Atomic/Nuclear Scientist

There were thousands of scientists, engineers, military and government officials involved in the production of nuclear weapons and atomic research during the mid ninteen-hundreds. In the following posts include: personal history of scientist or official - country, interesting info about the person, etc. Then focus on his/her specific research/actions/relationship with nuclear/atomic research. What did they do? Be specific and thorough so the reader obtains a real feel for and understanding of whom this person was and what they did!