Dave,
A few questions might help get you some answers. What craft are you in? What type of training are you looking to obtain? Are you hoping to work refuel outages or to get a house job at a nuke plant?
If you are looking to work outages your radworker training is usually given onsite, sometimes at a Union hall if the class size is large enough. If you get a house (permanent) job your radworker training is given onsite after you are hired.
There are many here with better answers but hopefully this will get you started.
Welcome to Nukeworker!
Tom