Fukushima and Chernobyl: Same Level on Disaster Scale; Very Different Disasters

By Valerie Ross | April 14, 2011 9:01 am

What’s the News: Japan raised its assessment of the severely damaged Fukushima Daiichi nuclear power plant to Level 7, “Major Accident,” the highest ranking on the International Atomic Energy Agency’s International Nuclear and Radiological Event Scale. The explosion at Chernobyl in 1986 is the only other nuclear accident to be ranked at Level 7. Both accidents were extremely severe, the two largest nuclear power accidents ever—but there are some big, important differences between them.

What’s Similar:

  • A Level 7 accident is a “major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures,” according to the IAEA. Both plants clearly meet these criteria: Fukushima will require an extensive clean-up effort, and the international community is still working to make the area near Chernobyl safe.
  • The situation at Fukushima also qualifies as Level 7 by the numbers. Japanese officials estimate the reactors have released between 370,000 and 630,000 terabecquerels (or, between 370 and 630 quadrillion becquerels) of radioactive material, far more than the equivalent of tens of thousands of terabequerels iodine-131 that is the cutoff for a Level 7 accident.
  • A spokesman for Japan’s Industrial and Nuclear Safety agency said in a press conference that the Fukushima reactors are still releasing radiation, and total levels could eventually exceed those released by Chernobyl.

What’s Different:

  • The Fukushima reactors have containment structures, an extra safety layer that has helped limit the spread of radioactivity; Chernobyl had no containment structures.
  • The two accidents happened under very different conditions: Fukushima’s reactors shut down after the March earthquake, then overheated as a result of later cooling system malfunctions. The reactor at Chernobyl, on the other hand, was still running when it exploded, causing a much larger release of heat.
  • The accident at Chernobyl’s reactor was a full core meltdown, while the accident at Fukushima was a possible partial meltdown.
  • The accident at Chernobyl unfolded much more quickly. The explosion there spewed debris and radioactive materials over a wide distance, and sparked a fire that burned for days. The surroundings had to be evacuated within hours. At Fukushima, the reactors have been releasing radiation at a much slower rate.
  • To date, the Fukushima plant has released much less radiation: only one-tenth as much as Chernobyl, according to Japan’s Nuclear and Industrial Safety Agency.
  • Dr. Robert Peter Gale, leader of the medical team that responded to the Chernobyl accident, estimated that, if the situation doesn’t worsen, radiation from the Fukushima accident would cause fewer excess cancer cases an Chernobyl did. Chernobyl resulted in 6,000 additional cases of thyroid cancer, says Gale, while Fukushima would lead to few additional thyroid cancer cases, and 200 to 1,500 total additional cancer cases over the next half-century. (The actual number of cancers and deaths that resulted from Chernobyl is a scientifically and politically tricky question.)
  • Precautions taken by Japan—including monitoring of food and water supplies and timely distribution of potassium iodide tablets—may lessen the severity of human health effects of the Fukushima accident, according to World Nuclear News.

What’s the Context:

  • The raising of Fukushima to a Level 7 accident doesn’t mean that the situation at Fukushima is worsening; in fact, the reactors’ condition seems increasingly stable.
CATEGORIZED UNDER: Environment, Physics & Math, Top Posts
  • Robin Davies

    One BIG difference is there is 10 times more radioactive fuel at Fukushima in reactors and storage pools (40 years worth) than at Chernobyl and also Chernobyl only had a problem with one reactor where Fukushima has 4 reactors with problems.

  • RT

    And the biggest difference: the Fukushima disaster isn’t over yet! This could go on for months or even years, since TEPCO’s strategy seems to be following the plan at TMI, where the partially melted core was cooled for years until it could be dismantled and removed. How are they going to plug all the leaks in the cooling systems, since it’s way too hot to get in there? The “good” news is most of the contamination is going into the ground and the sea rather than the atmosphere, so hopefully the health impacts will be less than with Chernobyl.

  • http://yahoo Cliff

    Although both reactor desasters differed in terms of initial severity. Eg. 7to10% at Japan and 98to100% at Chernobyl. At some point would the severity of radiation released and the enviromental effect become equil?? Japan has significant damage to 6 reactors and thousand of tons of fuel rods, all of which will be emitting levels of radiation for months vs the two week duration at Chernobyl. Also the Japan reactor(s) utilized MOX fuel which is currently leaking and more severe.

