2011年3月29日 星期二


TEPCO says damage possible to reactor pressure containers

Editor's note: We will update our earthquake news as frequently as possible on AJW's Facebook page: http://www.facebook.com/AJW.Asahi. Please check the latest developments in this disaster. From Toshio Jo, managing editor, International Division, The Asahi Shimbun.

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Tokyo Electric Power Co. acknowledged for the first time possible damage to core pressure containers at the crippled Fukushima nuclear plant--the last line of defense in preventing radioactive materials from spewing out.

TEPCO officials told reporters Monday morning that despite the continuous pumping in of water to cool down the No. 1, No. 2 and No. 3 reactor cores, water levels were not rising as expected, meaning the pressure containers may not be completely sealed off.

The water, which is believed to be mixing with radioactive materials from the fuel rods within, is likely leaking from the pressure containers, they said.

The tsunami that hit the Fukushima No. 1 nuclear power plant after the March 11 Great East Japan Earthquake knocked out the emergency generators at the three reactors. The systems that circulate water within the pressure containers to cool the fuel rods also stopped working.

Workers have been pumping in water through pipes to the pressure container to submerge the fuel rods and directly cool the decay heat that continues to be emitted even after the reactors were stopped.

But the water level meters for the three reactors have not risen as expected.

TEPCO officials said a possible reason the water levels were not rising sufficiently were breaches in the lower part of the pressure containers. They said they did not know what caused the possible damage.

A pressure container holds nuclear fuel pellets placed in metal rods that have been bundled together. A containment vessel, located within the building housing the reactor, surrounds the pressure container.

The pressure containers at the Fukushima plant are made of steel 16 centimeters thick. The lower part of the containers have openings for measuring and other equipment. Water may be leaking from around those parts, the officials said.

TEPCO has cited the possibility that fuel rods may have been damaged due to overheating after being exposed above the water's surface in the core.

According to experts, if the fuel rods are damaged and crumble, the melted fuel could fall and accumulate into a lump at the bottom of the pressure container. In that scenario, it would be more difficult to cool because of the fuel's larger surface area. The experts also said damaged fuel rods could have reached high temperatures that melted the walls of the pressure container.

However, TEPCO officials said major structural damage was unlikely and the soundness of the pressure container has probably been maintained because the pressure within the container remains at higher levels than the outside atmosphere.

TEPCO officials are trying to restart the cooling systems that circulate water so that they can stop discharging the water to the outside. But they have run into problems in obtaining a stable electric power source.

For now, they said the pumping will have to continue to cool the fuel rods, which raises concerns about highly contaminated water leaking steadily through breaches in the pressure containers.

At the same time, the Nuclear Safety Commission of Japan said Monday that extremely high levels of radiation have not been recorded outside the reactor buildings, making it possible to continue pumping in water and releasing steam to cool the core, even if water continues to leak.

The NSC also commented on the water accumulated at the basement of the turbine building of the No. 2 reactor that had radioactivity levels about 100,000 times above the normal level.

The commission said the water likely flowed into the turbine building from the core containment vessel after coming in contact with fuel rods that had temporarily melted.


Why No Nukes? The Real Cost of U.S. Nuclear Power

Paulo Fridman/Corbis; Pallava Bagla/Corbis; AFP/Getty; Getty

The chaos at the Fukushima Daiichi nuclear plant — explosions, fires, ruptures — has not shaken the bipartisan support in partisan Washington for the U.S.'s so-called nuclear renaissance. Republicans have dismissed Japan's crisis as a once-in-a-lifetime fluke. President Obama has defended atomic energy as a carbon-free source of power, resisting calls to halt the renaissance and freeze construction of the U.S.'s first new reactors in over three decades.

But there is no renaissance.

Even before the earthquake-tsunami one-two punch, the endlessly hyped U.S. nuclear revival was stumbling, pummeled by skyrocketing costs, stagnant demand and skittish investors, not to mention the defeat of restrictions on carbon that could have mitigated nuclear energy's economic insanity. Obama has offered unprecedented aid to an industry that already enjoyed cradle-to-grave subsidies, and the antispending GOP has clamored for even more largesse. But Wall Street hates nukes as much as K Street loves them, which is why there's no new reactor construction to freeze. Once hailed as "too cheap to meter," nuclear fission turns out to be an outlandishly expensive method of generating juice for our Xboxes. (See pictures of an aging nuclear plant.)

Since 2008, proposed reactors have been quietly scrapped or suspended in at least nine states — not by safety concerns or hippie sit-ins but by financial realities. Other projects have been delayed as cost estimates have tripled toward $10 billion a reactor, and ratings agencies have downgraded utilities with atomic ambitions. Nuclear Energy Institute vice president Richard Myers notes that the "unrealistic" renaissance hype has come from the industry's friends, not the industry itself. "Even before this happened, short-term market conditions were bleak," he tells TIME.

Around the world, governments (led by China, with Russia a distant second) are financing 65 new reactors through more explicit nuclear socialism. But private capital still considers atomic energy radioactive, gravitating instead toward natural gas and renewables, whose costs are dropping fast. Nuclear power is expanding only in places where taxpayers and ratepayers can be compelled to foot the bill. (See pictures of the worst nuclear disasters.)

In fact, the economic and safety problems associated with nuclear energy are not unrelated. Trying to avoid flukes like Fukushima Daiichi is remarkably costly. And trying to avoid those costs can lead to flukes.

The False Dawn
In 1972 a federal safety regulator, worried that GE's Mark 1 reactors would fail in an emergency, urged a ban on containment designs that used "pressure suppression." His boss was sympathetic but wrote in a memo that "reversal of this hallowed policy, particularly at this time, could well be the end of nuclear power" and "would generally create more turmoil than I can stand thinking about." Four decades after this bureaucratic pressure suppression, Fukushima Daiichi's Mark 1 reactors seem to have failed as predicted. And while newer reactors don't have those problems, 23 Mark 1 reactors still operate in the U.S., including a Vermont plant that was relicensed for 20 more years the day before the disaster in Japan.

When Karl Marx, who would have appreciated nuclear economics, wrote that history unfolds first as tragedy, then as farce, he got U.S. nuclear history backward. America's initial experiment was a cartoonish disaster, with construction timelines doubling and costs increasing as much as 1,000% even before the Three Mile Island meltdown. In the 1980s, the industry required bailouts before bailouts were cool. But the U.S. industry has matured and learned from its mistakes. It still runs the world's largest nuclear portfolio, and it hasn't had a serious accident since 1979. Meanwhile, global-warming fears have positioned nuclear power as a proven alternative to fossil fuels that works even when the sun isn't shining and the wind isn't blowing, producing 20% of our electricity and 0% of our emissions. No-nukes outrage has burned out, with a recent poll registering 71% support.