NUCLEAR CRISIS: The stricken reactors at the Fukushima Daiichi nuclear power plant, pictured here on March 18, continued to struggle, though time continues to diminish the risk.
Image: © DigitalGlobe
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As night fell on Friday in Japan, workers and soldiers continued heroic efforts to douse the potential meltdown underway at the Fukushima Daiichi nuclear power plant. The covering darkness is not the only reason for confusion: vital systems monitors have lost power, making the status of critical elements—such as the integrity of the nuclear fuel rods in reactor No. 2 or of the steel vessel containing them—unavailable.
But what measurements are available are worrying. Electrical pump systems for cooling water remained inoperative as of 6 pm Eastern, although Reuters reported that Tokyo Electric Power Company succeeded in laying a giant extension cord to the stricken nuclear power plant early Saturday morning in Japan, which could be used to power up the site's pumps for cooling water. That might represent the best hope for cooling down the fuel rods in reactors No. 1, No. 2 and No. 3 as well as the used rods stored in pools in No. 3 and No. 4.
At the same time, the earthquake, subsequent tsunami, hydrogen explosions and seawater flooding, among other recent incidents, may have damaged the electrical equipment necessary for those pumps to run. Otherwise, portable diesel generators transported to the site should have enabled pumping to resume.
The buildings housing reactors Nos. 1, 2, 3 and 4 have all suffered damage from hydrogen explosions, caused by the high-temperature, high-speed interaction of fuel rods and steam. With the roofs off and other paths for hydrogen to escape—hydrogen is the only element capable of escaping Earth's gravity—the chance of suffering another such explosion has been diminished, except at reactors No. 5 and 6. But those reactors' spent fuel pools are benefiting from a diesel generator that is still working to keep cooling water in place, according to World Nuclear News, though temperatures are beginning to rise in these pools as well.
Steam continues to rise in the spent fuel pool at reactor No. 3, indicating that at least some water is reaching the hot rods. Workers spray, allow the radioactive steam to dissipate and then spray again—radiation levels near reactor No. 3 are the highest at the plant, roughly 400 milliSieverts per hour. Worse, reactor No. 3 also employed so-called mixed oxide fuel—or uranium fuel rods made from recycled materials that include plutonium—creating extra cause for concern of nuclear fission restarting itself. Reactors employing mixed oxide fuel may require extra control rods, made of boron or other neutron-absorbing materials, to slow down more fissile plutonium.
The water level is low at reactor No. 4's spent fuel pool as well. The Fukushima Daiichi site in total has some 11,000 such fuel rods in the seven spent fuel pools—500 or more of which in reactor No. 4's spent fuel pool are still quite hot having only been removed from that reactor in December, according to The New York Times. TEPCO may have made the problem worse, according to some experts, by storing more spent fuel in some of the pools than they could safely cool. Such "re-racking" is a common practice in the U.S. nuclear industry, under regulation from the U.S. Nuclear Regulatory Commission, given the lack of an off-site solution for storing used nuclear fuel rods. In the event of a loss of water, such re-racking can make it more difficult to prevent used fuel rods from overheating, according to a 2006 study by the National Academy of Sciences.
The Japan Atomic Industrial Forum also estimates that the fuel rods actually in reactors Nos. 1, 2 and 3 have boiled away even the seawater and boric acid workers have injected via lines that pass into the sealed concrete and steel containment structure to put out fires. Those fuel rods are now likely exposed and generating heat, on their way to a potential meltdown.
Such a boil off would suggest that pressure should be rising inside the steel and concrete structures that contain each of these nuclear reactors. In fact, atmospheric pressure rapidly increased eightfold before the explosion in reactor No. 1 on March 12 (nuclear power plants typically operate at roughly 4 atmospheres of pressure). But pressure readings—and none are available for reactor No. 1, the first to melt down—are low for reactors No. 2 and No. 3, suggesting that cracks or other holes in containment may have formed.
And that means there may be two direct paths for radioactive particle byproducts of nuclear fission, such as cesium 137 and iodine 131, to escape and spread radiation—cracks in containment as well as the spent fuel pools now open to the air.
