True facts about Ocean Radiation and the Fukushima Disaster

On March 11th, 2011 the Tōhoku earthquake and resulting tsunami wreaked havoc on Japan. It also resulted in the largest nuclear disaster since Chernobyl when the tsunami damaged the Fukushima Daiichi Nuclear Power Plant. Radioactive particles were released into the atmosphere and ocean, contaminating groundwater, soil and seawater which effectively closed local Japanese fisheries.

Rather unfortunately, it has also led to some wild speculation on the widespread dangers of Fukushima radiation on the internet. Posts with titles like “Holy Fukushima – Radiation From Japan Is Already Killing North Americans” and “28 Signs That The West Coast Is Being Absolutely Fried With Nuclear Radiation From Fukushima” (which Southern Fried Science has already throughly debunked ) keep popping up on my facebook feed from well-meaning friends.

I’m here to tell you that these posts are just plain garbage. While there are terrible things that happened around the Fukushima Power Plant in Japan; Alaska, Hawaii and the West Coast aren’t in any danger.  These posts were meant to scare people (and possibly written by terrified authors). They did just that, but there is a severe lack of facts in these posts. Which is why I am here to give you the facts, and nothing but the facts.


The radioactive rods in the Fukushima power plant are usually cooled by seawater [CORRECTION: they are usually cooled by freshwater. As a last ditch emergency effort at Fukushima seawater was used as a coolant.]. The double whammy of an earthquake and a tsunami pretty much released a s**tstorm of badness: the power went out, meltdown started and eventually the radioactive cooling seawater started leaking (and was also intentionally released) into the ocean. Radioactive isotopes were also released into the air and were absorbed by the ocean when they rained down upon it. These two pathways introduced mostly Iodine-131, Cesium-137, and Cesium-134, but also a sprinkling of Tellurium, Uranium and Strontium to the area surrounding the power plant.

There aren’t great estimates of how much of each of these isotopes were released into the ocean since TEPCO, the company that owns the power plant hasn’t exactly been forthcoming with information, but the current estimates are around 538,100 terabecquerels (TBq) which is above Three-Mile Island levels, but below Chernobyl levels. And as it turns out, they recently found contaminated groundwater has also started leaking into the sea. TEPCO, the gift that keeps on giving.


Units of Radiation are confusing. When you start reading the news/literature/blogs, there are what seems like a billion different units to explain radiation. But fear not, I’ve listed them below and what they mean (SI units first).

Becquerel[Bq] or Curie[Ci]: radiation emitted from a radioactive material  (1 Ci = 3.7 × 1010 Bq)

Gray [Gy] or Rad[rad]: radiation absorbed by another material (1Gy = 100 rad)

Sieverts[Sv]* or “roentgen equivalent in man”[rem]: how badly radiation will damage biological tissue (1 Sv = 100 rem)

Simpsons Guide to RadiationYou can convert from Grays and Rads to Rem and Sieverts, but you have to know what kind of radiation it is. For example alpha radiation from naturally occurring Polonium-210 is more damaging to biological tissues than gamma radiation from Cesium-137. Even if you absorbed the same number of Grays from Cesium or Polonium, you would still effectively receive more damaging radiation from Polonium because the number of Sieverts is higher for Polonium than Cesium. And kids, Sieverts and Seavers  are both dangerous to your health but please don’t confuse them.


Cesium-137 is product of nuclear fission. Before us humans, there was no Cesium-137 on earth. But then we started blowing stuff up with nuclear bombs and VOILA!, there are now detectable, but safe, levels of Cesium-137 in all the world oceans.


There are a bunch of maps being thrown around on the internet as evidence that we are all going to die from Fukushima radiation. I’m going to dissect them here. Apologies in advance for dose of snark in this section because some of these claims are just god awful. Spoiler: radiation probably has reached the West Coast but it’s not dangerous.

MAP OF TERROR #1: The Rays of Radioactive Death!

This is not a map of Fukushima Radiation spreading across the Pacific. This is a map of the estimated maximum wave heights of the Japanese Tohuku Tsunami by modelers at NOAA. In fact, tsunamis don’t even transport particles horizontally in the deep ocean. So there is no way a Tsunami could even spread radiation (except maybe locally at scales of several miles as the wave breaks onshore). Dear VC reporter, I regret to inform you this cover image could be the poster child for the importance of journalistic fact-checking for years to come.


I mean I guess this is a bit better. At least this map used an ocean model that actually predicts where radioactive particles will be pushed around by surface ocean currents. But it still gets a BIG FAT FAIL. The engineering company that put this image/piece of crap out there couldn’t even be bothered to put a legend on the map. Their disclaimer says “THIS IS NOT A REPRESENTATION OF THE RADIOACTIVE PLUME CONCENTRATION.” Then what do the colors mean?


It’s true, oceanographic models have shown that radiation from Fukushima has probably already hit Aleutians and Hawaiian Island chain, and should reach the California Coast by Fall 2014 [Behrens et al. 2012]. The map above is showing the spread of Cesium-137 from the Fukushima reactor would look like right now, I mean radiation is apparently EVERYWHERE! But what is missing from most of the discussion of these maps is what  the colors ACTUALLY mean.

We shall now seek guidance from the little box in the upper right hand corner of the map called the legend**.  The colors show how much less radioactive the the decrease in the radioactive concentrations of Cesium-137 isotopes have become since being emitted from Fukushima. For example, the red areas indicate the Fukushima Cesium-137 is now more than 10,000 times less radioactive concentrated than when released. The California Coast, more than a million times less. The punchline is that overall concentrations of radioactive isotopes and therefore radioactivity in the Pacific will increase from Pre-Fukushima levels, but it will be way less than what was seen in coastal Japan and definitely not enough to be harmful elsewhere (we’ll get to more of that later).

