SENDAI, Japan (AFP) - Radiation levels have surged in seawater near a tsunami-stricken nuclear power station in Japan, officials said Saturday, as engineers battled to stabilise the plant in hazardous conditions.
Urgent efforts were under way to drain pools of highly radioactive water near the reactors after several workers suffered radiation burns while installing cables as part of efforts to restore the critical cooling systems.
An aerial view taken by Tokyo Electric Power Co (TEPCO) in 1998, shows TEPCO's Fukushima No.1 nuclear power plant and its drainage gate to the Pacific Ocean at Okuma town in Fukushima prefecture. Radiation levels have jumped 10-fold in days in seawater near Japan's tsunami-hit nuclear plant. The iodine-131 level in the Pacific Ocean waters just off the Fukushima plant was 1,250 times above the legal limit on March 26, 2011. (AFP PHOTO / HO / TEPCO VIA JIJI PRESS-Yonhap)
The new safety worries further complicated efforts to bring the ageing facility under control, and raised fears that the fuel rod vessels or their valves and pipes are leaking.
"It is becoming very important to get rid of the puddles quickly," said an official at the nuclear safety agency, Hidehiko Nishiyama.
One of the worst-case scenarios at reactor three would be that the fuel inside the reactor core -- a volatile uranium-plutonium mix -- has already started to burn its way through its steel pressure vessel.
"Highly radioactive water is flowing inside the buildings and then into the sea, which is worrying for fish and marine vegetation," said Olivier Isnard, an expert at France's Institute for Radiological Protection and Nuclear Safety.
"One hypothesis is that the reactor vessel is breached and highly radioactive corium is coming out."
Fire engines have hosed thousands of tons of seawater onto the plant in a bid to keep the fuel rods inside reactor cores and pools from being exposed to the air, where they could reach critical stage and go into full meltdown.
Several hundred metres offshore in the Pacific Ocean, levels of iodine-131 some 1,250 times the legal limit were detected on Saturday, a tenfold increase from just days earlier, operator Tokyo Electric Power Co. (TEPCO) said.
Drinking a half-litre (20-ounce) bottle of fresh water with the same concentration would expose a person to their annual safe dose, Nishiyama said, but he ruled out an immediate threat to marine life and seafood safety.
"Generally speaking, radioactive material released into the sea will spread due to tides, so you need much more for seaweed and sea life to absorb it," he said.
Because iodine-131 decays relatively quickly, with a half-life of eight days, "by the time people eat the sea products, its amount is likely to have diminished significantly," he said.
However, TEPCO also reported levels of caesium-137 -- which has a half life
of about 30 years -- almost 80 times the legal maximum. Scientists say both
radioactive substances can cause cancer if absorbed by humans.
Government assurances did little to lift the gloom that has hung over Japan since a 9.0-magnitude quake struck on March 11, sending a huge tsunami crashing into the northeast coast in the country's worst post-war disaster.
The wave easily overwhelmed the world's biggest sea defences and swallowed entire communities. The confirmed death toll stood at 10,489 as of 9:00 pm (1200 GMT) on Saturday, Kyodo News said, citing the National Police Agency, with 16,621 listed as missing.
The tsunami knocked out the cooling systems for the six reactors of the Fukushima plant, leading to suspected partial meltdowns in three of them.
Hydrogen explosions and fires have also ripped through the facility.
High-voltage electric cables have since been linked up to the reactors again and power has been partially restored in two reactor control rooms.
Worried about the salt buildup in the crippled plant, engineers have started pumping in fresh water into some of the reactors. The US military is supporting the effort by sending two full water barges from a naval base near Tokyo.
"I believe we have prevented the current situation worsening, taking steps towards real progress such as resuming power and injecting water," chief government spokesman Yukio Edano told reporters.
Radioactive vapour from the plant has contaminated farm produce and dairy products in the region, leading to shipment halts in Japan as well as the United States, European Union, China and a host of other nations.
Singapore extended a ban on food imports from Japan on Saturday, suspending imports of all fruit and vegetables from the whole Kanto region, a large area including greater Tokyo.
Higher than normal radiation has also been detected in tap water in and around Tokyo, some 250 kilometres (155 miles) from the plant, leading authorities at one stage to warn against using it for baby milk formula.
Japan widened the zone around the plant from which it suggests people evacuate to 30 kilometres -- still below the 80 kilometres advised by the United States.
