Tokyo Electric Power Co. on Monday started building a huge underground ice wall around the Fukushima No. 1 nuclear plant to reduce the generation of toxic water at the crippled complex.

Under the government-funded project, 1,550 pipes will be inserted into the ground to circulate coolant and freeze the surrounding soil. The measure is aimed at preventing groundwater from seeping into the plant's four cracked reactor buildings and mixing with heavily radioactive water leaking out of them.

Tepco, as the beleaguered utility is known, plans to finish the 1.5-km wall and have it up and running by the end of March 2015. It will then take a few months or so to fully freeze the soil, a Tepco official said.