Sunday, March 27, 2011

Higher Levels of Radiation Found at Japan Reactor Plant By Hiroko TABUCHI and Keith BRADSHER


 TOKYO — Sharply elevated radiation at the Fukushima Daiichi nuclear complex on Sunday raised the possibility of spreading contamination and forced an emergency evacuation of part of the damaged plant.


                                                                                                            Toru Hanai/Reuters
Protesters marched in an anti-nuclear rally in Tokyo on Sunday.


 The concerns began when a worker attempting to measure radiation levels of the water puddles there saw the reading on his dosimeter jump beyond 1,000 millisieverts, the highest reading. The worker left the scene immediately, said Takeo Iwamoto, a spokesman for the Tokyo Electric Power Co., the operator of the Fukushima plant.
 Michiaki Furukawa, a nuclear chemist and board member of the Citizens’ Nuclear Information Center, a Tokyo-based watchdog group, said exposure to 1,000 millisieverts an hour of radiation would induce nausea and vomiting, while levels between 3,000 to 5,000 millisieverts an hour could be lethal.
 Such high amounts of radiation would clearly make continued recovery work near the reactor very difficult. Tetsuo Iguchi, a professor in the department of quantum engineering at Nagoya University, said that at the sharply elevated levels of radiation, workers would be able to remain on site for only about 15 minutes before health considerations required them to leave.
 The Japanese government’s top spokesman, Yukio Edano, told an afternoon press briefing Sunday that it appeared the radioactive puddles had developed when the No. 2 unit’s fuel rods were exposed to air, but that “we don’t at this time believe they are melting. We’re confident that we are able to keep them cool.”
 The higher levels may have suggested a leak from the reactor’s fuel rods — from either the suppression chamber under the rods or various piping — or even a breach in the pressure vessel that houses the rods, the Japanese nuclear regulator said earlier.
 However, there was also an alarm about initial readings of radioactive iodine 134, which has a half life of only 53 minutes and would not be present in very large quantities unless fission had resumed — that would present the alarming possibility of an out-of-control reactor. Several hours after releasing the initial results, the nuclear company said that those readings had been in error, and that retesting had shown negligible amounts of the isotope.
 But they confirmed the overall high radiation readings at the plant, and utility officials continued to search for the exact source. And they still may need to retest for other radioactive isotopes that would cause concerns, and confirming those results could take hours or days.
 Sunday’s developments came after the world’s chief nuclear inspector said that Japan was “still far from the end of the accident” that struck the plant. Yukiya Amano, the director general of the International Atomic Energy Agency, acknowledged that the authorities were still unsure about whether the reactor cores and spent fuel were covered with the water needed to cool them and end the crisis.
 Mr. Amano, taking care to say that he was not criticizing Japan’s response under extraordinary circumstances, said, “More efforts should be done to put an end to the accident.”
 More than two weeks after the devastating earthquake and tsunami, he cautioned that the nuclear emergency could still go on for weeks, if not months, given the enormous damage to the plant.
 Asked by a journalist Sunday at a news conference what was the company’s projected timeline for emerging from the crisis, Sakae Muto, a vice president for Tokyo Electric Power, “We don’t have a concrete schedule.”
 Mr. Muto declined to answer a journalist’s question about a possible worst-case scenario, saying: “The important thing is to keep cooling the reactor and prevent the current situation from getting worse.”
 Mr. Nishiyama, of the Japanese nuclear safety agency, said that it was likely that radiation was leaking from the pipes or the suppression chamber, and not directly from the pressure vessel, because water levels and pressure in the vessel were relatively stable.
 Tokyo Electric said its analysis of the water in the No. 2 unit had identified radioactive isotopes of cesium, iodine, cobalt, molybdenum, technetium, barium and lanthanum. The company has not yet been able to determine the source of the leak.
 Michael Friedlander, a former nuclear power plant operator for 13 years, said that if the company had discovered the discovery of extremely high levels of radioactive iodine, it would not necessarily mean new problems at the reactor.
 Gaseous iodine is among the first materials released when fuel rods rupture, because the iodine accumulated under pressure during the months that the fuel rods were undergoing fission, he said. The release of the iodine does not necessarily mean that the fuel rods are actually melting, which would result in the release of a wider range of radioactive materials.
 It is not easy for any liquid to travel from the reactor building to the adjacent turbine building. There are only two pipes that connect them, and they have many valves along them that should have closed automatically after the earthquake and before the tsunami arrived.
 All Sunday, the government and company officials fielded questions from the Japanese media about whether plutonium might have escaped from one of the damaged facilities. Mr. Edano said the area around the reactors was being tested for plutonium, but “this is not an easy process.” He said that if the presence of plutonium was confirmed, “we will take measures depending on the situation.”
 The I.A.E.A. cited information from Prime Minister Naoto Kan’s office Sunday that Tokyo Electric had begun pumping water out of some of the turbine buildings at the Fukushima plant.
 Workers were pumping water from the No. 1 unit turbine to its main condenser and were making preparations to do the same at the No. 2 unit, the I.A.E.A. said, noting that a main condenser’s function in a nuclear power plant is to condense and recover steam that passes through the turbine. The company also was considering ways to remove water from the turbine buildings of the No. 3 and No. 4 units, the agency said.
 The No. 5 and No. 6 units are thought to be out of harm’s way.
 Separately, the I.A.E.A., citing data from the Japanese authorities, reported that two of three workers who were exposed to radioactive water last Thursday suffered “significant skin contamination over their legs.”
 “The Japanese authorities have stated that during medical examinations carried out at the National Institute of Radiological Sciences in the Chiba Prefecture, the level of local exposure to the workers’ legs was estimated to be between 2 and 6 sieverts,” the I.A.E.A. said on its Web site.
 “While the patients did not require medical treatment, doctors decided to keep them in hospital and monitor their progress over coming days.”
 Mr. Edano, the government spokesman, said he understood that the injured workers would be released from the hospital on Monday.
 Japan’s National Police Agency said on Sunday that the death toll from the quake and tsunami had risen to 10,668 persons, with 16,574 still missing.
 Meanwhile, radiation in the Tokyo water supply continued to diminish on Sunday, the authorities said. At two of three monitoring stations operated by the municipal waterworks bureau, there was no radiation detected. At a third, the level was 27 becquerels per kilogram, well below the maximum recommended limits for both infants and adults.
 The elevated levels of radiation at and around the Fukushima plant will require careful monitoring of seafood in Japan, said Kimberlee J. Kearfott, a professor of nuclear engineering and radiological sciences at the University of Michigan.
 “It is extremely important that seafood be carefully monitored,” she said in an e-mail. “This is because many of the radionuclides are concentrated in the environment,” she added. “For example, iodines are concentrated in kelp (a Japanese food, seaweed) and shrimp.
 “Iodines, cesium and strontium are concentrated in other types of seafood,” she continued. “Fish can act like tea or coffee presses. When you push down the plungers, the grounds all end up on one side. In this case, that is the fish.”

Hiroko Tabuchi reported from Tokyo, and Keith Bradsher from Hong Kong. Reporting was contributed by David Jolly, Ayasa Aizawa, Ken Ijichi and Kantaro Suzuki from Tokyo, and William J. Broad from New York.

© 2011nytimes.com





No comments:

Post a Comment

Note: Only a member of this blog may post a comment.

Feedback Form
Leads to Insight
Related Posts Plugin for WordPress, Blogger...