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211 Responses to Comments

  1. repstock1 says:

    I presume that boron is not injected simultaneously because this would destroy the nuclear fuel even in the case of a false alarm, precautionary shutdown.

    • mitnse says:

      No, it is not injected simultaneously. Injection of boron would not destroy the fuel, but it does disrupt the water chemistry of the plant, and as such it’s delayed until absolutely necessary.

  2. repstock1 says:

    One further question:
    How much work has been done on processes which would allow Hot Shutdowns in cases like Japan, where there was no warning of catastrophic events? Is it even possible to subject the nuclear materials to processes or forces which would halt the nuclear reaction within the fuel rod assemblies?

    • mitnse says:

      When an unforeseen event like an earthquake occurs, signals within a power plant cause control rods to be inserted within the reactor, stopping the fission chain reaction. This is standard practice.

      The reactor continues to produce a small amount of power as a result of the decay of radioactive isotopes within the fuel (see our post on nuclear reactor decay heat for more). There is no means by which this can be avoided.

  3. leonalan says:

    The helicoptor dumping of water could be vastly improved if they used frozen water instead of the liquid phase. They could pick a temperature, size and shape of ice to minimize the wind drift associated with their water drops. Bombing could also occur from a high AGL (Above Ground Level) and reduce radiation exposure.

  4. What is the total amount of nuclear fuel at Fukushima Dai-ichi? They tell the number of fuel rods. I want to know how many tons.

    • I am guessing myself. Wikipedia(jpn) says a reactor consumes 69-94 tons of UO2/MOX per year. Assuming one load contains a couple of years of fuels, the total amount in six reactors is more than 1,000 tons. Please correct me if I am wrong.
      By the way, thank you very much for providing so much reliable information so far.

  5. repstock1 says:

    Do you know what instrument took the “Mext” readings shown in the tables? Was this an airborn instrument?

  6. dogsafire says:

    The problems being faced at Japan’s nuclear power generation plant once again have me asking why molten salt reactors have not supplanted the PWR design. MSRs seem like the nuclear industry’s dream come true, yet they seem to be completely ignored. What is the fundamental flaw with these reactors? We no longer need the plutonium produced by conventional reactors. It would seem that a billion or so dollars saved in construction costs for each reactor (over a PWR) would go a long way toward solving any remaining technological problems.

    Why is the MSR not receiving consideration?

    • mitnse says:

      The MSR concept has not been completely ignored. In fact, it has been the topic of research at MIT and at other institutions in recent years. The issues with them are the same as those present when the MSR was conceptualized:

      1. The salt is quite corrosive, and we’re as yet unable to deal with that.
      2. By not having a fuel cladding or pellet, we remove the first two barriers to radiation release. A simple pipe break would coincide with fuel and fission products being released to containment. The concept has other safety advantages, of course, but this disadvantage is one which our regulatory structure isn’t likely to approve.

    • dogsafire says:

      Thank you for that.

      The pelletization/cladding sounds like a straw man. These techniques have failed to provide barrier to radiation release in loss of coolant accidents. And I have difficulty believing that appropriate safeties could not be devised.

      The corrosion issue, though, I was unaware of. I had heard that the moderator had to be refurbished on a regular basis. Is this what you’re referring to? Or is it the piping of the system? Could you point me to some literature on that? I found corrosion references, but nothing indicating that it was the technologically limiting factor. Since there is no significant pressure in the system, it would seem that the corrosion would have to be very severe to affect operation and/or safety.

    • mitnse says:

      Your assessment neglects a broad variety of small loss of coolant scenarios in which release of fission products is prevented by the fuel and cladding structures.

      Most metals corrode badly when in contact with either chloride or fluoride salts. If you read up on the Aircraft Reactor Experiment and the Molten Salt Reactor Experiment of the 1950s and 1960s, you’ll see that this led to the development of Hastelloy N, which is a better candidate for a vessel and piping than others available. However, it’s costly, and it would still require more frequent replacement than most of the components in today’s plants.

  7. amac78 says:

    There is a presentation from March 16, 2011 that gives a comprehensive introduction to the physics and health physics of the Fukushima situation, aimed at a lay audience. The slides are excellent, in my opinion (I haven’t listened to the accompanying talk).

    “Asst. Professor Benjamin Monreal, U. California-Santa Barbara Department of Physics, [gives] an overview of radioactivity and reactors, radiation health and safety, and the ultimate fate of the materials coming out of the stricken reactors in Fukushima. Why is it worse than Three Mile Island? Why is it (probably) not as bad as Chernobyl? How worried are scientists? How worried should you be?”

    How Bad is the Reactor Meltdown in Japan?

  8. You wrote “…water would partially boil, and partially stay in place to continue cooling. Since the rods continue to generate heat, a long-term supply of cooling fluid is needed…” and later wrote “…measures have been and will continue to be taken to prevent re-criticality of the fuel. The pools already contain borated water and solid structures containing boron, and any additional water added to the pools will likely include additional boron.”

    Does the boron dissipate with the boiling away of the water, or stay concentrated in the pool, as only the water, but not its dissolved substances, boils away?

  9. az31 says:

    I have several questions:
    1. The explosions of reactor 1 and 3 looked very different. I am well aware that an explosive mixtures of H2 and O2 can be achieved in a very long range but the explosion at R3 also seemed to bring high ammounts of concrete and steel to at least 300 m to 400 m. There is massive damage on the areal pictures and i did not see any concrete structures inside the debris. If the readings published by NISA were to be correct (see 2) the reactor would not seem to stand straight up anymore (A= -1950, B= -2300 measured from top of rods). Do you aggree with the assesment, that the explosion of R3 was a hydrogen explosion?
    2. Do you believe that any of the measurements in the reactors published by NISA can be correct, or has the measurement equippment been damaged? To me the latter seems to be the case. R2 rpv had massive negative pressure of up to -79 kPa, R1 rpv pressure A and B were moving independently up and down.
    3. Is there any other way of knowing what is going on inside the reactors?
    4. The containment vessels of R1 and R3 are being continiously filled with sea water in case of a breach of the rpv is there enough time to make sure there is no water left?
    5. What would happen in a scenario in which this were not the case?

  10. Hi, here’s the last local news broadcast update on Japanese TV on today’s crisis management moves (it’s transcribed as closely as it was heard in Japanese-English translation, and so comes across as somewhat stilted). And it gives an idea of the reasons behind the change of power restoration as a priority targets (which is excruciatingly suspenseful for us because it postpones the pumping of seawater to the reactors later). I hope it will not be a fatal move. Anyway, here’s the transcription:

    – First off, they addressed the issue of why the disaster rating of 4 has been raised to 5 and why the Fukushima crisis is being to the Three Mile Island incident: because more than 3% of the radioactive heat [s-i-c] substances are being released from some of the reactors. Tokai Criticality incident was rated level 4.

    The expert being interviewed said that the current crisis is still not as serious as Tokai criticality or Chernobyl – fact:here the nuclear fission process has stopped therefore categorically different from Chernobyl.

    – There was an hydrogen explosion so the earlier spray-dousing operation by firetrucks and the scheduled nightime operations have been suspended.
    But the fuel rods have to be flooded in order to see some cooling effect.
    Judging from the radiation monitoring figures – before the dousing operation of no. 3 reactor: 3,484 microsieberts –> after: 3,339 a declining effect is seen. Once the fuel rods pool is covered, then we will be able to cool rods further and containment of radiation will be possible by submerging the fuel rods.

