Sofia
The Institute of Atomic Nuclear Weapons Research was established in complete secrecy. Nuclear weapons research certainly could not be conducted in a city; this stuff was highly dangerous. If an accident occurred, half of Sofia would be gone.
Choosing a site was no simple matter either. If it was too remote, the scientists would be unwilling to go. Such things could not be forced.
If these people were in a bad mood, who knew when results would come? Hadn't the Germans been screwed to death by exactly that?
Even if Bulgaria's reserves were now greater than Germany's, it could not withstand that kind of waste.
Atomic energy research naturally could not consist of just one project team. It was a systematic undertaking, with many supporting applications.
These included multiple projects such as nuclear power stations and nuclear energy applications.
Historically, when the Americans conducted nuclear energy research, no one initially knew the atomic bomb would be so devastating. Within the atomic energy program, the atomic bomb could only be considered a byproduct.
Bulgaria was the same now. Apart from Ferdinand, no one else knew just how powerful an atomic bomb was. Otherwise, persuading these scientists to take part in the research would have been a problem in itself.
Take anti-war advocates like Einstein, for example. Asking them to build atomic bombs—who knew what they might end up creating?
Ferdinand wisely had them conduct nuclear power research. It was something that benefited all mankind, so naturally they would not refuse. The people truly in charge of the nuclear weapons project teams were all purely Bulgarian scientists.
They had grown up steeped in patriotism and possessed a lofty patriotic conscience. For the sake of national interests, they felt not the slightest pressure no matter what weapons they were asked to make.