Hundreds of thousands of tons of highly contaminated water accumulating at the crippled Fukushima No. 1 nuclear plant will go untreated for some time, as key equipment to remove radioactive substances has been shut down completely.
According to Tokyo Electric Power Co., the last of three channels of the ALPS multinuclide removal equipment that treats contaminated water was switched off May 20 due to trouble with prior processing.
It is the first time for all three channels to be out of operation simultaneously. The equipment has been operating intermittently due to a series of glitches since it was introduced for trial runs in March 2013.
It seems likely that the failure of the ALPS will affect plans by the government and TEPCO to accelerate the decontamination operation by increasing the capacity of removing radioactive material from contaminated water this autumn.
Additional ALPS equipment was due to be installed to deal with growing stockpiles of radioactive water at the plant.
About 350,000 tons of highly contaminated water are in storage, awaiting purification with the ALPS.
The ALPS, short for advanced liquid processing system, is able to remove 62 types of radioactive substances, including strontium, from contaminated water, which is generated after water is used to cool melted nuclear fuel.
The three channels of the ALPS--called A, B and C--are theoretically able to treat a combined 750 tons of radioactive water a day.
However, this does not mean that the total amount of contaminated water stored in tanks at the plant gets less because the ALPS cannot remove tritium, a radioactive substance.
The equipment was introduced to reduce the risks in the event of contaminated water leaks from tanks.
In the treatment, contaminated water is filtered to remove substances such as calcium, which interferes with the absorption of radioactive material, as prior processing. After that process, the water is sent through many layers of absorptive material.
TEPCO said May 20 that the water that underwent prior processing for the C channel was found to be cloudy, instead of being transparent, when workers took samples in a routine check that day.
The concentration of calcium measured about six times the normal level.
TEPCO decided to suspend the operation of the C channel at 9 a.m. the same day.
All the channels had resumed operations last February. The B channel went out of operation March 18 after troubles with its filters caused water not to be treated properly and stored in tanks. It is expected to go back online May 23 or later.
The A channel was halted after a malfunction similar to the C channel on May 17.
Reducing the total of contaminated water piling up at the nuclear complex is proving to be an enormous challenge for TEPCO.
About 400 tons of groundwater flow into the reactor buildings daily and mix with highly radioactive water that was used to cool melted nuclear fuel.
TEPCO plans to build 1,500-meter-long underground walls of frozen soil around the reactor buildings to help cut the inflow of groundwater.
But the Nuclear Regulation Authority’s screening of the project has been stalled due to doubts raised about the safety of the engineering task.
A project to scoop up groundwater before it flows into the reactor buildings and release it into the sea began May 21. The bypass project is expected to reduce up to 100 tons of groundwater daily.
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