A leak of highly radioactive water into the Pacific Ocean from Japan's crippled Fukushima Daiichi nuclear plant has been stopped, its operator reports.

日本福岛核电站的运营公司宣布，高度放射性污水渗漏的源头已被堵住。

Reactor¹ No 2 was cracked by the quake" src="http://www.enread.com/upimg/allimg/110406/1_110406051739_1.jpg" width="304" height="171" />
The concrete pit near Reactor No 2 was cracked by the quake
Tepco said it had injected chemical agents to solidify² soil near a cracked pit, from where the contaminated water had been seeping³（渗出） out.

Engineers have been struggling to stop leaks since the plant was damaged by the earthquake and tsunami⁴ on 11 March.

Japan has asked Russia for the use of a floating radiation treatment plant.

In another development, government sources said that a plan to cover the damaged reactor buildings with special metal sheets could not be carried out until September at the earliest due to high-level radioactivity hampering⁵ work at the site.

The official death toll⁶ from the 9.0-magnitude earthquake and tsunami stands at more than 12,000 with some 15,000 people still unaccounted for, and more than 161,000 people still living in evacuation centres.

'Water glass'

Samples of water used to cool one of the plant's six reactors⁷, No 2, showed 5m times the legal limit of radioactivity, officials said on Tuesday.

In order to stem the leak, Tepco (the Tokyo Electric Power Co) injected ''water glass'', or sodium⁸ silicate⁹, and another agent near a seaside pit where the highly radioactive water had been seeping through.

Desperate engineers had also used sawdust, newspapers and concrete to try to stop the escaping water.

The company still needs to pump some 11,500 tonnes of low-level radioactive seawater into the sea because of a lack of storage space at the plant.

But officials said this water would not pose a significant threat to human health.

Russia's nuclear agency Rosatom said it was awaiting answers to some questions before granting Japan's request to lend its vessel¹⁰ the Landysh, known in Japanese as the Suzuran, which is used to decommission（使退役） Russian nuclear submarines in the far eastern port of Vladivostok.

One of the world's largest liquid radioactive waste treatment plants, the Landysh treats radioactive liquid with chemicals and stores it in a cement form.

It can process 35 cubic metres of liquid waste a day and 7,000 cubic metres a year.