In American football, there’s a move called the ‘Hail Mary pass’ – throw the ball down field and pray. That’s what filling the Fukushima reactors with sea-water has been described as, a Hail Mary pass. It just doesn’t seem to be coming off. Reactor 3 has started emitting more radiation, 4 is on fire, the core may be breached in 2. Even 5 and 6 pose a risk.
Radiation levels are still not immediately dangerous, even close by, but they are preventing workers staying in the vicinity of the reactors for long enough periods to do the work they need to do. In desperation, they tried getting the army to dump water into the spent fuel pond at 4 and the containment building of 3 but that was abandoned due to radiation levels. The plan now is to use police water cannons to get the water in.
The basic problem is that the fuel rods are emitting enough radiation to evaporate the water around them.
Inside the reactor cores, this steam is pumped out, leaving fuel rods exposed to the air. Without the water to absorb the radiation energy they’re putting out, they start to melt through their protective coating. When they touch water, they disassociate it, releasing raw hydrogen and oxygen, which are also pumped out of the core to explode in the outer containment building when they reach combustible levels. Without the water to cool them, the melting continues with the risk that the fuel rods melt through the thick metal casing of the reactor core, or even go critical again, starting the nuclear chain reaction that powers a nuclear plant in operation (the radiation given off at the moment is just the residual level). Reactors 1, 2, and 3 have all had explosions and partial meltdowns. Reactor 2 may also have a breach in its core containment.
In the storage ponds, the spent fuel rods are also putting out a lot of radiation (they’re only ‘spent’ in the sense that their radiation levels have dropped to uneconomic levels and the material can be recycled into useable rods). Again, this is evaporating the water that they’re stored in leaving them exposed and heating themselves. In Reactor 4, a fire, possibly caused by Reactor 3’s explosion has burnt away the building, leaving the spent fuel rods exposed to the air. Temperatures are also rising at Reactors 5 and 6 for the same reason. These three reactors were offline when the tsunami struck, so there’s no heat in the core to worry about.
The one ray of good news today is that the new power line to the plant is nearly complete. This will provide power to the pumping system. In normal operation, the pumping system takes water from the reactor through the turbines to generate electricity and on to a heat exchanger (often the iconic cooling tower, but not a Fukushima), thus cooling the water which then goes back to the core to take away more energy from the fuel rods. But will the pumping systems still be in operational order after all that has happened around them?
And let us not forget that there is still a huge crisis going on due to the earthquake and tsuanmi with over 4,000 confirmed dead and conflicting reports that put the missing at as high as 20,000. There’s also the likelihood of strong (7.0+) aftershocks in the next few days.
In a sign of just how serious this situation is, Emperor Akihito made a televised address to the public asking them to not give up hope. I haven’t been able to find out exactly how rare it is for the Emperor to make a broadcast to the public but the only other time I know of is the first – when Hirohito announced the surrender of Japan in 1945.