updated 3/20/2011 3:59:17 AM ET 2011-03-20T07:59:17

The operator of Japan's tsunami-damaged nuclear plant on Sunday backed away from plans for a tricky venting of radioactive gas at one of the troubled reactors, saying that pressure inside has stabilized.

Tokyo Electric Power company officials said the company decided that there was no immediate need to vent the pressure at the Unit 3 reactor of the Fukushima Dai-ichi plant. They said the pressure is relatively high, but that it has stabilized.

Meanwhile, the government warned that tests of spinach and milk from areas as far as 75 miles away exceeded safety limits. Tap water farther away turned up tiny amounts of radioactive iodine in Tokyo and other areas.

Food beyond Japan's borders was also reportedly tainted.  Radiation was detected on fava beans imported from Japan to Taiwan, Taiwanese officials said in what appears to be the first case of contamination in Japanese imports.

Taiwan's Cabinet-level Atomic Energy Council Radiation Monitoring Center said in a statement that a small amount of iodine and cesium had been found on a batch of Japanese fava beans imported to the island on Friday. The center said 11 becquerels of iodine and 1 becquerel of cesium were detected.

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The amount of radiation was well below Taiwan's legal limit and not harmful to human health, an official from the center told The Associated Press.

The official spoke on condition of anonymity because he was not authorized to deal with the media.

Caught off-guard
Amid concerns of wider contamination, a nuclear safety official said the government was caught off-guard by the accident's severity and only belatedly realized the need to give potassium iodide to those living within 12 miles of the Fukushima Dai-ichi nuclear complex.

The pills help reduce the chances of thyroid cancer, one of the diseases that may develop from radiation exposure. The official, Kazuma Yokota, said an explosion at the plant's Unit 3 reactor last Sunday should have triggered the distribution. But the order only came three days later.

"We should have made this decision and announced it sooner," Yokota told reporters at the emergency command center in the city of Fukushima. "It is true that we had not foreseen a disaster of these proportions. We had not practiced or trained for something this bad. We must admit that we were not fully prepared."

While four of Fukushima's six nuclear reactors have been dangerously overheating since the March 11 earthquake and tsunami disrupted cooling systems, Unit 3 has proved particularly troublesome.

After the government said Saturday that the unit appeared to be stabilizing after being doused with water, nuclear safety officials said the efforts may not have worked. Pressure was rising on Saturday inside the reactor's containment vessel, requiring a release of radioactive gas to prevent a more dangerous buildup, said safety agency official Hidehiko Nishiyama.

While battling Unit 3, emergency teams used an unmanned vehicle to spray water at another at-risk reactor — Unit 4 — while preparing to switch power back on for the first time since a March 11 earthquake and tsunami knocked out the plant's crucial cooling systems.

However, there was no guarantee the cooling systems would still work, even once power was restored.

Contaminated water
Minuscule amounts of radioactive iodine were found in tap water Friday in Tokyo and elsewhere in Japan — although experts said none of those tests showed any health risks. They also said radioactive dust and particles found in Greater Tokyo area also posed no risk to human health.

The Health Ministry also said that radioactive iodine slightly above government safety limits was found in drinking water at one point Thursday in a sampling from Fukushima prefecture, the site of the nuclear plant, but later tests showed the level had fallen again.

Six workers trying to bring the Fukushima Dai-ichi plant back under control were exposed to more than 100 millisieverts of radiation — Japan's normal limit for those involved in emergency operations, according to Tokyo Electric Power Co., which operates the complex. The government raised that limit to 250 millisieverts on Tuesday as the crisis escalated.

"We more or less do not expect to see anything worse than what we are seeing now," Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency said earlier.

Japan has been grappling with a cascade of disasters unleashed by the 9.0-magnitude earthquake on March 11. The quake spawned a tsunami that ravaged Japan's northeastern coast, killing more than 8,100 people and knocking out cooling systems at the Fukushima Dai-ichi nuclear plant, causing the complex to leak radiation.

