Don't worry about FFD, it is drugs and alcohol. Don't do illegal drugs and don't come in drunk for your interview. If you use prescription drugs, tell them when you are asked.
In the Nuke world, they appreciate what you know, but it is more important how you think.
Can you learn the material?
Can you make conservative decisions?
What is more important - safety or production?
Do you use procedures and follow them properly?
Do you stop when you are unsure and request assistance?
Can you accept coaching without being defensive?
Do you use your human preformance tools? Questioning attitude, situational awareness,STAR, take two, peer checking, etc?
If you do make a mistake, how do you respond to it?
Don't go into the interview with the expection that you can "ace" it. They will probably ask the usual "why do you want this job" type questions. They will probably also ask about your experience - What did you do to improve your previous work environment? What have you found wrong and how did you fix it? How did you handle conflicts with co-workers?
Good luck! Answer the questions honestly, and limit the unsollicited stuff. They are on a time limit and want to maintain control.