TEPCO sees success with "subdrain plan" as some groundwater flow stops

13 November 2015

Tokyo Electric Power Co. said on Nov. 12 it has confirmed that the inflow of underground water from a cable duct at the No. 1 reactor of the crippled Fukushima Daiichi nuclear power plant has stopped. The utility believes this is an apparent reflection of the effectiveness of its "subdrain plan" of pumping up groundwater around the reactor buildings and releasing it into the ocean after purification.

When surveyed in September, groundwater was found to have been flowing into the No. 1 reactor's turbine building through an underground duct for cables. But when checked on Nov. 12 after the subdrainage was launched, the flow had stopped, likely as a result of lower groundwater levels thanks to the subdrain operation.

Before the subdrain operation was put in place, about 300 tons of groundwater flowed into the building each day and became radioactively contaminated. Groundwater is still reaching the reactor building through other ducts and other channels, however, and TEPCO said it is continuing to verify the overall effectiveness of the subdrain plan.

(Translated by Kyodo News)