Why do Cleo and the other robots build a bug like creature using a nuclear battery?

The second law of robotics in Automata is that robots are not allowed to repair or modify themselves. While not specifically mentioned, this probably applies to creating new robots as well. But these new robots need a power source, something reliable, like the supposedly super rare nuclear batteries in the film (I say supposedly rare, because Jacq finds three in them in the course of like 2 days).

The spider-robot (as I call it) is presumably their first attempt at this new evolution of robots. But since they are never allowed to have tools or spare robot parts, they also don't have a spare battery to power it. A nuclear battery is nice, because it will produce electricity for decades.

[The head robot] says that humans are basically going to die out, but their memory will live on in the robots, noting they have hands only because humans do. Then this same jerk robot builds a new robot that looks like a spider. So much for the image of man living beyond the species. - Jack’s Bad Movies – Automata

Consequences of something designed by robot committee