Worse: without cooling, the fuel rods continue to meltdown and may completely burst the zirconium cladding—a ceramic material—that holds them together. At that point, the uranium pellets would fall to the bottom of the containment vessel and continue to overheat, potentially melting through the steel vessel itself eventually.
That, in itself, would not cause an explosion. The danger is that the hot melted fuel would fall into water, instantly vaporizing it and causing a steam explosion. Such an explosion would then waft the uranium and other radioactive particles into the air.
"We are making utmost efforts to prevent further explosions or the release of radioactive materials," the Japanese Prime Minister, Naoto Kan, said in a televised address to the nation on Monday morning, and those efforts continue.
But even should such a steam or hydrogen explosion somehow occur, the radioactive plume created would likely not travel high enough into the atmosphere to spread the dangerous materials very far.
"If the Japanese fail to keep the reactors cool and fail to keep the pressure in the containment vessels at an appropriate level, you can get this, you know, the dramatic word 'meltdown.' But what does that actually mean?" Sir John Beddington, chief scientific officer to the U.K. government told British embassy workers on March 16. "In this reasonable worst case you get an explosion. You get some radioactive material going up to about 500 meters up into the air."
He continued: "If you then couple that with the worst possible weather situation, i.e. prevailing weather taking radioactive material in the direction of Greater Tokyo and you had maybe rainfall which would bring the radioactive material down, do we have a problem? The answer is unequivocally no. Absolutely no issue. The problems are within 30 kilometers of the reactor." After all, 30 kilometers was the extent of the spread of dangerous radioactive material even at Chernobyl, a far worse nuclear accident that included an intense fire that wafted radioactive particles more than 9,000 meters into the air.
As a result of these ongoing problems, Japan's Nuclear and Industrial Safety Agency has raised the International Nuclear Event Scale rating for the Fukushima disaster from a 4 to a 5, the same level as Three Mile Island and meaning an accident with "wider consequences" that might include "several deaths" from radiation. Of course, even in the worst case, the Fukushima nuclear crisis pales in comparison to the 7,000 dead and 10,000 missing as a result of the March 11 earthquake and subsequent tsunami—no one has yet died from the Japanese nuclear accident.
And time is on our side. The steam indicates that at least some cooling is going on and the heat of such fuel rods drops off dramatically over a period of days or weeks. Though cooling will need to continue for months, the risk of a catastrophic meltdown diminishes with each passing hour.
Distance also helps, radiation decreases exponentially with distance from the source. While levels are dangerously high near reactor No. 3—400 milliSieverts per hour—levels at the border of the power plant grounds drop to just 0.6 milliSieverts an hour. But any radioactive particles that escape will carry their own radiation with them wherever the wind blows, until the rain washes them out of the sky. Hence the distribution of iodine pills to local residents in Japan in order to block any uptake of radioactive iodine. The Japanese diet may also help here: seafood and seaweed carry high levels of safe iodine.
Ultimately, Fukushima may share the fate of Chernobyl, entombed in concrete and sand while radioactive decay—and heat generation—continue. Such shielding is the final line in radiation defense.
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13 Comments
Add CommentYou state, "With the roofs off and other paths for hydrogen to escape—hydrogen is the only element capable of escaping Earth's gravity…."
Reply | Report Abuse | Link to thisYou may want to reconsider running that statement past an actual physicist before publishing it.
And then: "Worse, reactor No. 3 also employed so-called mixed oxide fuel—or uranium fuel rods made from recycled materials that include plutonium—creating extra cause for concern of nuclear fission restarting itself. "
Were you under the impression that nuclear fission had somehow ceased in those materials? Or did you actually mean to say, "...concern of the chain reaction restarting..."?
"And that means there may be two direct paths for radioactive particle byproducts of nuclear fission... to escape and spread radiation—cracks in containment as well as the spent fuel pools now open to the air."
