in the 50s, 60s & 70s we shutdown 14 and started 81,...
a fair number of those shutdown units were always planned to be shutdown after only a few to several years (the AEC demo reactors),...
the median age for the shutdowns to date is 17 years with an average age of 18 years,....
you don't want to know the numbers for the operating units,...
scary old, or, reassuringly overbuilt, depending on your bias,....