According to the book
Headquarters SAC Analysis of B-47 Accidents...
In short, #6 engine of the MacDill-based 52-0205 (a slight correction to your thread title, AF aircraft don't have a BuNo...that's Navy talk

) blew during a refueling from a KC-97.
The one page report mentions the navigator being rescued, no mention of the other crew members...there was a fourth man on board.
Primary causes
1. Material failure resulting in an uncontrollable fire in the vicinity of the #6 engine. Source unknown.
2. Although not conclusive, the most probable cause was turbine wheel failure, possibly induced by a prolonged compressor stall.
3. Another possible cause was the induction of raw fuel into compressor section from a fuel leak.