A record level of radioactivity was found in a well near a storage tank from which 300 tons of highly radioactive water leaked in the summer at the devastated Fukushima No. 1 nuclear power plant.
On Oct. 18, Tokyo Electric Power Co. said 400,000 becquerels of beta ray sources, including radioactive strontium, were detected per liter of water taken on Oct. 17, about 6,500 times more than the 61 becquerels recorded the previous morning.
The observation well is about 10 meters north of the tank where the leak was discovered in August. The tank was holding radioactive water with concentrations of 200 million becquerels, which was contaminated by the ongoing operation to cool the reactors.
High levels of tritium, a radioactive isotope of hydrogen, have been detected in this well, but not strontium, which moves more slowly than tritium. Strontium, which tends to accumulate in human bones, is believed to cause cancer and leukemia.
“There is a possibility that radioactive materials contained in the leaked contaminated water has reached the well,” a TEPCO official said. “We will examine details to find out why the radioactivity level rose sharply.”
The company said it has found no trace of additional leakage around the tank.
TEPCO also said Oct. 18 a record level of radioactivity was found in a drainage ditch, also near the tank in question.
The water taken on Oct. 17 contained 28,000 to 34,000 becquerels of beta ray sources, such as radioactive strontium, per liter, about 10 times higher than the previous day.
The levels apparently rose because radioactive materials on the ground flowed into the ditch during Typhoon No. 26 on Oct. 16, when swelling rainwater threatened to overflow barrier walls that surround storage tanks. The leak found in August is also suspected as a cause.
The location is 700 meters from the ocean. Water tends to accumulate because sandbags are placed immediately downstream.
TEPCO on Oct. 17 said 1,400 becquerels of beta ray sources were found per liter of water taken the previous day in a different part of a drainage ditch that leads directly to the ocean. The location is 150 meters from the ocean.
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