    Thus, today was the 1st successful step taken.

    – Around the reactors 150 microsieberts was the highest reading today – compared to 170 microsieberts yesterday – 50-60 at other spots, so no immediate threat to health.
    Radiation can damage DNA but body cells can be irradiated – exposure up to 1,000 levels body cells can be repaired and within [? indoor exposure or within the body? not clear], the exposure is one-tenth compared to outside.

    – Tokyo Fire Squad were seen in action today …blah blah blah
    interviewer- while understanding that the gov was preoccupied by tackling the reactor crisis urged the gov. to give as much accurate information and some kind of guidelines to people on what to do. Not knowing was hardest.

    – Re reaactor no 4 it’s hard to figure out whats happened there. TEPCO disclosed blown up photos on the TV screen of no 4 reactor
    Image of some white vapour was seen suggesting presence of water. Discussion of location of pond in which part of the building.
    The hydrogen explosion that occurred indicates the possibility that some of the fuel rods are exposed. It is thought that some water is in the pond but it is not known how much – from the photo some glinting light in the corner is seen – thought to be possibly water.

    – Scheduled further hosing operations were postponed tonight – why?
    Because (it was decided that) the restoring of electricity now takes priority.
    Discussion of how the reactor systems could have ended up in this situation – the loss of the cooling system, and then the loss of backup power by all the reactors – nobody could have imagined such an eventuality was possible.

    Important to note that when the nuclear reactors stopped, 6% of the heat was emitted. After the lapse of 7 days, less than 0.5% of heat – this means the heat level is gradually on the decline – but it is a paradox, we need heat in order to effect cooling.

    – Nos 1&2 now being given priority, but nos 3 &4 and repairs to 5&6 reactors all have to be tackled. How is the priority decided?
    Why is no. 2 now chosen as focus of power cable connection focus?
    Answer: Because the building nos 1&2 reactor buildings without damage, they are easier to focus upon in terms of restoration of electricity. And because no. 2 is the only with intact building structure – this makes it like a shield for heat, and harder to cool the fuel rods from without, therefore it should be given priority.
    In restoring power, the biggest problem is how to shield the workers.

    There are diverse cooling systems – the task is now to determine which cooling systems among the reactors are operable. Also which pumps – some pumps were exposed to seawater.
    [Video of control room panel and staff are shown]
    The need for electricity is crucial so that the control room can be operated again to ascertain which reactor equipment and pumps are still operable. Some of the control panel measurement equipment may be damaged. But following containment (of radiation) and resumption of power, the [strategy/priorities for tackling] reactor procedures will become clear.

    Radiation levels to which workers are exposed:

    Reactor no 1 – 10 millisieberts
    Reactor no 2 – 15 millisieberts

    Up to 100 millisieberts is allowable for disaster workers – but it[repairwork] is going to be hard work carried out in the dark in the race against time.

  11. llnola says:

    Thank you for making things clear for everyone.

    Considering the levels of radiation (lethal?) at the plant, I don’t understand why robots haven’t been used to cool the fuel rods. Is this not possible?

    • mitnse says:

      The doses to workers are being controlled by minimizing the time spent in the areas with the greatest radiation hazards.

      We’re not aware of whether any robotic equipment is available, or operational.

  12. simonofthebollocks says:

    thank you very much for providing this information. it has been very informative and the very definition of fascinating.

    i think a lot of people (myself included) think of radiation as something sinister, mysterious and barely understood even by scientists. this blog has helped dissipate those fears and enabled a more measured understanding.

  13. amac78 says:

    This is a for-the-record question that concerns a puzzling aspect of the 11 March design failure of the Fukushima Daiichi complex, with respect to tsunami preparedness. (You get this because you obviously read the comments!)

    Ian Hore-Lacy, a spokesman for the World Nuclear Association, was quoted by Bloomberg on 3/15/11 as saying, “Japanese authorities designed backup electrical generators to withstand waves 6.3 meters high, below the 7-meter surge that knocked out power at the [Fukushima] plant, disabling vital cooling systems.”

    This portrait seems to be inconsistent with the extent of the damage wrought by the waves at the complex, e.g. as shown by before-and-after satellite images. The tsunami disabled all backup generators, perhaps sweeping them off their pads. Fuel tanks, small outbuildings, cars, and equipment were all carried away. The sea reached well inland from the reactor buildings themselves. It seems to have flooded all the reactor buildings’ basements, submerging and perhaps ruining key electrical interconnects for all AC-operated emergency cooling systems. Access to fresh water was lost. Apparently, debris also fouled many of the plant’s seawater intakes.

    7.0 meters versus 6.3 meters: I find it hard to understand how a sea level rise that is only 70 centimeters higher than the design criteria could have accomplished all of this destruction, even post-earthquake. Design-plus-70 cm didn’t lead to the loss of one key system at one reactor, but to the loss of multiple key systems at all reactors. This is not fault tolerance, or “failing gracefully.”

    Perhaps 7.0 meters is an underestimate for this location — could local geography have somehow amplified the tsunami at the site?

    However, I wonder whether the “designed to 6.3 meters” claim refers to something non-obvious. For example, “a 6.3 meter tsunami that arrives at the lowest low tide of the year.”

    Though it does seem that the tsunami struck Fukushima Daiichi 90 minutes after the low tide mark. This online tide-chart engine gives the tides for March 11 at Ottozawa, Fukusima (sic) (very close to the complex) as:

    2011-03-11 06:45 JST 1.30 meters High Tide
    2011-03-11 14:10 JST 0.24 meters Low Tide
    2011-03-11 21:02 JST 0.89 meters High Tide

    The quake struck at 14:46 JST.
    The diesel generators failed at 15:41. ( IEEE Spectrum timeline)

    It seems to me that this paradox needs to be understood and explained, or the lessons that are learned from this catastrophe will be incomplete.

    • haroldancell says:

      Remember that this is in the context of a fantastically energetic “megathrust” earthquake that may have damaged the sea walls etc. and that also appears to have caused a lot of the coast to drop by around 2 feet. One of the interesting things that I noticed when reviewing that last link is this very interesting comment:

      A quake of this size usually has a rupture length of at least 480 km (300 mi) and requires a long, relatively straight fault line. Because the plate boundary and subduction zone in this region is not very straight, it is unusual for the magnitude of an earthquake to exceed 8.5; the magnitude of this earthquake was a surprise to some seismologists.

      So not only was the quake way beyond the design parameters of the plant it was perhaps beyond the reasonably foreseeable design parameters. And since the scale is logarithmic the jump from 8.5 to 9 is big (and there’s a lot more to the effects of any earthquake than just that one number, e.g. that last link claims this earthquake released almost double the energy of the 9.1 magnitude “Indian Ocean” one in 2004).

  14. pbaldo says:

    I am curious why 3 of the 6 reactors were off line at the time of the earthquake.
    We are told that the up time of nuclear power plants these days is around 90%, which would imply 5 reactors running, one down for service.

