Actually it depends heavily on the design of the reactor. I recall that more modern designs have either far higher or complete degrees of 'passive' safety. Th

Actually it depends heavily on the design of the reactor. I recall that more modern designs have either far higher or complete degrees of 'passive' safety. The very heat of the reactor being sufficient to circulate the cooling loop at a safe level. Really we should be planning for the active replacement of //ALL// infrastructure within it's designed service lifetime or less (since invariably it'll take longer than initially estimated to accomplish).