** As Eve Rickert has thoughtfully pointed out, my description of the image is a little confusing. I’ve added corrections in blue to clarify.


Practically, what does ten thousand or a million times less radiation mean? It means that these models estimate the West Coast and the Aleutians will see radiation levels anywhere from 1-20 Bq/m3,while Hawaiian Islands could see up to 30 Bq/m[Behrens et al. 2012, Nakano et al. 2012,  Rossi et al. 2013 ].

I could write a small novel explaining why the numbers differ between the models. For those that love the details, here’s a laundry list of those differences: the amount of radiation initially injected into the ocean, the length of time it took to inject the radiation (slowly seeping or one big dump), the physics embedded in the model, the background ocean state, the number of 20-count shrimp per square mile (Just kidding!), atmospheric forcing, inter-annual and multi-decadal variability and even whether atmospheric deposition was incorporated into the model.

Like I said before, the West Coast will probably not see more than 20 Bq/mof radiation. Compare these values to the map of background radiation of Cesium-137 in the ocean before Fukushima (from 1990), it’s only 4 Bq/min the Pacific. Radiation will increase in the Pacific, but it’s at most 10 times higher than previous levels, not thousands. Although looking at this map I would probably stop eating Baltic Herring fish oil pills and Black Sea Caviar (that radiation is from Chernobyl) before ending the consumption of  fish from the Pacific Ocean.



No it will not be dangerous. Even within 300 km of Fukushima, the additional radiation that was introduced by the Cesium-137 fallout is still well below the background radiation levels from naturally occurring radioisotopes. By the time those radioactive atoms make their way to the West Coast it will be even more diluted and therefore not dangerous at all.

It’s not even dangerous to swim off the coast of Fukushima. Buessler et al. figured out how much radiation damage you would get if you doggie paddled about Fukushima (Yes, science has given us radioactive models of human swimmers). It was less than 0.03% of the daily radiation an average Japanese resident receives. Tiny! Hell, the radiation was so small even immediately after the accident scientists did not wear any special equipment to handle the seawater samples (but they did wear detectors just in case). If you want danger, you’re better off licking the dial on an old-school glow in the dark watch.


For the most part the answer is YES. Some fisheries in Japan are still closed because of radioactive contamination. Bottom fish are especially prone to contamination because the fallout collects on the seafloor where they live. Contaminated fish shouldn’t be making it to your grocery store, but I can’t guarantee that so if you are worried just eat fish from somewhere other than Japan.

Fish from the rest of the Pacific are safe. To say it mildly, most fish are kinda lazy. They really don’t travel that far so when you catch a Mahi Mahi off the coast of Hawaii its only going to be as contaminated as the water there, which isn’t very much.Hyperactive fish, such as tuna may be more radioactive than local lazy fish because they migrate so far. As Miriam pointed out in this post, there is a detectable increase of radiation in tuna because they were at one point closer to Fukushima, but the levels are not hazardous.

To alleviate fears that you may be glowing due to ingestion too many visits to your local sushi joint, Fischer et al. figured out exactly how much damaging radiation you would receive from eating a tower of tuna rolls. Seriously. Science is just that awesome. Supermarket tuna hunters would receive 0.9 μSv of radiation, while the outdoors subsistence tuna hunter would receive 4.7 μSv. These values are about the same or a little less than the amount a person receives from natural sources.

To put 0.9 μSv of radiation in perspective check out this awesome graph of radiation by xkcd. You’ll get the same amount of radiation by eating 9 bananas. Monkeys might be doomed, but you are not.


I hope this list of facts has answered most of your questions and convinced you the Pacific and its inhabitants will not be fried by radiation from Fukushima. I certainly feel safe eating sustainable seafood from the Pacific and so should you. If you are still unsure, please feel free to ask questions in the comments section below.


There’s been a lot of discussion in the comments about the contribution from the groundwater leaks. I did some homework and here’s what I came up with. (Also thanks to everyone for the interesting discussions in the comments!)

The ground water leaks are in fact problematic, but what has been released into the ocean is MUCH less than the initial release (although I admit the groundwater itself has extremely high radiation levels).  The estimates from Jota Kanda are that 0.3 TBq per month (1012 Bq) of contaminated groundwater is leaking into the ocean, which has added another 9.6 TBq of radiation into the sea at most.  The initial releases were about 16.2 PBq (1015 Bq), about 1500 times more radiation. With this in mind, the additional radioactivity leak from ground water isn’t a relatively large addition to the ocean.

The models by Behrens and Rossi used initial source functions of 10 PBq and 22 PBq, which is on par with the most recent estimates.  Since their models used a much higher source function, that says to me that this relatively smaller input from groundwater still won’t raise the radioactivity to dangerous levels on the West Coast, Alaska and Hawaii.  Recent observations around Hawaii by Kamenik et al. also suggest that the models may have even overestimated the amount of radiation that hit Hawaii, which is good news.

But there are caveats to this information as well. The leaking groundwater contains strontium and tritium which are more problematic than Cesium-137. But it sounds like strontium accumulates in bones and is only a problem if you eat small fish with the bones in, like sardines (and it will only affect sardines caught near Japan since they don’t travel far). I suspect there might be some precedent for understanding the dangers of tritium in seawater from the 20th century nuclear testing in atolls, but I really don’t know. There is also 95 TBq of radioactive cesium is in the sediment around Fukushima, which is still super problematic for bottom dwelling fish and therefore local Japanese Fisheries. Lastly, another source is terrestrial runoff. These numbers haven’t been quantified but they are probably minor because they contain a fraction of the total deposition from atmospheric fallout, which itself was a fraction of what was released into the ocean.

