Fukushima continues to be a mess. I am also quite critical regarding whether it
was ever satisfactorily designed in the first instance. Huge local tsunamis are endemic in the
geological record along the Pacific Rim and the only defense is to ensure
survivability of the facility and its back up.
That process started with placing the backup power out of harms way and
seriously elevated.
Of course, they remain defiant regarding releasing
news to the public and we have a background of speculation instead. It is not pleasant.
In the meantime I have seen no plans afoot regarding
the ultimate decommissioning that needs to take place. How about fuel transfer/
Fukushima's
Radioactive Water Leak: What You Should Know
Patrick J. Kiger
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.
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, visitThe
Great Energy Challenge.
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