日本民眾近來憂心忡忡，但在東京繁忙的街道上，行色匆匆的路人並沒有將這種擔憂掛在臉上。這裡看似一切如常，難道日本人民真的相信官房長官枝野幸男信誓旦旦的許諾麼？
"多個檢測結果表明，核電站區域的輻射強度已經下降。現在即便下雨，對健康也無影響。"
過去幾天中，福島周邊區域的輻射值確實沒有繼續升高，強烈餘震後失電的其他核電站狀況也暫時穩定。 3月11日當天就緊急停堆的幾個核電站如今依然停運，女川核電站乏染料池中外溢的廢水也被認為是無害的。日本政府甚至還將重新許可福島縣的牛奶及蔬菜重新上市銷售。官房長官枝野幸男說：
"根據我們掌握的所有材料，我能確信這些食品已無輻射之虞，因此現在能夠解除當地農產品的銷售禁令。"
渡邊守男是一名上了歲數的稻農，飽經滄桑日曬雨淋的他如今蝸居在棒球場的地下室裡，這裡是近百位災民的家，他們把硬紙板當作隔牆，紙箱當作衣櫃，每天打地舖湊合度日。在日本，這般一貧如洗的災民目前超過16萬。渡邊守男現在自己也不清楚，能否再次回到富岡縣的稻田裡：
"聽專家說，土壤也已遭放射性污染。雖然我也不太懂，但是肯定還要好些年才能恢復正常。我現在完全不知道未來會怎樣。"
興許，福島核電站的工程師與工人們同樣也不知道未來會怎樣。反應堆的搶險工作仍在繼續，下一步將搭建一面大型鋼板，建造一道120米寬的堤壩，以阻止放射性廢水洩露進海洋。但是現在，還是有放射性廢水從反應堆建築內洩露，海水中放射性碘同位素的濃度是限值的63000倍。
作者：Horst Kläuser 編譯：文山
責編：雨涵
****
日本福島核一廠災難近月 問題多嚴重 大家還搞不清楚
Lack of Data Heightens Japan’s Nuclear Crisis
By HIROKO TABUCHI and KEITH BRADSHER
Published: April 8, 2011
TOKYO — Nearly one month after Japan’s devastating nuclear accident, atomic energy experts, regulators and politicians around the world are still puzzling over a basic question: How much danger is still posed by the Fukushima Daiichi nuclear power plant?
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That depends to a considerable extent on how hot the uranium fuel rods at the power plant remain, and whether fuel has escaped its containment, or might still do so. Yet remarkably little is known for sure about what is really happening inside the reactors because some areas remain far too radioactive for workers to approach, and some instruments have malfunctioned.
The paucity of data and the conflicting estimates of what the available information really means have prompted a series of confusing analyses and a rift between officials in Japan and those overseas — and even between one member of Congress and the United States Nuclear Regulatory Commission.
The commission speculated this week that the nuclear fuel in the core of one of the stricken reactors had probably leaked from its thick steel pressure vessel, its most important protective barrier. If that proved to be accurate, it would raise the prospect of continuing fuel leaks and high levels of radioactive releases that would vastly complicate containment and the cleanup.
But Japanese officials said there was no evidence of a compromised pressure vessel, and they wondered why they were reading about it in the newspapers.
“If they have a concern, they should inform us,” said Kentaro Morita of Japan’s nuclear regulatory body, the Nuclear and Industrial Safety Agency, after its American counterpart sounded the alarm over a possible nuclear fuel leak at the plant’s Reactor No. 2, clearly contradicting Japanese accounts. “They didn’t say such concerns to us directly,” Mr. Morita said.
A senior Foreign Ministry official, meanwhile, accused the foreign media of exaggerating the threat posed by the power plant and the radiation spreading from it. Radiation fears are hurting sales of Japanese products abroad.
Who is proved right in the scientific debate has great repercussions for how and when the nuclear crisis might be brought under control, and the potential implications if assumptions prove wrong.
From the start there have been differences, with the American authorities expressing a more pessimistic view than the Japanese.
The United States has advised Americans to stay at least 50 miles away from the Fukushima Daiichi plant. Japanese officials evacuated residents within a 12-mile radius, and have since said they are considering expanding the evacuation zone.
An assessment in late March by the Nuclear Regulatory Commission said that hydrogen explosions at the plant might have blown particles of nuclear fuel from the reactors’ spent-fuel pools up to a mile away. The Tokyo Electric Power Company, the operator of the Fukushima Daiichi plant, says that while the pools remain exposed at the most-damaged reactors, the fuel remains safely inside.
American officials are also concerned that mounting stresses on the reactors’ containment structures as they fill up with radioactive water used in emergency cooling make them vulnerable to rupture in an aftershock from the March 11 earthquake. Japanese officials have played down that concern, and on Friday they said a sizable aftershock that struck overnight had caused no further damage at the plant.
The rift also highlights the difficulty of a debate in which both sides are forced to extrapolate possible situations with little access to crucial readings from inside the reactors.
