Whether by virtue of regular testing of sirens, mailings about emergency plans or possibly the receipt of potassium iodide (KI) pills, there are frequent reminders for those who live within a 10-mile radius of a U.S. nuclear power plant of the need to be ready should a significant event occur at the facility.
This area is known as the 10-mile Emergency Planning Zone (EPZ), and it is well established in federal regulations as the focal point of preparing for a severe accident at a reactor.
Some confusion has cropped up in the media and elsewhere recently regarding the size of EPZs in the wake of developments involving the Fukushima Daiichi reactors and spent fuel pools in Japan. The source of this confusion appears to stem from the NRC advisory on March 16th for American citizens who were within 50 miles of the plant to evacuate: http://pbadupws.nrc.gov/docs/ML1108/ML110800133.pdf.
The advisory to evacuate to 50 miles was based on calculations done by NRC experts indicating releases from the three hobbled Japanese reactors and two fuel pools could – and a key word here is could – possibly exceed conservatively set safe radiation-exposure limits for the public. This advisory was made using limited data and conservative assumptions.
On its face, this recommendation seems to be at odds with the size used for American EPZs. In fact, it was consistent with the same kind of approach that would be used in the United States should a comparable, although extremely unlikely, event take place here.
In November 1976, a federal task force was formed to look at salient emergency planning issues for U.S. nuclear power plants. Out of that comprehensive evaluation came a recommendation that a 10-mile-radius EPZ would assure that “prompt and effective actions can be taken to protect the public in the event of an accident” at a plant. This was based on research showing the most significant impacts of an accident would be expected in the immediate vicinity of a plant and therefore any initial protective actions, such as evacuations or sheltering in place, should be focused there.
Put another way, the projected radiation levels would not be expected to exceed EPA protective action dose guidelines (1 rem to the body or 5 rem to the thyroid) beyond 10 miles under most accident scenarios.
That does not mean the protective actions could not expand beyond the 10-mile radius. Rather, emergency planners have always known such actions could be necessary if the situation warranted it. Indeed, U.S. nuclear power plants are required to consider and drill for the possibility of radiation releases that could have impacts up to 50 miles away, in addition to the required biennial exercises conducted in the vicinity of each nuclear power plant to assess implementation of the emergency plan within the 10-mile EPZ. Once every six years, each plant takes part in an exercise graded by the NRC and FEMA to demonstrate how it would handle such an event.
As the document NUREG 0654/FEMA-REP-1 on emergency planning states “In a particular emergency, protective actions might well be restricted to a small part of the planning zone. On the other hand, for the worst possible accidents, protective actions would need to be taken outside the planning zones.” (This joint document is the basis for emergency planning around nuclear power plants and adds background to our regulations found in 10CFR 50.47.)
The Japanese have been confronted with extremely challenging circumstances wrought by a record earthquake followed by a massive tsunami. As the NRC carefully monitored developments there, the agency used the best information available to it to make a protective action recommendation to the U.S. Embassy in Tokyo for Americans within 50 miles of the six-reactor Japanese site, which was experiencing problems in four reactors and two spent fuel pools.
Were a similar accident to occur in the U.S., the response would be guided by the same considerations. But it is worth noting the United States has no nuclear complexes of this size.
Once the salient facts regarding the events at Fukushima Daiichi are made clear to the NRC, it intends to assess its own regulations and practices for any pertinent lessons learned that can be applied here. This will include an assessment of current emergency planning guidance and policy.
As the NRC carefully monitored developments there, the agency used the best information available to it to make a protective action recommendation.
More information on emergency planning for U.S. nuclear power plants is available on the NRC website at: http://www.nrc.gov/about-nrc/emerg-preparedness.html .
Eliot Brenner
Public Affairs Director
U.S. NRC Blog 
Excellent post. The dose projections based on plant conditions are, by necessity very conservative however, real time monitoring and meteorology are being used to refine the dose projections. What are the results of plume monitoring interms of the extent of core damage and of the cumulative dose to the maximally exposed member of the Japanese public? Has the U.S. Department of Energy provided the results of its monitoring activities to the NRC? What are the results?
I was wondering when the specialists are going to address the cumulative affects of these so-called, miniscule levels of radiation that we are seeing in the NW and other parts of the U.S.? If we are breathing them in every day, they are accumulating in our children even faster. This can not be harmless when all is said and done. How can no one be addressing this?
The article above as the following statement “U.S. nuclear power plants are required to consider and drill for the possibility of radiation releases that could have impacts up to 50 miles away” Yesterday residents of Tokyo were warned about Iodine 131 contamination of the public water supply. Tokyo is some 125+ miles from the Fukushima Dai-ichi complex. This seems to indicate that impacts can extend well beyond 50 miles. I understand that the levels are minimal so far and that it is primarily a concern to very young chldren, but even though I have no children it is obvious to me that when the health and safety of young children is impacted it impacts much of the rest of the population, their families. My concern is for large population centers near nuclear plants such as Indian Point. I understand that the Shoreham plant was never granted an operational license due to the inability to efectively evacuate the high numbers of people on Long Island and nearby NY city. Should the wisdom of operating the Indian Point nuclear plant so close to NY city not be re-evaluated at least as to extraordinary preparedness to deal with emergency situations?
Why is no data being posted as to the amount of radioactive iodide, cesium, stronshium, and the particularly dangerious plutonium being detected in various areas of the U.S. where the plumes are passing over? Data such as below or above normal amount in air, ground, water, etc.? Is it true that one, one millionth of a grain of plontonium when inhaled can lead to lung cancer?