Re: Hasn't this already been researched ?
Non-functioning ones like Chernobyl and Fukushima might be more of a challenge.
You can have either high intensity particles which have a short half life, or a low intensity particles with a long half life.
The problem in Chernobyl is massive quantities of long lived particles randomly strewn over the area which is over a long term harmful for people rather than a massive level of high intensity radiation in one place.
The level of high energy particles that you could get inside a functioning reactor is going to be a lot higher than one that's been dead for 30 years.