The world might soon be able to breathe a giant sigh of relief.
At Japan’s crippled Fukushima Daiichi nuclear power facility, modest success in delivering desperately-needed water by helicopters and water-cannon trucks, and the impending restoration of limited electrical power to at least two of the facility’s six units, could be the framework for resolving the greatest industrial catastrophe involving nuclear technology since the Chernobyl explosion in 1986.
Water is critical to cooling the nuclear reactors and spent fuel storage ponds at the Fukushima facility, which otherwise could overheat and lead to troubling amounts of radioactive emissions.
Four of the six units require emergency attention, with units 3 and 4 particularly critical.
The use of helicopters and water trucks is a stop gap measure until restored electrical power can activate water pumping systems that normally do the job. That may not be as simple as it sounds. Wiring inside the units may be burned and need replacing. The water pumps themselves may be damaged. And with radiation levels within the plant boundary quite high, workers are hampered in performing their jobs.
But even if restoration of electrical power and water pumping is delayed, many nuclear engineers argue that, however cumbersome, the delivery of water by helicopter and truck should stabilize the reactors and cooling ponds sufficiently to stave off worrisome increases in radiation levels in Japan. Thus far, radiology specialists widely agree, the increased radiation levels experienced since the problems developed last week at Fukushima Daiichi pose no health risk to the general population in Japan. “The total exposure of the Japanese public to increased radiation has been insignificant,” says Professor Kim Kearfott, a nuclear engineering and radiology specialist at the University of Michigan.
Indeed, these same experts say, even a much-feared (and exceedingly unlikely) nuclear fuel “meltdown” would produce nothing even close to a health crisis in Japan.
That is not a license for complacency of course. While not a health catastrophe, the breakdown at Fukushima Daiichi is an industrial catastrophe of enormous proportions and global implications, necessitating as quick a resolution as possible.
In that context, reports of rifts between US and Japanese officials over information sharing and threat assessments seem highly-exaggerated. The ‘fog of war’ under such stressful and complex conditions understandably causes tension and disagreements, but that is a far cry from a dysfunctional breach of baseline trust.
AT THE PLANT: Helicopters and water trucks have concentrated on Unit 3 in recent days, and to a lesser extent Unit 4. Unit 3 has both a reactor vessel loaded with fuel rods that need cooling, and a storage pond with spent fuel rods that also need cooling. Government officials believe efforts to add water to the storage pond at Unit 3 were successful in the last day. The reputable World Nuclear News reported March 17 that Self Defense Force fire engines delivered 30 tons of water towards or into the spent fuel storage pond. The National Police Agency had plans to use a riot police force high-pressure water cannon truck to try to cool down the storage ponds at Unit 4. The truck can deliver water at high speeds from up to 100 meters. There is evidence the watering efforts have reduced radiation levels.
Meanwhile, Tokyo Electric Power (Tepco), owner of the distressed facility, launched power restoration efforts on March 17, involving some 320 workers. The company planned to run a cable from a high-voltage line owned by Tohoku Electric, connecting first to Unit 2, and later to Unit 1. Others will follow. The new cable will run a half-mile from a main high-voltage power grid. Electrical machinery giants Toshiba and Hitachi have dispatched teams of engineers to assist.
The reactor vessels and storage ponds pose different challenges, with the latter the more immediate.
The fuel rods in Units 1, 2, and 3 have almost surely suffered damage as a result of being left partially uncovered within reactor vessels. Rather than melting, Dr. John Lee, author of the forthcoming “Risk and Safety Analysis of Nuclear Systems,” says it is more likely the fuel rods partially liquefied, with zirconium from the fuel rods interacting with water to produce hydrogen. That’s what produced explosions at several units earlier this week.
Nevertheless, the reactor vessels have remained intact, limiting the release of radioactive particles. Even in the highly-improbable event that fuel rods melted, penetrated the steel of the reactor vessel, and then penetrated the thick concrete pad of the primary containment shell, the molten fuel would settle in the soil, releasing only limited amounts of radioactive particles. That’s not a pretty scenario, but it’s far from a disaster.
Some news accounts have claimed that Unit 3 is particularly dangerous because the fuel used is a uranium-plutonium mixture, and plutonium is extraordinarily toxic. But the fuel mixture in question actually uses plutonium dioxide, which is not readily absorbed by the body.
The cooling ponds for spent fuel pose a more serious problem. Lack of water removes a shield against radiation. It also allows for a heating up of the fuel rods, production of hydrogen, and the danger of an explosion that could more readily disperse radioactive particles than did the explosions caused by hydrogen from the reactors. For this reason, Japanese officials have placed priority on getting water to the storage ponds.
