Sims cannot die from just normal (non-singed) use of the Study Brain option. University technology majors use that object repeatedly during class activity (and use the Study Brain option). They won't even get singed from that option. The Study Brain option on either version is my go-to for raising Nerd influence. I've never seen that option backfire in any way.
The other options like Personality Programing or Genius IQ or perhaps the Brain Enhancement option will singe the sim when they backfire. I've never had a sim die from it though. OTOH, I've never tried to get a singed sim to use it either. I suspect @EgonVM is correct about the game not letting singed sims use the machine simply because the game won't let singed sims use the chemistry bench. If the Personality Programming option backfires the sim's traits will also be randomized. I've had Personality Programming and Genius IQ (from the more expensive one) backfire but I can't say I've ever had the Brain Enhancement option do that. Then again, I don't use that option very often.
