"PARIS -- From the time the world's first commercial nuclear power plants were switched on in the late 1950s, installed generating capacity rose rapidly over two decades. It leveled off in the 1980s as new building programs were scrapped in the wake of the accident at Three Mile Island, among other factors.
Contractors generally designed plants to last for 40 years -- a standard enshrined in the United States in the adoption by the Nuclear Regulatory Commission, or N.R.C., of a 40-year licensing regime.
A large part of the world's installed nuclear power capacity is now coming to the end of that designed life span.
Caught between approaching retirement deadlines and public opposition to new plants, industry operators are pushing to extend the life of their plants to 60 or even 80 years -- and this despite problems of premature aging of major components that have already obliged many to replace their plants' steam generators at heavy capital expense.
Running plants longer is one way to recoup the extra cost and raise returns on investment over the full life of the plant. But it has safety implications."