Reply | Report Abuse | Link to thisThis statement makes it sound as if the spent fuel pools are no longer contained, which I believe is incorrect. The water levels have dropped in the pools and the fuel rods have been exposed to air, but it is my understanding that the pools are still contained within the reactor and not open to the atmosphere.
I stand corrected. I just saw the image of the hole in the side of the reactor showing the spent fuel pool
Reply | Report Abuse | Link to thisGood, but "hydrogen is the only element capable of escaping Earth's gravity" -- really? A SciAm author not remembering HS Chemistry and why Helium was discovered first on the sun? Really?
Reply | Report Abuse | Link to thisThis is a simple example of why we're in so much climate/energy trouble today, after being warned for over 100 years by scientists. But, we allow our kids to be far down in math & science re the rest of the world, so why not our media too?
You state that "radiation decreases exponentially with distance from the source". This is incorrect.
Reply | Report Abuse | Link to thisRadiation goes as 1/(R^2), which is an inverse power, not an exponential.
If it decreased exponentially with distance, it would look like e^(-R).
"After all, 30 kilometers was the extent of the spread of dangerous radioactive material even at Chernobyl"?
Reply | Report Abuse | Link to thisChernobyl deposited dangerous radioactive fallout all over Europe especially on the countries directly downwind which they are still monitoring abnormally high radioactivity in the environment to this day. From Belarus to sheep farms in Scotland to Reindeer in Norway, the half-life of Cesium is about 30-years and Plutonium 24,000 years as well as a whole host of other radio-nucleotides released in the wind to end up who knows where around the world. Plus, Fukushima has a Plutonium reactor which Chernobyl didn't which makes this infinitely more serious and deadly. While the isotopes may be so "dispersed" in the air as to not set off any warning alarms on all the Geiger counters everywhere - the overall levels are still increased proving the fallout is present and going to eventually land in some "small" amount somewhere.
And no amount of monitoring is going to tell you if you just inhaled that 1 Plutonium isotope that is going to cause cancer. Or that 1 stray isotope on that head of lettuce you just ate for lunch or glass of water you just drank. You can't wash off a radioactive isotope that lodges itself in your lungs after inhaling it or organs after ingestion. So while the odds of coming in contact with the contamination may be much lower the further away you are - the affects are still the same so now really just a game of Russian roulette every time you eat, drink, breathe or otherwise come in contact with this fallout - good luck! Levels "measurable but minuscule" is a complete contradiction of terms as there is no "safe" level of Plutonium - just 1 isotope can kill you. No wonder cancer just surpassed heart attacks for the first time as the world's leading cause of death but there's no "immediate" threat as they are all saying in the media. These deadly isotopes will continue to cause problems for years and decades to come as life goes on while this deadly killer lurks invisibly in the background.
This "man-made" disaster didn't just happen "out-of-blue", they've been warned repeatedly over the years of the inherent risks of operating these out-dated 40-year old reactors and still they did absolutely nothing to prevent these meltdowns from happening. Just like with Chernobyl, they should draw a permanent exclusion zone around Japan and bury all their reactors in a thick layer of concrete - don't forget they still have 50 more of these ticking time-bombs around the country just waiting to blow up next.
@ Jimdoc and DrAlexC.
Reply | Report Abuse | Link to thisI think he's talking about atmospheric escape: http://en.wikipedia.org/wiki/Atmospheric_escape
although it has no bearing on the hydrogen escaping the building through upthrust.
Having traveled from Tokyo to Kagoshima, as well as Wakkanai and back, the people of Japan have my very deepest sympathy and and compassion.
Reply | Report Abuse | Link to thisThus I write:
I have seen pictures of young army personnel employed to fight the fire. When it comes to radiation and airborne radioactive isotopes, older people should be employed. Please consider not employing the young soldiers.
Bigger and better hydrogen re-combiners are in order for all nuclear plants.
