Three Mile Island Memories

Interesting piece by Cringely, who was apparently involved in the investigation of the Three Mile Island nuclear meltdown of 1979.

Quoting Bob Cringely:

Here’s how it was supposed to work.  Something went wrong.  The computer noticed what went wrong, set off audible and visual alarms, then sent a description of the problem to a line printer in the control room.  The operator would read the print-out, check the trouble code in one of many manuals, then make the adjustment specified in the manual.  Simple, eh?

Too simple, it turned out.

What happened at Unit 2 was a little more complex.  A cascading series of events caused the computer to notice SEVEN HUNDRED things wrong in the first few minutes of the accident.  The ONE audible alarm started ringing and stayed ringing continuously until someone turned it off as useless.  The ONE visual alarm was activated and blinked for days, indicating nothing useful at all.  The line printer queue quickly contained 700 error reports followed by several thousand error report updates and corrections.  The printer queue was almost instantly hours behind, so the operators knew they had a problem (700 problems actually, though they couldn’t know that) but had no idea what the problem was.

So they guessed.