What are the risks for kidney donors during a transplant? can it be fatal?

Overall none : There can be some post operative complications sometimes, though not concerning and are related to surgery itself. Over all survival is same in the long term with some increase in bp, more often in black patients. Black and hispanic patients can develop more chronic kidney disease. 1 in 3500 donation is fatal.

Very small : The surgical risks are small but not zero. There have been a few deaths shortly after kidney donation. But very rare, less than 1 in three thousand, is the number i recall. There is probably no safer major surgical procedure done today. That is due to the fact that donors are heavily screened and are in better shape than "average" patients.