On average a fuel element at Hunterston would have remained in the reactor for about four years and in this time would have provided enough electricity to keep a 1 kilowatt fire going for about 18 years.
The burn up or irradiation condition of each of the 32,880 elements in a reactor will vary, however according to its position in the core - ranging from a life of about two years in the centre to six or seven years on the fringes.
The natural uranium fuel came to Hunterston fully prepared as fuel elements from the United Kingdom Atomic Energy Authority factory at Springfields in Lancashire. When an element had served its purpose and is discharged from a reactor it will be stored under water for about 100 days to lose some of its radio-active properties and then returned to the UKAEA factory at Windscale in England where it will be processed to remove still valuable elements.
It will still contain about half its fissile U.235 attoms and in addition will have prodiced an almost equal amount of Plutonium 239. These seperate uranium and plutonium elements will be processed and recovered for future use.