So even with the new groundwater leaks, the available evidence still tells me I can eat fish from the West Coast, Hawaii, and Alaska.


For more in depth articles about radiation from Fukushima in the ocean you should definitely check out some of Marine Chemist’s Posts at Daily Kos. Written by Jay T. Cullen, a Marine Chemist at the University of Victoria, the posts walk you through the most current research on Fukushima Radiation from a variety of sources. I especially recommend his most recent post on Update on Fukushima Radionuclides in the North Pacific and Off the West Coast of North America, were he discusses the recent detection of Fukushima radiation off the coast of Canada. The most recent observations from June 2013 shows the spread of Cesium-137 was on par with the predictions by Rossi et al., but the concentrations are safe and lower than predicted.


[DISCLAIMER: The creators of the NOAA tsunami map work in my building. I secretly fangirl squeal when I walk past their offices. I recently had coffee with Joke F. Lübbecke, who also works in my building. It was caffeinated.]

*Confusingly, oceanographers also co-opted the acronym Sv for Sverdrups their unit for volume transport. 1 Sverdrup = 1 Sv = one million cubic metres per second = 400 Olympic swimming pools just passed your house in one second.


Behrens, Erik, et al. “Model simulations on the long-term dispersal of 137Cs released into the Pacific Ocean off Fukushima.” Environmental Research Letters 7.3 (2012): 034004.

Buesseler, Ken O., et al. “Fukushima-derived radionuclides in the ocean and biota off Japan.” Proceedings of the National Academy of Sciences 109.16 (2012): 5984-5988.

Fisher, Nicholas S., et al. “Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood.” Proceedings of the National Academy of Sciences (2013).

Nakano, Masanao, and Pavel P. Povinec. “Long-term simulations of the 137 Cs dispersion from the Fukushima accident in the world ocean.” Journal of environmental radioactivity 111 (2012): 109-115.

Rossi, Vincent, et al. “Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume.” Deep Sea Research Part I: Oceanographic Research Papers (2013).

Woods Hole Oceanographic Institution FAQ: Radiation from Fukushima

Explained: rad, rem, sieverts, becquerelsl. A guide to terminology about radiation exposure


Dr. Martini (156 Posts)

Kim is a Senior Oceanographer at Sea-Bird Scientific. She received her Ph.D. in Physical Oceanography from the University of Washington in 2010. Her goal in life is to throw expensive s**t in the ocean. When not at sea, she has used observations from moored, satellite and land-based instruments to understand the pathways that wind and tidal energy take from large (internal tides) to small scales (turbulence). Her current mission is to make your oceanographic data be the best data it can be.

283 Replies to “True facts about Ocean Radiation and the Fukushima Disaster”

  1. One more reference to the water disposal issue in The Guardian (UK)…”Tepco has cut the trees down now, to make room for 1,000 huge metal storage tanks. They hold more than 360,000 tonnes of radioactive water, enough to fill 140 Olympic swimming pools. The volume rises every day. Over the next three years, Tepco wants to add storage for another 270,000 tonnes of radioactive wastewater. Ultimately, the water must be returned to the Pacific. There is nowhere else for it to go.”…

  2. George: in the interest of maintaining the level of accuracy that this article started off with, I have felt compelled to correct a few of the things you have said that are simply wrong. These are not matters of opinion or points of view.

    Nuclear fuel doesn’t have to be an oxide (Fukishima was)

    There is an average energy release per fission
    Fission is not really controlled, in the sense of being kept down, by moderation. Moderation promotes thermal fission, so the way it controls fission is by making it happen more often.

    Again, boron is not a moderator in any way.

    Activity is a unit of radioactive decay (the Becquerel or Curie)—what you want to say is fission rate.

    Just because something is a particle doesn’t make it dangers. I’ve spent a lot of time working in rooms filled with neutrons (and I’ve even walked through a few neutron beams!). It the energy that is important.

    Statements like “keeps it from killing us” betray your emotional bias.

    The majority of redundant safety systems are for thermo-hydraulic concerns, not fission reaction rate.

    Again, you betray your bias with a phrase like “mere mortals.” You give the impression that physics is too tough to control; do you think nuclear power is an example of hubris?

    In a BWR, there is no flashing to steam during normal operations. It is a gradual shift from liquid water to a mixture of steam and water (a two-phase flow, in terms of matter states).

    Cooling of a shutdown core is not required indefinitely—it’s only until the radioactive decay of certain fission products makes the mass of decaying matter greatly decrease. This is why used fuel ends up in dry storage.

    The zirconium water reaction is the same thing as the “burning” of the cladding. The burning term is just an analogy for a chemical reaction conceptualization.

    Cladding can be damaged without necessarily having a breech, but usually if the cladding is already decomposing, emergency water isn’t going to get in there soon enough.

    It is not at all a requirement that the melted core restart fission. In fact, without water in the core, it is much less likely that there will be a fission reaction, let alone a sustained reaction, because there is no moderator.

    In addition, control rods and structural materials are melted together with the fuel, so there can be a lot of poison in the melt.

    If a fission reaction is out of control (as in a melted or slumped core) it is actually extremely unlikely for it to last more than an instant or so. The heat generated changes the geometry and the reaction stops. That’s why there were three separate detections of neutrons and gammas indicating a (fission) criticality event, at the wrecked plants.

    Just because something is out of control doesn’t mean that it is increasing—thermodynamics usually sees to it that out of control things stop.

