High-level nuclear waste is nasty, but there is much more intermediate level waste. New studies suggest that turning the latter into glass is a safer way to dispose of it than encasing it in concrete.
Nuclear waste comes in three flavors: high-level waste, which is the stuff you actually power a nuclear reactor with. That is, all the fission products from used fuel, which is highly radioactive and tends to have long half-lives. Intermediate level waste is often resins, chemical sludge and the cladding used on fuel rods.
How long the waste lives on can vary a lot.
Low-level waste involves paper, rags, tools, clothing or other things that come in contact with radioactive elements. Most low-level waste has a half-life or isn't all that radioactive to begin with; a lot comes from hospitals.
High-level waste is routinely turned into glass, or vitrified. In the United Kingdom, the radioactive elements, which are mixed with liquid, are dried out and mixed with crushed glass. Other countries vary the process slightly, but the result is the same: heavy pieces of thick glass containing the waste that won't dissolve in water and are really hard to break up.
Intermediate-level waste has historically been stored in concrete. But concrete can crack.
Some resinous wastes can swell up and break the container. That makes it less than optimal for decades-long storage. For the long term, vitrification wasn't thought to be practical because the intermediate waste itself is made of many different materials, which would complicate the glass-making.
A research team at the University of Sheffield found that the glass produced using intermediate waste was pretty tough. It resisted damage by energetic gamma rays, produced from the decay of the radioactive materials. A second study outlines the types of glass that are likely to work best; there were eight.
The glasses are now being tested. If a good glass can be found, then it simplifies storage of this kind of nuclear waste, as well as saves space at a storage facility.
The studies were published in the European Journal of Glass Science and Technology and the Journal of Nuclear Materials.
via University of Sheffield
