Depends on what you're looking for.
If you mean the generic fundamentals exams, yes, they are all in one place.
Go to the following link and you will see "Generic Fundamentals Examinations" on the right, broken up by type of power reactor. Under each link, you can find the entire exam bank, or individual exams.
http://www.nrc.gov/reactors/operator-licensing.htmlFurthermore, for generic fundamentals, here is an excellent site for generating your own quizzes;
http://nuclear.allenmurrow.com/If you're talking about licensing exams, that is a different story. They are in the NRC library, but they aren't bundled up in a nice package like generic fundamentals. You have to search the ADAMs database for what you're looking for. And it isn't easy, or intuitive. It took me a few hours to find the last 5 exams my station put out.
http://adams.nrc.gov/wba/Good luck, hope that helps.
Justin