Something I learned back in the 1970's working as a contract Tech at Commonwealth Edison:
Keep track of the proper name of the site where you worked, its address and your supervisor(s)
start and stop dates at every job;
the dates during which you wore a TLD;
maintain copies of your exposure records as you receive them;
where you stayed while on that contract;
whom you worked for - contract company, their address, phone number(s), site coordinator(s).
If you've worked at commercial nuclear power plants, PADS should have a record of when and where you worked. I keep two files in my computer: A work history record capturing most of the above information and an exposure record. A detailed resume is also helpful for tracking this information. I also track any periods of unemployment greater than thirty days and who might be able to vouch for my actions during those periods (neighbors, landlord, friends, etc.). It may be a bit of a pain in butt at first but it's well worth the effort when you have to fill out a ten-year background file for a government background check.