A very unusual exchange is about to take place over the Atlantic. The UK is sending some 700 kilograms of highly enriched uranium to be disposed of in the US, the largest amount that has ever been moved out of the country. In return, the US is sending other kinds of enriched uranium to Europe to help diagnose people with cancer.The vast majority of the UK’s waste comes from its fleet of nuclear power stations. Most of it is stored at the Sellafield site in north-west England.