Why I am not worried about Japan’s nuclear reactors – From MIT’s Dr. Josef Oehmen

March 13, 2011



With every mistake we must surely be learning.

While My Guitar Gently Weeps
George Harrison

I don’t noramally copy other people’s posts.  In fact, this is a first.  But the subject matter is too important and needs to be disseminated now. This comes from Jason Morgan at Morgsatlarge-Blogorific. 

Please examine a partial list of Oehmen’s publications and his curriculum vitae

Update 5/29/12

From Nature, 5/24/12…

Fukushima’s doses tallied”  Nature 485, 423–424 (24 May 2012)

Studies indicate minimal health risks from radiation in the aftermath of Japan’s nuclear disaster. 

Few people will develop cancer as a consequence of being exposed to the radioactive material that spewed from Japan’s Fukushima Daiichi nuclear power plant last year — and those who do will never know for sure what caused their disease. These conclusions are based on two comprehensive, independent assessments of the radiation doses received by Japanese citizens, as well as by the thousands of workers who battled to bring the shattered nuclear reactors under control.

Update 10/25/11
Fallout forensics hike radiation toll,” Nature 478, 435-436 (2011) 

Update 10/3/11
Fukushima impact is still hazy,” Nature 477, 139-140 (2011) (free article)

I was exposed to excessive levels of ultraviolet radiation.

From New Scientist concerning this viral post from Josef Oehmen.

Update 3/19/11
Here is a relevant update from UC Santa Barabara’s Ben Monreal in pdf or various video formats.


This post is by Dr Josef Oehmen, a research scientist at MIT, in Boston.

He is a PhD Scientist, whose father has extensive experience in Germany’s nuclear industry. I asked him to write this information to my family in Australia, who were being made sick with worry by the media reports coming from Japan. I am republishing it with his permission.

It is a few hours old, so if any information is out of date, blame me for the delay in getting it published.

This is his text in full and unedited. It is very long, so get comfy.

Why I am not worried about Japan’s nuclear reactors – Josef Oehman

I am writing this text (Mar 12) to give you some peace of mind regarding some of the troubles in Japan, that is the safety of Japan’s nuclear reactors. Up front, the situation is serious, but under control. And this text is long! But you will know more about nuclear power plants after reading it than all journalists on this planet put together.

There was and will *not* be any significant release of radioactivity.

By “significant” I mean a level of radiation of more than what you would receive on – say – a long distance flight, or drinking a glass of beer that comes from certain areas with high levels of natural background radiation.

I have been reading every news release on the incident since the earthquake. There has not been one single (!) report that was accurate and free of errors (and part of that problem is also a weakness in the Japanese crisis communication). By “not free of errors” I do not refer to tendentious anti-nuclear journalism – that is quite normal these days. By “not free of errors” I mean blatant errors regarding physics and natural law, as well as gross misinterpretation of facts, due to an obvious lack of fundamental and basic understanding of the way nuclear reactors are build and operated. I have read a 3 page report on CNN where every single paragraph contained an error.

We will have to cover some fundamentals, before we get into what is going on.

Construction of the Fukushima nuclear power plants

The plants at Fukushima are so called Boiling Water Reactors, or BWR for short. Boiling Water Reactors are similar to a pressure cooker. The nuclear fuel heats water, the water boils and creates steam, the steam then drives turbines that create the electricity, and the steam is then cooled and condensed back to water, and the water send back to be heated by the nuclear fuel. The pressure cooker operates at about 250 °C.

The nuclear fuel is uranium oxide. Uranium oxide is a ceramic with a very high melting point of about 3000 °C. The fuel is manufactured in pellets (think little cylinders the size of Lego bricks). Those pieces are then put into a long tube made of Zircaloy with a melting point of 2200 °C, and sealed tight. The assembly is called a fuel rod. These fuel rods are then put together to form larger packages, and a number of these packages are then put into the reactor. All these packages together are referred to as “the core”.

The Zircaloy casing is the first containment. It separates the radioactive fuel from the rest of the world.

The core is then placed in the “pressure vessels”. That is the pressure cooker we talked about before. The pressure vessels is the second containment. This is one sturdy piece of a pot, designed to safely contain the core for temperatures several hundred °C. That covers the scenarios where cooling can be restored at some point.

The entire “hardware” of the nuclear reactor – the pressure vessel and all pipes, pumps, coolant (water) reserves, are then encased in the third containment. The third containment is a hermetically (air tight) sealed, very thick bubble of the strongest steel and concrete. The third containment is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. For that purpose, a large and thick concrete basin is cast under the pressure vessel (the second containment), all inside the third containment. This is the so-called “core catcher”. If the core melts and the pressure vessel bursts (and eventually melts), it will catch the molten fuel and everything else. It is typically built in such a way that the nuclear fuel will be spread out, so it can cool down.

This third containment is then surrounded by the reactor building. The reactor building is an outer shell that is supposed to keep the weather out, but nothing in. (this is the part that was damaged in the explosion, but more to that later).

Fundamentals of nuclear reactions

The uranium fuel generates heat by nuclear fission. Big uranium atoms are split into smaller atoms. That generates heat plus neutrons (one of the particles that forms an atom). When the neutron hits another uranium atom, that splits, generating more neutrons and so on. That is called the nuclear chain reaction.

Now, just packing a lot of fuel rods next to each other would quickly lead to overheating and after about 45 minutes to a melting of the fuel rods. It is worth mentioning at this point that the nuclear fuel in a reactor can *never* cause a nuclear explosion the type of a nuclear bomb. Building a nuclear bomb is actually quite difficult (ask Iran). In Chernobyl, the explosion was caused by excessive pressure buildup, hydrogen explosion and rupture of all containments, propelling molten core material into the environment (a “dirty bomb”). Why that did not and will not happen in Japan, further below.

