Why in flying Hades would anyone want to be a government employee? I guess if you lack self-respect and initiative, it might hold some slight shred of attraction...
When it comes to similar jobs with a federal agency, e.g. HHS, USDA, Commerce ~ you'd probably need private sector employment in related fields first, and before that you'd probably need to work for the state or a school
If you're happy to get a job and sit there 40 to 50 years in the same position ~ maybe putting red flags on highway warning sign machines, that's different.
BTW, others who've had federal, state or local government employment experience have reminded me over the years many times that for the most part it's useless to discuss the reality of government employment with shopkeepers and guys with fast food franchises ~ they just don't know except when the Board of Health comes around to shut them down, or the weights and measures guys want to check their scales. Still, i try. Spent decades explaining to them and their cousins in the private sector in almost every industry in existence how to properly pay postage on bulk, presort and special rate mail ~ and why. They all want to know why ~ it's like they've never run a business ~ got that feeling once when the entire General Motors Board of Directors called me regarding some high ticket advertising matter ~ like none of them had ever run a business. As it turned out they were doing it badly!
BTW, if you want to have regular employment as a nuclear physicist, you really do need to get a job with a government somewhere. I hear they are hiring in Iran for example.