Leaking pipe connecting tanks adds more woes at Fukushima plant

September 02, 2013

THE ASAHI SHIMBUN

A leaking pipe connecting storage tanks of radiation-contaminated water at the crippled Fukushima No. 1 nuclear power plant has been found, adding another source of concern for potential leaks along with the bolted sections of the steel plates of tanks.

Plant operator Tokyo Electric Power Co. announced on Sept. 1 that highly radioactive water had been found in a different section of tanks used to store the vast amounts of water used to cool the plant's crippled reactors. That leak raises fresh doubts about the network of piping on the site through which contaminated water is being transferred between tanks.

On Sept. 2, Prime Minister Shinzo Abe said the government will implement prompt, comprehensive measures to resolve the continuing water-leakage problems at the Fukushima No. 1 plant. During a liaison meeting between the government and his ruling Liberal Democratic Party, Abe vowed that the government will compile a basic policy to resolve the crisis as soon as possible.

“From now on, the government will be out front in initiatives to implement necessary measures, not leaving the situation in the hands of TEPCO,” the prime minister said. “We will also implement comprehensive measures; not the haphazard ones that have been taken so far.”

The government will convene the Nuclear Emergency Response Headquarters and announce a set of concrete policy measures as early as Sept. 3.

The latest leak was found in a section of tanks called the H5 area, which is situated about 100 meters southwest of the H4 area, where about 300 tons of contaminated water was found to have leaked on Aug. 19.

That came after a worker patrolling the H5 section on Aug. 31 pressed on insulation outside a pipe connecting two tanks and drops of water trickled out. Radiation levels on the floor were measured at about 230 millisieverts per hour. When the insulation was removed, workers found a drop of water leaking from the connecting section every 90 seconds or so.

Workers also measured radiation levels at a tank in the H3 area that reached 1,800 millisieverts per hour on Aug. 31. Readings at the same location were 1,100 millisieverts on Sept. 1, but radiation levels on the opposite side of the same tank were 1,700 millisieverts per hour.

An exposure of 1,800 millisieverts per hour for about four hours is considered fatal to a human being. But workers can be shielded from the deadly radiation with the proper protection because it is mostly beta rays, which have weak penetrating power.

TEPCO officials plan to move the contaminated water in the tank to another tank.

INCREASED PATROLS FIND MORE LEAKS

The greater frequency at which leaks of radiation-contaminated water are being discovered at the Fukushima plant can be attributed to the increased manpower and patrols inspecting the tanks.

Conversely, it shows the shoddy and lackadaisical manner in which TEPCO had been monitoring the ever-increasing tonnage of contaminated water.

The utility will increase the number of workers patrolling the tanks from about 10 to 60 from Sept. 2.

Until now, patrols were conducted twice a day by a team of two workers.

Each worker patrolled different areas. But because each would be responsible for about 500 tanks over a two-hour patrol period, a simple calculation showed a worker had only 15 seconds for each tank.

That meant the workers did not have time to thoroughly inspect their respective areas.

Radiation levels also were not measured unless a worker suspected something was wrong. Moreover, because rainwater easily collected at the concrete foundations where the tanks were lined up, workers rarely considered puddles around the tanks to be suspicious, and often radiation measurements were not taken.

The leaking of about 300 tons of contaminated water from a tank was announced by TEPCO on Aug. 19. But officials believe the water leaked slowly from around July, meaning the utility was unaware of the leak for about six weeks.

With the increased manpower to be used on patrols, the frequency of the patrols will be increased to four daily. On two of those patrols, workers will measure radiation levels while walking completely around a tank.

Patrols will also be conducted at night, and radiation levels will be measured whenever a puddle is discovered.

Because patrols will be strengthened, there will be a greater possibility that leaks overlooked until now will be found. Signs of potential leaks can also be uncovered with greater frequency.

The finding that leaks may have occurred at the pipes connecting the tanks represents another major headache for TEPCO.

Tanks that are welded together were believed to be less susceptible to leaks than the so-called flange-type tanks that have steel sheets connected by bolts.

However, both types of tanks use the same connecting structure of piping through which contaminated water is being transferred.

When members of the Nuclear Regulation Authority visited the Fukushima plant site on Aug. 23, Commissioner Toyoshi Fuketa suggested that not only the flange-type tanks but welded tanks as well be inspected.

Piping coming out of the welded tanks was laid on the ground and if leaks should occur at the connecting sections of those tanks, the contaminated water would immediately seep into the ground.

"While we hold very strong concerns about the flange-type tanks right now, that does not mean we can be confident about the welded tanks," Fuketa said. "There are many things we have to be concerned about."

Not only have leaks been found from connecting sections in the past, but because an extensive network of pipes is laid within the Fukushima plant site, there is the potential for contaminated water to leak from anywhere.

Meanwhile, mayors of municipalities in the vicinity of the Fukushima No. 1 plant raised concerns that the recent reports about leaking contaminated water will only further discourage residents who have evacuated.

"The desires of residents who want to return are gradually disappearing," said Tamotsu Baba, the mayor of Namie, Fukushima Prefecture.

He said the central government should take a more comprehensive approach and bring together experts on nuclear and civil engineering to evaluate the current situation and the problems that exist.

"The measures being taken now are haphazard," Baba said. "As the saying goes 'slow and steady wins the race,' so it would be preferable to calmly put together fundamental measures to deal with the problem."

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