I think you're oversimplifying it. The temperatures are unpredictable, with molten nuclear fuel possibly at 2000 degrees celcius (it might not be there because

I think you're oversimplifying it. The temperatures are unpredictable, with molten nuclear fuel possibly at 2000 degrees celcius (it might not be there because it's since cooled down, maybe there are temperature probes that can tell you what the current situation is) There are gases circulating around, free hydrogen gas, volatile gases that could explode if exposed to a spark - so the robot has to be built to not spark or have inert mechanisms for turning, moving, etc. Parts are submerged, so this robot needs to be water tight to irradiated water and have some mechanism of moving when submerged (buoyancy control). Radiation is the highest danger to electronics, it's said that all the wires degrade, all the parts of the robot steadily break down when trying to get inside. The chips and control circuitry needs to be radiation hardened, and I bet the "wires" the article refers to means servo control wires - which needs to be linked to servos that are on the limbs - so it's harder to shield. (whereas control chips, the cpu, etc can be shielded by lead plates in a central location)