Hi,

What do you meant by 'practical'? If you are thinking about an 'experimental' thesis on fuel rod design, I should say this is almost a thermo-mechanical work which needs a little amount of neutronic studies. By the way, as a nuclear physics student you should focus on more relevant topics which lays within the scope of nuclear reactions.

I can give you more realistic/practical examples, but maybe later.

An example of a master's thesis that you can easily realize is to measure the natural and artificial radioactivity in the soil in your area by gamma spectrometry