    • mitnse says:

      Those three reactors were down for refueling and other maintenance activities. We don’t know why three were being refueled at once. The 90% capacity factor you’ve heard refers to the fractional amount of time that a reactor is at full power. So if those three reactors are at full power 90% of the year, that means a 90% capacity factor. It doesn’t have to mean that 90% of available reactors are operating at one time.

  15. For the first time today, in Q&As on local news, the question of whether criticality would be reached – was brought up but nobody has bothered to explain criticality. Would you be explain? (We are always grateful for and amazed at your fantastic and easy to understand expositions for lay people like us.)

    • mitnse says:

      Criticality refers to the sustained fission chain reaction. If any of the fuel material were to achieve criticality, the heat produced by the fuel would increase and new fission products would be produced. For this reason, efforts at cooling the facility have made use of borated water, since boron absorbs neutrons, preventing that chain reaction from becoming sustainable.

  16. siggy7 says:

    Can I add to the weight of comments above praising your blog for the breadth and depth of information you are supplying. I have one comment about your article on “Meltdowns”. I work in the nuclear industry in the UK, and here we would describe the melting of the Zircaloy as a “Fuel Clad Melt” event. A meltdown implies significant fuel clad melt, leading to production of significant quantities of corium and damage to the reactor structure. Now that the Fukushima reactors have been shut down, a meltdown in our use of the term is extremely unlikely given that power levels are about 0.5% or less of steady-state full power operation.

    • mitnse says:

      Thanks for your comment. In light of the confusing and incorrect information out there, our post was intended to describe a sequence of events which may have already completed, or be in progress.

  17. Hi, updates again, from 2:30 news report

    They’ve just finished 3 rounds of spraying from SDF fire engines, an operation begun from 2 pm at no. 3 reactor. A planned total of 50 tonnes of water from 7 fire engines (1 report says 6 but SDF spokesperson says 7) is going to be discharged in total today at reactor no. 3. There’s a break right now as water has to be sprayed at intervals of 5 – 10 minutes. They were planning to line up a few fire engines at the same time but found that the rubble and debris on the site was hampering them so that they could only go one fire engine at a time. So far 3 rounds of spraying have been conducted, and right after, the LIVE FOOTAGE showed larges plumes of black smoke billiowing off towards the sea. This they say could be evidence that the dousing was effective. Altogether 100 tonnes is necessary, so they say the operation may extend over several days.

    On a separate operation, Tokyo Firefighters’ Department is mobilizing 28 out of their 30 vehicles at Iwaki base and moving to the advanced base at Fukushima.

    Operation still ongoing…

  18. steffenfrost says:

    TEPCO and other sources give uncertainty as to the water level of the spent fuel storage tanks. To get a better look-see without getting a lethal dose of gamma, would something like this help?

    (not affiliated with the company)

  19. unclearthur2 says:

    Terrific blog, better info in an hour here than 24 hours of CNN, ABC etc.
    2 questions:

    i) Lots of discussion of radiation levels outside the plant but little of what contamination (eg Iodine, Cesium ….) there is. Given the radiation levels outside the plant are relatively low, isn’t contamination the bigger issue? (ie the short lived stuff will disappear but Iodine and esp. Cesium will be around for a while)

    ii) Everything (reactors and fuel storage) depend on keeping things cool. I can’t understand why in the 1st 72 hours after the accident enough capacity in portable generators and pumps wasn’t brought in. There is plentiful water (and water access to the site). I can understand some of the challenges in getting cooling into the reactor ….. but the fuel storage pools, at worse you can just pour water on top to keep it full. Obviously letting the stored fuel go dry has compounded their problems massively because of the high radiation fields. I am missing something here. What stopped them from setting up enough temporary pumping capacity early on?

    • mitnse says:

      i) Those contaminants are part of what is contributing to the radiation field. The reason we keep discussing those two in particular, however, is that they’re easily aerosolized, and chemically reactive.

      ii) Much of the difficulty concerned flooding of electrical switching stations. For a period of time, it was impossible to make electrical connections with the emergency power supplies which were brought in. Our understanding is that the crew on site is working to remedy this.

  20. Re: your graph “Relative Amount of Nuclide vs. Time (Half-life)”
    Since the graph refers to a decaying nuclide the x-axis should read “Relative Amount of Radionuclide”.
    The y-axis is confusing because neither 0.5 of the initial amount nor one half-life is a labeled amount on the graph. I doubt that many people who don’t already know what “half-life” means will “get it” from this graph.

  21. theyads says:

    Thank you so much for hosting this information. I wish the media was more responsible in their reporting but since they are not it is great you all are willing to put the time into helping keep the rest of us informed in an straightforward analytical way as well as providing the facts and science we need to contextualize what is occurring.

  22. gweschuck says:

    Sorry for the massive post, but it is terribly interesting. The first statement is most interesting. It shows how these things have been considered historically.

    Wesley Williams, Ph.D. Course 22 (2007)

    Peach Bottom is a Mark I GE BWR similar to those in Japan.

    If you go check out Peach Bottom’s PRA you can find the following statements:

    “Also presented in
    these displays of containment failure information
    is evidence that there is a high probability of early
    containment failure during external events such as
    fire and earthquakes. Specifically, the seismic
    analysis indicates that the conditional probability
    of early containment failure from all causes, i.e.,
    direct containment structural failure or related
    failure from the effects of a core damage event,
    could be as high as 0.9.”

    “The Peach Bottom containment is maintained
    in an inerted state, i.e., nitrogen
    filled. This inerted containment condition
    significantly reduces the chance of hydrogen
    combustion in the containment, thereby removing
    a major threat to its failure. However,
    hydrogen combustion in the reactor
    building is a possibility for some severe accident

    “In the BR seismic analysis, the probability of
    containment survival in a severe accident is small;
    the increased likelihood of early containment failure
    is the result of substantial motion of the reactor
    vessel and subsequent damage to the containment
    during a major earthquake (well beyond the
    plant’s design level) and a reduced recovery potential
    that increases the likelihood of containment
    failure as described for the fire sequences.”

    “Peach Bottom Plant (Mark I Design)
    * The analyses indicate a substantial likelihood
    for early drywell failure in severe accident
    scenarios, primarily as the result of direct
    attack of the drywell shell by molten core debris.
    * Considerable uncertainty exists regarding the
    likelihood of failure of the drywell as the result
    of direct attack by core debris. Although
    this is the dominant failure mechanism in the
    analyses, other loads on the drywell can lead
    to early drywell failure, such as rapid overpressurization
    of the drywell. A sensitivity
    study was performed in which the drywell
    meltthrough mechanism of failure was eliminated.
    The resulting reduction in mean early
    containment failure probability was from
    0.56 to 0.2 (Ref. 9.3).
    * The principal benefit of wetwell venting indicated
    by the study is in the reduction of the
    core damage frequency. Although venting is
    not effective in eliminating some early drywell
    failure mechanisms, venting could eliminate
    other sequences that would result in
    overpressure failure of the containment.
    * There is substantial potential for the arrest of
    core damage prior to vessel failure. The likelihood
    of containment failure in arrested scenarios
    is small.
    * The likelihood of early containment failure is
    higher for fire and seismic events than internally
    initiated accidents because of the decreased
    likelihood of ac and dc recovery resulting
    in higher drywell shell meltthrough

    “In the RSS analyses for the Peach Bottom plant,
    two sequences dominated the risk: a transient
    event with loss of long-term heat removal from the
    suppression pool and an anticipated transient
    without scram (ATWS). Loss of long-term heat
    removal is an extended accident in which heating
    of the suppression pool leads to overpressure failure
    of the containment and consequent loss of
    makeup water to the vessel. With the procedures
    now available to vent the Peach Bottom containment
    to outside the reactor building, the likelihood
    of loss of long-term heat removal leading to
    core meltdown has been reduced to the point
    where it is no longer a substantial contributor to
    core damage frequency or risk.”

