The operator of Japan's crippled Fukushima nuclear plant has begun work on a large underground ice wall to isolate toxic water it has produced.

 

The 1.5km wall will be made by inserting 1,550 pipes into the ground. Coolant circulating in the pipes will freeze the surrounding soil. Some experts have expressed concerns over whether the project will work.

 

The plant experienced several leaks of radioactive water since being crippled by an earthquake and tsunami in 2011.

 

Last week, the Nuclear Regulation Authority agreed that plant operator Tepco could begin construction work on the frozen wall.

 

The government-funded ice wall is intended to stop nearby groundwater from seeping into the plant and mixing with contaminated water inside.

 

"We plan to end all the construction work in March 2015 before starting trial operations," a Tepco official said, adding that the ice wall could be operational months after construction.

 

The 2011 disaster knocked out cooling systems to the nuclear plant's reactors, three of which melted down.

 

Water is now being pumped in to cool the reactors, but storing the resultant large quantities of radioactive water has proved a challenge for Tepco. The operator has also struggled to safely store groundwater that has mixed with the radioactive water and become contaminated.