situation at the Fukushima Daiichi reactors unfolded in Japan, several
employees at the U.S. Department of Energy’s Argonne National Laboratory were
lacing up their boots.
the Radiological Assistance Program (RAP) team, region five, their normal
operating ground covers 10 Midwestern states—but this time their expertise was
needed abroad. Trained in radiation detection and monitoring, RAP teams are on
call twenty-four hours a day to respond to any release of radiological
materials in the U.S.
reactors at Fukushima Daiichi began to emit radioactive material, the
Department of Energy’s national emergency response assets, including several
RAP teams, responded to calls from both the U.S. Department of State and the U.S. military.
They wanted guidelines on protecting U.S.
citizens and military personnel stationed in Japan from radiation hazards; but
this raised the enormous task of finding out how much radiation had been
March, several Argonne members flew to Japan
to take over shifts from the initial response team members, who had been
working around the clock to take measurements at U.S.
military bases, other U.S.
interests, and elsewhere in the 50-mile radius around the reactors.
ground, small teams set out to comb the earthquake-stricken countryside,
radiation detectors in tow. They took hundreds of readings and collected soil
samples, mostly between the 20 to 80 km zone from the plant.
into challenges right away.
of the problems we ran into was accessibility,” says Dave Chamberlain, an Argonne chemical engineer with RAP. “When you
practice going out to get samples, the classic technique is to divide the area
into a grid and take samples say, every 10 m. But many of the areas we were sampling
were mountainous, forested and damaged by earthquakes, so you can’t stick to
the grid plan. We were often limited to roadside sampling.”
other difficulty was that we wanted samples from ground that hadn’t been
disturbed since the accident,” explains Chamberlain. “If someone had
plowed or watered the ground, it changes the dynamics of the distribution—and
that time of year is rice planting season in Japan.”
measured both the dose rate and the gamma ray spectrum in each area. Gamma ray
spectroscopy is a measure of the gamma rays emitted by radioactive particles,
and it can be analyzed to determine how much of each different radiological
isotope is present. Dose rate is a measure of the dose a human would receive in
a particular location over a given amount of time.
and samples collected by the teams will be analyzed in labs around the country,
providing both information for Japan’s
recovery and a more detailed understanding of what happens to radioactive
material after it’s released.
radiation disperses from a source, you get a plume that travels, and it changes
according to wind, moisture and particulates in the air,” explains Argonne
RAP scientist Frank Moore. “But once it’s laid on the ground, it moves
get an accurate picture, you have to measure the same location several times
over a period,” he says. “Radiological material doesn’t just sit
there; it migrates into the environment. It can soak into the soil, or can run
off in rivers and streams and collect in low areas. Near roadways, it might
collect in the ditches. And it can be taken up into plants.”
Department of State coordinated sharing the data with Japanese authorities, Moore says. They also
left several detectors behind and trained both U.S. military and Japanese
personnel how to use them.
RAP team isn’t responding to threats, they provide radiation training to law
enforcement—including police, FBI, firefighters, and Border Control
guards—around the country. Though airports, shipping ports, and border
crossings are often equipped with radiation detectors, interpreting results
from the sensitive instruments can be tricky.
For example, medical patients can sometimes set off radiation monitors in
airports; certain procedures use small amounts of radioactive tracers to map
the body, and it can take several days for the tracers to decay. But guards
with detectors need to be able to tell the difference between medical scan
residue and a potentially dangerous source of radiation; the RAP team members
provide training to distinguish threats.