I can't say what kinds of security analyses we had to do to meet regulatory requirements, because there's a host of things you have to do to even know what security requirements there are. That's not even close to publicly available, for good reason.
I can say we have to analyze to massive vehicle bombs, armed assault, etc.
Here's what the possibly interesting, counterintuitive analysis showed. If you have a plant where a massive bomb can't cause damage to exceed regulatory standards (...we are talking about a truly miniscule amount of material here in this micro fission powerhouse in comparison with the nuclear plants you are probably thinking of... literally not more than a meter tall and wide, underground, below layers and tonnage of concrete and steel) and if an armed assault can't cause damage like that either, are you doing a favor by having a host of armed people on site? Probably not, in fact. Insider risk is then too large. There you go!
(totally agree with no "move fast and break things" here. I'm about 8 years into working on this company and still see many years ahead. we wouldn't be doing anything great if we weren't bringing forward the safest emission-free power plant to reality)
This is exactly why I always find it fun to read discussions about nuclear power on HN. Lots of people here are hardwired to only think in terms of software (where it's all 1s and 0s and you can do whatever you want), and then they apply that thinking and logic to real world engineering fields and the logic collapses. Doubly so for the nuclear sector because you can cause catastrophy if you aren't careful.
Do we really want nuclear anything in remote areas without human guards? What if someone decides they might like to cause an unnatural disaster?
Everyone says nuclear is safe... but where's the proof it would still be safe without the level of hand wringing we currently have?
If someone wants to do nuclear, they have to prove it's safe. Move fast and break things has no place here.