This looks like a more hardware focused job listing, so if you have a typical CS background you probably lack some of the expected skills for it. Note the mentions of RTOS, embedded, hardware schematics/bring up, and ARM core knowledge.

What happened to PPB? I haven’t seen it in a while despite a ton of PPB worthy posts

I wonder if largest meant “most people in a building”?

The trick with the economics of nuclear is that building it is the main cost, once the plant is operable the cost is much lower than other sources. So by the time you have a working plant, you might as well use it to get value out of it since you have already paid for it.