From what I understand, when the earthquake struck, the nuclear reactors had shut down (control rods were inserted). As a result, the power coming from the steam turbine generators were shut off.At the same time, the earthquake had knocked out Japan's power grid, so power coming from outside the power plant was out.Then the emergency diesel generators went into effect, but was knocked out an hour later as well, and people suspect it was from the tsunami.Would the disaster still have happened if they kept the steam turbine generators running (which means never shutting down the reactor via control rods), and water pumping, instead of shutting it down and letting the backup power direct the emergency cooling?
Had they not shutdown the reactors there would have been enough power to run the cooling system without using the emergency diesel generators. But as you said the grid was knocked out. It took several days to get up a power line from an other power plant to Fukushima after the earthquake struck. Without a grid to get rid of the electrical energy the steam turbine generators overheat. There wasn't a choice to not shutdown the reactors once the electrical grid was down. Do you know that a simple Tornado has all it takes to start the same kind of desaster in the US? Tornado throws enough debris on the roads to ensure that no transport vehicles can reach the reactors for the next 12 hours. Tornado tears apart the emergency generators diesel tanks. Tornado tears down the grid near the power plant so that the reactors have to go into shutdown and that no electrical energy from other power plants is available. All we need is a simple tornado.
if hte control rods had not be inserted it would of catastrophic. the reactors would be working at 100% and no one can shut it down becasue there is no power. left for too long and unable to stop the reaction, it could lead to an actual meltdown like at the Chernobyl. there's a good reason why during any emergency the control rods are inserted. its standard protocol since the very first nuclear reactor experiments back in the late 1930s under some gym in the eastern USA. you want to shut down the most dangerous thing first, the one that has the most potential for catastrophe before doing anything else.
As you point out it was the double-punch of the earthquake and tsunami that caused the problems at Fukushima. The diesel generators were enough to handle the pumps to cool the reactor but then the tsunami came and swamped them. Shutting down the reactor after an earthquake is standard safety procedure. The diesel generators were designed to be a backup in the event of an earthquake. They functioned fine even after the huge quake. If the quake didn't occur, but instead the planet was just hit by the tsunami, the other planets in unaffected areas of Japan would still be operating so this means the engineers onsite could have jerryrigged something so that the pumps would be powered by the national power grid even if the diesel pumps were knocked out. Not shutting the reactors down would have resulted in even more radiation being released due to the damaged buildings and containment units.
