As impossible as it is to imagine now, Annie Jacobsen explains (in Area 51), in the early days of atomic testing there was no such thing as a HAZMAT suit:
Instead, workers combed the desert floor dressed in white lab coats and work boots, looking for particles of nuclear fallout. According to Atomic Energy Commission documents made public in 1993, this radioactive debris varied in size, from pinhead particles to pencil-size pieces of steel.
Much to the surprise of the nuclear scientists, the atomic weapons tests revealed that sometimes, in the first milliseconds of destruction, the atomic energy actually jettisoned splintered pieces of the bomb tower away from the intense heat, intact, before vaporization could occur. These highly radioactive pieces were then carried aloft in the clouds and deposited down on places like Groom Lake, and Atomic Energy Commission workers could then locate them with magnets.