Japan's Reactors Lose Power: Spent Fuel Pools at Risk
Fukushima 1 Was Bad Enough: Are We Ready for Fukushima 2? (News Analysis)
On March 11, 2011, an earthquake-tsunami double-punch delivered a knockout blow to Japan's Fukushima Daiichi nuclear reactor complex. Electric power was lost, causing a failure of the emergency cooling systems which, in turn, left three reactor cores to overheat and explode, sending clouds of radiation across land, sea and air. The atmospheric contamination was detected across the US, in Stockholm and below the Equator.
History may be repeating itself. On the morning of March 18, 2013, the damaged Fukushima facility once again lost outside electrical power.
In the early hours of the blackout, the Tokyo Electric Power Company (TEPCO) assured the press that the site's reactors were "unaffected and no other abnormalities were found." (Of course, these reactors are still suffering from the "abnormality" of having exploded and experienced meltdowns — with molten fuel, in at least one case, escaping the metal reactor vessel and spilling onto the floor of the containment room.)
The Spent Fuel Pool Risk
But the damaged reactors are not the only issue. The fate of the spent fuel pools (SFPs) that line the coastal facility are also a matter of grave concern. A dispatch from Mochizuki, an anti-nuclear blogger who posts at Fukushima Diary, reports: "The coolant system of the spent fuel pools of reactor1, 3 and 4 has been out of operation for over 3 hours already. Seismic isolation building has lost power, too. Tepco is still investigating the reason. It is currently the top Japanese news story." (The Fukushima Diary website also posted a computer animation, attributed to the meteorological agency of Switzerland, that projects "the emission from Fukushima would reach Tokyo area by wind after 15:00 of 3/19/2013.")
The Kyodo news service reported the power failure occurred shortly before 7 p.m. Monday disabling three of the site's seven SFPs. Japan's Nuclear Regulation Authority was quoted as saying "the incident so far has not affected the ongoing water injection to the Nos. 1 to 3 reactors, which suffered core meltdowns in the early days of the March 2011 nuclear crisis." However, the Kyodo news service also noted, "as of 1:45 a.m., TEPCO has not been able to work out steps to ensure bringing the system back online." Adding to the problems, a severe weather system was bearing down on Japan.
TEPCO Mystified by Power Failure
TEPCO has confirmed that three of the site's SFPs were without emergency cooling and assured the public the stored nuclear wastes would remain safe "for at least four days without fresh cooling water." Takeo Iwamoto, a TEPCO spokesman, promised the utility planned to restore the SFP cooling power "as soon as [TEPCO] can determine the cause of the failure."
Why is this is a cause for alarm? Because, if the thousands of densely packed uranium-filled fuel assembly rods become too hot — especially if water is lost to evaporation as the pools begin to steam and boil — they could ignite. Takeo Iwamoto, a TEPCO spokesman, promised the utility plans to restore SFP cooling power "as soon as [TEPCO] can determine the cause of the failure."
Ever since the devastating quake struck, workers at the plant have been relying on "makeshift" systems to control radiation leaks and temperature increases. But these makeshift systems rely on electric power. Without emergency cooling, the fuel in the SFPs — mounted 100 feet above the ground on the building rooftops with no enhanced containment structures — could overheat and create a new disaster that some nuclear watchdogs have warned could eclipse the fallout that rained down after the fire and explosion at Russia's Chernobyl plant.
What Happens When Fuel Pools Overheat?
A 2006 study by the National Research Council of the National Academies detailed what can happen if SFP water levels drop enough to expose the tops of the fuel assemblies. Quickly rising temperatures would accelerate the oxidation of the exposed zirconium alloy that encases the uranium fuel pellets. Exposure to air and steam further increases temperatures while generating explosive hydrogen gas. This can lead to a self-sustaining “runaway” fire, with a moving “burn front” that crackles like a fireworks sparkler.
As temperatures rise further, the captive fuel begins to expand until it forces the cladding to bulge and burst, releasing superheated isotopes into the air. At 3,300°F (1,816°C), the contents and the containment merge to form a growing molten mass of zirconium-uranium-oxide. At this point, the exposed fuel rods continue to reignite like “trick birthday candles,” posing the risk of a chain-reaction fire, jumping from one assembly to the next. Nuclear engineer Arnie Gundersen has calls the prospect of a runaway combustion of fuel assemblies "Chernobyl on steroids."
In March of 2011, fear of a spent fuel fire was so intense, the Japanese government began secret preparations to order the evacuation of Tokyo’s 13 million residents. In the end, the plans were not revealed in order “to avoid panic.” As one senior government official told the Japan Times, "The content [of the emergency response plan] was so shocking that we decided to treat it as if it didn’t exist."
This isn't the first time Fukushima's SFPs have posed a threat. In mid-October 2011, after hydrogen gas was reported to be accumulating in the pipes at Unit 1, TEPCO admitted that the spent fuel pools at the three reactors had been damaged, releasing incredibly high levels of cesium-137 and cesium-134.
The Damage from Fukushima 1 Could Be Exceeded by a Fukushima 2
The consequences of the 2011 fallout cloud were dramatically apparent. Some 100,000 people were forced to flee their homes and1.5 million were affected by dangerous fallout levels well beyond the official 12.5-mile evacuation zone. One-third of Fukushima Prefecture — an area the size of Rhode Island — was contaminated. The region’s $3.2-billion-a-year agricultural sector was wiped out. By July 2011, it was clear the radiation had entered the human food chain.
Then, as now, the fate of the Unit 4 reactor remains a major concern. The building was severely damaged by the quake and left tilting dangerously. The 1,535 nuclear fuel rods stored in the SFP 100 feet above the ground pose a grave hazard. If Unit 4’s 460 tons of spent fuel were to fall to earth, it could crash into the 6,375 fuel rods in a nearby “common pool.” Together, Fukushima’s 11,138 spent fuel assemblies contain 134 million curies of cesium-137. The US National Council on Radiation Protection estimates this is roughly 85 times the amount of cesium-137 released at the Chernobyl accident.
Japan’s former Ambassador to Switzerland, Mitsuhei Murata, has warned the United Nations that a collapse at Unit 4 could "destroy the world environment and our civilization…. The fate of Japan and the whole world depends on the No. 4 reactor."
Nuclear critics have pointed out that nuclear accidents can have long-lasting effects. The cleanup of the March 2011 Fukushima meltdowns is expected to last 40 years and cost $240 billion. If the disabled emergency cooling systems are not restarted in a timely manner, the world could face Fukushima 2 — a catastrophe even more horrific and devastating than the original disaster.
Gar Smith is the author of Nuclear Roulette: The Truth about the Most Dangerous Energy Source on Earth (Chelsea Green). Nuclear Roulette was recently nominated for two national book awards.