First things first, count rate does not translate into biological hazard measured in Sv. Biological effects change with the energy of the radiation imparted and the type of radiation. If you take apart your smoke alarm at your house and put a Geiger counter to it, you will get thousands of counts in a matter of seconds. But there is no danger because the source inside emits alpha particles which bounce of your skin. The biological effects also depend on energy of the radiation, and the [1] EPA link you provided demonstrates this. Depending in what gamma energy range the detector is set up to detect, it will register radically different count rates. As you can see they register over 1000 CPM in gamma energy range 2. So your claims of " 7k+ CPM is about 49 mSv" is just not science and doesn't mean anything.
Second, radiation is really easy to detect, even in incredibly tiny levels, which is why accidents that happen half a world away, like in Chernobyl or Fukushima, can be picked up here in the US. So the idea that any harmful event could be covered up is ridiculous. If a significant release happened in Indiana, the Turkey Creek Point plant in Miami Florida would pick up the radiation.
Third, the assertion that somehow this is a nuclear caused event. Like I stated above the CPM varies with the energy range the detector is set, so it could be that the Lower Level Discriminator (LLD) broke on those detectors. But even if it didn't, that doesn't mean the uptick in radiation is nuclear related. The nuclear plant by Crystal River in Florida gets false alarms frequently from the radiation that comes blowing over from the coal plant only a few miles away.