    “Hydrogen combustion is not a threat to the Mark
    I design because it normally operates with a nitrogen-
    inerted containment and thus has insufficient
    oxygen concentration to support combustion.”

    “Direct attack of the drywell shell is the dominant
    failure mechanism at vessel breach in the Peach
    Bottom plant. Overpressurization can also lead to
    leakage failure in the drywell by lifting the drywell
    head or to failure in the wetwell.”

    “BWR risks are driven by events that fail a
    multitude of systems (i.e., reduce the redundancy
    through some common-mode or support
    system failure) or events that require a
    small number of systems to fail in order to get
    to core damage, such as ATWS sequences.
    The accidents important to both early fatality
    and latent cancer fatality risk at Peach Bottom
    are station blackouts and ATWS;”

    “The NRC has performed an assessment of the
    need to improve the capabilities of containment
    structures to withstand severe accidents (Ref.
    13.1). Staff efforts focused initially on BWR
    plants with a Mark I containment, followed by the
    review of other containment types. This program
    was intended to examine potential enhanced plant
    and containment capabilities and procedures with
    regard to severe accident mitigation. NUREG-
    1150 provided information that served to focus attention
    on areas where potential containment performance
    improvements might be realized.
    NUREG-1 150 as well as other recent risk studies
    indicate that BWR Mark I risk is dominated by
    station blackout and anticipated transient without
    scram (ATWS) accident sequences. NUREG-
    1150 further provided a model for and showed
    the benefit of a hardened vent for Peach Bottom
    (discussed above and displayed in Figure 13.1).
    The staff is currently pursuing regulatory actions
    to require hardened vents in all Mark I plants,
    using NUREG-1150 and other PRAs in the costbenefit

  23. crayonwalls says:

    In one of your posts you mention that radiation drops as you move further away from the source as 1/r^2. I was wondering whether its possible that the radiation source could be transported through wind currents, or other mass transfer effects? This would effectively shift the source of some of the radiation, potentially resulting in higher readings than otherwise predicted, in say Tokyo or other nearby cities.

    Do you know if the radiation measured in Tokyo in line with the r^-2 law?

    Also, thanks for your efforts in providing some really informative coverage of these events, much appreciated.

    • This is the local NHK news report and following Q&A session just in between 1 -2 pm. Pardon any layman errors and attempt to repeat as verbatim as possible what came over the TV:

      The translator was a little garbled sounding today, worse than listening to the news in English… but it will make sense combining NHK, TEPCO and the Q&A session with U of Tokyo professor… here goes:

      Today, efforts are two pronged and concurrent operations are being launched: power connection to get cooling system up and running – and getting the waterpump working – and to continue to douse reactors 1, 3 and 4 by firetrucks.

      Status of reactors:
      No 2 still has water
      No 1 – water is most depleted (According to the U of Tokyo professor no 3 is most depleted)
      No 3 Water was pumped in yesterday – the radiation levels went down slightly – the level is deemed to have stabilized, but more water needs to be pumped in to bring the temperatures down and to cool much further. With the experience of the first attempt, They are studying how to improve accuracy of bringing water into reactor no. 3 before making the second attempt.
      Radiation levels before operation: 309 microsieberts
      Radiation levels after operation: 292 microsieberts
      Radiation levels this morning: 271 microsieberts (i.e. gone down slightly and remains stable.)

      No 4 still has water however the level of water is decreasing and fuel rods are exposed (as per yesterday’s report)

      30 firetrucks have been harnessed and are in place though not all can be mobilized at the same time due to space and strategic considerations. Operations on reactors no 1 and 4 cannot go on concurrently – something about their positioning. So today firetrucks will target nos 1 and 2 concurrently first.

      Power and Water pump operation:

      Goal: To restart cooling system, they need to connect the power cables in order to bring in electricity from external sources. According to earlier report, they have already connected the cables to a relay station near the reactor building and are attempting to connect the cables to a transformer at no. 1 building via the reactor no 2 building (sounds complicated I don’t understand this myself). According to the later report, they have extended the cable and are establishing a circuit board to connect the power lines to the reactor buildings’ internal cables. This job should normally take half a day. However, because the electrical workers are fighting radiation levels of 20 millisieberts per hour, they may take longer in trying to connect the internal cables to the external power cables. But this is crucial, because once the circuit is completed, the internal pumps will be able to work with the running power cables. And once the power is reactivated, they will be able to get the water circulating side the reactor system and the cooling system will be up and running.

      The firetrucks may begin spraying operations as early as 2 pm.

  24. mgarbin1 says:

    The answer that liquid nitrogen would be boil off immediately is true BUT enough would allow everything to cool down so THEN water could be used on a less temporary basis. Isn’t that the first objective, STOP the spiral? Why doesn’t this give them the most valuable thing right now ie Time?

    • mitnse says:

      It could potentially provide time. It could also cause all of the material with which it comes into contact with to shatter. This could exacerbate problems by releasing dusts into the air, and by placing the system into a geometric configuration which is not easily cooled. It’s an interesting idea, but comes with its own problems.

  25. imthatoneguy says:

    Do we know what the end-game is at this point? I thought the goal was to wait for the residual heat in the core to be released, but if the reactor that was disabled months ago is also boiling off its water does that mean that the newly deactivated reactor cores would still need continuous cooling for months and years? Your chart put the temperature output at something less than 0.5% already. If it’s still a crisis situation with 0.5% will we not still be in a crisis situation at 0.1% months from now?

    Certainly we can’t keep up the current response for more than a few weeks. What’s the longer term solution?

    • mitnse says:

      Nuclear fuel needs to be cooled for a long period of time, on the order of a year, before it is of low enough power level to be moved to a dry cask. This is why spent fuel pools are used to hold the fuel discharged from a reactor.

  26. gweschuck says:

    Finally some clear facts. I am not sure what is worse news senstionism or pro-nuclear spin. I love MIT.

    Can someone please dig up and post some of the technical history of Mark I containments? I seem to remember a fiasco over design flaws and fixes that actually bypass containment in order to “save” containment from failure. Likewise can someone elaborate on hydrogen recombiners and why there are hydrogen explosions occurring in spite of nitrogen inert gas inside the containment.

    Furthermore, why is spent fuel stored on site at a highly seismic zone, isn’t there something else that can be done with it?

    • mitnse says:

      We’ll work on posting about Mark I containments, as there have been a lot of questions about them.

      As for your question on hydrogen: the hydrogen explosions occurred in the secondary containment structure, which is not inert.

      Spent fuel is stored on site for a period of time, because, as recent events have made clear, it needs to be cooled by water until the decay heat is low enough that it can be transferred to dry cask storage. It’s not feasible to move the fuel over long distances while maintaining water cooling.

