I was surprised that the humans could manage to build a nuclear power plant while engaging in a world wide war with the Votans and amid falling space debris.
The war lasted for seven years before Arkfall began in 2030. The plant was built two years into the war, in 2025. It was necessary because the war had disrupted fossil fuel availability.
Besides, war generally promotes industry, so long as it's in service to the war effort. Look at how WWII helped pull America out of the Great Depression due to the surge in employment for building bombers, ships, and so forth. A nation at war would need reliable energy sources as well.