Tokyo Electric Power Co. will build a new drainage channel at its crippled Fukushima No. 1 nuclear plant as part of efforts to prevent radioactive water from directly flowing into the Pacific when there is a storage tank spill, officials said.

The current channel drains into the sea outside the plant's man-made harbor, which is protected by breakwaters and its water has been partially enclosed to contain radioactive discharges. The new channel, to be completed by the end of March, will drain into the harbor, Tepco said Monday.

Tepco decided on the move after 300 tons of highly radioactive water leaked in August from one of the tanks, some of which is believed to have flowed into the Pacific via the drainage channels.

Under the plan, workers will build a new ditch that diverts from a main one that currently empties directly into the ocean. When there is a spill, Tepco will dam the existing ditch so the toxic water will flow instead into the harbor.

At the Fukushima plant, hundreds of tanks have been set up to store radioactive water created as a result of continuing water injections into the three crippled reactors that suffered meltdowns during the 2011 nuclear crisis.

It is also believed, however, that some 400 tons of radioactive groundwater is flowing into the sea daily after passing under the stricken reactor buildings.