It depends on what you do. The DOE itself has very few actual employees, and most of them are beaureaucrats. Nearly all their work is performed by contractors. Unless you have a lot of letters after you name, there is not much in DOE for you. You'd be better off looking for a civilian job with the Navy
https://chart.donhr.navy.mil/index.asp, at a shipyard, or (if you'd like some actual money in your paycheck) some private sector company.
Actually, I'd like to offer some advice. Stop thinking of that 7 years as wasted. That time was well spent in teaching you a set of skills (more than you know about) that can be the foundation of a career.
If you think that the only way to make those years valuable is to add them in with a bunch more years at a low-paying job with no hope for advancement or control over you own destiny, you are wrong. People who work for the government are paid only a fraction of what they would be paid in the private sector with the same skills.
If you think that you need a government job to follow up on your Navy time, that is like turning down $100 bills because the $1's match the ones you already have.
By the way, if you limit yourself to Rad Protection, or nuclear power, because that is what you did in the Navy, you are making the same mistake. If you were a Navy nuke, you can do almost any job there is. Most of us start out with what we know best, but we almost all end up discovering that we can do other things as well if not better.
If that job you have now is a good one, keep it while you put out some feelers for better ones. If it sucks, do the same thing only faster. But don't think that you need a government pension to win at this. In reality, you should think of that as your plan of last resort.