Actually the Tsunami did not cause the Fukushima Disaster.
The earth Quake did not cause the Fukushima Disaster.
The Fukushima distaster was caused by Government Corruption and Corporate Greed
At anytime the disaster could have been avoided by pressing this button
and to blame the disaster on the fact that emergency power generators went offline is miss-direction and a lie.
"In any reactor, a SCRAM is achieved by a large insertion of negative reactivity. In light water reactors, this is achieved by inserting neutron-absorbing control rods into the core, although the mechanism by which rods are inserted depends on the type of reactor. In PWRs, the control rods are held above a reactor's core by electric motors against both their own weight and a powerful spring. Any cutting of the electric current releases the rods. Another design uses electromagnets to hold the rods suspended, with any cut to electric current resulting in an immediate and automatic control rod insertion. A SCRAM mechanism is designed to release the control rods from those motors and allows their weight and the spring to drive them into the reactor core, in four seconds or less, thus rapidly halting the nuclear reaction by absorbing liberated neutrons. In BWRs, the control rods are inserted up from underneath the reactor vessel. In this case a hydraulic control unit with a pressurized storage tank provides the force to rapidly insert the control rods upon any interruption of the electric current, again within four seconds. A typical large BWR will have 185 of these control rods. In both the PWR and the BWR there are secondary systems (and often even tertiary systems) that will insert control rods in the event that primary rapid insertion does not promptly and fully actuate."
These back up systems are known as Neutron Poisons. Often in the form of Boron Dust.
So why did Tepco not SCRAM the reactors?
Well your looking at a serious bill is why.
to the tune of several Million for each reactor.
Especially if you use neutron poisons the reactor core (the expensive bit, is essentially a write off)
This is why TEPCO did not shut down the reactor.
However, this is where the government should have stepped in and ordered TEPCO to SCRAM the reactors.
But the Gov was / is in bed with TEPCO (isn't corruption great!).
So this was not done.
But they say - "oh we lost power"
and I am sure they did, However these things are designed to SCRAM without power.
There would be no problem re-starting the Nuclear reactors - as long as the regulating authority can be independent.
Though i think in the current climate that may be hard to do.
My advice to Japan would be to have an independant (non Japanese) organisation be the ultimate reluatory body.
TEPCO have failed.
Government have failed.
This is why corruption is not something you should shrug your shoulders at