  27. clarkbeast says:

    Attempts to get water in the spent fuel pools at #3 and #4 by helicopter airdrop and water cannon appear to have been, as of yet, relatively unsuccessful. Current reports suggest that restoration of external AC power is progressing and that the plant’s internal pumps might be able to come back on line and refill the pools.

    But what if the pools have lost their integrity and are leaking/unable to be filled, whether the problems are cracks in the concrete structure or damage to the associated piping? If the pools cannot adequately hold water from any source, what would Plan B look like?

  28. arcatdmz says:

    Dear members of MIT NSE,

    I am a graduate student at the University of Tokyo.
    On behalf of Japanese, I would like to thank you for your effort to provide a detailed, precise but easily understandable article about the Fukushima plant.
    I thought that the revised article is rather worth reading than the original article which was already translated into Japanese by several people.

    Therefore, I and my friends have translated your “Modified version of …” into Japanese.
    We have not only translated the article but also added figures (some from Wikimedia, others created by ourselves)

    I uploaded the translated article here:

    Please add a link to our article in yours if it helps.

  29. Thank you very much for maintaining this blog. It really helps to make the situation more understandable.

    My question is in regards to the spent fuel rods and the stainless-steel lined, concreate storage pools, which, according to the diagrams I have seen on the New York Times and elsewhere, seem to be located above and off to the side of the reactor, but without much other containment, other than the roofs which have been damaged by explosions.

    (I hope these are not ignorant questions. It’s been a long time since I took high school chemistry, and I never took physics.)

    Under normal operating circumstances, how long do fuel rods last? And how many are there?

    Once fuel rods have spent their fuel, I imagine the reactor is shut down cold for maintenance, the rods are removed and replaced with new ones. Are they replaced all at once, or are they replaced one by one?

    Could you describe the replacement process in general terms? How are they handled? Is this some kind of an automated process? How do the spent fuel rods (which to my understanding are highly radioactive) get from the reactor to their new home in the big pool on the roof? Is this a temporary storage place? Do they eventually get refilled or placed into dry storage somewhere?

    Finally, what is the technical reason for storing spent fuel rods so close to the reactor? Is is safer to store them there (less handling and transport) than moving them to an area on the Daiichi site farther away from the reactors?

    I understand that when designed nuclear power facilities, there needs to be a certain economic use of space, but it also seems that having these rods stored so near the reactors is exponentially compounding the gravity of the workers’ radiation exposure situation and greatly impeding their ability to bring the situation under control.

    Thanks in advance for your help.

    Brandon Ferguson
    Dublin, Ireland

    • mitnse says:

      > Under normal operating circumstances, spent fuel can be stored in the pools indefinitely. An active cooling system is in place to remove the residual decay heat and the water also provides effective radiation shielding. The amount of fuel that can be stored into the pool can vary according to the capacity of the pool itself, but most spent fuel pools are design to be able to store many reactor cores at once.
      > During the refueling operation the reactor is shut down, all the areas between the reactor and the spent fuel are flooded with water (to provide radiation shielding) and fuel elements are moved one by one from the reactor to the spent fuel pool where they are re-racked. Refueling can occur every 12-18 months and during a single refueling shut down, up to one third of the fuel elements of the core are replaced. All the operations are conducted remotely under water through cranes and special equipment to avoid radiation exposure to the workers.
      > The spent fuel is usually stored in the spent fuel pool for a number of years, depending on the spent fuel capacity and on regulations, and after that period they are usually dry stored in concrete casks located on the site outside the reactor buildings.

    • tpasser says:

      Thank you guys for this blog. Your help in shedding light on the issue is precious.

      I’ll follow up on Brandon’s question, it seems to me as well that the spent fuel pools are designed to be less safe than the rest of the plant.

      As your post suggests (“What are Spent Fuel Pools”) the containment structure surrounding the pool is not as robust as the one surrounding the reactor. Even if unlikely, the release of radioactive fission products from the fuel rods in the pools is possible: if that happens, the containment could be inadequate. Doesn’t this violate the “depth of defense” principle?

      Tiziano Passerini
      Atlanta, GA

  30. Thanks for the blog, it is a lifeline of sanity and reason for many of us here.

  31. chaevans says:

    Some topics I’d love to learn about:

    The reactor byproducts. I’ve seen iodine and cesium isotopes but a pie chart with all the byproducts, phases, and half-lifes would be informative. I know there’s a lot more.

    Any radioactive dispersion research. Does it dilute by distance squared/cubed/other? How do these 30km and 50km recommendations come about? Are they swags or prudently researched values.

    • mitnse says:

      Thanks for the suggestion about fission products. We’ll see about making a post or FAQ addition about this one.

      Dispersal is a complicated function of the manner of release, distance from the source, and weather patterns. The recommendations released come as a result of both computer simulation of these variables (validated by experiment and the results of previous releases like Chernobyl, atomic bomb tests, and so on) and expert opinion.

  32. Having read through a number of comments, it seems to me that once a power supply has been connected to the water pumps to fill the pools most of the problems, and worst case scenarios that people are speculating will not come to fruition.

    Is that correct in my understanding, that they need water to cool everything down, and a lack of power to run water pumps is the reason for everything heating up?

    • mitnse says:

      Yes, everything is heating up because power to operate pumps has been unavailable for most of the duration of the event. We’ve also received reports that additional pumps are being brought to the facility by Japanese defense forces, the U.S. Navy, and others. We’re not able to confirm whether this means that some of the existing pumps have been damaged, however, it seems that help is on the way.

  33. dpm25 says:

    guys, thanks so much for this blog. amazingly helpful.

    i have a question. It seems a lot of focus now is on the spent fuel pools and this operation to fill them by helicopter. Do any of you know the dimensions/volume of these pools and therefore whether filling them 7 tonnes of water at a time is a feasible way of solving the problem ?

    Also, what do you make of these latest comments that mention reactor number 5, from what we know this was turned off at the time of the quake so why would this be a problem ?

  34. Hi,

    We are a community based in Japan and we follow your reports which are considerably behind current events in Japan – I suppose due to the time difference between US and Jpn.

    While your explanations appear to give the reassuring impression that the situation poses no concern for citizens living outside the evacuation zones, we are unsettled by the widely different worst case scenarios given by various sources – it would be helpful if we could know the worst, when we should expect to be worried and begin evacuation or to stay indoors or to understand the chances of a “meltdown” and more importantly, the reach of such a meltdown on the J. population at large.

    The French and Germans have ordered full evacuations of their citizens, the US ordered evacuation within a 80 km radius. The Brits agree with the Japanese enforced evacuation limits. Why this huge discrepancy even among nuclear experts?

    We have looked at worst case scenarios offered by the few sources available:

    – Emergency Special Report II Quake Monitor: Meltdown has started – Saturday 12 March (noon Japan time zone)
    Meltdown is underway. Japan’s Industrial Nuclear Safety Agency reported that the radioactive isotopes cesium and iodine were detected by a monitoring station in the Fukushima No.1 nuclear power plant. The presence of these substances in air samples is a sure indicator that an uncontrolled chain reaction has started. Overheated uranium rods have eaten through their protective metal casings and have started nuclear fission. The regulatory agency’s announcement overturns the earlier claim of plant operator TEPCO that all uranium rods were intact.

    – No water in spent fuel pool at Japanese plant: U.S. | CTV News

    – How a reactor shuts down and what happens in a meltdown and US Calls Radiation ‘Extremely High’..

