Can something be made which would survive being so close to a nuclear detonation that it gets engulfed by the million degree fireball? The US actually tested steel and aluminium spheres in experiments involving nuclear weapons. These test articles were named for the physicist who performed the experiment - Lew Allen's Balls - and we can affirmatively say that Dr Lew Allen literally had balls of steel that were tough enough to survive the inferno inside of a nuclear blast.

The actual scientific results are available for those who want more details and fewer jokes about spheres.
https://apps.dtic.mil/sti/pdfs/AD0340...