Dismantling France's nuclear reactors and storing their radioactive waste will eventually cost around 79 billion euros ($103.5 billion), the national audit office said on Tuesday.

It put the cost of dismantling France's 58 electricity-generating reactors, run by the state firm EDF, at 18 billion euros.

Storing their highly radioactive waste at a long-term site deep underground would cost an additional 28.4 billion euros.

Annual maintenance costs will more than double, from 1.5 billion euros on average in 2008-10, to 3.7 billion euros by 2025, partly as a cost of incorporating post-Fukushima safety measures, it said.

France derives three-quarters of its electricity from nuclear, the highest proportion of any country in the world.

Debate over its nuclear programme has been spurred by the Fukushima disaster and the future of reactors built after the 1970s oil shocks, most of which are now 30 years old or more.