RADIATION EXPOSURE: In no case, says Dr. Lee, is it possible to have a Chernobyl-style explosion. Instead, he recommends that the Three Mile Island case of 1979 be seen as a reference point for the unfolding events in Japan. Fukushima is already worse than TMI by simple virtue of the fact that there are several troubled units, whereas as TMI had only one reactor. The comparison is still useful.
“In the areas surrounding Three Mile Island,” Lee says, “the worst radiation exposure among the general public was the equivalent of two chest x-rays. In the Fukushima case, the worst would be somewhat higher, but well below levels we should worry about.
“Within the current evacuation zone of up to 19 miles or so, the very worst case scenario would be an increased exposure equal to 1 CT scan, which is equivalent to 100 chest x-rays.”
Lee insists: “There cannot be a massive release of radioactivity, especially if there is some amount of water maintained in the reactor vessel, and the storage pools. And I don’t see why that is not possible at this point.”
CONCERN FOR ON-SITE WORKERS: For workers engaged in emergency operations at the Fukushima facility, the Japanese government is adhering to strict safety standards roughly in line with those followed in the US. Under normal circumstances, Japan’s occupational guidelines for nuclear-related jobs is actually tougher than that of the US, with each worker limited to exposure to 2 Rem (a unit of measurement for uranium dosage) per year, compared with 5 Rem in the US. Under emergency circumstances, the US raises the limit to 25 Rem, while Japan goes up to only 10 Rem. However, during the Fukushima crisis, Japanese authorities raised the limit inside Japan to 25 Rem.
To put that in some perspective, it takes about 100 Rem to induce symptoms of radiation sickness. About 500 Rem is a lethal dose.
A US-JAPAN SPLIT: Meanwhile, frustrations in Washington and throughout Japan notwithstanding, there is little evidence to support accusations that the Japanese government is somehow withholding information, anymore than there was evidence last year that the Obama administration withheld information about the BP oil leak in the Gulf of Mexico. The earthquake and tsunami, followed by the nuclear power crisis, add up to the biggest crisis in post-war Japan. The response of the Japanese government, while perhaps not a model of management efficiency and communication skill, hardly matches the cartoonish combination of obfuscation and incompetence often portrayed in parts of the US and Japanese media. How would any US government have dealt simultaneously with Three Mile Island, the BP oil leak, and Hurricane Katrina, which is about what the triple whammy of the earthquake, the tsunami, and the nuclear crisis amount to in Japan?
As evidence of a US split with Tokyo, some analysts have cited the Congressional testimony on Wednesday by Nuclear Regulatory Commission chairman Gregory Jaczko, in which he seemed to question the validity of some Japanese government assessments of the unfolding nuclear problem in Japan.
In particular, Jaczko said the US had concluded that the spent fuel storage pool in Unit 4 was empty of water, with the implication that the Unit’s dysfunction posed a bigger radiation threat than Japanese officials had yet to acknowledge.
Based on that assessment, the NRC recommended that US citizens in Japan living in the vicinity of the Fukushima plant evacuate to a distance of 50 miles – far further than the 20 miles the Kan government in Tokyo recommended for Japanese citizens.
Japanese officials, backed by French counterparts, insisted there was at least some water in Unit 4’s storage pond, and the NRC later backed off by saying “the evidence is so far inconclusive.”
The NRC evacuation radius recommendation was based on guidelines in place for US emergencies: to move people to an area where they would be subject to radiation levels no higher than one Rem. Subsequent tests conducted by US officials with American instrumentation found that to achieve the goal of one Rem exposure limitation, the 12-19 mile evacuation zone established by the Japanese government was sufficient. (No evidence of faulty information from Tokyo in that regard…)
In hindsight, it seems fair to say that Jaczko’s Congressional testimony, and subsequent evacuation zone recommendation for US nationals in Japan, stemmed in large part from a desire to maintain his own, and the NRC’s, credibility with a Congress and US public that are already beginning to ask questions about the safety of US nuclear power facilities.
A better sense of US thinking about cooperation with Japan came on Thursday, when Jaczko joined Deputy Secretary of Energy Dan Poneman at the White House for a press briefing on the nuclear crisis in Japan and its implications for the US. Both Jaczko and Poneman repeatedly referred to the complexity of the situation in Japan, and showed what seemed to be genuine sympathy for the extraordinary management difficulties involved.