More than 12,000 people are still missing, and more than 452,000 are living in shelters. The quake and tsunami has likely killed more than 15,000 people in Miyagi prefecture alone, Kyodo news agency said Sunday, quoting local police.

'No immediate health risk'
Chief Cabinet Secretary Yukio Edano, meanwhile, insisted the contaminated foods "pose no immediate health risk."

The tainted milk was found 20 miles from the plant, a local official said. The spinach was collected from six farms between 60 miles and 75 miles to the south of the reactors.

Those areas are rich farm country known for melons, rice and peaches, so the contamination could affect food supplies for large parts of Japan.

More tests were being done on other foods, Edano said, and if they show further contamination, then food shipments from the area would be halted.

Disaster at a glance

Officials said it was too early to know if the nuclear crisis caused the contamination, but Edano said air sampling done near the dairy showed higher-than-normal radiation levels.

Iodine levels in the spinach exceeded safety limits by three to seven times, a food safety official said. Tests on the milk done Wednesday detected small amounts of iodine-131 and cesium-137, the latter being a longer-lasting element that can cause more types of cancer. But only iodine was detected Thursday and Friday, a Health Ministry official said.

Calming a jittery public
After the announcements, Japanese officials immediately tried to calm an already-jittery public, saying the amounts detected were so small that people would have to consume unimaginable amounts to endanger their health.

"Can you imagine eating one kilogram of spinach every day for one year?" said State Secretary of Health Minister Yoko Komiyama. One kilogram is a little over two pounds.

Edano said someone drinking the tainted milk for one year would consume as much radiation as in a CT scan; for the spinach, it would be one-fifth of a CT scan. A CT scan is a compressed series of X-rays used for medical tests.

The Health Ministry said iodine levels slightly above the safety limit were discovered Thursday in drinking water samples from Fukushima prefecture. On Friday, levels were about half that benchmark; by Saturday, they had fallen further.

Drinking one liter of water with the iodine at Thursday's levels is the equivalent of receiving one-eighty-eighth of the radiation from a chest X-ray, said Kazuma Yokota, a spokesman for the prefecture's disaster response headquarters.

The trace amounts of iodine were found in Tokyo's water on Friday, the first day since the government ordered nationwide daily sampling due to the nuclear crisis, the Ministry of Education, Culture, Sports, Science and Technology said. A ministry statement said the amounts found did not exceed government safety limits. But tests on water, which for decades were only done once a year, usually show no iodine.

At the Fukushima plant, emergency workers have been struggling to cool the reactors and the pools used to store used nuclear fuel, as well as to put the facility back on the electricity grid.

A replacement power line reached the complex Friday, but workers needed to methodically work through badly damaged and deeply complex electrical systems to make the final linkups without setting off a spark and potentially an explosion. Company officials hoped to be able to switch on the cooling systems Sunday.

Quake risk at nuclear plants

Once the power is reconnected, it is not clear if the cooling systems will still work.

A fire truck with a high-pressure cannon pumped water directly from the ocean into one of the most troubled areas of the complex — the cooling pool for used fuel rods at the plant's Unit 3. Because of high radiation levels, firefighters only went to the truck every three hours to refuel it.

Holes were also punched in the roofs of units 5 and 6 to vent buildups of hydrogen gas, and the temperature in Unit 5's fuel storage pool dropped after new water was pumped in, according to officials with Tokyo Electric Power Co., which owns the complex.

More workers were thrown into the effort — bringing the total at the complex to 500 — and the safety threshold for their radiation exposure was raised 2½ times so they could keep working.

Officials insisted that would cause no health damage.

The Associated Press and Reuters contributed to this report.

Video: Radiation found in food as Japan rushes to curb crisis

  1. Closed captioning of: Radiation found in food as Japan rushes to curb crisis

    >>> we want to turn now to the crisis in japan. there are new worries on the radiation leak and the food supply now.

