Excess heat is returned to the source. Raising the temperature reduces the oxygen content of the water, creating an environmental stress on many kinds of living organisms. The heated water does, however, offer some possibilities for commercial aquaculture, allowing for warm-water species to be harvested in colder regions. The excess heat can also be used for commercial greenhouses or other applications. Air cooling is possible.
Critics also suggest that mining safety is an issue with the use of nuclear energy.
The ore is slightly radioactive. Radon gas is often present at the mine site. The disposed tailings contain trace amounts of uranium. Unless they can be disposed of properly, they can cause ground water contamination and environmental damage to the land on which they are dumped. The entire cycle, from mining the fuel to its eventual disposal after use, is called the nuclear fuel cycle .