TOKYO (AFP) – Shares in the operator of Japan's crippled nuclear plant plunged Tuesday after Tokyo Electric Power Co. started pumping radioactive water into the sea as part of emergency operations.

The embattled utility's share price fell to 376 yen at one stage -- below TEPCO's all-time closing low of 393 yen, with no quick end in sight to the Fukushima nuclear plant disaster, the world's worst since Chernobyl in 1986.

"A couple of weeks ago, the company said all they have to do is to cool the reactors, but the situation doesn't seem to be improving," said one trader.

"Compensation to be paid will likely balloon with this contaminated water release," said the trader at a Japanese brokerage.

The wider economic fallout from Japan's triple calamity -- the massive March 11 earthquake, giant tsunami and the nuclear crisis -- is likely to drive the country into recession in coming months, said a survey of economists.

The disaster -- which has left 12,321 dead and 15,347 missing -- has also hit exports, lanced business confidence and dampened consumer spending, the Nikkei daily said in the survey of 11 major private economic institutions.

The world's number three economy had been on the upswing but may now shrink 0.6 percent in the January-March period from the previous quarter, and by 2.6 percent in May-July, the institutes predicted on average.

More than three weeks since the 9.0-magnitude quake, workers at the nuclear plant kept up frantic efforts to spray cooling water onto partially melted fuel rods and to contain the highly contaminated runoff.

In order to find safe storage space for the most radioactive water -- so dangerous that it is halting crucial repair work -- TEPCO has been forced to empty containers with lower-level radioactive water into the ocean.

On Tuesday it kept pumping the 11,500 tonnes, or more than four Olympic pools-worth, into the sea, adding to toxic runoff that has already leaked into the ocean and raised iodine-131 levels to over 4,000 times the legal limit.

Fishing has been banned within 20 kilometres (12 miles), matching the radius of the evacuation zone on land, where tens of thousands of residents have been moved out. People have also been encouraged to leave the 30 km zone.

Fukushima prefecture on Tuesday started three days of radiation measurements at 1,400 kindergartens, elementary and junior high schools, except in the 20 km evacuation zone around the plant, Kyodo News reported.

Radiation from the plant has wafted into the air and seeped into the soil. Radioactive iodine above legal limits has been detected in regional vegetables, dairy products, beef and mushrooms, triggering shipping bans.

The Yomiuri Shimbun on Tuesday reported TEPCO has decided to offer provisional damage payments to residents and farmers near the plant before official damage amounts are estimated later.

Some analysts estimate TEPCO could face compensation claims of more than 10 trillion yen ($120 billion). The company last week said it had secured 2 trillion yen in funding but warned that this would not be enough.

Officials have said none of the food presents an imminent health threat, and that seafood -- a key source of protein in the island-nation -- is less at risk because ocean currents and tides dilute the dangerous isotopes.

The health ministry however said Monday that iodine-131 at a level of 4,080 becquerels per kilogram had been detected in a small fish called konago, or sand lance, caught off Ibaraki prefecture, south of the plant.

Fishing of the species was stopped locally, media reports said, but no wider ban was issued. The government said it has not set a maximum iodine-131 limit for fish and that officials planned to determine one.

The permitted level for vegetables is 2,000 becquerels per kilogram.

The top government spokesman, Yukio Edano, said at a press conference on Tuesday he was "sorry for the fishermen and those involved."

"Fishing has not resumed in Fukushima and there is no plan for that.... Regarding the coast of Ibaraki, we plan to reinforce monitoring. We are asking the public to stay calm so that rumours won't spread."

-- Dow Jones Newswires contributed to this story --