Botched gauge settings might have contaminated Fukushima groundwater from April onward: Tepco

The discovery of falsely configured monitoring equipment at the stricken Fukushima No. 1 nuclear power plant means the groundwater flowing underneath it might have gotten contaminated from April onward, Tokyo Electric said Friday.

The utility said incorrect gauge settings were used to measure groundwater levels in six of the wells near reactors 1 and 4. This resulted in groundwater readings about 70 cm higher than reality, which means the beleaguered power utility has been mismanaging the groundwater there for months.

To prevent tainted water from leaking from the plant, Tokyo Electric Power Company Holdings Inc. installed water gauges so it could keep the groundwater levels in the wells a meter higher than the contaminated water in the buildings.

Tepco adjusts the amount of water in wells called subdrains around the buildings to keep the groundwater higher than the tainted water inside them, which prevents it from flowing out. If the groundwater levels sink below the level of the radioactive water, it might leak out.

On Friday, Tepco said the estimated groundwater level in one of the six subdrain wells close to reactor 1 fell below the level in the reactor building at least eight times during the five-day period to May 21 because the gauges were set incorrectly.

Groundwater levels were 2 mm to 19 mm lower than the level in the buildings, Tepco said, adding that it does not know precisely how long each of these problematic situations lasted because water level data is collected by the hour.

Tepco said groundwater levels in five other wells affected by the incorrect settings did not fall below the levels in the nearby reactor buildings.

All six are in the area surrounded by an underground ice wall designed to prevent groundwater leakage.

According to Tepco, the incorrect settings date as far back as April 19. The earliest error affected the gauge in a well where groundwater fell to hazardous levels.

In the world’s worst nuclear disaster since Chernobyl, reactors 1, 2 and 3 at the plant experienced core meltdowns and reactors 1, 3 and 4 were severely damaged by hydrogen explosions following a massive offshore earthquake that spawned large tsunami in March 2011.

LATEST NATIONAL STORIES

Mikiko Shiroma's re-election as Naha mayor seen as boost for newly elected Gov. Denny Tamaki

Incumbent Mikiko Shiroma, 67, was re-elected as Naha mayor on Sunday, beating Masatoshi Onaga, backed by the ruling Liberal Democratic Party and Komeito coalition. Shiroma's victory adds...

Osamu Shimomura, co-winner of 2008 Nobel Prize in chemistry, dies in Nagasaki aged 90

Marine biologist Osamu Shimomura, a co-winner of the 2008 Nobel Prize in chemistry, has died at the age of 90, Nagasaki University announced Sunday. Shimomura, a graduate of the universi...

Horse whipping at Kumamoto shrine festival blasted as cruel

A video tape showing a horse getting whipped at a traditional festival held last month in the city of Kumamoto has caused a public outcry, with many people calling it a form of animal abuse....