The longevity of nuclear power plants has averaged about 10 years, only about 25% of their expected life, due to the need for new government-mandated safety designs. 20-25 years due to unexpectedly high levels of corrosion and embrittlement. 40-50 years, longer than imagined, because neutrons tend to stabilize the building materials. 40 years, as expected, due to routine maintenance and the replacement with new longer-lasting materials