In order to control the nuclear chain reaction, the reactor operators use so-called “control rods”. The control rods absorb the neutrons and kill the chain reaction instantaneously. A nuclear reactor is built in such a way, that when operating normally, you take out all the control rods. The coolant water then takes away the heat (and converts it into steam and electricity) at the same rate as the core produces it. And you have a lot of leeway around the standard operating point of 250°C.

The challenge is that after inserting the rods and stopping the chain reaction, the core still keeps producing heat. The uranium “stopped” the chain reaction. But a number of intermediate radioactive elements are created by the uranium during its fission process, most notably Cesium and Iodine isotopes, i.e. radioactive versions of these elements that will eventually split up into smaller atoms and not be radioactive anymore. Those elements keep decaying and producing heat. Because they are not regenerated any longer from the uranium (the uranium stopped decaying after the control rods were put in), they get less and less, and so the core cools down over a matter of days, until those intermediate radioactive elements are used up.

This residual heat is causing the headaches right now.

So the first “type” of radioactive material is the uranium in the fuel rods, plus the intermediate radioactive elements that the uranium splits into, also inside the fuel rod (Cesium and Iodine).

There is a second type of radioactive material created, outside the fuel rods. The big main difference up front: Those radioactive materials have a very short half-life, that means that they decay very fast and split into non-radioactive materials. By fast I mean seconds. So if these radioactive materials are released into the environment, yes, radioactivity was released, but no, it is not dangerous, at all. Why? By the time you spelled “R-A-D-I-O-N-U-C-L-I-D-E”, they will be harmless, because they will have split up into non radioactive elements. Those radioactive elements are N-16, the radioactive isotope (or version) of nitrogen (air). The others are noble gases such as Argon. But where do they come from? When the uranium splits, it generates a neutron (see above). Most of these neutrons will hit other uranium atoms and keep the nuclear chain reaction going. But some will leave the fuel rod and hit the water molecules, or the air that is in the water. Then, a non-radioactive element can “capture” the neutron. It becomes radioactive. As described above, it will quickly (seconds) get rid again of the neutron to return to its former beautiful self.

This second “type” of radiation is very important when we talk about the radioactivity being released into the environment later on.

What happened at Fukushima

I will try to summarize the main facts. The earthquake that hit Japan was 5 times more powerful than the worst earthquake the nuclear power plant was built for (the Richter scale works logarithmically; the difference between the 8.2 that the plants were built for and the 8.9 that happened is 5 times, not 0.7). So the first hooray for Japanese engineering, everything held up.

When the earthquake hit with 8.9, the nuclear reactors all went into automatic shutdown. Within seconds after the earthquake started, the control rods had been inserted into the core and nuclear chain reaction of the uranium stopped. Now, the cooling system has to carry away the residual heat. The residual heat load is about 3% of the heat load under normal operating conditions.

The earthquake destroyed the external power supply of the nuclear reactor. That is one of the most serious accidents for a nuclear power plant, and accordingly, a “plant black out” receives a lot of attention when designing backup systems. The power is needed to keep the coolant pumps working. Since the power plant had been shut down, it cannot produce any electricity by itself any more.

Things were going well for an hour. One set of multiple sets of emergency Diesel power generators kicked in and provided the electricity that was needed. Then the Tsunami came, much bigger than people had expected when building the power plant (see above, factor 7). The tsunami took out all multiple sets of backup Diesel generators.

When designing a nuclear power plant, engineers follow a philosophy called “Defense of Depth”. That means that you first build everything to withstand the worst catastrophe you can imagine, and then design the plant in such a way that it can still handle one system failure (that you thought could never happen) after the other. A tsunami taking out all backup power in one swift strike is such a scenario. The last line of defense is putting everything into the third containment (see above), that will keep everything, whatever the mess, control rods in our out, core molten or not, inside the reactor.

When the diesel generators were gone, the reactor operators switched to emergency battery power. The batteries were designed as one of the backups to the backups, to provide power for cooling the core for 8 hours. And they did.

Within the 8 hours, another power source had to be found and connected to the power plant. The power grid was down due to the earthquake. The diesel generators were destroyed by the tsunami. So mobile diesel generators were trucked in.

This is where things started to go seriously wrong. The external power generators could not be connected to the power plant (the plugs did not fit). So after the batteries ran out, the residual heat could not be carried away any more.

At this point the plant operators begin to follow emergency procedures that are in place for a “loss of cooling event”. It is again a step along the “Depth of Defense” lines. The power to the cooling systems should never have failed completely, but it did, so they “retreat” to the next line of defense. All of this, however shocking it seems to us, is part of the day-to-day training you go through as an operator, right through to managing a core meltdown.

It was at this stage that people started to talk about core meltdown. Because at the end of the day, if cooling cannot be restored, the core will eventually melt (after hours or days), and the last line of defense, the core catcher and third containment, would come into play.

But the goal at this stage was to manage the core while it was heating up, and ensure that the first containment (the Zircaloy tubes that contains the nuclear fuel), as well as the second containment (our pressure cooker) remain intact and operational for as long as possible, to give the engineers time to fix the cooling systems.

Because cooling the core is such a big deal, the reactor has a number of cooling systems, each in multiple versions (the reactor water cleanup system, the decay heat removal, the reactor core isolating cooling, the standby liquid cooling system, and the emergency core cooling system). Which one failed when or did not fail is not clear at this point in time.

So imagine our pressure cooker on the stove, heat on low, but on. The operators use whatever cooling system capacity they have to get rid of as much heat as possible, but the pressure starts building up. The priority now is to maintain integrity of the first containment (keep temperature of the fuel rods below 2200°C), as well as the second containment, the pressure cooker. In order to maintain integrity of the pressure cooker (the second containment), the pressure has to be released from time to time. Because the ability to do that in an emergency is so important, the reactor has 11 pressure release valves. The operators now started venting steam from time to time to control the pressure. The temperature at this stage was about 550°C.