    The decay heat of one of those melted cores (unit 1, for example) is about 11 MW—this isn’t exactly the face of the sun. The cores were elevated and there was tens of meters between them and the rock before they melted the vessel. Nobody knows how far down they’ve gone, but there is an awful lot of thermal conduction and convection going on there. If you want to make some calculations, check out this paper that has thermal properties of rocks and minerals:

    There is no way that anybody has shown that the 11MW of core has burned through everything below it. I’m not saying that it can’t have—I’m just saying that that is not a fact, just gratuitous painting of an emotional picture.

    Something that is melted cannot “melt more.”

    Removing heat from a melted core is not going to stop it from having criticality excursions. The temperature is not a factor in the way you say it is.

    If pouring water onto the melted core doesn’t make a steam explosion, then why do you think there will be a steam explosion if it were to go as deep as the water table? Concrete is full of water—which is why it blows up when heated—I haven’t heard of any recent concrete explosions.

    Self-fission is not a phrase that makes sense.

    It was probably not a neutron count that made somebody “say” fission—it was probably a gamma signal.

    What does highly radioactive mean, as opposed to moderately radioactive?

    If the water poured onto the core is being continually washed out to sea, then what is being put into those tanks?

    (All of the things that I’m bringing up are not matters of opinion—they are matters of science and logic).

    Fuel is not “extremely exothermic.” Exothermic is a word typically applied to a chemical reaction; nuclear fuel does not run on chemical reactions. I have plenty of pictures of ME posing with real nuclear fuel rods, holding them in my bare hands and smiling for the camera!

    These same fuel pins (that I’ve posed with) are stored in tubes with perhaps a dozen of them lying on top of each other. Thus, bringing them close together does not make them any hotter.

    Neutron emission is a very uncommon form of radioactive decay.

    Only a handful of elements (the fissile atoms) will break up (fission) if they are hit by a neutron.

    There is no reason why a chain reaction has to increase in population. If that were the case, there would be an infinite number of all species of animals (population statistics apply to all populations).

    The release of a neutron in fission is not where the heat is—it is the kinetic energy (the speed) of the two parts that were split apart—they fly apart.

    Atomic bombs are definitely not run away chain reactions. They’d never work if they were out of control—the control part is what makes it a bomb. As I’ve said before, out of control things tend to take the shortest path to stopping whatever is happening.

    Moderators—and this is a really REALLY terrible mistake—are not what controls the neutron population in a nuclear reactor the way you are describing.

    Boron (for the third time) is not a moderator. Actually, in all western commercial cores, there cannot be a chain reaction if the moderator is not there. What you said is the exact opposite of true.

    Neutrons are not “2,000,000 degrees.” That makes absolutely no sense—you didn’t even provide units (Celsius, Fahrenheit)! Temperature is a measure of the average speed of a population of particle (see Kinetic theory of the gasses). The rest mass energy (the E in E=mc^2) is not the same energy as the momentum. The temperature of a neutron is its kinetic energy. A room temperature neutron is most probably moving at 2200 meters/second, for example. This is also called a thermal neutron.

    Plutonium is not a by-product of fission. In fission, one big thing breaks up into two smaller things. Plutonium is bigger than uranium, so I really don’t see how something that is real (as in, not just a mathematical construct) can break into parts that are larger than itself.

    God of the underworld, huh? I’m getting the feeling that you are afraid of nuclear power and want to feel justified in your fear by having others feel the same way. How do you feel about Francium? It’s named after France!

    1/1E6 of a gram can give you lung cancer? Maybe. But it also might not. Statements like that have no scientific value.

    Exposed fuel rods in a spent fuel pool with definitely not instantly melt. They are producing less power than when they were taken from the core. They might have a chemical reaction with the air, but it’s only because they’re made out of zirconium alloy. And only if they’re hot enough. Stainless steel rods wouldn’t have the same problem.

    Moderation is not a way of controlling a spent fuel pool in the way you are describing. If enough moderation were added, there would be a fission reaction. The water is there to keep them cool, but also to keep air off them and to keep the radiation from going far.

    “Kill everybody–” Everybody everywhere? Without water in the spent fuel pool, I doubt there will be too much fission—just a good amount of heat. (Tens of MW thermal power).

    “Spiked with plutonium?” You pick biased, emotionally charged words.

    What knowledgeable person thinks that the MoX fuel in a spent fuel pool at unit 4 was made to fission by the MELTING (melting is a heat thing, not a nuclear thing) in other units? That sounds really interesting and I’d like to read it.

  3. Well, gosh, where to start? Is MOX spiked with Plutonium? Yes or no?

    We were discussing the oxide of BWR’s were we not? Take your misleading complaint elsewhere.

    Let’s put eleven Megawatts of heat into a small place and see how hot it gets. The molten blobs are out of your control, Mister Neutron. You can’t even look at them, and do not know their temperature now. Trying to minimize the danger of thousand-ton molten radioactive cores may be good for the industry, but misleading to the rest of us. Tell the folks here what happens if one gets to the water table. Be specific and complete.

    Shall I show you the probabilities of magnitude 7 or more earthquakes in the next year at Fukushima? They range from 70% to 90%. If one happens when they are trying to extract damaged fuel rods, what happens?

    Are you really interested in the charge of possible fission from the intense Neutron flux? I do not think it is so but others do.

    You want to dispute the effective temperature? Wiki: “Neutron sources generate free neutrons by a variety of nuclear reactions, including nuclear fission and nuclear fusion. Whatever the source of neutrons, they are released with energies of several MeV.