    >> reporter: lester, the desperate effort to stop the radiation disaster is showing some encouraging signs, but it is far from over and the discovery of contaminated milk and spinach shows why the race against time . 1,500 tons of water should be enough to fill the tank which should look like this covers spent fuel rods that have been exposed and emitting radiation. if the tank does not have a major leak.

    >> we think we have succeeded in stabilizing the situation.

    >> engineers will try to get the pumps running again. in five and six, diesel powered generators have the water circulating again and the temperature is dropping.

    >> there is a slight chance that one of the reactors will have a late failure. they are getting cooler all the time and they seem to have a way of getting water into the cool r er cores. it is a fragile situation and there is a potential for a mistake.

    >> reporter: the damage has been done. the contaminatta damage tame.

    >> the spinach was found 60 mile to the south.

    >> most of the limits are set low to begin with. so five times higher than the legal limit still would not be enough to cause a discernible health effect .

    >> reporter: the government said drinking a glass of contaminated milk for a whole year would expose a person to the radiation found in one ct scan . people leaving fukashima were recommended to take iodine tablets.

    >> reporter: those don't exceed safety standards du s but experts say if the reactor was brought under control tomorrow and it won't be, rad yo active contamination will continue for weeks

Photos: After Japan's earthquake and tsunami - week 8

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  1. A radiation measuring instrument is seen next to some residents in Kawauchimura, a village within the 12- to 18-mile zone around the Fukushima Daiichi nuclear plant, on April 28. Most residents of Kawauchimura have evacuated in order to avoid the radiation, but some remain in the area of their own accord. (Koichi Kamoshida / EPA) Back to slideshow navigation
  2. A brazier heats the house of Masahiro Kazami, located within a 12-mile radius of the Fukushima Daiichi nuclear plant, April 28. (Koichi Kamoshida / EPA) Back to slideshow navigation
  3. Volunteers help clean a cemetery at Jionin temple in Ishinomaki, Miyagi prefecture, northeastern Japan, on April 29. Many volunteers poured into the disaster-hit region at the beginning of the annual Golden Week holiday. (Hiro Komae / AP) Back to slideshow navigation
  4. Japanese government adviser Toshiso Kosako is overcome with emotion during a news conference on April 29 in Tokyo announcing his resignation. The expert on radiation exposure said he could not stay on the job and allow the government to set what he called improper radiation limits for elementary schools in areas near the tsunami-damaged Fukushima nuclear plant. (AP) Back to slideshow navigation
  5. Fuel rods are seen inside the spent fuel pool of the Fukushima Daiichi nuclear plant reactor 4 on April 30. (Reuters) Back to slideshow navigation
  6. A volunteer girl from Tokyo works to clean the debris of a house in Higashimatsushima, northern Japan, on April 30. (AP) Back to slideshow navigation
  7. Farmer Tsugio Sato tends to his Japanese pear trees in Fukushima city, May 1. He said he expects to harvest the pears in October. Farmers and businesses face so-called "fuhyo higai," or damages stemming from the battered reputation of the Fukushima brand. (Hiro Komae / AP) Back to slideshow navigation
  8. Members of Japan Ground Self-Defense Force in protective gear receive radiation screening in Minamisoma in Fukushima prefecture, after searching for bodies at an area devastated by the March 11 earthquake and tsunami. (Reuters) Back to slideshow navigation
  9. Ruriko Sakuma, daughter of dairy farmer Shinji Sakuma, rubs a cow at their farm in the village of Katsurao in Fukushima prefecture on May 3. Thousands of farm animals died of hunger in the weeks following the quake. (Yoshikazu Tsuno / AFP - Getty Images) Back to slideshow navigation
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Map: Japan earthquake

