Yugoslavia "explored" the possibility of developing nuclear weapons from 1954 until 1965, and invested in some dual-use nuclear technologies (with a lot of foreign "peaceful" nuclear assistance). In 1974, however, Tito did order that a nuclear weapons program be begun. For the next 13 years or so, this order remained in effect, though the project was not treated with a lot of urgency. They were not successful at making them, apparently because the program was extremely poorly managed. There were definitely efforts to bring "peaceful" nuclear energy to the country.

The best overall narrative that I know about is William Potter, Djuro Miljanic, and Ivo Slaus, "Tito's Nuclear Legacy" Bulletin of the Atomic Scientists 56, no. 2 (March/April 2000), 63-70. There is also discussions of why it failed in Jacques Hymans, Achieving Nuclear Ambitions: Scientists, Politicians, and Proliferation (Cambridge University Press, 2012), chapter 5 ("Proliferation implications of international civil nuclear cooperation: theory and a case study of Tito’s Yugoslavia"). The Nuclear Threat Initiative profile of Yugoslavia also has some discussion of their efforts.