This is when the reports about “radiation leakage” starting coming in. I believe I explained above why venting the steam is theoretically the same as releasing radiation into the environment, but why it was and is not dangerous. The radioactive nitrogen as well as the noble gases do not pose a threat to human health.

At some stage during this venting, the explosion occurred. The explosion took place outside of the third containment (our “last line of defense”), and the reactor building. Remember that the reactor building has no function in keeping the radioactivity contained. It is not entirely clear yet what has happened, but this is the likely scenario: The operators decided to vent the steam from the pressure vessel not directly into the environment, but into the space between the third containment and the reactor building (to give the radioactivity in the steam more time to subside). The problem is that at the high temperatures that the core had reached at this stage, water molecules can “disassociate” into oxygen and hydrogen – an explosive mixture. And it did explode, outside the third containment, damaging the reactor building around. It was that sort of explosion, but inside the pressure vessel (because it was badly designed and not managed properly by the operators) that lead to the explosion of Chernobyl. This was never a risk at Fukushima. The problem of hydrogen-oxygen formation is one of the biggies when you design a power plant (if you are not Soviet, that is), so the reactor is build and operated in a way it cannot happen inside the containment. It happened outside, which was not intended but a possible scenario and OK, because it did not pose a risk for the containment.

So the pressure was under control, as steam was vented. Now, if you keep boiling your pot, the problem is that the water level will keep falling and falling. The core is covered by several meters of water in order to allow for some time to pass (hours, days) before it gets exposed. Once the rods start to be exposed at the top, the exposed parts will reach the critical temperature of 2200 °C after about 45 minutes. This is when the first containment, the Zircaloy tube, would fail.

And this started to happen. The cooling could not be restored before there was some (very limited, but still) damage to the casing of some of the fuel. The nuclear material itself was still intact, but the surrounding Zircaloy shell had started melting. What happened now is that some of the byproducts of the uranium decay – radioactive Cesium and Iodine – started to mix with the steam. The big problem, uranium, was still under control, because the uranium oxide rods were good until 3000 °C. It is confirmed that a very small amount of Cesium and Iodine was measured in the steam that was released into the atmosphere.

It seems this was the “go signal” for a major plan B. The small amounts of Cesium that were measured told the operators that the first containment on one of the rods somewhere was about to give. The Plan A had been to restore one of the regular cooling systems to the core. Why that failed is unclear. One plausible explanation is that the tsunami also took away / polluted all the clean water needed for the regular cooling systems.

The water used in the cooling system is very clean, demineralized (like distilled) water. The reason to use pure water is the above mentioned activation by the neutrons from the Uranium: Pure water does not get activated much, so stays practically radioactive-free. Dirt or salt in the water will absorb the neutrons quicker, becoming more radioactive. This has no effect whatsoever on the core – it does not care what it is cooled by. But it makes life more difficult for the operators and mechanics when they have to deal with activated (i.e. slightly radioactive) water.

But Plan A had failed – cooling systems down or additional clean water unavailable – so Plan B came into effect. This is what it looks like happened:

In order to prevent a core meltdown, the operators started to use sea water to cool the core. I am not quite sure if they flooded our pressure cooker with it (the second containment), or if they flooded the third containment, immersing the pressure cooker. But that is not relevant for us.

The point is that the nuclear fuel has now been cooled down. Because the chain reaction has been stopped a long time ago, there is only very little residual heat being produced now. The large amount of cooling water that has been used is sufficient to take up that heat. Because it is a lot of water, the core does not produce sufficient heat any more to produce any significant pressure. Also, boric acid has been added to the seawater. Boric acid is “liquid control rod”. Whatever decay is still going on, the Boron will capture the neutrons and further speed up the cooling down of the core.

The plant came close to a core meltdown. Here is the worst-case scenario that was avoided: If the seawater could not have been used for treatment, the operators would have continued to vent the water steam to avoid pressure buildup. The third containment would then have been completely sealed to allow the core meltdown to happen without releasing radioactive material. After the meltdown, there would have been a waiting period for the intermediate radioactive materials to decay inside the reactor, and all radioactive particles to settle on a surface inside the containment. The cooling system would have been restored eventually, and the molten core cooled to a manageable temperature. The containment would have been cleaned up on the inside. Then a messy job of removing the molten core from the containment would have begun, packing the (now solid again) fuel bit by bit into transportation containers to be shipped to processing plants. Depending on the damage, the block of the plant would then either be repaired or dismantled.

Now, where does that leave us?

  • The plant is safe now and will stay safe.
  • Japan is looking at an INES Level 4 Accident: Nuclear accident with local consequences. That is bad for the company that owns the plant, but not for anyone else.
  • Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants’ chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again.
  • There was some limited damage to the first containment. That means that some amounts of radioactive Cesium and Iodine will also be released into the cooling water, but no Uranium or other nasty stuff (the Uranium oxide does not “dissolve” in the water). There are facilities for treating the cooling water inside the third containment. The radioactive Cesium and Iodine will be removed there and eventually stored as radioactive waste in terminal storage.
  • The seawater used as cooling water will be activated to some degree. Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the “main” nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities.
  • The seawater will then be replaced over time with the “normal” cooling water
  • The reactor core will then be dismantled and transported to a processing facility, just like during a regular fuel change.
  • Fuel rods and the entire plant will be checked for potential damage. This will take about 4-5 years.
  • The safety systems on all Japanese plants will be upgraded to withstand a 9.0 earthquake and tsunami (or worse)
  • I believe the most significant problem will be a prolonged power shortage. About half of Japan’s nuclear reactors will probably have to be inspected, reducing the nation’s power generating capacity by 15%. This will probably be covered by running gas power plants that are usually only used for peak loads to cover some of the base load as well. That will increase your electricity bill, as well as lead to potential power shortages during peak demand, in Japan.

