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These radioactive plumes from severe nuclear accidents were calculated by NRDC based on the actual weather patterns of March 11-12, 2011. The result on any given day will vary according to the type of reactor accident and on the prevailing weather patterns at the time.

These five nuclear power plants had emergency shutdowns in 2011:

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. See what could have happened if a reactor in your area had a severe nuclear accident on March 11, 2011.info

Legend

  • Threshold for Radiation Sickness (75 rads)*
  • Maximum Radiation Dose Recommended for Emergency Responders (25 rads)*
  • Evacuation Recommended (5 rads)*
  • Sheltering Recommended (1 rad)*
  • 10-mile Evacuation Zoneinfo
  • 50-mile Potential Contamination Zoneinfo

* Acute radiation dose based on 48 hour exposure, assuming no sheltering. Sheltering can reduce radiation dose by a factor of ten or more.

Why U.S. nuclear power plants are vulnerable to severe accident with nuclear fallout

A future severe nuclear accident at a U.S. nuclear power plant is a real 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 backup power systems kicked in at these plants and a disaster was averted. But weather is not the only risk factor. Other risk factors include:

  • 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. On the map, NRDC experts assigned a red flag to a reactor if it is a BWR.
  • 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. On the map, NRDC experts assigned a red flag to a reactor if the NRC has approved the reactor to operate for 60 years.
  • Power level of reactor – The NRC has approved many utility operators to increase the operating power of their nuclear reactors, including for Fukushima-type reactors, and in some cases multiple times and to significantly higher power levels. These so-called "power uprates" push reactors beyond what they were originally engineered to do, and could increase the radiation hazard if a nuclear accident occurred. On the map, NRDC experts assigned a red flag if the NRC has granted a reactor a power uprate.

If a person received one rad of radiation from a nuclear accident, it would increase one's chance of getting cancer by 1 in 1,000 (averaged over all ages and both sexes). And although the NRC believes that the chances of a severe accident with fallout in a core meltdown for any one of the 104 U.S. nuclear reactors is small (probability of less than 1 in 10,000 per year), can we afford the risk? Millions of Japanese people were exposed to radiation from Fukushima, increasing their risk of developing cancer, and the cost of the Fukushima accident is projected to exceed US$100 billion, and the environmental effects will last for generations. What if a meltdown occurred at one of the 65 nuclear power plants in the United States?

Why we need urgent federal action to reduce the risks of U.S. nuclear accident fallout

With 6 million Americans living within 10 miles of a U.S. nuclear power plant – the evacuation zone defined by the federal government – and more than 120 million Americans living within 50 miles of a U.S. nuclear power plant – the distance the U.S. government told Americans to evacuate from the area around the Fukushima plant – we cannot afford to stand by and hope the worst won't happen here, especially with extreme weather intensifying around the globe.

Red flags for heightened risk factors of a severe nuclear accident abound in the United States. Currently 23 U.S. nuclear reactors are the same type of reactor, a boiling water reactor (BWRs), which was involved in the Fukushima nuclear disaster. Some BWRs are operating near major American cities like Philadlephia. Nearly all of the 104 nuclear reactors operating in the United States were designed and built three to four decades ago. Despite being originally engineered for a 40-year lifespan, the NRC has approved 71 reactors at 32 nuclear power plants to operate for 60 years. And 90 percent of U.S. nuclear reactors have had their operating power increased beyond the original design engineered for them.

Yet the NRC hasn't yet made a single U.S. nuclear power plant any safer than it was since the Fukushima accident about one year ago. After the Fukushima disaster, a task force assembled by the commission's chairman identified a list of safety improvements including top tier items to be "started without unnecessary delay." But these important safety upgrades are still years away from being implemented, if ever. In fact, some of these safety improvements have been on the commission's to-do list since the 1990s.

What happens in a severe nuclear accident like at Fukushima

Even after the nuclear chain reaction at a power plant is stopped by its operators, the reactor core still needs to be continually cooled, or the fuel rods will rupture and melt from the remaining radioactive decay heat. And if the level of cooling water falls below the core, the metal sheaths containing the uranium in the fuel rods will react with steam, producing explosive hydrogen gas. Therefore if power to run reactor core cooling is lost just for a matter of hours, it can lead to a meltdown – potentially releasing plumes of radioactive material into the air.

In Fukushima an earthquake caused the regional electric grid to go down, cutting off the nuclear plant's primary power. Then a tsunami flooded the low-lying diesel generators that were in place to provide backup power. Without power to cool the cores of its three fueled reactors, the severe accident at Fukushima began. Operators had to vent radioactive gases into the air in an attempt to reduce mounting pressure inside the reactor vessels. Hydrogen gas ignited and exploded in the reactor buildings, spewing plumes of radiation. Some of this fallout was blown out to sea by prevailing winds, but a plume of intense radiation spread northwest from the stricken plant for more than 50 miles. Because of the radioactive materials deposited by the plume, including cesium-137 and strontium-90, large areas in Fukushima Prefecture will be uninhabitable for generations. Lower levels of radiation drifted across other Japanese states and as far as Tokyo.

NRDC's methodology for building the U.S. nuclear fallout map

NRDC's nuclear fallout calculations were made using the weather reports from the National Oceanic and Atmospheric Administration for the specific days of March 11, 2011 and March 12, 2011. Using this historical weather data from the first days of the Fukushima accident, NRDC modeled where the radiation plumes released at Fukushima would have spread if it were a U.S. nuclear reactor that had melted down. For this work NRDC used the Department of Defense computer model "HPAC" – Hazard Prediction Assessment Capability. Some of the fallout patterns extend far from the nuclear plant, carried by strong winds blowing on those days. At other plants where the air was still in mid-March 2011, the fallout hovered over and settled on the vicinity of the plant. In our computer model of these severe nuclear accidents, the accident takes place over the course of two days with multiple releases of radiation, similar to what happened at Fukushima. As the wind changed direction over that period of time the fallout may be carried in different directions from the plant. Also shown in NRDC's map are the U.S.-government defined 10-mile evacuation zone, and 50-mile zones where the potential for land contamination would still be high in a severe nuclear accident.

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