Correction:

An earlier version of this article incorrectly said that graphite stoppers in the reactor cores would begin to melt at 350 degrees Fahrenheit. Graphite has a high melting point, about 6,600 degrees Fahrenheit. The stoppers would not melt at 350 degrees but could begin to “degrade,” according to nuclear engineer Arnie Gundersen. This version has been corrected.

Radiation levels at Japan nuclear plant reach new highs

TOKYO — As radiation levels at the Fukushima Daiichi nuclear plant reached a new high Sunday, workers contended with dark, steamy conditions in their efforts to repair the facility’s cooling system and stave off a full-blown nuclear meltdown. Wearing respirators, face masks and bulky suits, they fought to reconnect cables and restore power to motor pumps the size of automobiles.

Leaked water sampled from one unit Sunday had 100,000 times the radioactivity of normal background levels, although the Tokyo Electric Power Co., which operates the plant, first calculated an even higher, erroneous, figure it didn’t correct for hours.

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The battle to contain radioactivity at Japan's damaged Fukushima Daiichi nuclear power plant was continuing amid fresh worries over the release of radioactive iodine. A 6.5 magnitude aftershock also shook rattled northeastern Japan Monday. (March 28)

The battle to contain radioactivity at Japan's damaged Fukushima Daiichi nuclear power plant was continuing amid fresh worries over the release of radioactive iodine. A 6.5 magnitude aftershock also shook rattled northeastern Japan Monday. (March 28)

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Tepco apologized Sunday night when it realized the mistake; it had initially reported radiation levels in the leaked water from the unit 2 reactor as being 10 million times the norm, which prompted an evacuation of the building.

After the levels were correctly measured, airborne radioactivity in the unit 2 turbine building still remained so high — 1,000 milli­sieverts per hour — that a worker there would reach his yearly occupational exposure limit in 15 minutes. A dose of 4,000 to 5,000 millisieverts absorbed fairly rapidly will eventually kill about half of those exposed.

The latest confusion in the operation to stave off a full-scale nuclear meltdown at the crippled facility underscores the immense challenges for the several hundred workers in a desperate battle to restart the critical cooling systems. Seventeen workers have been exposed to high levels of radiation, including three who were hospitalized last week, as technicians conducted highly nuanced electrical work in dark conditions that one nuclear industry expert termed “hellish.”

Japanese authorities say efforts to control Fukushima’s overheated reactors will take months and during that time radiation will continue to leak into the environment, extending a nuclear emergency that already ranks as the world’s most serious in a quarter-century. Several hundred workers now shoulder the responsibility for limiting the crisis, amid potentially lethal radiation levels, and on Saturday the chief of Japan’s nuclear agency called on Tepco to improve its worker safety.

On Monday morning, Japan's Chief Cabinet Secretary Yukio Edano made a plea to residents from the 12-mile radius evacuation zone surrounding the crippled nuclear plant to please stay away "until safety is confirmed."

Police stationed in the area have noticed more people returning to gather belongings and “there is a risk” of returning home now, Edamo said. Many families fled quickly after the earthquake and tsunami struck more than two weeks ago with only the clothes they were wearing.

Evidence of rising contamination in and around the plant has tempered optimism from a week ago, when engineers began work to restore power to the first of the damaged reactor buildings. Japan’s Nuclear and Industrial Safety Agency said Sunday that a new measurement of seawater taken about 1,000 feet from the facility showed an iodine level 1,850.5 times the legal limit, higher than a reading taken the previous day.

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