2 or 3 technical interviews with engineers. Mostly calculus and physics, but potentially chemistry or technical fields related to the academic concentration of the candidate. FInally, one behavioral interview with the 4-star admiral in charge of all naval nuclear reactors. He will ask questions about motivation, times you've failed (grades below a B), books you've read, etc. Technical interviews last 25-45 minutes each. Admiral interview lasts under 5 minutes and is the ultimate deciding factor in the hiring process.