    Since the kinetic energy, E, can be related to temperature via:

    E=frac{1}{2}mv^2=frac{3}{2}k_B T

    the characteristic neutron temperature of a several-MeV neutron is several tens of millions of degrees Celsius.”

    If you doubt whether the loss of cooling water can cause the rods to catch on fire, I will look it up for you.

    You allege “Plutonium is not a by-product of fission.” but where did we get ALL of it on Earth today? It is from Uranium reactors. Ever hear of “breeding”?

    Boron 10 is a Neutron moderator. Why do you think the US Navy sent tons of it to the Japanese immediately? Why else did they dump into the TMI II reactor cooling loop?

    I am not “afraid” of nuclear power, I fear the folk who think they understand it, and repeatedly and repeatedly get shown they cannot be trusted to deal with this stuff.

    “The release of a neutron in fission is not where the heat is—it is the kinetic energy (the speed) of the two parts that were split apart—they fly apart.” Nope – Gamma carries the heat. Things do not get hot from speed, they get hot from absorbing Gamma, turning to thermal. Flying away does not make things hot.

    Fuel rods are not used “lying on top of each other”.

    You allege “Statements like “keeps it from killing us” betray your emotional bias.” without knowing I got the statement from the GE tutorial on the history of the BWR, with the Mark I, II, and Mark II Containment and the differing configurations of the cooling systems. I changed their word “safety” to the more realistic description of Fukushima.

  4. Sorry for the inadvertent tone of my response. I appreciate the writings of Neutronium, his input, and this dialogue.

  5. George, as I should have tried harder to convey it was not my intention to piss of someone I don’t know. I was just correcting what I saw as counterfactual and /or non-true. Everything I wrote was with the notion that you’d read it, see what I was saying, and then verify my points for yourself. It seems as if you like nuclear power—you know more than almost anyone because almost no one knows anything. I happen to be one of the very few experts. I, like my peers, got into nuclear-in-general field because the topic was really interesting to us. Nobody paid me to find it interesting in the first place. I am sorry to have “unloaded” like that, but I was in great need of some procrastination from the projects I ought to be working on.

    I wasn’t disputing whether MoX was being used and contained plutonium. Technically, ‘mixed oxides’ means a mixture of anything that is oxidized—it could be rust and water (iron oxide and hydrogen oxide) and still called MoX. If you read carefully, I was pointing out the use of the word spiked. Unit 3 was fueled with MoX.

    11 MW in a small space? I don’t know if the melt is in a small space or a large space. As someone knowledgeable (formally educated) in heat transfer, there is much opportunity for conduction and convection. That 11 MW isn’t staying put. In fact, it can now lose heat more easily, due to contract with dense solids (ie steel), than it could when it was trapped in tubes and suspended in the air. Given that “they” are pouring water on them but there isn’t any steam…I have no indication that it is exceptionally hot.

    As an aside, as a nuclear engineer I have absolutely no good words for Tepco. I see them as an existential threat to my field and a criminal corporation. I LOATHE criminal corporations, I assure you. I am no authoritarian.

    The mass of the core is not what makes it dangerous. I don’t work in industry (or in reactors or in reactor design)—I’m just highly educated in this field.

    Why the water table? Why would it go there rather than stick to the floors of the building below it or the rock? If it’s melted, then why is it imagined to be remaining as a blob rather than spreading out as a disk? Gravity affects a liquid by flattening them out, like an ice cube melting. The melted ice makes a disk–it doesn’t stay as a cube. If a molten core—as an unrealistic ball—went into “the” water table then I guess it wouldn’t really stop moving. The water table is not a subterranean lake—it’s just the depth at which the solid and/or compressed rock mixture is saturated with water (like a sponge). If the now-low power part of melted core that went through all the rock above met rock saturated with water below, I don’t think that it would have reason to stop. The thermal conductivity of the saturated rock wouldn’t really be that much different than the solid rock above. As I said, if there are no steam explosions on the concrete, then why would there be if it remained as one blob and kept going down? 11 MW thermal is easily cooled via natural convection in water. Considering the density of water is much less than the density of steel and/or concrete, I don’t really see the core destroying everything in it’s path.

    As for telling me to be specific and complete—I do understand that you were trying to describe nuclear reactors in plain terms, but I couldn’t help myself since this is my ‘thing.’ I don’t know what would happen and that’s not really a nuclear question. The radioactivity is not the governing phenomena–it’s the heat, heat transfer, chemistry and material properties. I am confident that I haven’t said anything wrong, though. I am versed in heat transfer and have an uncommon intuitive grasp of physics that leads me to make the points that I make.

    I never contested the danger of removing the spent fuel, so I’m not sure why you are asking a “what happens as if” question in relation to that. I don’t know what would happen—this isn’t a nuclear question—as a certifiably learned engineer in one field, I’d guess that is more of a civil engineering and construction logistics issue. I think it is an extremely dangerous thing to do and it has more potential to negatively impact me than most other people.

    I am extremely interested in the idea that neutrons from a melting core (a melting core is not melting because of fission–this is because small fission products are radioactive and are decaying) from a shielded reactor containment building hundreds of meters away caused criticality excursions in tubes in a pool of water (filled with water and boric acid (and maybe BorAl)) on top of a containment building. Seriously. I am a nuclear engineer. That’s like telling an automotive engine designer that fuel leaked from the car down the street and caused your car engine to start up—that engineer would probably want to see how that worked. That’s why people become engineers—they want to know how things work. Radiation intensity follows an inverse-squared law in distance, so neutron intensity at that distance from the source is something I need to see second hand (at least).

