Treatment of radioactive water at the Fukushima No. 1 nuclear plant has been suspended indefinitely after a malfunction shut down the entire purification process and fouled up storage conditions, the plant operator said.
Treatment of radioactive water at the Fukushima No. 1 nuclear plant has been suspended indefinitely after a malfunction shut down the entire purification process and fouled up storage conditions, the plant operator said.
The latest failure in the ALPS multinuclide removal equipment has exacerbated Tokyo Electric Power Co.’s struggles in dealing with the stockpile of radioactive water, which is growing at a rate of 400 tons a day, at the crippled nuclear plant.
TEPCO said up to 900 tons of water that was not properly purified in the ALPS equipment flowed into a network of 21 tanks holding about 15,000 tons of treated water.
Workers are trying to gauge the extent of the contamination, TEPCO officials said, adding that nobody noticed problems in the system before March 18 because water sampled on March 14 showed no abnormalities.
Not only have the 21 tanks been rendered unusable to store more purified water, but their contents of 15,000 tons of contaminated water will also have to be re-treated.
In addition, the contamination affected temporary storage tanks and conduits for treated water. TEPCO has yet to determine if this equipment can be cleaned.
“We never expected radioactive water to flow into the storage tanks,” said Masayuki Ono, acting general manager of TEPCO’s Nuclear Power & Plant Siting Division. “We should have been better prepared. We have no idea how long it will take to clean them if we decided to do so.”
The ALPS, short for advanced liquid processing system, is supposed to be able to remove 62 types of radioactive substances, including strontium, from contaminated water generated when water used to cool melted nuclear fuel mixes with groundwater.
The system sends radioactive water through many layers of absorptive material, which bonds with and removes radioactive substances. The equipment, with a maximum daily treatment capacity of 750 tons, has been under trial runs since March 2013.
Although the ALPS cannot remove tritium, a radioactive isotope of hydrogen, the purification of water through the system is expected to reduce damage levels if water leaks from storage tanks.
TEPCO workers on March 17 sampled water that was supposed to have been treated along one of the three channels of the ALPS system. They found the water still contained one-10th of the original concentration of radioactive substances, although the system is supposed to reduce that level to one-100,000th of the initial readings.
The finding prompted TEPCO to shut down ALPS operations along all three channels on March 18.
Aberrations occurring along only one channel indicate the cause may have to do with the replacement of some filters, which took place in early March, a TEPCO official said.
According to TEPCO, 340,000 tons of radioactive water in storage tanks were awaiting treatment by the ALPS on March 18.
The government and TEPCO have set a goal of doubling the capacity of ALPS and treating all radioactive water in the storage tanks by the end of fiscal 2014.
The ALPS system, however, has been operating only intermittently amid a succession of problems.