You can start at the bottom by working as a decon tech at a commercial site - or maybe DOE - and work your way up to Junior RP, then Senior. You can take the training and get your DOE Core card by clicking the tab above. DOE doesn't rally have the same classifications. Their RCT's are either qualified or not. Having a Core card, and site-specific training (plus an oral board in some cases) makes you qualified. Prior to finishing that, there is an OJT program.
Or, you can get into the Navy nuclear program, but that will mean six years before you can come back to the DOE.
Certainly you must have some contacts at the DOE site where you work(ed). Ask them to get you in touch with the RCT's or a vendor company who supplies them. Having a Q might make you quite interesting to them. It takes away a big part of the investment on their part. I'm guessing that it is easier and cheaper to train a Q to be an RCT than it is to get a Q clearance for someone already trained who doesn't have one. I assume you already have the 40 hour HAZWOPER. That makes you even more interesting to them, since they don't like paying for that either.