Tokyo Electric Power Co. said there has been a sharp spike in the radioactivity of water samples taken from an observation well built by the sea at the crippled Fukushima No. 1 nuclear power plant.
The samples, collected from the well on Monday, contained a record 251,000 becquerels of radioactive cesium per liter — 3.7 times the amount recorded in a sample collected last Thursday.
The observation well, located to the east of the damaged No. 2 reactor, is one of several installed close to the seawall in the plant’s port. Monday’s reading was the highest recorded in water samples from any of the wells.
The samples also contained 7.8 million becquerels per liter of radioactive beta particle-emitting substances, such as strontium-90, an almost fourfold increase from Thursday’s level.
The amount of gamma ray-emitting substances, such as cobalt-60 and manganese-54, included in the samples was also at a record high.
The well is positioned close to an underground trench by the sea that is connected to the No. 2 reactor building.
Speaking at a press conference on Tuesday, Tepco official Isao Shirai told reporters that the increased radioactivity in the water could be due to higher levels of groundwater caused by recent typhoons mixing with radioactive elements left in the soil after the triple reactor meltdowns at the plant.