When a nuclear reactor has problems, an emergency shutdown is called a SCRAM. In most reactors, this is accomplished by pushing the neutron absorbing graphite control rods into the reactor pile to moderate the fission reaction. This also has to be accompanied by the application of coolant to release the residual heat. Believe it or not, almost every reactor has manual backup systems to perform both functions in an emergency.

The reason the Fukushima reactors failed was the tsunami knocked out their coolant systems and despite the control rods, the heat of the nuclear material continued to rise, melted the control equipment, got so hot that it denatured water into its constituent components oxygen and hydrogen. This gas eventually exploded, rupturing the containment vessels, causing the catastrophic failure.

Hydrogen explodes as the Fukushima reactor fails catastrophically.

While many people like to point to Fukushima and Chernobyl as proof that nuclear power is too dangerous to trust, both are bad examples. Chernobyl was a bad design asked to do something stupid. Fukushima was hit by one of the most powerful earthquakes in recorded history and a tsunami.

Reactor design stopped in the seventies. Very few new reactors have been built, and older ones were decommissioned and not replaced. It's past time to revisit these designs, apply modern technology, techniques and fuels to create a new generation of reactors that are safer, cleaner and more cost-effective.