1 - Physics of Uranium and Nuclear Energy - World Nuclear Association - https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/introduction/physics-of-nuclear-energy.aspx - [Under: Nuclear fission - the process].

2 - World Uranium Mining Production - https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/mining-of-uranium/world-uranium-mining-production.aspx.

3 - Nuclear Power Reactors in the World - International Atomic Energy Agency - https://www-pub.iaea.org/MTCD/Publications/PDF/rds2-35web-85937611.pdf - [pg. 74]

 4 - Nuclear Reactor Types - Institute of Electrical Engineers - http://large.stanford.edu/courses - [pg. 3]

5 - Nuclear Explained - U.S. Energy Information Administration - https://www.eia.gov/energyexplained/nuclear/us-nuclear-industry.php

6 - Chernobyl: the true scale of the accident - World Health Organization - https://www.who.int/news/item/05-09-2005-chernobyl-the-true-scale-of-the-accident