> When there was xenon poisoning in the upper half of the core, the safety rods were designed in such a way that, at least initially, they were increasing (and not decreasing) the core reactivity.

I wonder if any reactor-design groups do "fuzz testing" on simulated models, checking that they can recover from very weird states even if it's not clear how the state could have been reached in the first place.

For example, having one section just arbitrarily xenon-poisoned, while another is arbitrarily too hot.