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| Workers in protective suits prepare Thursday to decontaminate two nuclear plant workers in Fukushima, Japan. |
STORY HIGHLIGHTS
- An official says high radiation in water indicates nuclear fuel in Unit No. 3 is damaged
- Plant operator is urged to improve its radiation control measures
- Work continues to control temperatures at all the plant's six reactors
- Pressure had risen at the No. 1 unit, though it now seems "rather stable"
(CNN) -- The water three men were exposed to while working at the Fukushima Daiichi nuclear power plant had 10,000 times the amount of radiation typical for that locale, an official with the Japan nuclear and industrial safety agency said Friday.
The high levels indicate the nuclear fuel inside the No. 3 reactor "is damaged," the official said.
The incident raised questions about radiation control measures at the plant as 536 people -- including government authorities and firefighters continued working there Friday, according to an official with the plant's owner, Tokyo Electric Power Co.
Workers are undertaking a broad array of measures to prevent the further release of radioactive substances into the air and beyond.
Some 17 people already have been exposed to 100 or more millisieverts of radiation since the plant's crisis began two weeks ago after a 9.0-magnitude earthquake and subsequent tsunami struck.
A person in an industrialized country is naturally exposed to 3 millisieverts of radiation a year.
But Japan's health ministry recently raised the maximum level of exposure for a person working to address the crisis at the nuclear plant from 100 millisieverts to 250 millisieverts per year.
RELATED TOPICS
The three workers exposed to radiation Thursday had the highest levels recorded so far, Tokyo Electric said.
They had been laying cables in the No. 3 reactor turbine building's basement when they stepped in the water. It seeped into the ankle-height boots of two, according to the power company.
The workers remained in the 15-centimeter (5-inch) deep water for about 40 to 50 minutes.
Two of them were admitted to the hospital: one in his 30s who was exposed to 180.7 millisieverts and the other in his 20s who tested at 179.37 millisieverts.
A third man, who was exposed to 173 millisieverts, did not go to the hospital because his boots were high enough to cover his skin, the power company said.
The water in this location is typically boiled and has low levels of radiation, Hidehiko Nishiyama of Japan's nuclear and industrial safety agency said.
The high measure prompted a top official with Nishiyama's agency to urge Tokyo Electric to "improve its radiation management measures."
The No. 1 reactor remains a chief concern, with the Japan Atomic Industrial Forum noting Friday that its containment vessel was experiencing "increased" pressure.
Earlier, buildups of hydrogen gas had driven up pressure that led to explosions at three of the nuclear plant's reactors, including the No. 1 unit.
Nishiyama conceded that "controlling the temperature and pressure has been difficult" for that reactor. Still, he told reporters Friday that the situation then was "rather stable," given indications the pressure was decreasing.
As to that unit's spent nuclear fuel pool, Nishiyama said the hope is to start pumping in fresh water -- rather than seawater, as has been done.
Such pools, which are distinct but tied to a given reactor, have nuclear fuel rods that can emit radiation especially if they heat, which is more likely to happen without any functional cooling system in place and when the rods are not fully covered in water.
Switching to fresh water, instead of seawater, is also a priority for the No. 2 reactor's core (as well as for its spent fuel pool), said Nishiyama. The aim is to prevent further corrosion and damage inside, which may be worsened by the buildup of salt.
The No. 3 reactor has been another pressing concern, especially after black smoke was seen wafting from its east side on Wednesday. The smoke had subsided by the next day, but remains a concern because its cause is still known.
Thursday's incident has further made it a focus, and Nishiyama said Friday that "radiation levels are high" in some locales near that unit.
He said that authorities were considering "other routes" to accomplish their goals of restarting its cooling systems, keeping its spent nuclear fuel pool in check and other aims.
To this end, firefighters from Tokyo and Kawasaki were expected to resume spraying toward the No. 3 reactor and its fuel pool on Friday afternoon, according to Nishiyama.
Efforts are ongoing, too, on the Nos. 4, 5 and 6 reactors -- each of which have their own concerns, though less pronounced because the units were on scheduled outages when the quake struck. None of these three units had nuclear fuel inside their reactors, though efforts are ongoing to control temperatures inside the spent fuel pools.
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Mothers
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Adachi ward of Tokyo. The government has warned
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infants should not be allowed to consume tap water.
(Haruyoshi Yamaguchi, Bloomberg / March 24, 2011)
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