The Department does not publish data on levels of output from individual nuclear stations. Data on recent historic nuclear generation unavailability are published in the National Grid Winter consultation report which is available at:
http://www.nationalgrid.com/NR/rdonlyres/4B475A5C-D41A-4039-9089-30B282276577/26306/WinterOutlookConsultationReportJune2.hpdf.
BERR publishes a table of fuel used in electricity generation by major producers, which shows the contribution to overall generation from all sources including nuclear plant on an annual basis going back to 1995. This is available on the BERR website at
http://berr\gov.uk/energy/statistics/source/electricity/page18527.html.