The dissociation of water in the presence of very hot (yellow-hot) metal has been observed in steel mill accidents (liquid steel spilling into water puddles). The current accident begs the question: Can a properly designed and constructed reactor be used for the sole purpose of dissociating the water molecule? If so, this might provide the basis of the future "hydrogen economy". The process would be; dissociate, cool, separate, distribute and sell! Hopefully all without ignition! Sounds simple enough. But keeping in mind the Rulison project, which sought to use a small nuclear device to fracture shale to release natural gas - which resulted in a substantial radiactive component, can hydrogen be generated by a reactor without resulting in radioactive contamination (that can not be filtered out?)?
It seems that another experiment is in order!
I suggest someone look into the effective use of "Bleed and Feed". According to a computer modeling program done by MIT the chance of the success of using this method on a when the cooling system of a boiling water reactor using high pressure steam is a little over 50 percent. Those calculations were done assuming that the reactor lost its cooling system for ten minutes. These three reactors have been without cooling for days. I am a newspaper reporter with a BS in Chemistry. I don’t have the technical background to look into this, but as I understand it the “bleed and Feed” cool down method has never been used on reactors of this size.
Reply | Report Abuse | Link to thisHopefully at some point there will be an investigation about the decision making and actions taken both before and after the tsunami. I cannot understand why the backup power was located in an area that could be impacted by an earthquake or tsunami or that why in the time immediately after they did not bring in emergency power. We all know that providing 99.999999...% reliable back up power is one of the most important issues at a nuclear power plant
Reply | Report Abuse | Link to thisThe earthquake caused an Oil Refinery to blow up near Tokyo, with Giant 2000 ft high fireballs, and roasted to death dozens of citizens - got almost negligible coverage from the Main Stream Media. It took firefighters 10 days to finally put out the fires (probably when the Oil was all burned) - they couldn't get close enough to put them out due to the extreme heat. Notice NOT ONE MSM news show asks why an Oil Refinery far from the epicenter is destroyed in a deadly fire. During the inferno tons of Hydrocarbons combined with vaporized Heavy Metals, including Mercury, created some of the most deadly organo-metallic carcinogens, teratogens, embryotoxins, & mutagens the Earth has ever seen. These toxins were dumped on the general population and have entered the food chain. Unlike Iodine-131 which decays with a half-life of 8 days, these environmental toxins lasts for centuries, and bioaccumulate in the food chain, concentrated in livestock & fish. When a radioisotope decays it no longer causes mutation or DNA/Cell damage. When these carcinogenic chemicals enter the body they keep destroying DNA and Human Cells until they are finally expelled from the body. VASTLY more dangerous than Radioisotopes. These Oil Refineries and NG pipelines and LNG facilities often use asbestos for pipe insulation and electrical swithroom tiles. This asbestos fibers will be released into the atmosphere and will be absorbed into people's lungs, going deeply into the air sacs causing scar tissue to form and deadly cancers like mesothelioma. As an example, do you know any movie actors or actresses who died of radiation effects? No you can't. Well Steve McQueen died of asbestos related mesothelioma.
Reply | Report Abuse | Link to thisAnd a Hydro dam collapsed in the Fukushima district which wiped out 8,000 homes and killed hundreds. The MSM news have not even covered the story. While the Fukushima Nuclear power plants saved 800 lives, since all workers at the plants except for one, survived the earthquake and tsunami. If they had been at home, or worked at typical workplace in the city, they likely would have been killed.
How to construct new, larger containment, with secondary containment,whose function is similar to the damaged smaller primary containment with breached reactors, is the answer, not just constructing sarcophagus as in Chernobyl.It must be real larger primary containment and secondary containment totally enclosing the existing damaged primary containment and breached reactors and to function the same, only the damaged containment and breached reactors are now the new reactor.
Reply | Report Abuse | Link to thisThis is something new.
jsaldea12
4.2.11
The answer is this: construct new, larger primary containment, to totally enclose the smaller ruined primary containment with breached reactor, such new primary containment to replace the function of the ruined stated containment with the breached reactor which now becomes, as a whole, the new reactor!! A secondary large new containment would complete the new construction.
Reply | Report Abuse | Link to thisjsaldea12
4.2.11