Any reactor larger than ca. 400 MWe needs active cooling system, because power output is larger that can be cooled down passively. However, 300 MWe and less can be cooled down after the shut down just submerging reactor into water, hence they are inherently safe. And there won't be reactor pressure vessel breach if active cooling fails. For example, Kursk's nuclear reactor did not suffer any damage in the accident and it is still fully operational reactor. It was kept cool by surrounding sea water.
It would be best to have small modular reactors. However nowadays politicians count nuclear power as a number reactors. Hence they allow building new reactors one at the time and if number of individual reactors is limited, industry of course will build the biggest reactor on the market! For example, here in Finland politicians allowed to be build one (1) nuclear reactor into Olkiluoto, and of course industry chose to build one 1600 MWe EPR (world largest!) that is just waiting for Chernobyl/Fukushima scale disaster if every planned backups fails like they did fail in Chernobyl/Fukushima. Olkiluoto 3 EPR reactor was commercial failure, it is now some five years delayed, mostly because of the safety issues that are inherently extremely difficult and demanding for that scale reactor. It would be far more wise to build modular 5x300MWe reactors. Safety issues are much cheaper and the grid reliability is higher (single module can be maintained at the time while others are running), but it is almost impossible to get licence for five (5) nuclear reactors in current political atmosphere! ―Jouni On 3 Apr 2012, at 22:47, Jed Rothwell <[email protected]> wrote: > Axil Axil <[email protected]> wrote: > > I believe that the design of the Fukushima reactors were Pre-Three Mile > Island. > > As far as I know, the design of the reactor itself is not at fault. The > accident was caused by the destruction of the backup power supplies. > > As far as I know, none of the commercial reactors now sold have passive > cooling after shutdown. So any reactor would have the same problem. Even > CANDU reactors have to be actively cooled. > > The Three Mile Island accident was caused by a defective reactor design, with > a stuck valve and a badly designed instrument panel. > > - Jed >
