Lonewolf, Read the article, even the power plant will melt down if it doesn’t power up for a long time like one year or more. Also the spent rods need to stay cool and with no power to send cold water to keep them cold then the melt down starts. Look at what happen in Japan, if it was that easy to turn everything off they would have done that in Japan, it is not. There is 1,000% more radiation stored in spent rods because there are so many spent rods. The power plants are all full of spent rods.
Also we really do not know for sure what will happen in an EMP attack if some of the nuclear power plants will blow up because of the real high current that melts the rest of the grid. There maybe many fires from this too.
We just do not know all that may happen. If you read the article you will see that they talk about melt downs at nuclear power plants.