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发帖数: 22092 | 1 U.S. Flights Over Plant Gather Crucial Data
By DAVID E. SANGER and WILLIAM J. BROAD
Published: March 17, 2011
http://www.nytimes.com/2011/03/18/world/asia/18intel.html?_r=1&
WASHINGTON — The first readings from American data-collection flights o
ver the stricken Fukushima nuclear plant in Japan show that the worst of
the contamination has not spewed beyond the 18-mile range of highest co
ncern established by Japanese authorities, but there is also no indicati
on that another day of frantic efforts to cool nuclear fuel in the react
ors and spent fuel ponds has yielded any progress, according United Stat
es government officials.
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Status of the Nuclear Reactors at the Fukushima Daiichi Power Plant
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(March 18, 2011)
U.S. Calls Radiation ‘Extremely High;’ Sees Japan Nuclear Crisis Worse
ning (March 17, 2011)
Scientists Project Path of Radiation Plume (March 17, 2011)
The Lede Blog: Japan Earthquake and Tsunami: How to Help (March 11, 2011
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The data was collected in the first use of the Aerial Measurement System
, among the most sophisticated devices rushed to Japan by the Obama admi
nistration in an effort to help contain a nuclear crisis that the top Am
erican nuclear official said Thursday could go on for “possibly weeks.”
The data show ground-level fallout of harmful radioactive pollution in
the immediate vicinity of the stricken plant — a different standard tha
n the trace amounts of radioactive particles in an atmospheric plume now
projected to cover a much broader area.
While the findings were reassuring in the short term, the United States
declined to back away from its warning to Americans to stay at least 50
miles from the plant, a far larger perimeter than the Japanese governmen
t has established.
In interviews, American officials said their biggest worry was that a fr
enetic series of efforts by the Japanese military to get water into the
four reactors — including water cannons and fire-fighting helicopters t
hat dumped water but appeared to largely miss their targets — showed fe
w signs of working. Another effort by the Japanese, to hook electric pow
er back up to the plant, only began on Thursday and was likely to take s
everal days to complete — and even then it was unclear how the cooling
systems, in reactor buildings battered by the tsunami and then torn apar
t by hydrogen explosions, would work, if at all.
“What you are seeing are desperate efforts — just throwing everything
at it in hopes something will work,” said one American official with lo
ng nuclear experience, who would not speak for attribution. “Right now
this is more prayer than plan.”
After a day in which American and Japanese officials had radically diffe
rent assessments of the danger of what is spewing from the plants, the t
wo governments attempted Thursday to join forces. Experts met in Tokyo t
o compare notes. The United States, with Japanese permission, began to p
ut intelligence-collection aircraft over the site, in hopes of gaining a
view for Washington as well as its allies in Tokyo that did not rely on
the announcements of officials from the Tokyo Electric Power Company. O
fficials say they suspect that company has consistently underestimated t
he risk and moved too slowing to contain the damage.
Aircraft normally used to monitor North Korea’s nuclear weapons activit
ies — a Global Hawk drone and U-2 spy planes — were flying missions ov
er the reactor, trying to help the Japanese government map out its respo
nse to the quake, the tsunami and now the nuclear disaster.
President Obama made an unscheduled stop at the Japanese Embassy to sign
a condolence book, writing, "My heart goes out to the people of Japan d
uring this enormous tragedy.” He added: “Because of the strength and w
isdom of its people, we know that Japan will recover, and indeed will em
erge stronger than ever.”
But before the recovery can begin, the nuclear plants must be brought un
der control. And so American officials were fixated on the temperature r
eadings inside the three reactors that had been operating until the eart
hquake shut them down, and at the spent fuel ponds, looking for any sign
s that they were decreasing. So far they saw none, but on the Web site o
f the International Atomic Energy Agency, the United Nations nuclear wat
chdog, it was clear that there were no readings at all from some critica
l areas. Part of the American effort, by satellites and aircraft, is to
identify the hot-spots, something the Japanese have not been able to do
in some cases.
Critical to that effort are the “pods” flown into Japan by the Air For
ce over the past day. Made for quick assessments of radiation emergencie
s, the Aerial Measuring System is an instrument pod that fits on a helic
opter or fixed-wing aircraft to sample air and survey the land below. Th
e information is used to produce colored maps of radiation exposure and
contamination.
The sensors on the instrument pod are good at mapping radioactive isotop
es, like Cesium-137, which has been detected around the stricken Japanes
e complex and has a half-life of 30 years. Its radiation can alter cellu
lar function, leading to an increased risk of cancer.
Cesium-137 mixes easily with water and is chemically similar to potassiu
m. It thus mimics how potassium gets metabolized in the body and can ent
er through many foods, including milk. Cesium gets widely distributed in
the body and its concentrations are said to be higher in muscle tissues
and lower in bones.
On Wednesday when the American Embassy in Tokyo, on advice from the Nucl
ear Regulatory Commission, told Americans to evacuate a radius of “appr
oximately 50 miles” from the Fukushima plant, the recommendation was ba
sed on a specific calculation of risk of radioactive fallout in the affe
cted area.
In a statement, the commission said the advice grew out of its assessmen
t that projected radiation doses within the evacuation zone might exceed
1 rem to the body or 5 rem to the thyroid gland. It is extremely sensit
ive to Iodine-131 — another of the deadly radioactive byproducts of nuc
lear fuel that causes thyroid cancer.
A rem is a standard measure of radiation dose. |
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