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U.S. boosts radiation-sniffing system

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A RadNet radiation monitor is seen on the roof of the Bay Area Air Quality District offices in San Francisco.

Last updated 1:50 a.m. ET March 17:

Federal agencies are beefing up their radiation-monitoring capabilities at home and abroad, even as they insist that significant amounts of fallout won’t waft from Japan onto U.S. territory.

At home, the Environmental Protection Agency said it's adding seven monitors in Alaska, Hawaii and Guam to its RadNet radiation-tracking system, which operates about 100 air-sniffing stations nationwide. Putting in those extra stations "allows us to gather data from a position closer to Japan," EPA said in an online question-and-answer guide.

Looking beyond America's borders, the U.S. Air Force is sending out a high-tech aircraft to sniff the air over Japan for radiation. The Nuclear Regulatory Commission and the Department of Energy's National Nuclear Security Administration are also sending experts to Japan to help counter the growing crisis at Japan's Fukushima Dai-ichi nuclear plant complex.

The NRC and the NNSA have teams who track how hazardous materials spread through the atmosphere, based on computer modeling and other methods. It was the NRC's revised analysis that led to today's advisory telling Americans to evacuate the area within 50 miles (80 kilometers) of the Fukushima reactors.

White House spokesman Jay Carney acknowledged that the NRC's advice goes far beyond what the Japanese government is telling its own citizens — that is, for residents to evacuate the area within a 12-mile (20-kilometer) radius of the plant, and to take shelter if they're within 19 miles (30 kilometers).

"The advice the Japanese government is giving, based on information it has, is different from the advice that we would be giving if this incident were happening in the United States of America," Carney said. "It is not about the quality of information. It is about the standards set by the Nuclear Regulatory Commission here in the United States and the kind of advice it would be giving should this incident happen in the United States."

For what it's worth, the NRC calls for protective action when projected doses exceed 10 millisieverts (1 rem) or 50 millisieverts (5 rem) to the thyroid. Radiation levels at the damaged plants rose as high as 400 millisieverts per hour.

How the calculations are made
The NRC's analysts make detailed calculations to work out what the potential radiation exposure would be at various distances.

"Usually these calculations are very specific," NRC spokeswoman Viktoria Mitlyng told me. "You have to consider the particular radioisotope, and at what concentration it's going to occur, and what distance it is going to travel, and whether it's going to travel at all toward the United States. ... The farther away you are from the radiation source, the less impact it's going to have."

Commercial sales of Geiger counters are, um, hot in the United States — but EPA's RadNet provides a much more reliable read when it comes to detecting radioactive fallout if it ever comes across the Pacific. The radiation-monitoring network not only sniffs the air, but also samples drinking water, milk and precipitation. The first elements of the system were set up back in 1959, even before the EPA was created, to monitor U.S. military nuclear testing.

You can check the EPA's archived radiation readings for your own locale by clicking through an online database, or reviewing the quarterly data journals. By the way, radiation measurements for Japan are available via this Web page.

Pentagon watches radiation, too
The Department of Defense is keeping close tabs on radiation levels in the Fukushima area and beyond — not only because it has thousands of people working on the humanitarian relief effort, but also because of the potential risk to 50,000 military personnel in Japan and the impact on military installations in the Pacific.

Air-monitoring equipment on the aircraft carrier USS George Washington detected low levels of radioactivity while the ship was in port at Yokosuka in Japan, a military spokesman said Tuesday. On another carrier, the USS Ronald Reagan, 17 helicopter crew members had to be decontaminated with a soap-and-water scrubdown after returning from search-and-rescue duty. Potassium iodide pills, which can guard against the uptake of radioactive iodine, were issued to some of those crew members, the Defense Department said.

The radioactive plume from Fukushima's reactors can't be detected by satellites in orbit, but it can be tracked by the U.S. Air Force's Constant Phoenix WC-135 jets, which are designed to monitor airborne fallout from nuclear weapons tests. Constant Phoenix came into play after the 1986 Chernobyl nuclear disaster in Ukraine to sample the air over the Atlantic. "Most recently, WC-135 was used to detect seismic events associated with North Korea's claim of a nuclear test in October 2006 and again in May 2009," an Air Force spokesman, Maj. Chad Steffey, told me in an e-mail.

Steffey confirmed that a Constant Phoenix WC-135 would be sent to sample the air wafting from Japan, in response to a Japanese government request. The planes would be brought from Offutt Air Force Base in Nebraska. Steffey said he didn't yet have details about the timing of the operation. 

Speaking on condition of anonymity, a senior U.S. defense official told NBC News that Constant Phoenix's involvement was "absolutely" a significant event. "We are using it to help out a nation," the official said. "It's significant."

Extra credit:I sent the NRC's Viktoria Mitlyng some questions asking how the agency comes up with its projections for radiation exposure, and here are the answers she sent back:

Q: Are there computer models that are run to figure out how material is dispersed, or how specific radionuclides could affect residents at given distances?

A:Yes, the NRC uses a particular model for determining dispersal analysis for radionuclides from nuclear power plants.

Q: Given the distance from Japan to U.S. territories, is it a given that there will be no effect?

A:The NRC uses the limit of 1 rem [10-millisievert] dose limit to the whole body to recommend evacuation. It is highly unlikely that radiation can reach the U.S. from Japan and result in this type of exposure.

Q: What levels of emission would cause concern, based on what’s known about radioactive particulates and their dispersal?

A: The NRC recommends evacuation at 1 rem dose limit to the whole body. Models are run with varying sets of data and the results are analyzed to determine what kinds of response if any is warranted to protect public health.

Q: What sorts of resources and personnel are engaged in this sort of analysis?

A: Trained health physicists and other experts have been monitoring the situation in Japan at the NRC’s Headquarters Operations Center around the clock since the beginning of the crisis in Japan.

CTBTO via New York Times

This chart, attributed to the Comprehensive Test Ban Treaty Organization, shows the potential projected path of atmospheric plumes sent out from Japan's stricken Fukushima Dai-ichi nuclear plant. Click on the image for the full story from The New York Times.

Update for 1:50 a.m. ET March 17: The New York Times reports that the Comprehensive Test Ban Treaty Organization, a U.N. agency based in Vienna, has drawn up a simulation showing the progress of Fukushima's radioactive plume across the Pacific. Assuming that the plume began to rise on Saturday, and assuming that the radiation levels were detectable, the readings might be picked up in Alaska's Aleutian Islands today (Thursday) and in Southern California late Friday, the Times reported.

However, this projection is based merely on a reading of the weather patterns between Japan and the United States, and how those patterns might disperse material in the plume. Officials at the test ban agency made clear that this was not a prediction that radiation would be detected at any particular level. Rather, the projection was meant as guidance for atmospheric monitoring stations. Over the next few days, air-sniffing authorities should have a better fix on Fukushima's radioactive releases.   

More on the disaster in Japan:

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