    – “The Congressional testimony by Gregory Jaczko, the chairman of the commission, was the first time the Obama administration had given its own assessment of the condition of the plant, apparently mixing information it had received from Japan with data it had collected independently.

    Mr. Jaczko’s most startling assertion was that there was now little or no water in the pool storing spent nuclear fuel at the No. 4 reactor of the Fukushima Daiichi Nuclear Power Station, leaving fuel rods stored there exposed and bleeding radiation into the atmosphere.

    As a result, he said, “We believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures.”

    His statement was quickly but not definitively rebutted by officials of Tokyo Electric Power, the Daiichi’s plant’s operator, and Japan’s nuclear regulatory agency.

    “We can’t get inside to check, but we’ve been carefully watching the building’s environs, and there has not been any particular problem,” said Hajime Motojuku, a spokesman for Tokyo Electric. Speaking on Thursday morning in Japan, Takumi Koyamada, a spokesman for the regulatory agency, said that when it was checked 12 hours earlier, water remained in the spent fuel pool at reactor No. 4.

    “We cannot confirm that there has been a loss in water,” he said.

    On Wednesday night, Mr. Jaczko reiterated his earlier statement and added that commission representatives in Tokyo had confirmed that the pool was empty. He said Tokyo Electric and other officials in Japan had confirmed that, and also stressed that high radiation fields were going to make it very difficult to continue having people work at the plant.

    If the American analysis is accurate and emergency crews at the plant have been unable to keep the spent fuel at that inoperative reactor properly cooled — it needs to remain covered with water at all times — radiation levels could make it difficult not only to fix the problem at reactor No. 4, but to keep servicing any of the other problem reactors at the plant. In the worst case, experts say, workers could be forced to vacate the plant altogether, and the fuel rods in reactors and spent fuel pools would be left to meltdown, leading to much larger releases of radioactive materials

    Another scenario (I can’t retrieve the press report) says the worst case is if all fuel rods eventually fuse together … that there would be a massive release of radiation and that catastrophe is imminent.

    We have been relying on your reports until now, please update us and tell us of your worst case scenario and what kind of contamination or poisoning to expect.

    Thank you,

    Aileen Kawagoe (

    • mitnse says:

      Thank you for your question. We feel it would be irresponsible to pose a “worst case” scenario given the state of our available information. There are simply too many variables, of which we have no knowledge, to be able to guide your community in making sound decisions about if, when, or how to evacuate or take cover.

      We want you to know that your local governments are monitoring current radiation levels closely, and that various scenarios are being analyzed by our NRC’s experts in dispersal of radiation. We do not have access to the results of this analysis, but we know that they are being used to advise local governments on if, when, and how to protect the population. We strongly encourage that you follow any instructions issued to you by your local government.

  35. jdoddsgw says:

    Thanks for this blog. Great work.
    The NYTimes of 3/15
    says the NRC Chairman Jackzo said that the Unit 4 spent fuel pool has little or no water in it. Your blog implies otherwise
    Can you please clarify if possible? Thanks

    • mitnse says:

      We are working to keep the blog up to date with information, as reliable information rolls in.

      Because Chairman Jaczko’s statement differs from those made by the spokesmen of TEPCO and Japan’s regulatory agency, we’ve been waiting for more details.

    • The NHK news has just said that all they know that is that there is still a little water left in the pool but they don’t know how much. They estimate that at least a third of the pool needs to be covered with water to avert disaster and have just tried to pour seawater via one helicopter but the winds were very strong and the water dispersed in a wide fashion – part of the problem was that the roof was still intact though with holes, meaning that not all of the 7.5 tonnes water dumped could reach the pool. They have said this is their last stage measure and today’s operations will be critical. I have no idea why they could not have harnessed a chain of helicopters to storm-waterbomb the reactor, but they seem to be doing just two helicopters at a time. They tried just 4 dumpings of water – 3 on reactor 3 and 1 on 4. After dumping on 3, there were still small plumes of steam – either suggesting the operation wasn’t successful or that according to their explanation, the dumping of the water itself would have set off the steam plumes. There were live images of the aerial operations. As for the cannon trucks (that normally disperse water on rioters), they haven’t even started yet, probably in typical Japanese grid-locked preparations, according to their commentary, they are trying to determine that the conditions are not dangerous to their firefighters. [I suppose that the conditions on the ground must be so chaotic with the wreckage and all that they aren’t able to get many vehicles in.]

  36. amac78 says:

    Barry Brooks’ “BraveNewClimate” seems to be a fairly high quality source of information and analysis (it’s on your blogroll). Prof. Brooks has hosted a guest post by Luke Weston, Design Basis Godzilla. In it, Weston writes,

    There is a small fuel transfer pool in the reactor building at each of these GE BWRs, near the top of the reactor pressure vessel, that is used for the temporary transfer of used nuclear fuel during refueling. However, the longer-term storage of the used nuclear fuel is done in a pool elsewhere on the site. Those storage pools, outside the reactor buildings, are seismically hardened and defended-in-depth, just like the reactors themselves, and there are no indications of any problems with them. Since there was no refueling going on at the damaged reactors at the time of the earthquake, there is little or no fuel in the fuel transfer pools.

    That’s my understanding of the situation, anyway.

    I certainly hope that this is correct. Alas, I suspect Weston is misinformed, and that most or all of the onsite used-fuel rod storage is in the vulnerable pools that are sited up and to the side of the reactor containments (as other reports indicate).

    Can you comment on this question?

  37. axellieb says:

    Greetings from Tokyo and thanks for the cool tone here. The media hype is unhelpful for anyone living here. I know you don’t like engaging in speculation around worst case scenarios but obviously worst-case scenarios are exactly what concerns people living here. So let me ask a few worst-case scenario questions.

    My understanding is that the current greatest worry is the situation around the spent fuel store in reactor 4. The worry is that they might heat to the point where they begin a chain reaction, then melt out of the storage facility and then… well, that is my question #1: then, what? Drop into the concrete catchment base at the bottom of the facility? And what would you estimate as a time-line for this to become a possible scenario? And indeed, is this the biggest worry from a public health perspective?

    Question #2. I understand the difference between acute exposure and non-acute exposure as may be the result of particles blown around by winds. Is my understanding correct that acute exposure is only possible in the immediate vincinity of the plant?

    Question #3. If a “meltdown” of some sort occurs, and active material is exposed to the open air, what sort of consequences would this have for people in the Kanto area (so, the densely populated area to the south of Fukushima, including Tokyo)? Also, is such exposure to air even a possibility here?

    Thanks, and I understand that some of the above is probably way too imprecise and confused to allow any direct answer. Feel free to rephrase my questions to the point where you can give some feedback.


    • mitnse says:


      The spent fuel pool needs to be kept cool because of the heat produced by radioactive decay products within the fuel. The amount of boron ( a neutron poison) contained by the pool means that criticality would be unlikely in the present conditions.

      In the event that the fuel makes contact with concrete, it will start to ablate the concrete at a slow rate, on the order of millimeters per minute. We know this from a sequence of experiments conducted in our national labs over the past two decades. We also know from those experiments that the molten material can be quenched, or cooled down so that it resolidifies, reducing its mobility.

