How long does radioactive waste last

Structural investigations show crystal defects due to alpha irradiation

Cambridge (UK) / Richland (USA) - The disposal of radioactive waste is arguably the most important unsolved problem in nuclear power generation. Melting down in glass containers has so far been considered a relatively safe method of shielding even long-lasting fission products from the environment. British and American researchers have now found out that glasses made of zirconium silicate leak much faster than previously assumed due to the radioactivity of plutonium. The researchers report on this result, which is important for the nuclear energy industry, in the journal "Nature".

"In the long term, alpha decay in these ceramics seriously destroys the crystalline structure," write Ian Farnan of the University of Cambridge, UK, and colleagues from the Pacific Northwest National Laboratory in Richland. Radioactive waste can only be safely stored in long, stable jars. In their experiments with zirconium containers containing the alpha emitter plutonium, they observed that the crystal structures decompose about five times faster than previously assumed.

With this knowledge, they were able to estimate that a zirconium container could show significant damage to the crystal structure after around 210 years. After 1400 years at the latest, it is quite possible that radioactivity could escape from the actually protective glass envelope. For safe final disposal, however, a period of ten half-lives is assumed. For plutonium, that means 241,000 years.

Despite these sobering results, the scientists believe it is possible that sensible alternatives to zircon could be found. These would be able to withstand the radioactive radiation much longer. The task now is to find and test these materials for safe glass containers in the future.