Seriously, the dude is pretty clearly ill informed about what he was doing. In the end, though, he asked for help from the right place. He didn't do irreparable harm (or any harm period) to anyone. There was no significant amount of radiation found in the apartment.
Most people on HN are going to see right through politician scare tactics. In this case, it seems completely reasonable for this guy to get a slap on the wrist and probation from use of radioactive materials (that is, if caught with radioactive materials again, he is in for some serious jail time).
Edit:
It is also important to send the right message: dealing with dangerous chemicals and substances is dangerous and should be handled in a controlled environment. However, you should always feel comfortable asking your regulatory agencies what should and should not be done. And intellectual curiosity isn't going to get you thrown in jail.
Of course, but it should never be too late to do the right thing. It's better for everyone if people feel safe to contact the people in the know at any point than for them to think that it is too late and that if they just ignore the problem it will go away.
Speaking rather generically, at a certain point, a crime has been committed and a line has been crossed.
Naturally, during sentencing it should be taken into account that someone started acting responsibly and owned up to what they had done, but that doesn't mean they haven't done anything wrong.
No, there's no such thing as "serious jail time" in Sweden. You could get away with a few years if you murder someone here. This kind of thing would maximum lead to a few months in jail if even that - even if repeated.