"Maintenance procedures were in progress, which required the main central control rod to be manually withdrawn a few inches to reconnect it to its drive mechanism; at 9:01 p.m. this rod was suddenly withdrawn too far, causing SL-1 to go prompt critical instantly." wiki
... a gruesome question (and we here at Atomic Annihilation specialize in gruesome questions) During the five days that elapsed between the accident and the removal of the third body, which was skewered to the ceiling, was there any decay of the corpse? The unfortunate technicians body was stuck to the ceiling directly above a nuclear reactor core that had been split open and part of it's fuel scattered all around the work room. There was a huge amount of radiation!
Could the bacteria necessary for the decomposition of organic material have survived under those conditions?