  1. Above: Map Japan earthquake
  2. Interactive Japan before and after the disaster
  3. Image: The wave from a tsunami crashes over a street in Miyako City, Iwate Prefecture in northeastern Japan
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    Timeline Crisis in Japan

Explainer: The 10 deadliest earthquakes in recorded history

  • A look at the worst earthquakes in recorded history, in loss of human life. (The March 11, 2011, earthquake and tsumani that affected eastern Japan is not included because the fatalities caused, about 15,000, are fewer than those resulting from the temblors listed below.) Sources: United States Geological Survey, Encyclopedia Britannica

  • 1: Shensi, China, Jan. 23, 1556

    Magnitude about 8, about 830,000 deaths.

    This earthquake occurred in the Shaanxi province (formerly Shensi), China, about 50 miles east-northeast of Xi'an, the capital of Shaanxi. More than 830,000 people are estimated to have been killed. Damage extended as far away as about 270 miles northeast of the epicenter, with reports as far as Liuyang in Hunan, more than 500 miles away. Geological effects reported with this earthquake included ground fissures, uplift, subsidence, liquefaction and landslides. Most towns in the damage area reported city walls collapsed, most to all houses collapsed and many of the towns reported ground fissures with water gushing out.

  • 2: Tangshan, China, July 27, 1976

    Chinese Earthquake
    Keystone  /  Getty Images
    1976: Workers start rebuilding work following earthquake damage in the Chinese city of Tangshan, 100 miles east of Pekin, with a wrecked train carriage behind them. (Photo by Keystone/Getty Images)
    Magnitude 7.5. Official casualty figure is 255,000 deaths. Estimated death toll as high as 655,000.

    Damage extended as far as Beijing. This is probably the greatest death toll from an earthquake in the last four centuries, and the second greatest in recorded history.

  • 3: Aleppo, Syria, Aug. 9, 1138

    Magnitude not known, about 230,000 deaths.

    Contemporary accounts said the walls of Syria’s second-largest city crumbled and rocks cascaded into the streets. Aleppo’s citadel collapsed, killing hundreds of residents. Although Aleppo was the largest community affected by the earthquake, it likely did not suffer the worst of the damage. European Crusaders had constructed a citadel at nearby Harim, which was leveled by the quake. A Muslim fort at Al-Atarib was destroyed as well, and several smaller towns and manned forts were reduced to rubble. The quake was said to have been felt as far away as Damascus, about 220 miles to the south. The Aleppo earthquake was the first of several occurring between 1138 and 1139 that devastated areas in northern Syria and western Turkey.

  • 4: Sumatra, Indonesia, Dec. 26, 2004

    Aerial images show the extent of the devastation in Meulaboh
    Getty Images  /  Getty Images
    MEULABOH, INDONESIA - DECEMBER 29: In this handout photo taken from a print via the Indonesian Air Force, the scene of devastation in Meulaboh, the town closest to the Sunday's earthquake epicentre, is pictured from the air on December 29, 2004, Meulaboh, Aceh Province, Sumatra, Indonesia. The western coastal town in Aceh Province, only 60 kilometres north-east of the epicentre, has been the hardest hit by sunday's underwater earthquake in the Indian Ocean. Officials expected to find at least 10,000 killed which would amount to a quarter of Meulaboh's population. Three-quarters of Sumatra's western coast was destroyed and some towns were totally wiped out after the tsunamis that followed the earthquake. (Photo by Indonesian Air Force via Getty Images)

    Magnitude 9.1, 227,898 deaths.

    This was the third largest earthquake in the world since 1900 and the largest since the 1964 Prince William Sound, Alaska temblor. In total, 227,898 people were killed or were missing and presumed dead and about 1.7 million people were displaced by the earthquake and subsequent tsunami in 14 countries in South Asia and East Africa. (In January 2005, the death toll was 286,000. In April 2005, Indonesia reduced its estimate for the number missing by over 50,000.)