If you want to stay informed, please forget the usual media outlets and consult the following websites:



  1. Some sanity amongst the hysteria!

    Why the News Services have to portray the sensational and refuse to allow accuracy to interfere with a “good story” is an ongoing issue.

  2. Really cool article. I’m a reactor operator stationed on the USS George Washington here in Japan, and the only thing I’m worried about from the Fukushima incident is a higher electric bill! To correct you, you say that the Cs 137 will never be seen again, but it has. It blew onto the USS Ronald Reagan! Please keep all of those affected by the tsunami in your thoughts and prayers.

    • Japanese engineer Masashi Goto, who helped design the containment vessel for Fukushima’s reactor core, says the design was not enough to withstand earthquakes or tsunamis and the plant’s builders, Toshiba, knew this. I suspect Goto knows a wee-bit more than a business professor (with vested interests) on the topic.

  3. not the brightest bulb.

    • Dear Ms. Anonymous,

      Thank you for your comment. I always take anonymous comments the most seriously.

      Best Regards,

      • LOL – and where do you live sweety? japan?

      • I guess it is easy for somebody in say, Washington state, where 75% of the electicity is produced by abundant hydro-power to be critical of others for using nuclear power. But Japan has very little hydro potential, and the people have not been inclined to live in energy poverty. Nor should they.

        I hope the hysterics do not win the PR war.

    • to the point…especially given the latest news.

  4. Thank you for this very informative post.

  5. I know why you are not worried about it, it’s cuz you are in the comfort of your home, not here in Japan.

  6. I found this to be an interesting and informative message. Functionally, I knew nothing about how a nuclear reactor operates, not to mention the safety measures put in place to try to handle a disaster like the one Japan is experiencing. The writer has a real gift for sharing what is obviously a complex issue. Thanks for sharing.

    One comment I have however is that being able to explain something (no matter how eloquently) does not necessarily make it so; just because we can detail a thing, in this case a scenario, does not mean we can (or will) control the variables, surely many unforeseen, that would (and will) be required to make that thing come to pass.

    Human cleverness may very well succeed in Japan. It also may not. I hope it does. But whether or not we are clever enough to prevent a greater catastrophe, we would be wise to reconsider (certainly question) the logic of even our ‘brightest bulbs.’ None of us are infallible. We are bound to make mistakes. I can live with that, I have no choice! But I ask myself: do I want to live with that understanding and things like nuclear energy? Frankly, I’m not certain I do. But then again I may have little choice in that as well.

    • interesting response. i think i agree with you…

    • Sean,

      Thank you for the comment.

      You are most certainly correct that “we would be wise to reconsider (certainly question) the logic of even our ‘brightest bulbs.'”

      For thirty years those that fancy themselves as the ‘brightest bulbs’ have been telling us of the dangers of nuclear energy. Yet the record tells a very different story, even with Three Mile Island and now the Japanese disaster.

      Every human endeavor carries a risk. There are about 40,000 deaths in automobile accidents in the US each year. People die from improper use or overdose of prescription drugs. Every type of food causes deadly allergic reactions in somebody. Should cars, prescription drugs, and food be deemed too dangerous for society?

      I don’t thind so, because their benefits outweigh their problems. In each case we learn from our mistakes and make engineering and process improvements. Reasonable safety measures are applied to automobiles, some required, some optional. Perscription drugs are regulated and some are banned, but the entire industry is not thrown out.

      Nuclear energy is like automobiles or prescription drugs. The benefits far outweigh the harm. The industry evolves and adapts with knowledge and experience. By the way, nobody was killed at Three Mile Island. And my guess is that Chernobyl was not as bad as you may think.

      I encourage you to keep questioning, but please have an open mind.

      Best regards,

  7. Professor Oehmen states “The plant is safe now and will stay safe.” I would suggest you do as he asks, and do your own research, and not rely on his “assessment”. His explanations seem sound, but his predicting outcomes seem foolish at best. From one of the websites he suggested:
    Dramatic escalation in Japan

  8. This is why it’s unwise to make definitive statements such as “There was and will *not* be any significant release of radioactivity” about dynamic situations. The radiation level was measured to be at 400 millisieverts near reactor 3. An increase in cancer can occur at an exposure level of 100 millisieverts per year. So, I don’t know what counts as significant to the mechanical engineer who decided to try to put everyone at ease but I think this should serve as a demonstration of reckless commentary.

  9. Oehmen states it clearly “The plant is safe now and will be safe”. Plant is safe but there is possibility of nuclear radiation to be confirmed.

  10. Josef Oehman will become the definition of hubris. How many flights or beers come with warnings to change your clothes if you’ve been outside, or that your exposure will cause sterility?

  11. Good morning,

    Thanks for the continued discussion.

    I have to disagree with your statement that ‘nuclear energy is like automobiles or prescription drugs.’ Nuclear science results in terrible messes that are extremely dangerous for unimaginable lengths of time. The question of nuclear waste disposal itself is still unanswered let alone an accidental holocaust.

    I do agree that we take many other risks to quench our thirst for energy (and for things like transportation and alleged medicine). Yet, none of these risks make nuclear power safe.

    I also think an argument can be made that the energy crisis is not being caused by a scarcity but by ignorance, built into our education system, and weakness of character. By this I mean to say that we do not use energy well (even most of the brightest bulbs) and we do not have an effective energy policy in place.

    We might consider that we would very likely use ‘clean energy’ every bit as wasteful as we do nuclear, coal, oil and gas.

    The energy crisis is not just a test of logic; it is a moral issue as well. And this heightens the importance of ongoing discussions.

