13 ms·
While you are correct that it is less than the nominal heat output, we are still talking about 50MW a minute after shut down and 5MW one day after the shutdown
by petschge 7y ago
While you are correct that it is less than the nominal heat output, we are still talking about 50MW a minute after shut down and 5MW one day after the shutdown of a 700MW reactor. So even a day after the shutdown you are able to boil of 2kg of water every second.
- rwcarlsen 7y agoYes, it is still a lot of heat. But to a lay reader, it might be easy to believe that the pool needing to be able to cool the reactor means that the pool has to cool an operating plant during an accident which is incorrect. I was just trying to make the distinction here. Also the drop from (your very approx numbers) 50 MW to 5 MW is mostly exponential - and so very quickly drops away from 50 MW. After that, any remaining heat is diffuse enough to not actually boil away water from the pool. Fuel-melting risk (which is not the chain reaction restarting for any who may be limited in fission plant understanding) is generally only a concern for the first couple days after reactor shutdown.
- petschge 7y agoFunny little detail that might interest you: Due to the presence of a large number of different fission products (with different half lifes), the drop does not really follow an exponential but is better described by P(t) = P_0 * a * (t^-0.2), i.e. a power law, where P_0 is the power before the shutdown, a is a couple of percent and t is the time since the shutdown in seconds.