  • RT

    Cliff, my layman’s view is the overall quantity of radiation released could surpass that seen at Chernobyl, but most of it will stay in the area. At Chernobyl they went for entombment immediately, while at Fukushima they keep injecting water. We never hear about the rate at which water is coming back out of the reactor vessels, which would indicate the amount of leaking.

  • http://DiscoverMagazine Templar 7

    Seems to me a more accurate assessment is that this accident will probably end up being Chernobyl(4).
    Seeing how there is 4 reactors, times full meltdowns,( i prefer worst case scenarios, that way anything better pleasantly suprises me), and that there is pools of even more radioactive waste(An X Factor), we end up with the formula: Chernobyl(4)X—>Fukishiima.

  • dave chamberlin

    It seems to me they need about three higher levels. Level 10 would be time to find a new country that will take us. The Fukushima reactors had numerous reckless design flaws. It had the potential to be far worse than Chernobyl because of them. 1)There are six reactors in close proximity to each other. If one became so radioactive that it’s killing zone included the reactor next to it than one by one down the line all six would experience full melt downs. 2) It is built on the ocean which is reckless for two reasons. Tsunamis and the water table is right underneath the buildings. Much rarer but much more destructive are tsunamis caused by massive avalanches into the ocean. 3)They now have a design where they shut down automatically without power. 4) Storing the spent fuel rods near the plants is a bad idea but storing them over the top of them is retarded. 5) The safety agencies meant to police the plants were and are a joke. Tepco was fined for repeated violations like ignoring if their back up generators would even run.

    Things will be all right. There will probably be a zone around the plants smaller than the one at Chernobyl where people will not be able to live. The other positive in relation to Chernobyl is the winds primarily blow west over 2000 miles of Pacific ocean. I don’t think the public realizes just how many hundred of tons of uranium were stored or being used at Fukushima, someone can correct me if I’m wrong but the number I have heard is 10 times that at Chernobyl. If left alone (or in this case so radioactive it is unapproachable by humans) the radioactive material would have reached a temperature of 5000 degrees and melted down through everything in it’s path between these molten blobs and the water table. Then 30 million people living 125 miles away in the Tokyo metropolitan area would need to move or face a considerably shortened life. Eating fish out of the Pacific ocean would be like eating fish out of Lake Michigan. You can eat a very limited number per year but keep them away from pregnant women, which translates to no thanks I don’t want any for most of us. Not trying to be anti nuclear, just hoping we can learn from our mistakes.

  • dave chamberlin

    It seems to me they need about three higher levels. Level 10 would be time to find a new country that will take us. The Fukushima reactors had numerous reckless design flaws. It had the potential to be far worse than Chernobyl because of them. 1)There are six reactors in close proximity to each other. If one became so radioactive that it’s killing zone included the reactor next to it than one by one down the line all six would experience full melt downs. 2) It is built on the ocean which is reckless for two reasons. Tsunamis and the water table is right underneath the buildings. Much rarer but much more destructive are tsunamis caused by massive avalanches into the ocean. 3)They now have a design where they shut down automatically without power. 4) Storing the spent fuel rods near the plants is a bad idea but storing them over the top of them is retarded. 5) The safety agencies meant to police the plants were and are a joke. Tepco was fined for repeated violations like ignoring if their back up generators would even run.

    Things will be all right. There will probably be a zone around the plant smaller than the one at Chernobyl where people will not be able to live. The other positive in relation to Chernobyl is the winds primarily blow west over 2000 miles of Pacific ocean. I don’t think the public realizes just how many hundreds of tons of uranium were stored or being used at Fukushima, someone can correct me if I’m wrong but the number I have heard is 10 times that at Chernobyl. If left alone (or in this case so radioactive it is unapproachable by humans) the radioactive material would have reached a temperature of 5000 degrees and melted down through everything in it’s path between these molten blobs and the water table. I’m not sure they would have the option of digging underneath the buildings and pouring more concrete like they did at Chernobyl. Typical soil composition near the ocean is water saturated sand that leaks water back into any hole faster than it can be pumped out. They were able to entomb the majority of the radioactive material at Chernobyl, that would not have been the case with Fukushima in it’s worst case scenario. The radioactivity would be steadily released to the atmosphere through steam for I don’t know how long. Then 30 million people living 125 miles away in the Tokyo metropolitan area would need to move or face a considerably shortened life. Eating fish out of the Pacific ocean would be like eating fish out of Lake Michigan. You can eat a very limited number per year but keep them away from pregnant women, which translates to no thanks I don’t want any for most of us. Not trying to be anti nuclear, just hoping we can learn from our mistakes.

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