  • 5: Haiti, Jan 12, 2010

    Haitians walk through collapsed building
    Jean-philippe Ksiazek  /  AFP/Getty Images
    Haitians walk through collapsed buildings near the iron market in Port-au-Prince on January 31, 2010. Quake-hit Haiti will need at least a decade of painstaking reconstruction, aid chiefs and donor nations warned, as homeless, scarred survivors struggled today to rebuild their lives. AFP PHOTO / JEAN-PHILIPPE KSIAZEK (Photo credit should read JEAN-PHILIPPE KSIAZEK/AFP/Getty Images)

    Magnitude 7.0. According to official estimates, 222,570 people killed.

    According to official estimates, 300,000 were also injured, 1.3 million displaced, 97,294 houses destroyed and 188,383 damaged in the Port-au-Prince area and in much of southern Haiti. This includes at least 4 people killed by a local tsunami in the Petit Paradis area near Leogane. Tsunami waves were also reported at Jacmel, Les Cayes, Petit Goave, Leogane, Luly and Anse a Galets.

  • 6: Damghan, Iran, Dec. 22, 856

    Magnitude not known, about 200,000 deaths.

    This earthquake struck a 200-mile stretch of northeast Iran, with the epicenter directly below the city of Demghan, which was at that point the capital city. Most of the city was destroyed as well as the neighboring areas. Approximately 200,000 people were killed.

  • 7: Haiyuan, Ningxia , China, Dec. 16, 1920

    7.8 magnitude, about 200,000 deaths.

    This earthquake brought total destruction to the Lijunbu-Haiyuan-Ganyanchi area. Over 73,000 people were killed in Haiyuan County. A landslide buried the village of Sujiahe in Xiji County. More than 30,000 people were killed in Guyuan County. Nearly all the houses collapsed in the cities of Longde and Huining. About 125 miles of surface faulting was seen from Lijunbu through Ganyanchi to Jingtai. There were large numbers of landslides and ground cracks throughout the epicentral area. Some rivers were dammed, others changed course.

  • 8: Ardabil, Iran, March. 23, 893

    Magnitude not known, about 150,000 deaths

    The memories of the massive Damghan earthquake (see above) had barely faded when only 37 years later, Iran was again hit by a huge earthquake. This time it cost 150,000 lives and destroyed the largest city in the northwestern section of the country. The area was again hit by a fatal earthquake in 1997.

  • 9: Kanto, Japan, Sept. 1, 1923

    Kanto Damage
    Hulton Archive  /  Getty Images
    1923: High-angle view of earthquake and fire damage on Hongokucho Street and the Kanda District, taken from the Yamaguchi Bank building after the Kanto earthquake, Tokyo, Japan. (Photo by Hulton Archive/Getty Images)
    7.9 magnitude, 142,800 deaths.

    This earthquake brought extreme destruction in the Tokyo-Yokohama area, both from the temblor and subsequent firestorms, which burned about 381,000 of the more than 694,000 houses that were partially or completely destroyed. Although often known as the Great Tokyo Earthquake (or the Great Tokyo Fire), the damage was most severe in Yokohama. Nearly 6 feet of permanent uplift was observed on the north shore of Sagami Bay and horizontal displacements of as much as 15 feet were measured on the Boso Peninsula.

  • 10: Ashgabat, Turkmenistan, Oct. 5, 1948

    7.3 magnitude, 110,000 deaths.

    This quake brought extreme damage in Ashgabat (Ashkhabad) and nearby villages, where almost all the brick buildings collapsed, concrete structures were heavily damaged and freight trains were derailed. Damage and casualties also occurred in the Darreh Gaz area in neighboring Iran. Surface rupture was observed both northwest and southeast of Ashgabat. Many sources list the casualty total at 10,000, but a news release from the newly independent government on Dec. 9, 1988, advised that the correct death toll was 110,000. (Turkmenistan had been part of the Soviet Union, which tended to downplay the death tolls from man-made and natural disasters.)

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