Although the nuclear fuel cycle emits only small amounts of global warming pollution, nuclear power still poses significant risks to the world. In a number of countries, peaceful nuclear materials and equipment have already been diverted to secret nuclear weapons programs, and could be again. Even worse, they are susceptible to theft by, or eventual sale to, terrorists or international criminal organizations.  Storage pools of spent nuclear fuel are likewise vulnerable to terrorist attacks that could disperse lethal levels of radioactivity well beyond the plant perimeter. The release of radioactivity, whether from a reactor accident, terrorist attack, or slow leakage of radioactive waste into the local environment, poses the risk of catastrophic harm to communities and to vital natural resources, such as underground aquifers used for irrigation and drinking water.

There are continuing occupational and public health risks associated with uranium mining and milling, especially in areas where such activities are poorly regulated. And underground repositories, meant to isolate high-level radioactive waste and spent fuel from people and the environment for thousands of years, are subject to long-term risks of leakage, poisoning the groundwater for future generations.  From the Natural Resources Defense Council's New Nuclear Power Plants Are Not a Solution for America's Energy Needs.

Greg Palast, award winning investigative reporter for BBC, the Guardian, and the Observer, cautions that adequate safety precautions have not been observed and false test results have been reported by nuclear corporations in both Japan and the U.S.  Read his article, "Tokyo Electric to Build US Nuclear Plants: The No BS Info on Japan's Disastrous Nuclear Operators." Bloomberg News points to decades of faked safety reports for Japanese nuclear plants:  Japan Nuclear Disaster Caps Decades of Faked Reports, Accidents by Jason Clenfield - March 18, 2011.

Third generation nuclear power reactors, which are replacing the older second generation reactors, have safety factors which operate automatically instead of relying on human action and have standard designs so the approval process is shorter.  Like the second generation reactors, they produce nuclear waste which lasts hundreds of thousands of years.  Both second and third generation reactors use water to cool the reactor core.  

Currently scientists in many countries are working on fourth generation reactors which would use new technologies.  Their design uses a variety of methods to enhance safety, to minimize radioactive waste by recycling and using waste in the generation process, and to eliminate proliferation of weapons grade materials.   The aim is to have a reactor which produces very little radioactive waste which has a much shorter life span, a few centuries.   The United States has research groups working on a sodium cooled fast reactor and on a very high temperature reactor.   China, the USA, the UK, France, Japan, Canada, Argentina, South Korea, Republic of South Africa, Switzerland, and Brazil, are leading the development of the fourth generation reactors.  They hope to have designs certified for commercial use by 2030.  The lead laboratory for the U.S. is the Idaho National Laboratory.  For further information, see the Department of Energy's Generation IV Nuclear Energy Systems.

Nuclear reactors mainly use uranium as a fuel.  Known uranium resources can provide about  80 years of fuel for today's reactors at current worldwide levels of use.  Generation IV nuclear reactors under development will use 1/50 as much uranium so current known supplies will last 5,000 years.  The U.S. Department of Energy expects Generation IV reactors to be available for commercial use in 2030.  The U.S. gets only 10% of its uranium from domestic mines, mostly in Wyoming and New Mexico.  U.S. and world uranium supplies will last much longer if we can use other renewable resources as much as possible until the Generation IV nuclear reactors are available.