    Yes I do want to dispute that effective temperature. I am made out of matter, all of the atoms in my body other than hydrogen-1 have neutrons. What is my temperature? The average fission neutron energy is between .9 and 1.0 MeV, not several. Check that link I sent; here is another that applies to fission neutrons:
    It’s called the effective temperature, rather than “the temperature” for a reason. The reason is because that is the velocity distribution that you would expect of a gas measured to have such a temperature. “Effectively” is like saying it’s “as if” it were that temperature—that is not actually the temperature.

    As someone who wrote a 120 page thesis on a particular type of neutron source, I tell you with firsthand knowledge as a researcher that neutrons can be produced with no kinetic energy at all. That’s what I was getting at with the kinetic theory of the gases. See ultracold neutrons:

    More on the kinetic theory of the gasses: the only way you can get a temperature is to have a population of particles, each with some finite velocity. One single neutron that has .9 MeV of kinetic energy does not have an effective temperature. The keyboard you are typing on is made out of hydrocarbons, I venture. There are an awful lot of neutrons in that keyboard you’re typing on—are your hands burning at tens of millions of degrees Celsius?

    If you think that I wrote that a loss of cooling water cannot cause rods to catch on fire—then you should re-read what I wrote. As I said, it depends on how long they have been burned. My Facebook picture is of me holding a fuel rod and my (bare) hands are definitely not on fire.

    Zirconium oxidation by steam happens at very high temperatures. Fuel rods that have been left to cool off are no longer producing enough heat to make this reaction possible:

    Breeding is not the result of fission; breeding is when something adds neutrons to something else. A core, for the purposes of this discussion, needs to have U-238 in it for plutonium to be bred. A core running on pure U-235 would have zero plutonium in it. A Thorium-U235 core will have zero plutonium in it. You said that Pu is a byproduct of fission. It is not.

    In modern commercial reactors in the west, there is U238 in the core and it absorbs neutrons that are coming from the fission reactions. This is called also called neutron activation. The phrase by-product is indicative of the resultant of a (chemical)—this is not a byproduct.

    (to be clear, I have a dual BS, one subject in nuclear engineering, the other in physics, and an MS in nuclear engineering. I really do know what I am talking about!)

    George, (I have been trying to avoidad hominem arguments)—do you really want to argue that boron is a moderator? I’m honestly questioning whether you are serious or some sort of agent provocateur. You should read this wiki to understand what a moderator does: . Then—try to see why nobody would want to add moderation to a meltdown in a thermal reactor.

    You bring up that the boron was put into the cooling loop—I’m curious, why is that significant? Boron in not a coolant (nor is it a moderator). The reason: easy access—it was close and available.

    “Fear the folk that think they understand it?” […]

    You argue that “the” gamma ray carries the heat? What is the speed of a gamma ray? What about it’s effective temperature, via the kinetic theory of gasses. (I’ll help—a gamma ray has no mass and travels at the speed of light. It has no effective temperature because it has no mass).
    You previously accepted that the kinetic theory of the gasses is a representation of heat and then argue that the momentum of particles is not the definition of heat.

    I didn’t say that fuel rods are used lying on top of each other. I said that’s how they are kept (and they are).

    So—you took the phrases of GE writers, found in technical documents and swapped out their words for ones that you felt were appropriate and now claim that the statement made by the author in the original document is unchanged.

    George, like I said, it was not my intention to piss of someone I don’t know. I was just correcting what I saw as counterfactual. It is not personal because it can’t be—I don’t know you. I have no interest in fighting. I was pleasantly surprised to find somebody that knew anything at all about anything nuclear, when i found this page.

    1. I appreciate your long posts in this forum. I do not intend to irritate someone with an “intuitive grasp of physics”. Nor am I telling you what will happen. I am telling you possibilities, not probabilities. Do you know the probability of a 7-level earthquake there in the time period they are trying to extract the fuel rod assemblies? I read 70-90%. I am not telling you it will happen.

      I have to go today, but will return and continue the discussion.

      Thank you for your participation.

      You havee an extensive technical education in the field. I am taking issue with points. Some of your answers are irrelevant examples or assume the rest of us do not understand anything .

      My field is the integration of systems. I am a generalist, having been a technical spook in the Vietnam War in Electronic Reconnaissance, Got to be on X-15 Launch Teams,

    2. Can I ask your opinion on the scientific feasibility of this article:

      which contains this quote:

      “The un-irradiated rods inside the Unit 4 spent-fuel pool are, in all probability, made of a new type of MOX fuel containing highly enriched plutonium. If the frame collapses, triggering fire or explosion inside the spent-fuel pool, the plutonium would pulse powerful neutron bursts that may well possibly ignite distant nuclear power plants, starting with the Fukushima No.2 plant, 10 kilometers to the south.

      The scenario of a serial chain reaction blasting apart nuclear plants along the Pacific Coast, is what compelled Naoto Kan, prime minister at the time of the 311 disaster, to contemplate the mass evacuation of 50 million residents (a third of the national population) from the Tohoku region and the Greater Tokyo metropolitan region to distant points southwest.(7) Evacuation would be impeded by the scale and intensity of multiple reactor explosions, which would shut down all transport systems, telecommunications and trap most residents. Tens of millions would die horribly in numbers topping all disasters of history combined.”

