Ok, thanks for that input.
Guess I was under the impression that the operational life of a nuclear plant would be more like the 100 years. 20 years licensing for a plant that may have taken almost that long to permit and build seems low to me.
The original licenses were for 40 years, but all plants keep what are called coupons in the core exposing them ot the radiation and heat. some are removed at every refueling and sent off to Argonne Labs for analysis. These analyses are what encourages the utilities to extend the licenses. I have talked to metallurgists who told me there should be absolutely no problem with 80 years, and that would be likely to extend another 20 years, if not more. The NRC has decided to do 20 year increments.
Even fossil plants are designed for 40 year lifetimes. trying to operate past this requires either a lot of new equipment, or less operating time. Given the temperatures and pressures they operate at - 3500-4000 psi/1100F vs 2500psi/625F (nuke) - the moving parts wear out faster and metal fatigues faster.
