Re:Small nuclear reactors: tiny NuScale reactor gets safety ...
by evgen on Friday September 04, 2020 @08:27AM
(#24374310)
Seems to me that you are also assuming that the water is not dumping any heat on its own. I would bet that most of that decay heat is going to conduct from the water to the pool containment vessel and from there to the rest of the environment faster than the reactor is putting more heat into the pool.
Re:Small nuclear reactors: tiny NuScale reactor gets safety ...
by Cthulhu_ on Friday September 04, 2020 @04:51AM
(#24373073)
Makes me think; the water will not boil if the pressure goes up, was the Fukushima explosion caused by a hidden mechanism where if the water starts to evaporate, the steam can't go anywhere as to push the pressure up to keep it liquid?
Re:Small nuclear reactors: tiny NuScale reactor gets safety ...
by smilespray on Friday September 04, 2020 @05:25AM
(#24373265)
That was a hydrogen explosion.
So if you have one of them in an olympic size swimming pool 50x25x2 meters, 2500 m^3, it'd need ~8 hours to evaporate the whole pool at full output.
If you assume decay heat as 1% of regular output (https://en.wikipedia.org/wiki/Decay_heat), you'd need to add (or have stored) ~3 m^3 of water per hour, or slightly less than a liter per second, to keep it from melting down.
If you assume an average of 2% for the first two hours, that'd be 8 MWh -> 12-13 m^3 for the first two hours, so a 5x5x5 = 125 m^3 pool (only considering the part above the "must always stay submerged" level) should be able to cool it for days.
I think _as long as the containment pool is intact_ (and you manage to SCRAM the reactor), this isn't going to be a major issue. But if e.g. an earthquake breaks the pool...