Your eyes, and if you are male your testicles, are the organs most easily damaged by microwaves. It doesn’t take much to go from “ow that hurts” to “holy fuck you blinded me you bastard!” which makes me more than a little leery about using this sort of thing for crowd control.
Actually, the U.S. began developing this kind of technology back in World War II, though they weren’t using nukes to generate the pulses. It was hailed as THE NEXT BIG THING because the ENEMY BOMBERS WERE JUST GOING TO FALL OUT OF THE SKY!!! The weapons didn’t live up to the hype. They were able to get bomber engines to stop running in controlled tests, but in the real world the weapons proved to be almost completely ineffective.
The only difference with nuke generated pulse weapons is you get a bigger pulse. They still don’t quite live up to the hype, though. EMP weapons have two basic problems which limit their effectiveness. The first is the inverse square law. Your EMP drops off at a rate equal to the square of the distance. So at 10 feet it’s 1/100th, not 1/10th, as powerful as it was at 1 foot. At 1000 feet, it’s 1/1,000,000th as powerful. This is why you need a nuke to generate an effective EMP. Anything smaller pretty much won’t be effective at any usable distance. The second problem is that any metal box or structure makes a natural Faraday cage, protecting what is inside of it. A shopping mall is an effective EMP shield to some degree just because the roof and a lot of the structure is made out of steel.
As for Bell Island, the History Channel lately has become very fond of throwing up all kinds of psuedoscience nonsense and presenting it as if it is accepted fact. It seems to me that they are trying to play to the UFO and conspiracy theory crowd in an effort to get ratings. I wouldn’t put a lot of weight on their speculation.