      1. It is unlikely that there would be unirradiated fuel in the spent fuel pool. The spent fuel pool is where spent fuel goes when it is pulled out of the reactor. Adding fresh fuel (unirradiated) to the pool makes very little sense, given that the plant wasn’t undergoing a refueling and that space in spent fuel pools is at an extreme premium. This is because the businessmen want to maximize the risk so that they can take home the most profit. Spent fuel pools, in these reactors (which includes those in the US) were never meant for storage like this. Politicians and intervenes that are against nuclear power have created an extremely dangerous situation where the plants have no way of disposing of their waste. If these were coal power plants, they could just dump the coal in lakes and have golf courses and luxury homes built around it–but that’s another story. ( )

        Fresh fuel consists almost exclusively of alpha radiation which can’t get out of the cladding. The gamma ray intensity should be pretty low. I checked the reference that your link cited for the claim that there is fresh fuel in the spent fuel pool and, not surprisingly, that article says nothing of the kind. Read it here:

        Plutonium is not really more dangerous than uranium, from a criticality point of view. Plutonium is more dangerous from a human toxicity point for view.

        While it is often good to ask what if type questions, one needs to keep a measure of reality in mind. What that means is that some people find it oddly satisfying to contemplate the worst occurrences they can possibly imagine without regard for reality or precedent. For an example, see all of the disaster and alien invasion movies.

        That said, a question like “what if the frame collapses” is probably warranted because it is in regard to an engineered system. While I don’t and haven’t searched out information on the subject, I don’t see crane and other rigging systems collapsing all that often, on the news. One would hope that in such an important procedure, there would be extra measures of safety involved, both on the civil engineering and nuclear engineering sides of the problem.

        Humans have learned to not mess around with materials in criticality situations without the use of numerous forms of neutron poisons and absorbers (such a BORON and gadolinium). It seems obvious that these pools with be covered with dissolved poisons and chunks of poison material that would prevent excursions if the racks collapsed onto each other.

        Without knowing the thermal power of the spent fuel that is in the pool, one cannot say whether it is still hot enough to make the zirconium oxidation reaction happen. If it were to catch fire, that would not be because of fission but because the fission products in the spent fuel are literally hot because they are decaying and the charged particle (electrons and helium nuclei, or beta and alpha) radiation these emit is bumping into the electrons that surround the other nuclei in the spent fuel. The result is an electromagnetic “pushing” of the other nuclei in the spent fuel which is effectively causing them to move, which is the definition of heat.

        As for powerful neutron bursts “igniting” distant plants: this is totally non-physical. Before I explain why, note that fission is not any type of burning, so the word ignition doesn’t apply. Sometimes it is used as an analogy, but it also indicates that whoever is using the word really doesn’t know what they are talking about.

        If it were the case that neutron sources could make distant facilities critical, then, for example, the USSR or the USA could have set off nuclear explosions in their own territory and wiped out the enriching capabilities of the opponent and/or destroyed their cities that had power plants with out ever needing to fly to the opponent’s location. If this were possible, no one would ever have built any power plants anywhere because that would be too easy of a target.

        For every 1 meter (3 feet) away from a single point where neutrons are emitted, the intensity of the radiation decreases by 92%. At a distance of 10 km (kilometers), there would neutron intensity would only be 7.9577*10^-10 as big as it was at the source. As a percentage, my calculator doesn’t have the ability to distinguish the decrease in neutron intensity as something less than 100%. This is also assuming that there was literally a vacuum between the source and the distant plant.

        I could write more, but I have work that I need to attend to. Let me know if you have more questions–I may have more to say later today, also.

  6. Response to Maureen Smith
    Maureen – Let’s try to address your “gut”-instincts, by thinking about your body-potassium. So, roughly, you’d best have enough potassium in you to fill a block about an inch & two-thirds on edge, because it does all manner of wondrous things for us, including allowing our neurons to think. Now, a tiny, tiny (~one per ten-thousand) fraction of those potassium atoms are quite peculiar: not only are they stable enough to always be with us (only half vanish in a tenth the age of the universe), but quite-rarely, they triple-route decay (by either beta, gamma, or positron emission). They are radioactive!

    So, to visualize this portion, we have gone from a bit more than a golf-ball of comforting and quite vital potassium, to about as much terrifying p-40, as would fill a space roughly sized so you could think of it as half a rice-grain. Much of the disquietude which feeds our fears of radioactivity stems from the all but un-image-able tiny-ness of the atomic realm. Thus, the facts thus far mentioned, might lead one to surmise, that not much could be happening in that rice grain. The famous historian of the A-bomb, Richard Rhodes, analogized that each fissioning atom releases about the energy of an exploding popcorn kernel, but radioactivity is only a percent or two as powerful. How-some-ever, if you still had half of your p-40 left, or a quarter-rice grain, even should you live for a billion years, you might think not many kernels are a’popping, say, per hour. The fact is, 4,400 of your p-40s blow up each second!

    Potassium is a metal, and should we be able to hold
    our imaginary broken rice grain in our hand—its heat would surely be sensible to the touch. There is no easy way to sort out the rice isotopes from your potassium golf ball, thank Christ, but if there were, and if one could place it in a specific location in our bodies, it would rather magically transform itself from harmless “us”, into something similar to the ultra terrifying menace of inhaled plutonium. Well, not quite similar, because plutonium is an alpha emitter, but, the mechanism which makes microscopic plutonium dust-specs lethally carcinogenic, is their capacity to repeatedly bombard and damage the same adjacent cells in the human lung. This “magical” dimension to ionizing radiation is rather subtle, however. So, for example, one could lie on a bed of metallic plutonium, warmed by its decay without harm, because the alphas cannot penetrate a piece of paper, or your outer layers of un-living skin.

    Now, lets think about the 4,400 decays each second in a 154 pound, typical human, and try to relate this to Dr. Martini’s depiction of the Fukushima radiation enhancement in the Pacific. Simple divisions gives us a potassium shine of 29 disintegrations per second per pound. This is near to the decay rate of each gram of full potassium (31), and about double the dose in a banana, which is fifteen pops-per-second. THIS is our becquerel: One fifteenth of a banana’s p-40 decay rate. One atom-burst per second.