  12. A very good, informative article.

    Oehmen even got the relative earthquake energy scale right. Earthquake magnitudes are reported on the moment/magnitude scale. On this scale each unit corresponds to a factor of about 31.6 (sqrt 1000) in energy released.


    • Ah, yes – what a genius.

      Too bad (sincerely) our respected ‘scientist’ got the important points completely wrong: The fail-safes DID NOT work as they were supposed to. (Why on earth do you think they’re pumping sea water into the reactors?)

      How do we know the fail-safes in fact failed: Radiation is now wafting into Tokyo, and as far away as 500 miles off shore.

      The unfolding Fukushima crisis shows how one failure can cause another in ways engineers could not foresee.

      I tell you there are some really bizarre optimistic takes on this now failed assessment. I assure you that the Japanese do not share such naive opinion.

  13. the author of the original article has already been discredited :

  14. Thank you for this detailed and clear article. However, there are several important things Dr. Oehman has not taken into account, and so it is too optimistic.

    The first overlooked item is that each reactor also has a pool where spent fuel is stored outside the ractor. These pools must also be cooled, but their cooling has failed. These pools are not surrounded by containment–several are even open to the sky due to the explosions. If the water boils away, then the spent rods will catch fire, spreading very severe radiation widely. So these pools really pose much more danger than the well-contained reactors.

    The second item overlooked is the effect of radiation on workers. Now that severe radiation has already been vented, it may be impossible to approach the pools and keep them filled. Likewise, all the necessary steps outlined above to clean up the mess and restore normal cooling will be much more difficult in a radioactive environment. Workers will be limited to very short work times, perhaps even minutes. Skilled workers, communication, and familiarity with the equipment (as fresh workers are brought in) will be hard to come by. Simple tasks will become much more difficult.

    Consequently, I am not as optimistic as Dr. Oehman. Inevitably, real situations are more complex and unpredictable than they are in plans, textbooks, or theory.

    (My qualifications: Ph.D. in biology; read two books on the Three-mile Island disaster, have followed many disasters closely.)

    • agreed. oversimplified and incorrect. one just needs to read the assessments rolling in.

  15. For the record…

    All of the following comments have come from the exact same IP address:

    Anonymous 3/14 9:20am
    Anonymous 3/14 10:54am
    Sean 3/14 3:23pm
    Jess 3/14 5:56pm
    Anonymous 3/14 11:33pm
    Sean 3/15 9:54am
    in seattle too 3/15 12:23pm
    in seattle too 3/15 12:24pm

    Some of them are thoughtful comments and deserve to be answered. And I will answer them when I have more time.

    Tom Moriarty

    • That’s right – same location, two computers. Part of a ‘book club’ of sorts actually. Several of us commenting, and we’re in disagreement here about nuclear power and what’s ‘really’ going on in Japan. I liked the article although I’m not convinced nuclear power is the best solution. Thanks for the initial post and comments, there will likely be more from here.

      • lol- some of us just live here!

  16. […] Why I am not worried about Japan’s nuclear reactors – From MIT’s Dr. Josef Oehmen I don’t noramally copy other people’s posts.  In fact, this is a first.  But the subject matter is too important and […] […]

  17. MIT has moved the original article you are referencing and the department of nuclear science and engineering has updated it for accuracy. The new updated article is at http://mitnse.com/2011/03/13/why-i-am-not-worried-about-japans-nuclear-reactors/

    The original author explains why his article was moved and edited at https://morgsatlarge.wordpress.com/2011/03/13/why-i-am-not-worried-about-japans-nuclear-reactors/

  18. Perhaps not.

    • Wow Paul Hansen, I read your link and it is quite a rant.

      The problem is that you have concocted some bizarre conspiracy theory that goes something like this (if I can untangle you your genius prose):
      1. Josef Oehmen’s original work (which is quoted verbatim in my post) and updates have been adopted by http://www.mitnse.com
      2. http://mitnse.com claims to be associated with MIT
      3. But you claim that that association is a fraud. Your evidence?

      mitnse.com was registered yesterday, through wordpress.com. That was a Sunday, right? And while the contact information says it’s for MIT, the admin contact is given for an independent contracter, with the contractor’s phone number. The contractor is a graphic designer who has done prior work for the department.

      But Paul, here is the funny thing: The MIT site says…

      Josef is the author of the essay “Why I’m not worried about Japan’s nuclear reactors”. It was an email he sent to his family in Japan. When his cousin posted it on his blog, it went viral.

      As a result, a team from MIT has been working to provide a response to the interest the post has generated and the clear need for timely and accurate information. The original blog has been migrated to an MIT site managed by a team of faculty and staff in MIT’s Department of Nuclear Science and Engineering (NSE). Please visit the newly launched MIT NSE Nuclear Information Hub.

      Note that the last link in the above quote is the very same “http://mitnse.com” around which you have built your conspiracy theory, and that it is clearly endorsed by the nuclear folks at MIT.

      Paul, here is a little pointer for you. In my experience, those who proclaim themselves to be a genius usually aren’t.

      For those who have a thirst for more of Paul’s fine logic, here is a sample of the insightful work form his “GeniusNow” websit…

      There is no bottom line here because what is infinitely challenging and amusing starts with human survival. It only makes sense – if the species doesn’t survive, we don’t survive. That probably doesn’t work in reverse – if I die, the species most likely survives. It better not , because we’re most likely going to die.

      Sooner or later. But remember that probably, it’s important. Another useful point -your regional species (community) has to survive for you to. This isn’t really optional. Where it balances out is your tribe, your kin, your culture, your people. You as a person may or may not survive better than your small group does. That’s the way it is.

      So the next question is “what is necessary and sufficient for survival at each level survival?” It’s important to add the “sufficient” – otherwise you’re in the dark room with the elephant. A lot of other questions flow from that. Some of us call this “resilience theory”. Some of don’t call it anything, and just live.

