“It seems beaked whales may be more sensitive
than other species to sound.” — PEtER tyack
Japan nuke accident seen in Seattle
By Devin Powell
Radioactive particles wafting from
Japan to Seattle have been used as a window on recent events inside the crippled
Fukushima Daiichi nuclear power plant.
Working backward from trace nuclear
by-products, physicists have confirmed
that contaminated steam is the source
of this radiation, not spent fuel rods or
material ejected into the atmosphere
directly from the reactor core.
“We haven’t seen any of the heavier
stuff that would come right from the
core, which people saw 30 years ago
during the Chernobyl accident,” says
Andreas Knecht, a nuclear and particle
physicist at the University of Washington in Seattle who, along with colleagues,
published the new data online March 24
at arXiv.org.
Starting March 16, Knecht’s team saved
and analyzed filters that clean 100 million
liters of air every day in the ventilation
system of the University of Washington’s
physics and astronomy building. With
a detector originally designed to spot
neutrinos coming from outer space, the
researchers searched for gamma rays
originating in the by-products of nuclear
fission. The first such by-products from
Japan were detected on March 18.
The mix of elements found in the filters
drives home the differences between the
Chernobyl and Fukushima disasters. The
total meltdown of the Chernobyl reactor
in 1986, which exposed the core, belched
tons of radioactive material from fuel
rods directly into the atmosphere. At the
time, scientists in Paris detected 20 different isotopes. The partial meltdown of
Fukushima, in contrast, released only five
isotopes measurable by the Seattle team:
iodine-131, iodine-132, tellurium-132,
cesium-134 and cesium-137.
The absence of iodine-133, an ephem-
eral isotope that breaks down in days,
confirmed that the radiation spotted by
Knecht had been traveling for at least
a week or so. And the presence of tel-
lurium-132, a fission by-product that
degrades over weeks, suggests that the
windblown radiation came from mate-
rial that had recently seen fission inside
a nuclear reactor. This rules out older,
spent fuel rods as a source and points to
the fuel rods that were generating power
when the March 11 earthquake struck.
Beaked whales
can’t stand sonar
new study suggests species
are highly sensitive to noise
By Rachel Ehrenberg
Navy sonar unquestionably disturbs
beaked whales, concludes an analysis
investigating how underwater sound
affects these deep-divers. The results,
published online March 14 in PLo S ONE ,
suggest that noise-exposure limits for
beaked whales need to be lowered.
Beaked whales are especially sensitive
to underwater sound, which can disrupt
their behavior, a new study concludes.
the compound cesium iodide — probably
contaminated steam released to control
pressure inside the damaged reactors.
“This is what we expected to see,” says
Knecht. “But obviously it doesn’t hurt
to check.”
The team’s findings tell the same story
repeated by scientists at the Environ-
mental Protection Agency, the University
of California, Berkeley and other institu-
tions monitoring the West Coast: Only
minute amounts of radiation are reaching
the United States. Levels of radioactive
iodine, a cause for concern in Japan
itself, were in Seattle a mere hundredth
of the safety level set by the EPA.
“We’d like to confirm that what’s
coming over here is at a level which is
tolerable,” says Ed Morse, a nuclear
engineer at UC-Berkeley. “So far that’s
consistent with what we’re seeing.”
During sonar exercises at the U.S.
Navy’s underwater test range in the
Bahamas, beaked whales stopped their
chirpy echolocations and fled the area,
experiments employing a huge array of
underwater microphones revealed.