    Thirty becquerels is also the maximum potential enhancement cited for Hawaii, while the Aleutians and West coast could see from 1 to 20—per cubic meter of seawater. A cubic meter of sea water weighs roughly 1030 kilos, and floats 0.04% (wiki—seawater), or 412 grams of potassium. At 31 becquerels per gram, that works out to 12,770 Bq of natural background for each cubic meter of the seas, against which the Fukushima pollution ought be compared. The max Hawaii Fukushima enhancement, expressed as a percentage of this natural p-40 “poison” of seawater, is 2.3 tenths of one percent. And that’s not counting the carbon-14, uranium and thorium floating out there.

    I take this length to respond Maureen, not to lecture or condescend, but because I believe unless humanity crosses over from “gut” to mind in these matters, its chance of passing along an Earth as we have known it, is vanishingly small.

  7. Random findings: (After reading article and lively commentary)

    In 2007, GE CEO Jeffery Immelt told the
    London Financial Times that wind power
    is economically a far better investment
    than nuclear power. (GE previously said that Nuclear Power generation was TOOOO risky and they would be betting/gambling the worth of the company pursuing it)


    (2012) Nuclear waste-burning reactor moves a step closer to reality. Feasibility study shows GE-Hitachi’s proposed Prism fast reactor could offer a solution to the UK’s plutonium waste stockpile.

    So. . .

    Am I to feel good about this direction? As a GE stock-holder? As a simple naïve, out here among the great un-washed – trying to decide to keep or sell my tillable 50 acres?

    I can hear Kenny Rogers singing “The Gambler” in the background. . .

  8. “(2012) Nuclear waste-burning reactor moves a step closer to reality. Feasibility study shows GE-Hitachi’s proposed Prism fast reactor could offer a solution to the UK’s plutonium waste stockpile.”

    Yes, we can trust then THIS time, . . . . . . . can’t we?

  9. This is to respond to the request for information on a possible LOCA (Loss of Cooling Accident), wherein a large part of the cooling water is lost to a pipe break. The LOCA is the single most planned-for situation, and they thought they had every event covered, but it was only hubris, not intelligence.

    1. George: a loss of coolant accident (LOCA) is when all of the water leaks out of the reactor. There are a great many water systems in a nuclear power plant that have varying degrees of earthquake protection. It is pure speculation, and quite human, for those various workers to assume the worst and think that the main feedwater supply had been lost. To this end, that is why there are backup routes.

      The loss of the feedwater supplies (one or all of them) is not a LOCA. What is being described in you link, and agrees with my “insider” documents, is a loss of flow and a possible loss of feedwater systems.

      To see a detailed document of the plant heat transfer systems, check out this document:

      Page 86 of this pdf document (not the actual page number in the document) shows a decent cross section of what the core and main pressure boundary looks like. What should be noted is that as loss of the ability to put water into the containment is not a LOCA. These BWRs are a little different from other power plants because the shape that is shown on page 86 IS the containment–it is a totally different style than in a PWR. All of those outer concrete and steel buildings are not the containment. Check out page 25 of the pdf (again, not the document’s page numbers) to get an idea of the number of things that could have been leaking–and that is just the primary system, no backups shown. All fluid systems would be equipped with “check valves” in several locations to prevent the backflow of water from a pipe that has sheared or ruptured.

      Another great document is this one:

      It was produced in Germany and gives a good description of one of the accident time sequences.

      1. It also seems clear that the people that stole the truck knew what was in it. Given that the source is dangerous, why was it not guarded? This is a story about corruption.

  10. Mexico, Mexico Mexico.

    Our southern neighbor who we treat as an unwanted step child – except for oil and cheap labor to assemble our cars etc.

    It’s now being taken over lock stock and barrel by drug cartels. They are diversifying. Smart business model? Wait till they step on the toes of our beloved corporations . . . You thought the Iraq invasion was “shock and awe”?

    But, staying on point. What is happening around the world to nuclear stock piles (waste) – the reactors, at least a great number of them, are very close to waterways and I think the waste is being stored nearby. Scientists agree that the ocean level is expected to rise, and hurricanes, typhoons etc. are getting stronger. Is this being addressed in a mature manner. Is it being given more rational consideration than rebuilding a rollercoaster on the New Jersey coast??

  11. Before I go, I have one Question for Neutronium: You did a thesis on Neutron sources? Krytrons, perhaps? Do you work in the world of “boosted fission”, of tampers and Beryllium?

    If so, we have another full field to discuss.

      1. I find that just as interesting. I worked with 0.5 to 3.0 MeV electron beams for industrial purposes and industrial CW lasers. Also interesting stuff.

        How do you accelerate a neutral particle?

  12. BTW, TEPCO itself says there were 22 fuel rod assemblies of unirradiated fuel, whether it makes sense or not.

    I think it ties to the speculation of what they were doing with Mox. I do not believe the theory of neutron-activated flux causing an explosion in Unit four. But how did it happen?

  13. “George: a loss of coolant accident (LOCA) is when all of the water leaks out of the reactor. There are a great many water systems in a nuclear power plant that have varying degrees of earthquake protection. It is pure speculation, and quite human, for those various workers to assume the worst and think that the main feedwater supply had been lost. ”

    I got my information from the words of one of the workers, who said a major break occurred, and the radiation detectors on the periphery of the plant went off at the same time. It was minutes before the Tsunami.

Comments are closed.