TEPCO confirms risky n-plant water level moves

September 29, 2017

TOKYO- Tokyo Electric Power Company Holdings Inc. said Friday it has confirmed risky moves of the groundwater level in one of the wells around the four damaged reactors at its Fukushima No. 1 power plant.

TEPCO made the announcement after disclosing on Thursday the discovery of wrong settings for gauges to measure groundwater levels in six of the wells.

Gauges for the six wells near the No. 1 to No. 4 reactors indicated groundwater levels about 70 centimeters above actual levels because of the error, causing TEPCO to engage in inappropriate groundwater management for months.

TEPCO pumps up water from such wells to adjust groundwater levels around the reactor buildings at the northeastern Japan power plant, where three of the four reactors experienced meltdowns after the March 2011 earthquake and tsunami.

If the nearby groundwater levels fall below the water levels inside the reactor buildings, water heavily contaminated with radioactive substances may leak from the buildings.

On Friday, TEPCO said the estimated groundwater level, adjusted for the setting error, in a well close to the No. 1 reactor fell below the water level inside the reactor building at least on eight occasions, during the five days to May 21 this year.

The negative margin ranged from 2 millimeters to 19 millimeters, TEPCO said, adding that it does not know precisely how long each of the risky situations lasted because water level data are collected by the hour.

TEPCO said water levels did not fall below the levels at nearby reactor buildings at the remainder of the six wells affected by the setting error.

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

According to TEPCO, the wrong settings date as far back as April 19. The oldest error affected the gauge for the well where the groundwater decreased to the dangerous levels. Jiji Press