I was in the nuclear field as an HP Specialist for nearly 15 years. Is it difficult to get back in the field if I have been convicted of a non-violent felony (the lowest felony conviction).
Call 1-800-225-0385 (oh god, I still remember it...

) and ask to speak to Eric, who will put you in touch with one of their security people. If anyone can give you an answer, it'll be big blue....
Lots of DOE work opening up right now, DOE has different (not lower, just different) way of looking at things for security clearance.
Good luck