Where there's money, there's no need to save. And Nuka-World certainly wasn't run by anyone who hurt for money. The junkyard is a disposal ground filled with discarded pieces of equipment and malfunctioning robots, because why would one recycle when they can simply buy?
The junkyard has two distinct halves: the warehouse and the landfill. The warehouse is clean and stocked; the ground floor has a weapons workbench and power armor station, with an office and a trap animatronic alien upstairs. Notably, there's also a star core in the warehouse.
The landfill itself is a mess of corridors burrowing through and beneath the mounds of trash on the southern edge of the area; a Ultimate UFO from the Nuka-Galaxy attraction sits in the middle of the junkyard. It can be entered by equipping four fusion cores into the fuse box to the left of the door sitting next to the steamer trunk.
SCAV! issue #2 is next on the desk to the star core in the warehouse, upstairs. Nearby is the power distributor.
A star core is found in the terminal inside the warehouse, upstairs.
A fusion core lies in a generator in the warehouse. Another fusion core can be found on the shelf of the tipped metro car, just past where the sentry bot attacks, but before the hill to the space ship.