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Is Fukushima really as bad as Chernobyl?


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satellite image of Fukushima Daiichi explosionOne month to the day after the devastating twin blows of a magnitude 9.0 earthquake and subsequent 15-meter tall tsunami, Japanese officials have reclassified the accident at the Fukushima Daiichi nuclear power plant at the highest possible level. The partial meltdown of three reactors and at least two spent fuel pools, along with multiple hydrogen explosions at the site now rate a 7 on the International Nuclear Event Scale—a level previously affixed only to the meltdown and explosion at Chernobyl.

Fukushima is now officially a "major accident" per the scale—roughly 100 times worse than the worst civilian nuclear accident in the U.S.: the partial meltdown at Three Mile Island—constituting "a major release of radioactive material with widespread health and environmental effects."

The elevated level doesn’t mean that anything further has gone wrong with the stricken nuclear power plant, although efforts are ongoing to cool the nuclear fuel and prevent any further radioactive material from escaping. It simply means that the accident—one of 12 to occur at nuclear power plants since the dawn of the civilian Atomic Age in 1957—is far worse than anyone cared to admit during the past few weeks.

"Right now, the situation of the nuclear reactors at the Fukushima [power] plant has been stabilizing step by step," Japanese Prime Minister Naoto Kan said April 12 in a televised address. "The amount of radiation being emitted is falling."

Yet, it has become clear that for hours on March 14 and March 15 following hydrogen explosions on those days, the stricken nuclear power plant spewed tens of thousands of terabecquerels of radioactive material—one becquerel (Bq) is the measure of a material’s radioactive decay equal to one nucleus disintegration per second, so a terabecquerel is trillions of such decays.

The Nuclear Safety Commission of Japan estimates that 1.7 x 10 ^17 Bq of iodine-131 has been emitted by the three stricken reactors as well as 1.2 x 10^16 Bq of cesium-137—although the Japanese Nuclear and Industrial Safety Agency (NISA) announced lower estimates for cesium. The radioactive cesium will persist in the environment for decades, potentially causing cancer or other health effects if ingested.

The cumulative release of radioactive material now equals at least 1.8 million terabecquerels—enough to merit the 7 designation on the INES scale. The releases have created regional "hotspots" of radioactivity in northwestern Japan, such as the village of Iitate, 30 kilometers northwest of Fukushima Daiichi.

The stricken nuclear power plant has also dumped 11,500 metric tons of contaminated water into the surrounding sea, and high levels of radioactivity have been detected in fish pulled from coastal waters between Fukushima Daiichi and Tokyo to the southeast.

Chernobyl, however, was far worse than the current accident because it actually burned, a graphite fire with smoke that spread radioactive material 30 kilometers around the reactor as well as injecting it high into the atmosphere where it wafted at least 500 kilometers to Europe and beyond. All told 14 million terabecquerels of radioactive material are estimated to have escaped during what remains the world’s worst nuclear accident.

That means roughly 10 percent of the radioactive material released by the Chernobyl fire has spewed from the overheated Fukushima Daiichi reactors, according to NISA.

At the same time, those reactors—and surrounding spent fuel pools—continue to emit radioactive material and could, in time, surpass Chernobyl, as Tokyo Electric Power Co. conceded April 12 in a press conference. As it stands, the nuclear fuel rods in the three stricken reactors at Fukushima Daiichi remain "partially or fully" exposed, according to the Japan Atomic Industrial Forum.

Ultimately, Fukushima will resemble Chernobyl in another way: final containment will likely be achieved by entombing in it concrete and surrounding it with an exclusion zone to prevent visits by humans.

Image: Reactor No. 3 exploded March 14 at 9:01 A.M. local time. Smoke rises from the damaged building in this photo taken at 9:04 A.M. Credit: DigitalGlobe

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  1. 1. jtdwyer 5:55 pm 04/12/2011

    Is there some ‘official’ or standard criteria for ranking nuclear ‘accidents’? I don’t know of any, but some measure of peak and total radiation distribution should be considered. What was the exposure produced by nuclear weapons tests? What was Chernobyl’s peak emission level, and how was it distributed? What was the radiation level of exposed areas?

    One thin is certain: as long as Fukushima continues to release high levels of radiation that accumulate in the environment it’s an increasingly critical problem.

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  2. 2. eightyfiv 6:02 pm 04/12/2011

    Your numbers don’t add up. 10^17 Bq = 10^5 TBq. 14 million TBq = 1.4*10^7 TBq. 10% of 14 million TBq is 1.4*10^6 TBq, not 1.4*10^5. So you either mean the Fukushima emissions are around 1% of Chernobyl’s, or one of the raw emission numbers is wrong.

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  3. 3. eightyfiv 6:18 pm 04/12/2011

    Meh, nevermind, missed the 1.8 million TBq "total" figure. So, where’s the other 90% of this figure come from, since it’s mostly not the two isotopes quoted? (And if 90% of it is not the isotopes of principal concern, why is the figure a useful one?)

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  4. 4. anumakonda.jagadeesh 2:08 am 04/13/2011

    For the last one month so much is written on Fukushima nuclear disaster, one gets confused on the reality. There has to be authenticity in reporting on such crucial and sensitive issues.

