Those nuclear engineering students who are just starting school again, need to start thinking about summer already. The best route to getting a job after graduation is through the connections you make with internships. The experience you get with an internship will help you decide what aspect of nuclear engineering you want to work in after you graduate. They also give employers a chance to see how you work and if you are a good fit for their organization.
That being said, the internship process can be lengthy. I suggest that this month you start to talk to professors in your department about possible internships next summer. Tell them what you are interested in and ask for his/her advice. Then when you’ve identified the companies, and even better if its a manager, make contact this fall so that you are on the radar when hiring decisions are made.
The long lead time is important in nuclear due to security as well. Most facilities have some sort of back ground investigation before you can be admitted to the workplace. That means finding an internship in April is too late for a lot of places.
Good luck!