Hello,

To become nuclear engineer it may required masters degree or phd level of education. Firstly you will have to score very good marks in your 12th class so work hard for that. Secondly after 12th bachelor degree for 4 years needs to be obtained and for that student should have very good command on physics, maths, chemistry, english and all important area of maths. 

After graduation masters degree needs to be pursued and than phd if required at that time. 

This is how you will become nuclear engineer.

All the very best for your future.