Photograph from Kyodo/Reuters
Published August 7, 2013
Tensions are rising in Japan over
radioactive water leaking into the Pacific Ocean from Japan's crippled
Fukushima Daiichi nuclear plant, a breach that has defied the plant
operator's effort to gain control.
Prime
Minister Shinzo Abe on Wednesday called the matter “an urgent issue”
and ordered the government to step in and help in the clean-up,
following an admission by Tokyo Electric Power Company that water is
seeping past an underground barrier it attempted to create in the soil.
The head of a Nuclear Regulatory Authority task force told Reuters the situation was an "emergency." (See Pictures: The Nuclear Cleanup Struggle at Fukushima.”)
It marked a significant escalation in pressure for TEPCO, which has come under severe criticism
since what many view as its belated acknowledgement July 22 that
contaminated water has been leaking for some time. The government now
says it is clear that 300 tons (71,895 gallons/272,152 liters) are
pouring into the sea each day, enough to fill an Olympic-size swimming
pool every eight days. (See related, “One Year After Fukushima, Japan Faces Shortages of Energy, Trust.”) While Japan grapples with the problem, here are some answers to basic questions about the leaks:
Q: How long has contaminated water been leaking from the plant into the Pacific?
Shunichi Tanaka, head of Japan’s Nuclear Regulation Authority, has told reporters that it’s probably been happening since an earthquake and tsunami touched off the disaster in March 2011. (See related: "Photos: A Rare Look Inside Fukushima Daiichi.")
According to a report
by the French Institute for Radiological Protection and Nuclear Safety,
that initial breakdown caused "the largest single contribution of
radionuclides to the marine environment ever observed." Some of that
early release actually was intentional, because TEPCO reportedly had to
dump 3 million gallons of water contaminated with low levels of
radiation into the Pacific to make room in its storage ponds for more
heavily contaminated water that it needed to pump out of the damaged
reactors so that it could try to get them under control.
But
even after the immediate crisis eased, scientists have continued to
find radioactive contamination in the waters off the plant. Ken Buesseler,
a senior scientist with the Woods Hole Oceanographic Institution who
has analyzed thousands of samples of fish from the area, said he’s
continued to find the high levels of cesium-134, a radioactive isotope
that decays rapidly. That indicates it’s still being released. "It’s
getting into the ocean, no doubt about it," he said. "The only news was
that they finally admitted to this." (See related: "Photos: Japan's Reactors Before And After.")
Q: How much and what sort of radiation is leaking from the plant into the Pacific?
TEPCO said Monday that radiation levels in its groundwater observation hole
on the east side of the turbine buildings had reached 310 becquerels
per liter for cesium-134 and 650 becquerels per liter for cesium-137.
That marked nearly a 15-fold increase from readings five days earlier,
and exceeded Japan’s provisional emergency standard of 60 becquerels per
liter for cesium radiation levels in drinking water. (Drinking water at
300 becquerels per liter would be approximately equivalent to one
year’s exposure to natural background radiation, or 10 to 15 chest
X-rays, according to the World Health Organization.
And it is far in excess of WHO’s guideline advised maximum level of radioactivity in drinking water, 10 becquerels per liter.)
Readings fell somewhat on Tuesday. A similar spike and fall preceded
TEPCO’s July admission that it was grappling with leakage of the
radioactive water. (See related: "Would a New Nuclear Plant Fare Better than Fukushima?")
Scientists
who have been studying the situation were not surprised by the
revelation, since radiation levels in the sea around Japan have been
holding steady and not falling as they would if the situation were under
control. In a 2012 study,
Jota Kanda, an oceanographer at Toyko University of Marine Science and
Technology, calculated that the plant is leaking 0.3 terabecquerels
(trillion becquerels) of cesium-137 per month and a similar amount of
cesium-134
. While that number sounds mind-boggling, it’s actually
thousands of times less than the level of radioactive contamination that
the plant was spewing in the immediate aftermath of the disaster,
estimated to be from 5,000 to 15,000 terabecquerels, according to
Buesseler. For a comparison, the atomic bomb dropped on Hiroshima
released 89 terabecquerels of cesium-137 when it exploded. (See related:
"Animals Inherit a Mixed Legacy at Chernobyl.")
