Question: If I was to flood a nuclear power station what would happen? Apocalypse?

James Pope answered on 11 Mar 2015:

Hi Harry,

In a nuclear reactor the reactor containing the radiation is sealed in, so that it has no contact with the outside world. That is really important, if it leaks out or explodes out, then we have very dangerous risks, were Chernobyl is the most famous example.

The most likely example for your question, is what happened at the Fukishima Nuclear Power Plant in 2011 during a tsunami (a huge wave of water) after an earthquake off the coast of Japan.

The tsunami breached the tsunami defences (partly because of the height of the wave, partly because the earthquake had lowered that coast of japan by 1 metre!!!)

The tsunami flooded in, blew all the electrical power to the plant. The reactor was already shut down (a SCRAM event) as an automated response to the earthquake, so it was still radioactive material, but it wasn’t reacting. However, as the reactors (three I think) had been operating, there was still lots of heat in the reactor building. This should have been cooled by water flowing around the reactor, but with no electricity there was no water. A major emergency was declared and an urgent request for backup generators to provide electricty was made. However, due to the earthquake and tsunami the generators couldn’t get there in time.

Thanks to the SCRAM shutdown, there was no chance for the reactors to go out of control like with Chernobyl, but with building heat, the reactors could meltdown. Pressure was increasing, so they were forced to vent slightly radioactive gas (which later exploded and blew up the outer building of the reactor, but not the reactor) and they discharged some of the cooling water into the sea (again slightly radioactive). Eventually, teh reactors got so hot they melted through their casing and into a specially designed safety feature, a huge thick lead and concrete container rthat caught the sludge, like the trays under plant pots do.

Although some of the radioactivity reached all around the northern hemisphere, it was very limited in its effect outside of Japan. In Japan a number of young children had to have iodine tablets to prevent thyroid problems, which can be a side effect of iodine radiation. This was fairly common in Eastern Europe after Chernobyl, my fiancee is from Poland and her and all her friends had to have those tablets after that eruption.

Hope that answers your question, if the reactors had been running, then I guess the loss of electrical power would also have caused the SCRAM shutdown, but I don’t know for sure.

By the way, The Earthquake was 4 years ago today, the 11th March 2011!