Japan said Monday it would dump over 10,000 tons of low-level radioactive water into the Pacific as part of emergency operations to stabilise its crippled Fukushima nuclear plant.
The announcement of the last resort measure came as the Bank of Japan said business confidence had plummeted since the earthquake and tsunami hit on March 11, plunging the country into its worst crisis since World War II.
The UN atomic watchdog chief Yukiya Amano, said that the three-week-old emergency, which Japan has predicted will last for months, meant an end to a "business as usual" approach to nuclear power.
His comments appeared borne out when Japan signalled it may weaken its ambitious greenhouse gas reduction targets, which are based on a continued heavy reliance on low-carbon atomic power, in light of the nuclear disaster.
Japan has battled to prevent full reactor meltdowns at its tsunami-hit Fukushima Daiichi plant and poured thousands of tons of water onto overheating fuel rods, a stop-gap measure that has created highly radioactive run-off.
To free up storage space for the radioactive run-off -- which has hampered crucial repair work and leaked into the Pacific -- operator the Tokyo Electric Power Company (TEPCO) said it would have to get rid of less toxic water.
It insisted the release would not harm marine life or seafood safety.
If people ate seafood from the affected sea water daily for one year, they would absorb about 0.6 millisievert of radioactivity, or about one fourth of a year's normal radiation from the environment, a TEPCO official said.
Prime Minister Naoto Kan's top spokesman, Yukio Edano, said in a televised press conference: "We have no choice but to release water tainted with radioactive materials into the ocean as a safety measure."
Fire engines and concrete boom pumps have dumped water onto overheating fuel rods ever since the quake and tsunami knocked out cooling systems and led to partial reactor meltdowns at the six-reactor plant.
As a result of the massive dumping operations, "highly radioactive waste water has accumulated at turbine buildings at Fukushima Daiichi, especially at the reactor unit two," said a TEPCO official.
"There is a need to release already stored water in order to accept the additional waste water" totalling 10,000 tons, as well as 1,500 tons of water from pits under reactor units five and six, he said.
Dumping the water -- the equivalent of more than four Olympic sized swimming pools -- would come "as soon as necessary preparations are made", he said.
Contamination from the plant has been found in the air, ground, seawater and, at lower concentrations, in regional produce including vegetables, dairy products, beef and, most recently, shiitake mushrooms.
The nuclear emergency, which has in many ways overshadowed the quake and tsunami that killed 12,020 people and left 15,512 missing, has also hit the economy hard, sending stocks reeling and hitting manufacturing output.
An updated version of the central bank's quarterly Tankan survey -- a key influence on monetary policy -- showed business confidence in the outlook for the next three months had plunged since the disaster.
Meanwhile, the nuclear crisis at Fukushima, the world's worst since Chernobyl in 1986, looked set to impact UN climate talks in Bangkok.
Nuclear energy has enjoyed a renaissance as a low-carbon energy source, but the crisis in Japan has highlighted its dangers and led several governments, including Japan's, to announce reviews of their energy policy.
"I think there will be a lot of political considerations," said the EU chief negotiator Artur Runge-Metzger on Sunday. "Certainly, this is something that has an impact on climate negotiations."
In Vienna, UN International Atomic Energy Agency chief Amano said the disaster had changed the world's approach to atomic power.
"The crisis at Fukushima Daiichi has enormous implications for nuclear power and confronts all of us with a major challenge," Amano said in an opening address to a special conference on nuclear safety.
Japan's Edano said Tokyo's climate goal -- to cut emissions by 25 percent by 2020 from 1990 levels, if other big polluters do the same -- was now open to review along with many other policies.
"Not only the 25 percent reduction target but also many other challenges that Japan is facing now should be examined at one point because many areas have been impacted by the quake disaster," Edano said.
The Yomiuri Shimbun daily reported that the environment ministry's top bureaucrat Hideki Minamikawa had told reporters in Bangkok that "the reduction goal will be affected a great deal".
Because the carbon cut target was based on plans to build new reactors and to improve old ones, "both the target year and reduction percentage will be reviewed," Minamikawa was quoted as saying.
Resource-poor Japan meets about one third of its energy demand from nuclear energy and relies heavily on Middle Eastern oil, while its companies are leaders in energy efficiency and green technologies.