Another
potential worry: The makeup of the radioactive material being leaked by
the plant has changed. Buesseler said the initial leak had a high
concentration of cesium isotopes, but the water flowing from the plant
into the ocean now is likely to be proportionally much higher in
strontium-90, another radioactive substance that is absorbed differently
by the human body and has different risks. The tanks (on the plant
site) have 100 times more strontium than cesium, Buesseler said. He
believes that the cesium is retained in the soil under the plant, while
strontium and tritium, another radioactive substance, are continuing to
escape. (Related: "Japan's Nuclear Refugees")
Q: Why is the plant continuing to leak?
There
are at least a couple of possibilities. In an effort to cool and
control the damaged reactors, TEPCO has pumped enormous amounts of water
in and out. But that water is contaminated with radioactive material,
and it has to go someplace. According to a recent report
issued by the International Atomic Energy Agency, the plant operator
has been storing highly contaminated water in seven underground storage
ponds, which have a total of 60,000 tons (14.4 million gallons/54.5
million liters) of capacity. In April, TEPCO workers discovered that at
least three of the ponds were leaking. The IAEA concluded that the
company’s monitoring system, which hadn’t spotted the breach, was
insufficient to spot such outflow. So it could be that the faulty
containments, which are now being replaced, are the source of at least
some of the contaminated water that’s gotten into the ocean.
But
most experts seem to think that ordinary movement of groundwater
probably is the real culprit. An estimated 400 tons (95,860 gallons/
362,870 liters) of water streams into the basements of the damaged
reactors each day. Keeping that water from continuing to flow into the
ocean is crucial. As the IAEA noted in its report, "the accumulation of
enormous amounts of liquids due to the continuous intrusion of
underground water into the reactor and turbine buildings is influencing
the stability of the situation."
"Big surprise—water does flow downhill," said Dr. Janette Sherman,
a medical expert on radiation and toxic exposure who once worked as a
chemist for the Atomic Energy Commission, the forerunner of today’s U.S.
Nuclear Regulatory Commission. "If you’ve ever had a leak in your house
during a storm, you know how hard it is to contain water. There’s a lot
of water going into the plant, and it’s got to go someplace. It’s very
hard to stop this."
Q: What can be done to stop the leaking?
According to TEPCO’s latest full status report
on the cleanup of Fukushima Daiichi, issued in October 2012, the
utility company already had put in place an array of measures to try to
control the radioactive water. It built a groundwater bypass system,
which tries to siphon off and reroute groundwater flowing down from the
mountain side of the complex, before it can get into the basements of
the reactor buildings and be contaminated. But that doesn’t seem to have
made much of a dent in the problem. (See related: "Pictures: 'Liquidators' Endured Chernobyl 25 Years Ago.")
Plant
workers also tried to create an underground barrier by injecting
chemicals into the soil to solidify the ground along the shoreline of
the Unit 1 reactor building. But TEPCO officials Tuesday said the water
was seeping under or past this barrier. Officials also believe the water
is rising to the surface, which is a troubling development because it
could hasten leakage into the sea.
The company also
continues to add to a massive tank farm on the site, with capacity to
store about 400,000 tons (95 million gallons/360 million liters) of
contaminated water, and is planning to add an additional 300,000 tons of
capacity over the next three years. Unfortunately, TEPCO must deal with
an ever-increasing amount of contaminated water—nearly 150,000 tons
(35.9 million gallons/136 million liters) a year—so it’s inevitable that
the company is going to run out of storage space.
That’s
why TEPCO seems to be betting heavily on another solution—an elaborate
state-of-the art system for filtering the accumulated water and removing
radioactive materials from it. According to New Scientist, the new
system supposedly can filter out 62 different radioactive substances.
However, the April IAEA report noted
that the filtering system is still a work in progress, and that in
tests so far, "it has not accomplished the expected result" in terms of
removing radioactive material from the water.
