Answer:
False.
Explanation:
A small mass defect in a nuclear reactor is responsible for producing a large amount of energy. The end products might be radioactive and might have to be disposed correctly but I doubt that there would be any sort of greenhouse gas emission.
Coal on the other hand is a, vaguely speaking, a group of hydrocarbons, which on combustion gives carbon dioxide. Carbon dioxide is a major greenhouse gas responsible for greenhouse effect along with other gases like methane which could also be present in coal in some quantity.