      As for your questions regarding radiation exposures, there are simply too many uncertainties involved to make a good prediction on the impact to the region. We advise that you follow whatever instructions are issued by your local government, should conditions worsen.

  38. philiplevis says:

    Thanks so much for putting up this site and providing simple, accurate explanations. A few of my colleagues were confused on exactly what is going on and I pointed them here.

    Philip Levis
    Assistant Professor of Computer Science and Electrical Engineering
    Stanford University

  39. robroy94030 says:

    Thank you for the clarity you are bringing to this crisis.

    The bottom line is that a series of events led to multiple failures, which are compounded by 6 different reactors in close proximity to each other that are impacting dealing with each complex situation.

    The parallel when flying a plane is the need to “break” the pattern, which usually means landing the plane. In this case, getting power to the facilities will be a good start.

    I need to float a hypothesis regarding the radiation levels. By looking at the pattern of radiation spikes found at:

    One sees that a pattern has emerged from the spikes. Prior to the Tuesday explosion at reactor 2, there was a small spike. It got bigger with the explosion in reactor 2. Outside of the spike, is a window of opportunity to do things to stabilize the cooling systems.

    If we have complications from another problem, we will see more spikes and a randomness will occur.

    The cause of the spikes is unknown, but there is probably a high correlation between the spike and what is going on within reactor 2. It points to a cyclical buildup of pressure, followed by a release that could be explained by cracks in the reactor vessel for unit 2.

    The reactor(s) are talking to us through the release and spiking of radiation. What are they saying.

  40. broncopetroleum says:

    Wouldn’t keeping the fuel assemblies “out of the fire” be a safer alternative?

    I show a diagram of a hemispherically shaped dome for insertion and retraction of the fuel assemblies on my blog at:

    Is there a basic flaw in that (hemi) design or in the std. commercial Boiling Water Reactor Core design? What about the conventionally, close-packed fuel assemblies? The standard configuration looks like the whole works would be very hard to get-to and do much with – important, obviously in a chaotic emergency.

  41. steffenfrost says:

    If the spent fuel rods become damaged due to water loss, couldn’t they melt and congeal at the bottom and come into closer proximity to each other? Adding water to compromised rods could thermalizes (slows down) the neutrons of the remaining uranium pushing the rods back to critical. In this case the cooling ponds become unpressurized open air reactors?

    As long as you maintain the cooling, though higher than managing the decay heat, the water should provide enough shielding to prevent total disaster.

    So what is worse, leave dry damaged rods with decay heat only, or critical rods submerged in a pool?

    • mitnse says:

      Leaving the dry rods would be worse.

      As you mention, water provides shielding–so effectively, that there is an entire class of research reactors which operate open to the air, but submerged in water. In addition, measures have been and will continue to be taken to prevent re-criticality of the fuel. The pools already contain borated water and solid structures containing boron, and any additional water added to the pools will likely include additional boron.

  42. vwerc says:

    Could you explain why the U.S. media is focused on the Fukushima Nuclear Plant incident (where there has yet to be a nuclear-related fatality) while totally neglecting events such as the failure of the hydroelectric dam in the Fukushima prefecture caused by the earthquake which resulted in 1800 homes being washed away and a yet-to-be-determined, but undoubtedly high, number of people killed?

    • mitnse says:

      No, we can’t. But our thoughts are with those residents of Fukushima, and their loved ones, just as they are with those people affected by the events at Fukushima Dai-ichi.

      Our fellow students have been raising money to support the Red Cross in its relief efforts in Japan. We hope our readers will contribute as well, to aid in the massive undertaking of sheltering the survivors of the earthquake and tsunami.

  43. saj0001 says:

    First thank you for this blog, an oasis of sanity in an ocean of fear and political posturing.
    I belive you have a post on radtion levels planned so I’d like to share a point of confusion for me. I understand that exposure up to .25 sievert or 250 millsieverts is safe, but do not know what that means in relation to duration. For example, it is clear getting 300 millsieverts all at once leads to serious health issues. But is getting 100 millesievert exposure over three days just as dangerous? How about over three hours? There seems to be a duration of exposure factor that should be part of the discussion?

    • mitnse says:

      Excellent question.

      We define two types of health effects of radiation: acute and long-term. Acute doses are those accumulated in a time scale short enough that the body is not able to repair the damage caused early in the dose history. Your example of three exposures over three days would fall into this category, and could result in radiation sickness.

      However, long-term doses in these amounts do not result in radiation sickness. The link between long-term, low-level doses and biological effects such as cancer is complex.

  44. ghomem says:


    Everything is hard under several days of stress, huge responsabilities in hands, power outages, broken roads, etc.

    It is however not understood what went wrong for not being possible to deploy new generators during the 8 hours of battery power (metioned on the first post on I guess there should be extra off-site generators that could be moved to replace the broken ones in less than 8 hours, in case of a disaster but ..

    Maybe mitnse know more on this.

    • steffenfrost says:

      @ghomem, my sentiments exactly. When you have the entire resource base of Japan available to you (helicopters, generators, trucks, US Navy, etc.) and you still can’t bring up emergency power within 8 hours (now several days) at a site? Seems inconceivable.

      The infrastructure damage may have been so extensive that even external power wasn’t going to be enough or managerial incompetence.

      The post mortem on this situation will hopefully give answers on this.

    • Sorry for earlier error, I meant 1,300 tonnes (not 1.3 tonnes) estimated for the size of the pool probably more. i.e. helicopter is drop in the bucket. They would need 100 helicopters according to their calculations.

      I’ve just received this, I don’t know being a layman but the figures sure make things look a whole lot worse all of a sudden.

      Source: communication from Ed Turner

      All of Chernobyl was 180 tons.

      At Fukushima:
      Reactor# fuel
      #1 70 tons
      #2 90 tons
      #3 90 tons
      #4 90 tons
      #5 90tons
      #6 150 tons

      Spent fuel being stored next to the active fuel.
      #1 50 tons
      #2 100 tons
      #3 90 tons
      #4 130 tons (hottest)
      #5 160 tons
      #6 150 tons

      The older spent fuel is less hot.

      about 1400 tons

      Ref: 19 mile radius dead zone around Chernobyl today, happened in 1986

      Could you comment?

  45. steffenfrost says:

    Has anyone checked in to see what the status is of the Common Spent Fuel Storage Pool at #Fukushima and how is it holding up after being inundated by the Tsunami?

    Here is the November 2010 powerpoint from Tokyo Electric Company detailing how fuel storage works at the huge #Fukushima complex

    Also, how come they are having challenges with cooling ponds for No. 5 and 6? How hard can it be to get a generator and water pump to keep a pool filled with water?

    • mitnse says:

      We don’t at present have information on the condition of the common storage pool, but will look into it.

      The problem with the spent fuel pools is not a want of generators, but a want of electrical connection. Flooding of electrical switch gear has left the generators unable to be put into service.

    • Apparently, it’s very hard. The helicopter dropped only 7.5 tonnes and by the looks of it very little of what was dispersed reached the pool in no. 4. They estimated that on best case estimate of 1.3 tonnes of water needed to cover the rods (the volume of the pool could be more), they would still reqiure about 100 helicopter continuous dousings. (Analysis just off the local news)

    • According to some expert from a university earlier interviewed today, reactors no 3 and 4 have to be priority now … reactors 5 and 6 temperatures are supposed to be half-way to boiling point and by their calculations, the temperatures are rising very slowly and it gives them roughly 1 week to do something about the last two.

