PE Mechanical taking next year's PE Nuclear Exam

[MapuaTech]

I'm thinking if it's possible to take PE Nuclear Eng Exam next year 2013 by just registering thru NCEES and paying the Castle without informing the NYSED? It seems possible since I already have the records of credential evaluation and approved years of experience in NYSED. and I already passed the PE Mechanical- Thermal & Fluids exam. I choose to take the PE Nuclear since this is the closest "relative" of mechanical thermal fluids.

I tried registering for the October 2012 exam few minutes ago thru NCEES and ended up on the Castle World payment processing.

It may also be possible that even if I am a graduate of Mechanical, I can take any PE Exam.