What is an environmental consequences of nuclear energy?

Short answer: Contamination is a risk. Also, if you factor in all the work required to set nuclear energy into motion, you will see that it also contributes to adding carbon to the atmosphere.

Nuclear energy is not carbon-free as many believe. Mining and extraction costs carbon in fossil fuel; transportation costs carbon in fossil fuel; processing costs carbon in fossil fuel; building the nuclear power station costs carbon in fossil fuel. Then there's the question of highly radioactive waste storage for hundreds of thousands of years, leaks into the environment, coastal flooding of nuclear power stations like Sizewell. And the question of the added energy from splitting atoms which is extra to solar radiation and thus adds to the net energy input to the planet [an issue never even addressed]. It takes at least ten years to build a nuclear station so no quick fix, and decommissioning is even longer. It also costs billions, a price no government could hope to get taxpayers to pay, yet private industry won't fork out that sort of money. It's a pipe dream, something to use against those who argue renewable power is the only way to go.

It is true that nuclear energy is not purely carbonless. However, once you factor in the production and transportation costs, neither are solar, wind, geothermal, biomass, tidal, or hydroelectric power. One aspect that all of these energy sources, including nuclear, has in common are that once they are functioning they are emitting less CO2 into our atmosphere than coal and oil. Regardless of your feelings about coal and oil, they are not found on the earth in limitless supply, so therefore we as a society need to begin developing more renewable energy.

Obviously there will be environmental impact of mining the uranium (or another element thorium) that will be used to fuel the power plant. Uranium mines are under very strict guidelines that will help to prevent the surrounding mining area from any overly adverse affects (probably no more than what the uranium was doing naturally). Furthermore, nuclear power plants emit less radiation to the surrounding areas than coal fire power plants because the nuclear power plants are built more durably. The radioactive waste is a concern because right now our federal government will not allow this waste to be refurbished to be used again in a nuclear reactor like France does. Right now each power plant maintains their own waste. Decommissioning nuclear power plants is expensive but this is necessary in order to protect the environment . Overall, nuclear is one of many, not the only, solutions that our country needs to progress towards.