      Does anybody know if Dainii is in trouble too, I hope to God no!

    • alitamunich says:

      @heritageofjapan: here you get an updated reactor status report:
      Daini seems to be ok (all green🙂

  46. Windypundit says:

    Pumping seawater with fire engines? Re-filling the spent fuel pools by helicopter? It sounds like nearly all the problems at the Fukushima Daiichi plant would go away if it just had power to run the pumps. Yet I can’t find any information in the news reports about efforts to restore grid power or to bring in generating equipment. Do you have any information about the status of efforts to restore power to the site?

    • repstock1 says:

      CBC Canada is reporting that a new powerline is nearly complete, after hich they expect to resume cooling operations. This sounds promising, as does the huge drop in radiation. I hope it works.

    • mitnse says:

      repstock is correct. TEPCO spokesman Naoki Tsunoda stated this afternoon that the power line was almost complete, but did not specify when TEPCO expected the line to be completed.

    • According to within the hour reports, they are slated to restore power this afternoon, but the pumps have been damaged by seawater and they are working to repair the pumps or use makeshift pumps.

  47. ghomem says:

    “Units 1 and 2: TEPCO has released estimates of the levels of core damage at these two reactors: 70% damage at Unit 1 and 33% at Unit 2. They have also stated that Unit 1 is being adequately cooled.”

    Apparently it is not possible to post comments directly in the articles…

    I wonder what exactly “70% damage” means in a scenario where apparently no one can peak inside the building reactor. How did they estimate the “amount” (whatever that means) of damage? And do they refer to the cement enclosure, to the reactor vessel or to the fuel material?

    In the same post it is written that the workers were evacuated due to high radiation levels. We get the impression that whereas before people stood in the control rooms, now the plant was left empty. Is that what is happenning?

    Regarding the pumping of water, how is is being done? We heard today of “water cannons” being considered which might mean the regular piping is not working. Comments?

    • mitnse says:

      We don’t have complete information on how these estimations were made, or on how the evacuation of staff (which apparently lasted about an hour) took place.

      The water cannons you mention are being discussed as a means of reflooding spent fuel pools which have exhibited decreased water levels. The reactors themselves have been cooled using fire engines, which are capable of delivering water at high pressure to the reactor vessels.

  48. repstock1 says:

    Could you explain what 1500 “microsieverts” means in terms of background radiation and or any health effects. If I read the table correctly, a microsievert is an order of magnitude less than a millisievert.

    • mitnse says:

      A microsievert is three orders of magnitude less than a millisievert. 1500 microsieverts=1.5 millisieverts. This level of dose is not known to result in any health effects.

  49. amac78 says:

    It seems to me that most reports of “radiation” lack enough details to give an accurate picture of the circumstances.

    As far as I know, a given reading (in milliSv or REMs) at the Fukushima Daiichi station is referring to the combined dose delivered by (1) high-energy emissions (eg gamma rays and neutrons) from a nearby source; (2) emissions from rapidly-decaying nuclides (eg Nitrogen-16); and (3) emissions from slower-decaying nuclides (eg cesium-137 and iodine-131).

    Even assuming no ingestion or absorption, these sources are all bad for the (heroic) workers at the site.

    But the type of radiation being measured seems quite important to understanding the implications for the public. (1) and (2) will have lesser effects farther from the plant, and will not cause lasting contamination of the ground. (3) by contrast can travel far offsite, and some nuclides will persist for a long time.

    It would be useful if there was a primer on how this sort of categorization would apply to the reports from Fukushima. What sort of nuclides are contained in the steam being released from the overheating cores (freshwater/seawater, fuel undamaged/melted)? How about from the fuel pools (boiling water/uncovered rods)?

    I may not have described a good classification method, but it’s likely that there is some better way to inform about radiation than the way it’s being done at present.

  50. chandlerphd says:

    Thank you for helping us understand.
    Could you address why this has gotten so bad and keeps getting worse.
    At the beginning it seemed straight forward: keep things cool.

    • shroomduke says:

      I would like to know what a worse case senario might be, if the spent fuel rods in the storage pools catch fire, nuclear experts say, the high heat would loft the radiation in clouds that would spread the radioactivity.

      According to maps it would spread radiation across the Pacific to Canada and the states. This brings to mind the Japanese Balloon attacks during WW II where approx. 1k of 9k reached the US as far as Montana and Texas…

      What levels of Radiation will cause birth defects, cancer etc ?

    • mitnse says:

      Keeping things cool has remained the issue all along–it’s just that our inability to do that for a long period of time presented some complicating situations, such as the corrosion of the fuel cladding, which led to the buildup of hydrogen and eventual explosions.

      Shroomduke, the purpose of this blog is not to speculate on worst case scenarios, but to present the facts in a straightforward matter. The map to which you are referring has been called a hoax by Australian Radiation Services, the agency purported to have released it.

    • Which hoax radiation map are you referring to? I’d like to have the link, and would like to know that I haven’t disseminated misinformation. Who would do such a thing at such at time ….jeez…

    • mitnse says:

      It was provided in the New York Times through their work to conglomerate data from a variety of sources. Here’s the link
      It’s also listed below the posting on radiation health effects.

      Please note that the NYT reports this is the dose at the site boundary. The dose at the reactors is significantly higher, but how the radioactive particles leaving the site are being distributed around the country is not well known, meaning the dose is likely to be lower away from the site perimeter, but depending on weather patterns, could be higher or lower in other places away from the site.

      As you are well aware, there are conflicting reports on the status of the situation. It seems as if the dose has decreased enough to allow for helicopters to drop water on the site

      This article also suggests water cannons are being used to add water. Furthermore, it appears as though power cables will be connected potentially this afternoon! We hope these reports are true as that would indicate the engineers are one step closer to controlling the situation. That said, please take caution if you are within 30 km of the plant, and follow guidance from the authorities.

      We will keep updating when information is confirmed to be accurate.

    • mitnse says:

      This is the map to which we were referring: .

      It has at this point been denounced by the Australian Radiation Services, the U.S. NRC, and other organizations.

    • Well, as of tonight at 10 pm as Japan tries to go to sleep before doing battle again tomorrow, it seems like there was a small victory. Five huge SDF fire-fighting trucks (the puny blue riot cannon truck failed to get the water high enough to reach the reactor) managed to get 30 tonnes of water (looks like spot on) into reactor no. 3. They’re used for putting out fires at airports. They think it’s done the trick, but are prepared to do it all again tomorrow with one more similar dousing. If the reactor no 3 is OK, they’ll do the same to reactor no. 4 which requires 50 tonnes of water according to their calculations to do the trick, tick-tock tick-tocking. “It’s got to work” is the official byline now.

    • mgarbin1 says:

      Can someone explain why they are using water to get the reactor and rods cooled instead of piping liquid nitrogen into the specific area where the fuel rods are?

    • mitnse says:

      Nitrogen would boil off immediately, and escape to the atmosphere, while water would partially boil, and partially stay in place to continue cooling. Since the rods continue to generate heat, a long-term supply of cooling fluid is needed, rather than just a short term reduction in temperature.

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