Nope. Not an alien nuclear reactor but you are close.
It is the owner of the Black Stone found on the moon in “2001 Space Odessy”. He came to earth for a vacation after placing the stone on the moon but got sick and died.
Or, since it is 6 feet long, it’s the crypt of Boris Karloff from the original film, “The Mummy”. Must have been left there after filming ended and got buried by the sand.
Or, it is the final resting place of Judge Crater.
Definitely not Capone’s crypt. Just ask Geraldo.
Maybe they finally found Jimmy Hoffa?