Actually, I'm working on one right now that's part of a new elementary school. It's quite large because they are also calling it a "community" shelter. I wasn't involved in the design but it's well reinforced CMU (12" CMU with 2 #5 verticals per cell. Also the rebar is being joined with couplers instead of lap splices.
I don't have the specifications for the doors, the drawings just say "Specially Tested Doors HWDE At Storm Shelter Partition". There Are 4 Vent Louvers in the Shelter Area. The Approximate Dimensions of the Shelter Area Is 200' x 100'.