just so you know t there is no reaction going on. as soon as the earthquake hit the reactors were shut down, therefor stopping all the reactions.
the big problem they are having is keeping the reactor cool because there is still some heat being produced, but nothing similar to if the reactor was still running
same thing with the spent fuel rod pools, the fuel rods themselves are not reacting but they are still producing heat and they are evaporating the water in the pools. in order to keep the pools full they are dropping water on them because they cant pump water up to them.
its still a bad situation, the chances of radiation spreading is still very high but it is not a runaway reaction in the plant.