Nichole,
Some possible suggestions that may help.
Take the fundamentals of engineering exam if you haven't already, it helps show a breadth of knowledge. Taylor your resume or cover letter to emphasize the mechanical engineering aspects (heat transfer, fluid flow, etc.). The California Professional Engineer Board did a study (Title Act Study) and determined that ME and NE were the two most related engineering disciplines, so you should emphasize his fact in your cover letters.
Consider attending the Utility Working Conference in early August if you're a student member of American Nuclear Society. They're offering a student rate of $280, which is a steal if you can get a cheap place to stay (it's in Hollywood FL, just south of Ft. Lauderdale). Lots of mid and senior level utility management attends this meeting, so it would be a good networking opportunity.
Best of luck