That is a pretty loose sentence. It is not clear. I hear something like "The wrong people might use nuclear technology." "Problem" is vague, and the grammar is informal.
It's at moments like this one that I think I have no business posting here. The grammar of your sentence is quite gnarly, and I'm not sure I'm equipped to analyze it.
It's a problem what kind of people use nuclear technology.
The anticipatory "it" needs a referent, and the dummy "it" needs to make sense.
"What kind of people use nuclear technology" is not really