Some 2 trillion becquerels of strontium-90 and cesium-137 may have flowed into the bay of Tokyo Electric Power Co.’s crippled Fukushima No. 1 plant during the 10 months to May this year, it was learned Sunday.

The amount exceeds by 10 times the limit of radioactive material releases Tepco set before the March 2011 meltdown accident at the power plant in Fukushima Prefecture.

At the plant, tainted groundwater may be flowing into the bay, and highly radioactive water may be leaking into the bay from reactor buildings through trenches.

According to Tepco documents, some 4.8 billion becquerels of strontium-90 and 2 billion becquerels of cesium-137 are estimated to have flowed into the plant’s bay per day, based on their average concentrations near a water intake for the Nos. 1-Nos. 4 reactors between August last year and May this year.

The total during the 10 months is thus estimated at 1.46 trillion becquerels for strontium-90 and 610 billion becquerels for cesium-137.

The combined total for the two radioactive substances tops 2 trillion becquerels. Since tainted water in the plant has other substances, the radioactive contamination of water in the plant’s bay is believed to be more serious.

In August last year, Tepco estimated that 10 trillion becquerels of strontium-90 and 20 trillion becquerels of cesium-137 had flowed into the bay since May 2011.

The estimated amounts in the following 10 months were smaller because average concentrations of radioactive substances were lower, Tepco officials explained.

However, radioactive materials in the plant’s bay spread out into the open sea as the tide ebbs and flows. Also, it is noted that part of contaminated groundwater may be flowing directly into the open sea.