      It turns out that resilience theory is a pretty big box. It’s a much bigger box than economics. It has to be, because economics doesn’t solve for human resilience. It’s also a lot more fun – for me. Your Mileage May Vary.

      It’s more fun because of who I am and who you are. My life resolves for the question of resilience. It does not solve for economics. (frankly, that does not compute). It does not solve for morals or ethics. Resilience manifests my life meaning. I like that.

      Resilience offers millions of way out and ways in to everyone.

      OK Paul, time for your meds.

      • That IS quite a reply.

        An ad hominem claim is not required to refute Oehman’s primary argument that people will be able to respond to the nuclear crisis in Japan in a way that will cause no harm – or at least little harm – to people and environment.

        Given such a fantastic claim it’s no wonder why people are pecking at his credentials. But keep in mind being a nuclear physicist would not make his argument any more right or wrong than it is right now.

        Regardless of Oehman’s background he,

        1. understands the basics of nuclear power
        2. details his argument
        3. cares about who he’s addressing

        These things are vastly important. But they do not make his conviction correct.

        I realize we are dealing with ‘damage’ in terms of scale and that what is acceptable to one person may not be acceptable to another.

        That said, my feeling is that this academic, like most of us, is simply too far removed from the damage to have a sensible reaction. The response is to clinical.

        As an antidote to distance I suggest we ask how Oehman – along with ourselves – would respond to the following questions:

        1. Exactly how much poison are YOU willing
        to eat for the success of the free
        market and global trade?

        Please name your preferred poisons____________

        2. What sacrifices are YOU prepared
        to make for culture and civilization?

        Please list the monuments, shrines, and works of art you would most willingly destroy_______________

        3. In the name of patriotism and
        the flag, how much of YOUR beloved
        land are you willing to desecrate?

        List in the following spaces the mountains, rivers, towns, farms you could most readily do without______________________________

        4. State briefly the ideas, ideals, or hopes,
        the energy sources, the kinds of security,
        for which YOU would kill a child.

        Name, please, the children whom
        you would be willing to kill________________

        [These questions paraphrased from Wendell Berry’s powerful Questionnaire poem]

        They are the important questions.

        I understand too that they are unlikely to give peace of mind to those in harm’s way, which was Oehman’s intention anyway; but then again knowing the scale of the tragedy and working to avoid the possibility of such a disaster in the future might bring more solace than immediately recognized.

        In any case, at this point, Oehman’s faith was at least partially misplaced. People and places have been utterly ruined as a result of the disaster. That should be enough to make us pause to think seriously about what we’re doing to ourselves and our world.

        A response that we need to be resilient is only partially correct. While people will (hopefully) become better thinkers as a result of this disaster, people and places will not come through the experience unharmed, undamaged.

  19. Oehman,s article was written on 03/12. Since then events worsened spirally. Right now the situation is so clear that even an idiot knows he should run if he is in Fukushima. There are 3 kinds of people in the world: the real experts who are less than 1% of population, the idiots who have no scientific training and account for over 90%, and half-baked “experts” who thinks they know stuff but they don’t really. The last kind of people do more damage than an idiot.

    • While I disagree with the suggestion that Josef Oehman is an idiot, your point is well taken!

  20. Well reasoned article… However, this does not address any spent fuel that is stored outside of reactor (I’m not an expert so I don’t know what precautions they take with that).

    Another counterpoint is that apparently a number of people have received significant doses of radiation. This contradicts professor’s statements about giving up smoking if you were sitting on the plant’s chimney (or something like that)…

    Also, professor assumes that he has complete information about what happened. There is always potential for some s**t to go wrong especially in such dire circumstances. The event this happening is small, but nonetheless real…

  21. Well reasoned article… However, this does not address any spent fuel that is stored outside of reactor (I’m not an expert so I don’t know what precautions they take with that).

    Another counterpoint is that apparently a number of people have received significant doses of radiation. This contradicts professor’s statements about giving up smoking if you were sitting on the plant’s chimney (or something like that)…

    Also, professor assumes that he has complete information about what happened. There is always potential for some s**t to go wrong especially in such dire circumstances. The event this happening is small, but nonetheless real…

  22. Why are you leaving this article up without a comment that indicates that it has proven to be utterly wrong in its primary assertion. The article was irresponsible when it was written, but leaving it up now is just offensive. Please, write a brief note that put’s it in some context. Why are you leaving it this way without any recognition that it has been proven wrong?

  23. […] Here is a Post which should cheer one and all. It is by Dr Josef Oehmen, a research scientist at MIT, in Boston. https://climatesanity.wordpress.com/2011/03/13/why-i-am-not-worried-about-japans-nuclear-reactors-fro… […]

  24. Looks like the folks at Fukushima aren’t the only one’s doing damage control.

    Thank you for leaving this post up. Oehmen is trying to make all traces of the original disappear, because it is now so embarrassing for him. He needs to own up to what he did, but he’s trying to weasel out of it.

  25. Why don,t you let your readers know what kind of PHD research scientist Mr. Oehman is. His area of expertise has nothing to do with nucluer power plants. His research is in business not physics.

  26. Is this the quality of MIT PhD??

  27. http://morgsatlarge.wordpress.com/

    Please do not forget the back story to the original copied blog post. Jason received an email from his cousin, who happens to be a PhD at MIT, and not a Nuclear Expert. His cousin was only trying to answer his cousin’s understandable concerns about what was going on, since you can’t get the full story from todays mass-media hysteria.

    It was never intended to be public. It is clearly written as a personal note, with the intent of calming some fears and providing some background.

    Those who use this private communication that was unfortunately publicly posted by a naive person, either pro or con nuclear energy, do so without regard to the facts of the true “back story”. A not so uncommon phenomenon.

