What was the biggest screw up you've ever seen in your field?

It was a culmination of things.

To start with, the rbmk 1000 reactor was lacking in certain design features. It was a positive void coefficient design (if the water flashes to steam, it causes an increase in power), the control rods had graphite leaders that caused a localized increase in power in the bottom of the core as they are inserted (positive scram effect) and the reactor hall lacked a containment vessel above the upper bio shield to make it easier to swap fuel rods around (to allow it to make enriched materials for weapons research that required more frequent fuel rod swaps).

The test was actually going as planned until someone called them and told them to abort and put the reactor back up to full power to make up for a sudden demand on the grid (I think another plant had sudden issues and dropped production). The person in charge didn't know that it was a bad idea to do this (and nobody could override him). Then when the reactor started misbehaving, the operators (who were trained to checklists) didn't know what to do, so they wound up doing the wrong thing.

The whole incident is a hugely fascinating rabbit hole to get sucked into, especially if you branch out into other events like Mayak and Windscale. There were even a few incidents in the US besides the famous 3 mile island partial meltdown.

/r/AskEngineers Thread Parent