|FUKU: Kłopoty i kłamstwa TEPCO, a niebezpieczeństwo - dla świata (ang.)|
|Wpisał: THE ASAHI SHIMBUN|
FUKU: Kłopoty i kłamstwa TEPCO, a niebezpieczeństwo - dla świata (ang.)
Doubts cast over TEPCO's plan to block radioactive water at Fukushima plant
[Czym różni się ślepota od morderczej krótkowzroczności? md]
THE ASAHI SHIMBUN
After nearly 30 months of failure, Tokyo Electric Power Co. is still providing little reason for confidence in its ability to deal with the radioactive water leaking at its Fukushima No. 1 nuclear plant.
The utility continues to face criticism for its delay in releasing vital information about conditions at the crippled plant. Fishermen and residents have lost patience over the many setbacks in TEPCO’s preparations to decommission the reactors.
And now, the Nuclear Regulation Authority is raising doubts about the utility’s latest plan: constructing underground walls to prevent the contaminated water from reaching the Pacific Ocean.
The immediate concern is radioactive water seeping along the seaward side of the No. 1 to No. 3 reactors and spilling into the sea.
TEPCO is currently solidifying soil with chemicals near a levee to prepare the ground for the walls.
But as work has progressed, the water level in observation wells has risen sharply to about 1 meter from the ground’s surface, apparently due to the accumulation of groundwater blocked from the ocean.
Due to limitations in construction methods, the walls can only be built with their tops at 1.8 meters beneath the surface. That means the water levels in the observation wells have already risen above the top edges.
If such a situation continues, the completed barriers will be unable to prevent the water from reaching the ocean. In addition, calculations show that if the water levels continue to rise at the current pace, contaminated water will flood the surface in about three weeks.
One huge problem facing TEPCO in dealing with the water is the maze of pits constructed beneath the Fukushima No. 1 plant site for pipes and power cables.
Immediately after the nuclear accident started in March 2011, an estimated 11,000 tons of highly radioactive water spilled into the pits under the No. 2 and No. 3 reactors. Some of that water is believed to have leaked further underground from cracks in the pits caused by the magnitude-9.0 Great East Japan Earthquake.
The reactor buildings are still connected to the pits, making it difficult to shut off the flow of water that becomes contaminated in the cooling process of the melted nuclear fuel that remains in the reactors.
A working group of the NRA held its first meeting on Aug. 2 regarding the leaking of contaminated water at the Fukushima plant.
The nuclear watchdog raised concerns that TEPCO’s plan to construct walls to block the leakage would be insufficient, and proposed pumping up the contaminated groundwater.
However, a TEPCO official said installing a pump would have to wait until late August because of the continuing construction work on the walls.
According to one calculation, about 100 tons of groundwater would have to be pumped up daily to prevent the water from leaking into the ocean. But the plant is running out of storage space for the contaminated water.
TEPCO officials remain confident that the completion of the walls in October will alleviate the water problem.
“There should be considerable improvement once we complete the additional measures,” Masayuki Ono, acting general manager of TEPCO’s Nuclear Power and Plant Siting Division, said at an Aug. 2 news conference.
TEPCO has also floated a plan to pump up groundwater flowing from the mountain before it enters the damaged reactor buildings and becomes contaminated. This “clean” water would be released into the ocean, thereby reducing the volume of contaminated water at the site.
However, local fishermen oppose the move in part because of their anger at the latest leaks of contaminated water into the ocean. They have also steadily lost trust in TEPCO.
Water contaminated with extremely high levels of radiation reached the ocean from the pits in the No. 2 and No. 3 reactors in April and May 2011.
TEPCO implemented measures to stop the leaks, and officials said they believed they had properly dealt with the problem at that time.
But in reality, contaminated water continued to flow into the ocean. TEPCO officials did not admit to that problem until July 22.
On Aug. 2, TEPCO officials said between 20 trillion and 40 trillion becquerels of radioactive tritium had leaked into the ocean. That is about 10 to 100 times the volume emitted over a one-year period of operating the nuclear plant.
“There is only a minor effect on the environment because it is about the same level as the upper limits of emission standards during operating periods,” a TEPCO official said.
However, TEPCO officials noted an increase in the volume of contaminated groundwater reaching the ocean since May, when concentrations of tritium in the water within the port at the Fukushima No. 1 plant began rising.
The utility estimated that between 20 trillion and 40 trillion becquerels will have entered the ocean by the end of July.
The company will make estimates of the flow of strontium, which has greater effects on the environment and tends to accumulate in human bones.
THE ASAHI SHIMBUN