Additionally, the system
doesn’t remove tritium, which isn’t as radioactive as other materials in
the water, but which still is a health hazard if it is inhaled or
ingested. The Wall Street Journal recently reported
that TEPCO hopes eventually to be able to discharge the cleansed water
into the ocean, though that plan would likely meet intense opposition
from local fishermen. Sherman, who has a chemistry background, said
she’s skeptical that such a process could work on the enormous scale
required. "You can precipitate these things out in the laboratory, but
you’re talking about millions of gallons here," she explained.
In a July 26 press release,
TEPCO also said it would continue construction of a shielding wall
along the waterline, but that structure will not be finished until
September 2014. Marine scientist Buesseler isn’t sure that will work,
either. "You can build a dam, but eventually the water goes around it,"
he explained.
Q: How far is the radiation spreading, and how fast does it travel?
The
initial gigantic deluge of contaminated water dispersed through the
immediate Fukushima coastal area very quickly, according to a 2012 report
by the American Nuclear Society. But it takes years for the
contamination to spread over a wider area. A mathematical model
developed by Changsheng Chen of the University of Massachusetts at
Dartmouth and Robert Beardsley of the Woods Hole Oceanographic Institute
found that radioactive particles disperse through the ocean differently
at different depths. The scientists estimated that in some cases, contaminated seawater could reach the western coast
of the United States in as little as five years. Buesseler thinks the
process occurs a bit more rapidly, and estimates it might take three
years for contamination to reach the U.S. coastline.
NOTE: Are they still telling these lies, considering all of the radioactive sea life, dead seals and actual Fukushima radioactive debris, boats, homes that have already washed up on the shore just 1 year after.
Q: What are the potential risks to humans, and who might be affected by the contamination?
This
is a murky question, because it’s not that easy to determine whether
health problems that may not show up for decades are caused by exposure
to radioactive contamination. A report
released in February by the World Health Organization, which was based
upon estimates of radiation exposure in the immediate wake of the
accident, concluded that it probably would cause "somewhat elevated"
lifetime cancer rates among the local population. But figuring out the
effect of years of exposure to lower levels of radioactive contamination
leaking into the ocean is an even more complicated matter.
Minoru Takata, director of the Radiation Biology Center at Kyoto University, told the Wall Street Journal
that the radioactive water doesn’t pose an immediate health threat
unless a person goes near the damaged reactors. But over the longer
term, he’s concerned that the leakage could cause higher rates of cancer
in Japan.
Marine scientist Buesseler believes that the
leaks pose little threat to Americans, however. Radioactive
contamination, he says, quickly is reduced "by many orders of magnitude"
after it moves just a few miles from the original source, so that by
the time it would reach the U.S. coast, the levels would be extremely
low. (See related, “Rare Video: Japan Tsunami.”)
Q: Will seafood be contaminated by the leaks?
As Buesseler’s research
has shown, tests of local fish in the Fukushima area still show high
enough levels of radiation that the Japanese government won’t allow them
to be caught and sold for human consumption—a restriction that is
costing Japanese fishermen billions of dollars a year in lost income.
(But while flounder, sea bass, and other fish remained banned for
radiation risk, in 2012 the Japanese government did begin allowing sales of octopus and whelk, a type of marine snail, after tests showed no detectable amount of cesium contamination.)
Buesseler
thinks the risk is mostly confined to local fish that dwell mostly at
the sea bottom, where radioactive material settles. He says bigger fish
that range over long distances in the ocean quickly lose whatever cesium
contamination they’ve picked up. However, the higher concentration of
strontium-90 that is now in the outflow poses a trickier problem,
because it is a bone-seeking isotope. "Cesium is like salt—it goes in
and out of your body quickly," he
explains. "Strontium gets into your
bones." While he’s still not too concerned that fish caught off the U.S.
coast will be affected, "strontium changes the equation for Japanese
fisheries, as to when their fish will be safe to eat." (See related
blog, “Safety Question on Fukushima Anniversary: Should Plants of the Same Design Have Filtered Vents?”)
This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge.
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