How did they suvive the bombs of 2077?
One of the reasons that Project Valhalla was set in the old Boden Fortress is that it had long ceased being an important military installation. So it was calculated to be a non-target. Furthermore, the region is one of the most sparest populated in Europe so a bomb or missile targeted there would be like using a cannon to swat a fly. Being so far north, near the Artic Circle, means that less fallout traveled through the jet stream to the populace and animals that were not sheltered. So more of the civilian population survived the war and were able to acquire food enough to repopulate the region.