Concentrations of radioactive tritium in seawater from the port of the stricken Fukushima No. 1 nuclear power plant have risen between eight and 18 times in one week, Tokyo Electric Power Co. said Aug. 23.
It seems highly likely that the contaminated water is spreading into the sea beyond the port.
The latest levels are the highest since June, when TEPCO, the plant operator, strengthened its monitoring after discovering that groundwater contaminated with radioactive materials around the No. 1, No. 2 and No. 3 reactors was leaking into the sea. The latest concentration levels were still lower than the permissible standards stipulated by the government.
According to TEPCO, 68 becquerels of radioactive tritium per liter of water were detected in seawater collected Aug. 19 in the entrance area to the port, which is located some 500 meters from the nuclear plant. On Aug. 12, the concentration in the same area was lower than the limit for detection.
Fifty-two to 67 becquerels of radioactive tritium were also detected in seawater taken in four other locations in the port.
Meanwhile, after an on-site investigation on Aug. 23, the Nuclear Regulation Authority said that TEPCO has not properly recorded results of regular inspections on tanks used to store highly contaminated water.
The slipshod manner in managing the contaminated water in the tanks led to the leakage of a large amount of water from one of the tanks, according to the NRA.
The nuclear watchdog immediately instructed TEPCO to strengthen its inspection and management of the contaminated water in the tanks.
The utility has conducted inspections on those tanks twice a day to check for leaks. However, it failed to notice the leakage of about 300 tons of water from one of the tanks.
There are concerns the contaminated water has leaked into the sea.
On Aug. 23, Toyoshi Fuketa and other members of the NRA conducted an on-site investigation of the nuclear plant. They demanded that TEPCO show records of regular inspections on the storage tanks. However, it was found that the utility did not have the records on radiation levels, the time inspections were carried out or other details.
The NRA said that if TEPCO had measured radiation levels and recorded them, it likely would have noticed the leakage of contaminated water from the tank much earlier. However, TEPCO only observed the exteriors of the tanks to check for leaks.
On Aug. 23, a government committee to deal with contaminated water held a meeting in which many members called for a review of the storage methods for contaminated water. However, they were unable to find a drastic method to solve the leakage of contaminated water.
If an appropriate method cannot be found, the only option will be to lower the concentration of radioactive materials in water stored in the tanks. That will reduce the risk to the environment in the event of further leaks.
TEPCO has long intended to get what is known as the Advanced Liquid Processing System, which can remove a variety of radioactive materials from contaminated water, fully operational. Even though the process cannot remove tritium, NRA Chairman Shunichi Tanaka said, "If the ALPS is used, the risks will decrease drastically."
But that hasn't gone according to plan. Initially, TEPCO planned to start test operations last September. However, the start was delayed to March this year. Corrosion was discovered in some of the ALPS equipment during a test run of the system in July. The system is currently undergoing repairs and it is not known when it will be fully operational.
TEPCO is also grappling with the problem of halting contaminated groundwater around the No. 1, No. 2 and No. 3 reactors from flowing into the sea. The government estimates that about 300 tons of groundwater is flowing daily to the sea.
TEPCO has constructed shielding walls in the ground by solidifying the soil with a chemical agent. As a result, however, the levels of contaminated groundwater have risen, and there now exists the danger that water will rise beyond the shielding walls and flow into the ocean.
On Aug. 23, TEPCO completed the assembly of equipment to pump out groundwater to lower the water level in the ground. Using vacuum pumps, the equipment can remove a maximum of 70 tons of groundwater per day from 28 locations.
However, the shielding walls cannot completely prevent leakage of contaminated water into the sea.
TEPCO also said it is likely that of the highly contaminated water that has accumulated in pits, about 10 liters are flowing into the sea every day. On Aug. 22, TEPCO started to pump out the water from the pits.
Elsewhere, the latest developments prompted the Fukushima prefectural fishery recovery council on Aug. 23 to postpone the restart of commercial fishing on an experimental basis. The council had initially planned to restart fishing in early September.
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