While the undergraduate courses for both nuclear physicist and nuclear engineer are similar, graduate courses are different as are the job descriptions. Nuclear physicists do more theoretical things. They look at the essence of matter and develop and test out theories on how matter is constructed but at the subatomic level – what holds atoms together, what is dark matter, and where did the universe come from? Most of the scientists that you see on TV that discuss string theory and parallel universes are nuclear physicists. Nuclear engineers, like other engineers, are more concerned with taking theory and turning it into reality - how things work and how they can be used. As a nuclear engineer, I have worked on nuclear power plants, nuclear or radio-isotope powered space craft, detecting nuclear materials in transit and protecting people from radiation in general. Some nuclear engineers also work on designing nuclear devices for the military. Hope this helps.