). The researchers at the time were working on developing permanent magnets when they stumbled on the hydrogen properties of lantha- num-nickel. This became a new and exciting reversible hydride material. Lanthanum-nickel has a high hydrogen capacity and readily absorbs hydrogen at ambient pressures. Fur- thermore it can be easily activated at roo
