Radioactive waste at Fukushima threatens second nuclear catastrophe
Hiroko Tabuchi, Matthew Wald
May 28, 2012
TOKYO: What passes for normal at the Fukushima Daiichi nuclear plant today would have caused shudders among even the most sanguine of experts before an earthquake and tsunami set off the world's second most serious nuclear crisis after Chernobyl.
Fourteen months after the accident, a pool brimming with used fuel rods and filled with vast quantities of radioactive caesium still sits on the top floor of a heavily damaged building, covered only with plastic.
The public's fears about the pool have grown in recent months as some scientists have warned that it has the most potential for setting off a new catastrophe. The three nuclear reactors that suffered meltdowns are in a more stable state, but frequent quakes continue to rattle the region.
The worries gained new traction in recent days after the operator of the plant, Tokyo Electric Power Co., or TEPCO, said it had found a slight bulge in one of the walls of the reactor building, stoking fears over the building's safety.
To try to quell such worries, the government sent the Environment and Nuclear Minister to the plant on Saturday, where he climbed a makeshift staircase in protective garb to look at the structure supporting the pool, which he said appeared sound. The minister, Goshi Hosono, added that although the government accepted TEPCO's assurances that reinforcement work had shored up the building, it had ordered further studies because of the bulge.
Some outside experts have also worked to allay fears, saying that the fuel in the pool is now so old that it cannot generate enough heat to start the kind of accident that would allow radioactive material to escape.
But many Japanese have scoffed at those assurances and point out that even if the building is able to withstand further quakes, a claim that they question, the jury-rigged cooling system for the pool has already malfunctioned several times, including a 24-hour failure in April. Had the failures continued, they would have left the rods at risk of dangerous overheating.
Government critics are especially concerned, since TEPCO has said the soonest it could begin emptying the pool is late next year, dashing hopes for earlier action. ''The No. 4 reactor is visibly damaged and in a fragile state, down to the floor that holds the spent fuel pool,'' said Hiroaki Koide, an assistant professor at Kyoto University's research reactor institute and one of the experts raising concerns. ''Any radioactive release could be huge and go directly into the environment.''
The fears over the pool at reactor No. 4, amplified over the web, are helping to undermine assurances by TEPCO and the Japanese government that the Fukushima plant has been brought to a stable condition and are highlighting how complicated the clean-up of the site, expected to take decades, will be. The concerns are also raising questions about whether Japan's all-out effort to convince its citizens that nuclear power is safe kept the authorities from exploring other - and some say safer - options for storing used fuel rods.
''It was taboo to raise questions about the spent fuel that was piling up,'' said Hideo Kimura, who worked as a nuclear fuel engineer at the Fukushima Daiichi plant in the 1990s. ''But it was clear that there was nowhere for the spent fuel to go.''
The worst-case situations for reactor No. 4 would be for the pool to run dry if there is another problem with the cooling system and the rods catch fire, releasing enormous amounts of radioactive material, or that fission restarts if the metal panels that separate the rods are knocked over in a quake. That would be especially bad because the pools, unlike reactors, lack containment vessels to hold in radioactive material.
Attention has focused on No. 4's spent fuel pool because of the large number of assemblies filled with rods that are stored at the reactor building.
According to TEPCO, the pool at the No. 4 reactor, which was not operating at the time of the accident, holds 1331 spent fuel assemblies, which each contain dozens of rods.
Professor Koide and others warn that TEPCO must move more quickly to transfer the fuel rods to a safer location. But such transfers have been greatly complicated by the accident. Ordinarily the rods are lifted by cranes, but at Fukushima those cranes collapsed during the series of disasters that started with the earthquake and included explosions that destroyed portions of several reactor buildings.
TEPCO has said it will build a separate structure next to reactor No. 4 to support a new crane. But under the plan, released last month, the fuel removal will begin late next year. WAToday
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