Japanese media report that the barrier constructed at the Fukushima Daiichi NPP to prevent contaminated water from leaking into the ocean has tilted, developing a crack about 500 metres in length along its 780-metre-long base.

The tilt, which reportedly occurred as a result of heavy groundwater pressure on the wall, is only about 20cm but the crack increases the likelihood of ocean water becoming contaminated. Specialists from plant operator, the Tokyo Electric Power Company (Tepco), are trying to fill the crack and correct the wall tilt. The steel barrier, constructed 30 metres into the ground to block the flow of radioactive water, was completed in late October. Tepco says workers are buttressing the wall with steel pillars and are repairing the cracks to keep out rainwater and so prevent groundwater levels rising further.

Tepco had said that the wall was impermeable and would reduce the amount of contaminated water flowing into the sea from 400t to 10t a day. The wall was expected to reduce the amount of radioactive caesium and strontium entering the sea to one-fortieth of previous levels, and that of tritium to one-fifteenth of the previous levels, Tepco officials claimed.