There is also something that needs to be clarified and added here.
You should never aim your career towards a LOCATION or facility. That is just way too narrow. It is already hard enough to get a job in one's particular field of study. To narrow it down further by aiming for a particular type of location or facility, that's even worse. I cringe everytime I see some people here wanting to work at NASA or CERN, etc., rather than aiming for a broader field of study and let it lands where ever the opportunity opens.
Secondly, a large majority of people who do work at US Nat'l Lab are NOT employed by that lab! This may be shocking to know, but it is true. Many US Nat'l Labs are home to users facilities such as a synchrotron light source, a neutron spallation source, a particle accelerator, a particle collider, etc.. etc. Scientists and engineers from other institutions, and even from other country, perform their research using these facilities. So there is a constant presence of visitors to these various labs. This is also true for CERN and the LHC. Just look at the publications coming out of CERN. You will see that the overwhelming majority of the authors on those papers are NOT affiliated with CERN!
Thirdly, employees of US Labs have significantly tighter and stricter regulations to abide by, especially in terms of safety issues. You will be saddled with a lot more safety courses that you must take and update through the years, and are required to complied with a host of other government directives. Nothing like this is even close when you work at, say, universities.
Fourthly, in most cases, you are not a government employee, even though your are expected to obey most of the same rules as any government agency (such as your per diem expenses when you travel). You are usually considered as a government contractor, where your employer is the agency or institution that runs that lab under contract from the Dept. of Energy.
Lastly, a large percentage of your funding comes from the US Dept. of Energy, which owns that lab and everything that you do. While you can seek external funding from other agencies and private companies, one glaring agency in which you usually cannot get funding from directly is the National Science Foundation. While the NSF do fund projects that make use of DOE facilities, and in other cases, co-fund a major project with DOE, you can't, unlike employees of academic institutions, apply for funding from NSF. This means that a significant portion of US science funding is not available to you directly.
But on the upside, the benefits (medical and retirement) are usually generous, more so than in private sectors.
Zz.