There is considerable controversy over whether nuclear power can be considered sustainable, with debates revolving around the risk of nuclear accidents, the generation of radioactive nuclear waste, and the potential for nuclear energy to contribute to nuclear proliferation. These concerns spurred the anti-nuclear movement. Public support for nuclear energy is often low as a result of safety concerns, however for each unit of energy produced, nuclear energy is far safer than fossil fuel energy and comparable to renewable sources. The uranium ore used to fuel nuclear fission plants is a non-renewable resource, but sufficient quantities exist to provide a supply for hundreds of years. Pathways consistent with ambitious climate policy typically see an increase in power supply from nuclear, but growth is not strictly necessary.