Anything can fail. Nuclear reactors are built to last and designed to run safely with extensive safeguards. Yet what would happen if one failed in your US neighborhood such as as the Fukushima reactor did as a a result of a major earthquake? A new mapping tool was released by the Natural Resources Defense Council which illustrates the potential radiological impacts of a severe accident at the nation’s nuclear reactors and flags risk factors associated with each individual site. A future severe nuclear accident at a U.S. nuclear power plant is a possibility. In 2011 five nuclear power plants in the United States lost primary power due to earthquake or extreme weather events, including tornados, hurricanes, and flooding. Fortunately the designed backup power systems kicked in at these plants and a disaster was averted. There are 104 nuclear reactors in the United States. If one of them lost both primary and backup power for even a matter of hours, it could lead to a meltdown and an airborne radioactive plume. Besides natural causes there are other potential risk factors such as: Type of reactor — There are two types of reactors operating it the United States: Boiling Water Reactors (BWRs) and Pressurized Water Reactors (PWRs). Some experts judge that the design and structure of BWRs do not protect against the release of radiation during a severe accident as effectively as PWRs. The four reactors involved in the Fukushima nuclear crisis were BWRs. Age of reactor — Reactors were designed to operate for 40 years, yet the regulatory body that oversees nuclear safety in the United States, the Nuclear Regulatory Commission, has re-licensed some nuclear power plants to operate for 60 years, well beyond their originally engineered design lifetime. Power level of reactor — The NRC has approved many utility operators to increase the operating power of their nuclear reactors and in some cases multiple times and to significantly higher power levels. If a person received one rad of radiation from a nuclear accident, it would increase one\'s chance of getting cancer by 1,000 in 1,000,000 (averaged over all ages and both sexes). One out of every three Americans (330,000 in a million) will contract cancer during a full lifetime, when all causes are taken into account. In addition, the national risk of contracting cancer from radon gas exposure (a more natural exposure risk) is on the order of 1 in 500 (2,000 in a million). So the map tool is excellent for planning and general knowledge purposes but an evaluation of the true risk should be done by experts.