    Dr.A.Jagadeesh Nellore (AP), India

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  5. 5. Cramer 3:35 am 04/13/2011

    Don’t know where SA got its numbers.

    Japan’s Nuclear and Industrial Safety Agency said that the total amount of iodine-131 and cesium-137 emitted was 370,000 terabecquerels through 11 a.m. April 12.

    Japan’s Nuclear Safety Commission said that the total amount of iodine-131 and cesium-137 emitted was 630,000 terabecquerels through April 5.

    Both numbers were converted to Iodine-131 equivalent. Maybe SA numbers were not.

    Many sources reported the medium value of 500,000 terabecquerels of these two estimates which is approximately 10% of the amount emitted at Chernobyl. Same sources reported that 5.2 million terabecquerels was released at Chernobyl.

    Sources were Daily Yomiuri, Reuters, Wall Street Journal, Business Insider, NPR, USA Today, Environment News Service, Times of India, New York Times.

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  6. 6. heavyrunner 5:30 am 04/13/2011

    No. It’s worse. Where is the "swimming pool" from reactor #3? Apparently aerial images show empty space where it used to be. What happened to the core from reactor #4 which was sitting outside the containment on rollers as a part of the refueling process? How much of reactor #2′s core has escaped in the China Syndrome scenario which started there on March 30?

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  7. 7. jimmywat 6:39 am 04/13/2011

    The uncritical thinking of Sci Am is what has been misleading. Go to for a real scientific analysis of what is happening, not this warmed over propaganda from the corporations that support Sci Am and our ever truthful government

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  8. 8. poweringanation 12:00 pm 04/13/2011

    Yet another great article to put things into perspective. Great job, David! Comparison with Chernobyl certainly helps putting this accident into context. Still, it remains extremely dramatic. Why are the Japanese authorities waiting on sealing the reactors all together?

    On the other hand, 12 accidents in more than 50 years speaks of a fairly exemplary safety record. It would be interesting to compare health effects across different energy sources. For example, coal mining in China is probably way deadlier than nuclear…

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  9. 9. jtdwyer 12:02 pm 04/13/2011

    Great – so there’s nothing to worry about, except coal mining?

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  10. 10. poweringanation 12:25 pm 04/13/2011

    Of course there’s plenty to worry about – aggressive pursuits of energy always come with high costs (both financial and human). Rather, my point is that nuclear tends to spread more fear in the public opinion than other sources that are just, if not more, deadly.

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  11. 11. Cramer 1:41 pm 04/13/2011

    Yes, I agree that nuclear power creates more fear. A great analogy is road vs air transportation. There are over 30,000 fatalities per year in the US. If we just had 10% of that from aviation, we would probably not have much of an aviation industry.

    But then again, caesium-137 has an half-life of 30 years. And it is understandable that something can create more fear when:

    * something can keep hurting/killing after discontinuing its use,
    * something we don’t have an individual choice in using but can still hurt/kill us,
    * something that might be hurting/killing us but we can be unaware of its presence,
    * something that gets large media attention when a traumatic event occurs (auto accidents do not),
    * and whatever other factors I have not thought of.

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  12. 12. jtdwyer 11:48 pm 04/13/2011

    I agree with the more balanced sentiments in your response – thanks.

    It’s too bad the world didn’t respond more to the population increase following WWII rather than joking about the baby boom and aggressively pursuing increasing marketing opportunities. Now that the world’s population has nearly tripled since 1950 (the U.S. has more than doubled) energy, potable water, sea food, agricultural and urban land requirements and usage have all increased commensurately. The U.S. Census Bureau expects the world population to increase 33% by 2050, from nearly 7 billion to more than 9 billion people.

    Whatever choices we make in attempting to meet humanity’s resource requirements, and whatever their consequences, they will be aggravated by the continuation of uncontrolled demand.

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  13. 13. Plain-2009 7:12 am 04/14/2011

    Now that Fukushima accident has been put into the same level than Chernobyl what measures should be taken to protect human life? Nobody is coming up with a clear cut plan to clean the area. Should concrete be poured over the area immediately and with no delay to protect all forma of life in the area? This is clearly something that can not be dealt with in a few lines and on the surface. I hope every measure is taken to gather all pertinent data, and all that information is quickly transferred to everybody interested around the globe. If, for example, birds in the area survive with no trouble that could be a clue that the area is safe enough for humans. I hope scientists and people from educational institutions; universities, utilities, and government keep a close eye and come up with recommendations about how to protect other nuclear plants and people living nearby. Hopefully in the future we will be better prepared to deal with everything related with nuclear energy.

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  14. 14. ennui 1:07 am 04/15/2011

    If people like eightufiv think that Japan is overstating that fact, they should rent a room at that place. Preferably with their children. It would hardly cost anything.

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  15. 15. eco-steve 6:56 am 04/16/2011

    As a civil defence Officer, I was trained to measure radioactivity in units of RADs and REMs. But in the fukushima reports, radioactivity is measured using many different units, units which cannot be measured directly, meaning the public cannot get the true picture of what is going on. Whitewash!

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  16. 16. guspenskiy13 3:20 pm 03/1/2012


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