Environmental watchdog Greenpeace started its own monitoring near the plant, saying "authorities have consistently appeared to underestimate both the risks and extent of radioactive contamination".
The campaign group said it would provide "an alternative to the often contradictory information released by nuclear regulators".
근해 방사성물질, 기준 1,250배
0.5ℓ만 마셔도 1년 피폭기준 초과 ..세슘-137은 80배
(센다이.오사카 AFP.교도=연합뉴스) 후쿠시마(福島) 사고 원전 근해의 방사성 요오드 수치가 기준치의 1천250배까지 치솟았다고 일본 원자력안전보안원이 26일 밝혔다.
원자력안전보안원 관계자는 원전 운영사인 도쿄전력이 지난 25일 오전 후쿠시마 제1원전에서 남쪽으로 330ｍ 떨어진 태평양 해상을 조사한 결과 방사성 요오드-131 수준이 이같이 측정됐다고 말했다.
샘플 채취 지점은 원자로 냉각수 배출구 인근이다. 이 같은 수치는 원전 인근 태평양의 요오드-131 수치가 법적 기준치의 각각 126배와 145배에 이른다는 지난 22일과 24일 조사 결과보다 10배 가까이 높은 것이다.
오염도가 비슷한 물이 있다고 가정하면 단 0.5ℓ만 마셔도 연간 인체 피폭량 기준치 1mSv(밀리시버트)를 넘게 된다.
원자력안전보안원 관계자는 그러나 해양생태계와 수산물에 당장 위협이 될 만한 수준은 아니라고 설명했다.
이 관계자는 "일반적으로 해양 유출된 방사성 물질은 조류를 타고 확산되기 때문에 해조류나 바다생물이 흡수하려면 이보다 더 많은 양이 누출돼야 한다"고 말했다.
현재 사고 반경 20㎞ 이내 해역에서는 조업이 금지돼 있다.
그는 또 요오드-131의 반감기가 8일이라는 점을 들어 "수산물이 식탁에 오를 때쯤이면 방사능의 양이 현저히 줄어들어 있을 것"이라고 예상했다.
하지만 반감기가 30년이나 되는 세슘-137의 농도도 기준치의 79.6배에 이르는 것으로 나타났다.
반면 미 에너지부가 25일 공개한 후쿠시마 원전 상공 방사능 수치 측정 결과에 따르면 25일 원전 서쪽의 방사능 최고치는 전날에 비해 낮아졌다.
이런 가운데 국제 환경단체 그린피스가 직접 원전 근해 방사능 수치 측정에 나섰다. 그린피스는 "당국이 줄곧 방사능 오염의 위험과 정도를 과소평가하는 것 같다"며 "원자력 규제 당국의 모순적인 정보에 대안이 되는 정보를 제공할 것"이라고 밝혔다.
한편 도쿄전력은 지난 25일부터 원자로 1.3호기에 바닷물 대신 민물을 순환시킨데 이어 이날 2호기에도 민물 주입을 시작했다.
日원전 2호기 물웅덩이 방사능 정상치 1천만배
방사성 요오드 134 등 검출
(도쿄=연합뉴스) = 일본 후쿠시마(福島) 제1원자력발전소 2호기 터빈실에 고여 있던 물웅덩이의 성분을 분석한 결과 정상 운전 시 원자로 냉각
수의 1천만배 농도인 방사성 물질이 검출됐다고 NHK가 27일 보도했다.
방송에 따르면 2호기 물웅덩이에 포함된 '방사성 요오드 134'의 농도는 1㎠당 29억㏃(베크렐)이었다.
정상 운전 시 원자로 물에 포함된 방사성 요오드 134의 농도(수백 ㏃)의 1천만 배에 이르는 셈이다. 1, 3호기에서 발견된 물웅덩이의 방사성 물질 농도보다 1천배 나 높았다.
방사성 요오드 131은 1㎠당 1천300만㏃, 세슘 134와 세슘 137도 각각 230만㏃ 검출됐다.
교도통신은 물웅덩이 표면의 방사선량이 시간당 1㏜ 이상이라고 전했다. 도쿄전력은 2호기 물웅덩이에 포함된 방사성 물질에 반감기(8일)가 짧은 방사성 요오드가 포함돼 있다는 점을 근거로 이 물이 사용 후 연료 저장 수조가 아니라 원 자로 내부에서 흘러나온 것으로 추정하고 있다.