David Cameron is due to announce that the UK and the US will complete an exchange of high-level waste for highly enriched uranium at the biennial Nuclear Security Summit in Washington this week.
The plan is similar to previous waste substitutions schemes that have been used before and ensure that the same amount of radioactivity go in each direction even if the volumes are different. It has been agreed by the UK, the US and Eurataom.
In return for the waste currently held at Dounreay in Scotland the highly enriched uranium returned will be used for medical isotope production.
More details are expected to be available on this later in the week.