    • Marc,

      Note that I linked to the original source of Oehmen’s essay. That source made the “back story” very clear. There was nothing “naive” about posting the original essay.

  28. “The external power generators could not be connected to the power plant (the plugs did not fit).”

    That is just not fair, now they are piling rocket science on top of nuclear physics.

    What media “hysteria”? Now everyone knows all they need to do to avoid radioactive iodine, is not to drink local cow’s milk. Apparently, even mild exposure to radiation is enough to give everyone enough amnesia forget about the food chain from the ocean, where most of the rain from these radioactive plumes will fall.

    The most important “curriculum vitae” credibility to consider, is the extensive record of lying and corruption by TEPCO. They are as bad as BP.

  29. I’m not going to hold it against Dr. Oehmen, but this viral essay has already been debunked many times. The event is now up to a Level 6 — higher than Three Mile Island, but a tick under Chernobyl, thank God — and a significant amount of radiation HAS been released into the atmosphere, although at this point it doesn’t seem to have been enough to declare this a truly catastrophic event.

    Still, I think it’s irresponsible to leave this post up without mentioning that much of what appears in this essay is incorrect. MIT has taken it upon itself to correct it on behalf of Dr. Oehmen, who is not, it turns out, a nuclear expert of any kind. Why not post that version?

    As I said above, I can’t hold it against Dr. Oehmen for writing this. Clearly, he was trying to alleviate his friends’ fears, not write a peer-reviewed paper on nuclear safety. I’m sure he didn’t expect a hastily written e-mail to go viral, much less have it be read days later, when the information he presented was no longer applicable. But I can hold it against the blogs, magazines and other media outlets that continue to give this essay space on their pages.

    • Fourth Estate Sale,

      Please read what MIT said about adopting the Oehmen essay: “The original article was adopted as the authors believed it provided a good starting point to provide a summary background on the events at the Fukushima plant.” The original and MIT versions of the essay are substantially the same, and I have linked to the MIT version in comments here.

      My guess is that most people (probably including you) knew more about the events and risks after reading Oehmen’s essay than before. That is far more than I can say about almost all of what I have read in the press.

      • So, you work for MIT, do you? Sounds like you do. Sounds like you are trying to spread their obviously, embarrassed back-peddling on this message board. The fact is – as I see it – if this guy was one of my family members, and he had so carelessly tried to ease my apprehension about the realities of what he knew only a little bit about, I would disown him.

      • Bruce,

        No, I do not work at MIT. Never been there. I have spent the last 15 years as a scientist at the National Renewable Energy Laboratory where I work on photovoltaics (the conversion of light into electricity).

        The fact of the matter is that Oehmen’s provided a lot of good information. My guess is that if you read his essay, then you understand far more about the workings of that kind of reactor than you did before.

        Best Regards
        Tom Moriarty

  30. we really need someone to just tell us the truth!!

  31. So even a PHD from MIT can get it completely wrong. What a surprise.

  32. […] Why I am not worried about Japan’s nuclear reactors […]

  33. Here we have been discussing physicist Michio Kaku’s March 17, 2011 assessment of the ongoing disaster at Fukishima Dai-chi in Japan:


    Regardless of opinions on nuclear science in general, Professor Kaku clearly has a far better grip on what’s happening in Japan than anyone on these boards, including the well-meaning Professor Oehman.

    Japan is in a sinking ship…

  34. […] I don’t noramally copy other people’s posts. In fact, this is a first. But the subject matter is too important and needs to be disseminated now. This comes from Jason Morgan at Morgsatlarge-Blogorific. Please examine a partial list of Oehmen’s publications and his curriculum vitae ********************************************* This post is by Dr Josef Oehmen, a research scientist at MIT, in Boston. He is a PhD Scientist, whose father has exten … Read More […]

  35. OK, so now it’s March 17th, (18th in Japan) almost a week into this travesty. The big problem(s) have now spread to 4 out of 6 nukes at this sight and all are in big, big trouble. And the most recent attempts at solutions were straight out of Mutt & Jeff or maybe the Keystone Cops — I refer to dropping water from helicopters which was ridiculous (even without the wind) but demonstrates the extent to which they had used up Plans A, B, C, D and E. And then they tried the police water cannons — with equal success. (In fairness they then went to military water cannons and they MAY have had some minor effect — yet unquantifiable.)

    I note that a few posters have mentioned the ‘spent fuel’ onsite storage. Methinks this is far more of an issue than the rest of it. These pools are especially nasty and don’t have the ‘safety’ net built in the generators do (no real containment). And it seems that one of them has had already suffered some melting.

    Consider that in the USA we store the spent fuel at the site of each reactor. And we have more than 104 storage sites (some reactors have already been deactivated but their spent fuel pools still are there). The largest storage is in Hanford, Washington and Savannah River, S. Carolina where we used to send spent fuel rods before we decided it too dangerous to ship them. Both sites have had some very nasty and large spills (do a search if you want some scary reading).

    Go here for a map showing the amounts in each state (total approaching 100 thousand metric tons in about 40 states):

    Pogo had it right — “We have met the enemy and his is us.”

    Quick followup: David Sanger of the NY Times reports today:

    Figures provided by Tokyo Electric Power on Thursday show that most of the dangerous uranium at the power plant is actually in the spent fuel rods, not the reactor cores themselves. The electric utility said that a total of 11,125 spent fuel rod assemblies were stored at the site. That is about four times as much radioactive material as in the reactor cores combined.

  36. On BBC Radio yesterday it was stated that TEPCO had issued a statement saying the chances of criticality (presumably either in the damaged reactors or the ponds were “not zero”. If past form is anything to go by the situation is going to get worse before it gets better and the people on the ground, while working heroically and at great risk to themselves, don’t really have an adequate plan. Earlier in the week I tried to reassure my wife against catastrophism partly on the basis of what Oehmen wrote (and my conviction that no-one sets out to run a dangerous nuclear complex). However I have to say that in my small way I feel this has been stripped away from me. I doubt that Oehmen is ever going to live down the original post, even if he can’t be held fully responsible for the way that other people have used it to give false hope.