Much of the automated measurement equipment in the reactors has been damaged, either by explosions in the early days of the crisis or by intense radiation since then. Damage to the reactors, as well as high radiation, has prevented technicians from making detailed assessments.
The Pentagon has provided airborne surveillance drones that can help monitor ground-level radiation at the plant. It is possible that American officials are basing their analysis on data they have collected independently, though Obama administration officials say they have shared their information with the Japanese.
Even so, it is not easy to explain why such different theories are being offered on fundamental questions like whether radioactive fuel from the steel reactor pressure vessel at Unit No. 2 is leaking into the bottom of the containment structure.
The Nuclear Regulatory Commission cited high levels of radiation at one spot inside the containment structure at Reactor No. 2 as evidence for its analysis. In addition, extremely high levels of radiation were detected in the water from a recently stanched leak that ran from the reactor building into a drainage ditch and into the ocean.
The Japanese flatly deny that possibility. “At this moment we do not have any data that shows there has been leakage to the containment vessels,” said Hidehiko Nishiyama, deputy director general at the Japanese regulatory agency. He also said that the Japanese and American regulators, who talk every day, were no longer so far apart on this question.
Japanese officials believe that water pumped into the reactor to cool it — as opposed to the nuclear fuel itself — might have somehow leaked out. In addition, there is evidence that an explosion may have breached the primary containment structure, which may have allowed highly radioactive water into other parts of the plant and into the ocean.
Domestic political priorities appear to be driving at least some of the reactions in both countries. In the aftermath of the 1979 accident at Three Mile Island in Pennsylvania, nuclear regulators in the United States have often planned for and talked about the worst possibilities to avoid accusations that they are lax about safety.
The pressure on American officials to give well-rounded explanations about the potential threat remains high. In fact, some members of Congress who are critics of the nuclear power industry are skeptical that the regulatory commission has been as forthcoming as it should be about the risks posed by Japan’s nuclear crisis or the potential impact on American nuclear power plants that use similar technology.
This week, Representative Edward J. Markey, Democrat of Massachusetts, an outspoken critic, engaged in a running debate with members of the commission’s staff over the conditions at Reactor No. 2 in Japan. Mr. Markey said the regulators had told his staff that fuel was leaking from the reactor, but then the commission issued a more ambiguous public statement.
“I find it rather curious that some within the Nuclear Regulatory Commission are attempting to deny the findings their own technical staff conveyed to my office as soon as it became clear that this information showed a meltdown that is more severe than some people apparently wish to acknowledge,” Mr. Markey said in a statement.
On the Japanese side, officials have an obvious desire to avoid causing panic in public statements.
“We have a very conservative culture in the nuclear industry” in the United States, said Murray E. Jennex, a professor at San Diego State University and a specialist in nuclear containment structures. “There’s nothing to gain by the N.R.C. saying things are good. At the same time, there’s nothing to gain by Tokyo Electric not downplaying stuff.”
The Americans also appear to rely more heavily on complex computer programs like Melcor that use available data to extrapolate conditions in reactors after accidents. But the regulatory commission appears to have partly relied on data provided by Tokyo Electric, something that engineers skeptical of the power company say compromises the validity of the findings.
“When the input numbers are no good, the output numbers are no good,” said Satoshi Sato, a former engineer at General Electric, which designed the reactors at Fukushima Daiichi. He argues that the conditions in the reactors are probably worse than the Japanese have reported.
The Japanese also seem to prefer presenting raw data without explaining what they think it means, said Takashi Inoue, a professor of public relations at Waseda University. Every day, Tokyo Electric, the nuclear agency, the chief cabinet secretary and others hold news conferences at which they present a blizzard of facts and numbers but rarely make broader declarations about the conditions at Fukushima Daiichi.
Industry experts are split.
Yoichi Kikuchi, a Japanese nuclear engineer who helped design the containment vessel at one of the Fukushima Daiichi reactors, agreed with the Americans that a fuel leak was possible. He said that the pressure vessel at Reactor No. 2 was especially vulnerable because of openings at the bottom where control rods are inserted. If the fuel were melting, the metal welding around those openings would easily give way, allowing the fuel to travel into the drywell, he said. The fuel could then react with the water in the suppression chamber, setting off a vapor explosion and a huge release of radiation into the air, he said.
Shuichi Iwata, a nuclear fuel expert at Tokyo University, said that he thought a leak of fuel was probably occurring, but that the consequences might not be great. “The worst case is not happening, I think,” he said.
But Toshihiro Yamamoto, an associate professor in nuclear engineering at the Kyoto University Research Reactor Institute, said the nuclear agency’s explanation was more likely. He said that it was water, not fuel, escaping from the same openings, or perhaps from a damaged circulation pump higher in the vessel.
Masashi Goto, a former Toshiba nuclear power plant designer, said that Japanese officials appeared to have decided that they gained nothing but panic from predicting outcomes. “They will never speak about the worst-case scenario,” he said. “They will never predict.”
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