    • Paul,

      Maybe you and your wife will feel a little bit better if you show her this from Ben Monreal at UC Santa Barbara

      Oehmen’s hope was not false. Learn, educate yourself, and stop your own panic.

  37. Good article … comforting to know … BUT …
    what about this?

  38. Dr. Oehmen made a few “errors” himself, e.g. one of those reactors—#3—is running partially on plutonium rather than uranium. Plutonium is horribly toxic if inhaled. Being anywhere near a plutonium plume ain’t a good plan. I also agree with whoever commented on the spent fuel situation, e.g. that Oehmen ignored it. A friend of mine says that whenever she brings up the spent fuel problem in general nuclear discussions (not the Japanese emergency), whoever she is talking to changes the subject. Always, they change the subject—even her electric engineering brother changed the subject! Dr. Oehmen seems to be no exception to that observation.

    • Sharon Karpinski,

      Oehmen did not “ignore” the spent fuel situation, that aspect was unknown at the time. Please see the response to Dirk Faegre concerning the spent fuel.

  39. “Please name your preferred poisons____________”
    Vitamin D and/or Selenium

  40. Well time has gone by and put Oehmen into perspective. Now it’s time to become practical … Your Japanese readers might be interested in the pertinent question of how to treat their radioactively contaminated drinking water:

    • Crisismaven,

      Here is the liberal and alarmist NPR today:

      Authorities said the warning was prompted by readings of radioactive iodine in the city’s drinking water. At 190 to 210 becquerels per liter, the water exceeded the 100-becquerel limit for infants. But water officials said readings were still below the 300-becquerel limit for adults.

      The half life for iodine is 9 days. Half of the radioactive iodine that is there right now will be gone in nine days. In 90 days only a thousandth will still be there. In a year only a trillionth will be there. So pull yourself together.

      • It’s not just NPR…

        Here’s a reputable conservative news station reporting:

        “It is really scary. It is like a vicious negative spiral from the nuclear disaster,” said Etsuko Nomura, a mother of two young children ages 2 and 5. “We have contaminated milk and vegetables, and now tap water in Tokyo, and I’m wondering what’s next.”

        You’re waaaay too far removed from the disaster friend.

        Try bringing some of that sensible’fear’ home. Already you’ve been posed a question: Can you supply a list of children YOU might be willing to put in harm’s way to prove your point of safety?

        I doubt it.

        That’s exactly what you’re asking the people in Japan to do.

        Read more: http://www.foxnews.com/world/2011/03/23/radiation-levels-rise-tokyo-tap-water-new-evacuations-ordered-nuke-plant/#ixzz1HR3Nwdkt

      • Sean,

        I am saving your comments for special treatment at a later time. But I will get to it.


      • >The half life for iodine is 9 days. Half of the radioactive iodine that is there right now will be gone in nine days. In 90 days only a thousandth will still be there. In a year only a trillionth will be there. So pull yourself together.

        I don’t like the tone of that. If water contaminated to that degree was coming out of my tap today, would I find it consoling that, assuming there was no further contamination etc, it would be half as contaminated in 9 days [and statistically considered safe for babies]? I don’t think I would. Let me compare it with swine flu. The chances of catching it were quite low. Most people who got it weren’t very ill. Nevertheless it still caused me anxity to know that a number of people within a few hundred metres of me were going down with it daily and someone suffering from it might come through my door and want to talk to me. Of course we have to try and make sensible judgments about risk. But it’s much easier to do that when you don’t feel it’s right here right now.

      • Fukushima shows us once again that being able to quantify a situation does not necessarily mean that it can be controlled.

        The question arising is: was it worth the damage?

        Of course that will be answered by the people who have been frightened, made ill, and lost land as a result.

        We’re so far away that we callously toss information at them thinking it a some sort of salve.

  41. The genius of these so-called experts is being very well demonstrated at Fukushima:

    They can take a disaster, quantify it, and then divide it neatly into confusing data.

    By converting simple, observable truths into abstract data, they are (whatever the intention) misleading those who have only half the interest and/or capacity to know what’s taking place – in fact.

    If we want to use numbers, which can be meaningful, we need to be able to translate them into the real world.

    People have fears, bodies and places are not all the same, and there will be negative impacts from radiation despite what can be construed with numbers.

    Unfortunately, that is one result of living in a world of life rather than a world of abstractions.

  42. Tom,

    Okay, sounds good.

    Your blog is obviously appreciated.

  43. Josef Oehman states “There was and will *not* be any significant release of radioactivity.” False. “Japan is looking at an INES Level 4 Accident.” False; Level 7. “I believe the most significant problem will be a prolonged power shortage.” False. Mr. Oehman’s predictions were completely wrong, in terms of the final (and we still don’t know how bad yet) disposition of this situation. The article may have been helpful to some about the mechanics of a nuclear power plant, but absolutely useless in terms of predicting outcomes. Was his article helpful? Or very misleading?

  44. good show terrific pacing and video clips

  45. I suppose a janitor from MIT can write a paper as persuading….

  46. Oehmen’s predictions:

    – INES Level 4 Accident
    – No significant release of radioactivity
    – The plant is safe now and will stay safe


    – INES Level 7 accident
    – 10-30% as much radioactive release as Chernobyl, and counting
    – 30 km (19 mile) exclusion zone
    – 150,000 people still displaced as of October 2013
    – Extreme vulnerability to another tsunami

    Looks like he didn’t actually know more than “all journalists on this planet put together”.

  47. Very informative article, 5 stars, definitely would recommend to a friend.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: