1. A more accurate, but perhaps less attention grabbing headline would have been “Fukushima Containment Worked as Designed.”

    As if…

  2. Considering the event, the Fukushima Daiichi 1 containment performed better than I expected – but by no means is this Containment either functional nor an effective fission product barrier.

    Regarding the design function to limit release of fission products to maintain site boundary dose below analyzed limits, this accident was clearly beyond a DBA and so was the fission product release.

    Regarding the function to maintain a floodable volume to restore adequate core cooling by submersion following a RPV breach, the Drywell Design Temperature (Design 340F) was exceeded by temperature indications exceeding 900F. That white smoke observed for weeks was, in my opinion, likely partially due to Drywell electrical penetrations burning out.
    The utility has never succeeded in raising Water Level in the RPV or the Drywell above the initial Top of Active Fuel. I’d say there is not an intact floodable volume.

    I will agree that fuel migration has been arrested.

    So did the Containment work?

    No. The accident exceeded its Design Basis and the expected result of containment failure is, in my opinion, evident.

    A look back at the 1990s MELCOR analysis of Peach Bottom shows the predicted pressurized melt ejection observed at Fukushima Daiichi Unit 1 with a simultaneous loss of RPV Pressure and increase of Drywell Pressure ~ twice Design Pressure (and up to 900 kPa). This is followed by a Drywell failure predicted by a rapid drop in Drywell Pressure. It is theorized that Hydrogen leakage into the Reactor Building by NOT venting irrespective of release rates contributed to the explosion observed.

    I would not claim victory for this containment.
    I’d also fail a crew in a simulator for not venting to stay below Design Drywell Pressure.

    1. @Rob Brixey,

      Several questions,

      As has been discussed in other posts here as well as yourself, this is a beyond DBA event.

      So from my viewpoint there are two critical questions to be asked of the containment structure. Did it keep the public as safe as possible considering this was a beyond DBA event and secondly, will it continue to hold while mitigation work continues? In both cases my conclusion is that Fukushima 1 is not a failure. It can be vastly improved but it is not a failure.

      So my question is if you are stating that this is a failure of the containment since the reactor is now effectively destroyed? And as such that means this is a containment failure because the reactor cannot be restarted. That is how I am interpreting your comments. If I misunderstood please let me know.

      My second question concerns your comment about venting the drywell. I have not kept up on this question but were the operators in a position to vent post-tsunami? Post earthquake they were however post-earthquake the plants were not in a beyond DBA. But what about post-tsunami 45-50 minutes later? Would you fail a crew if they were faced with the same plant setup and post-tsunami crisis the operators had at Fukushima or can you point me to some root cause analysis that the crew did not follow proper protocol for their situation. It is my understanding that Fukushima cannot be compared to our facilities in the US as they did not update their plants to the same specifications as the NRC required years ago. If I am incorrect please let me know on this as well.

      My commentary goes to the idea of how the industry defines “failure” in a beyond DBA event. Containment failure in my viewpoint would be a complete breach of all barriers allowing fuel to migrate unimpeded into the open environment and/or a massive release of radiological material that makes the surrounding area uninhabitable. Neither of which has happened at Fukushima (the area can be cleaned up and people allowed to orderly go back home, it is a political decision not to right now).

      We know that components will be lost in a beyond DBA event and more than likely the plant will be unrecoverable. That is no different than a natural gas plant explosion or a coal explosion where the plants are effectively destroyed and need to be rebuilt.

      What I am concerned about is the problematic concept that a nuclear power plant must survive fully intact even in the event of a beyond DBA event which goes to the issue that nuclear power must be “perfect” to be used. I am not saying that the nuclear bar should be lowered to the level of natural gas or coal; in fact I am an advocate their bar should be raised closer to the nuclear design level. What I am saying is that if we in the industry define this as a failure then the public will then themselves define a future beyond DBA as a failure because the plant will not be recoverable and reusable.

      1. @Bill Rodgers
        “Did it keep the public as safe as possible?”

        That metric appears somewhat subjective – early venting would have preserved a far higher level of safety I’ll explain shortly.

        “Will it continue to hold while mitigation work continues?”

        It doesn’t hold anything in the operational sense of a Containment Barrier. The continued injection into the RPV should have flooded the Drywell to above Top of Active Fuel within days. It didn’t. That water is coming out, evidenced by the high volume of waste water being continually processed. TEPCO constructed a set of walls substituting for a Secondary Containment (Reactor Building) to control vapor and airborne releases. That was an excellent move – I do not believe the Unit 1 Drywell has maintained integrity.

        See NISA report to IAEA http://www.kantei.go.jp/foreign/kan/topics/201106/pdf/attach_04_1.pdf
        Attachment IV-1 Figure 3.1.3

        You will note that at ~0600 on 3/13/11, Primary Containment Pressure spiked off 900 MPa three times. This is likely the stretching of the Drywell Head Closure Studs “relieving” Steam, Hydrogen, Nitrogen, and Fission Product Gases into the Reactor Building. This buildup of Hydrogen in the RB likely contributed to the explosion observed following vent evolutions.
        Hydrogen in the Drywell is still inerted due to Nitrogen and Steam. In the Reactor Building, with no vent fans running, Hydrogen can build up and explode. This resulted in loss of function of the Secondary Containment, as RB walls were destroyed. A separate assumption involves a Primary Contyainment Leak at 50 hours post accident. Either case = no integrity. If the Drywell cannot be flooded to a level that would cover the Top of Active Fuel – then they cannot restore “Adequate Core Cooling” per the BWR Owners Group Emergency Operating Procedures / Severe Accident Guidelines definitions.
        Submergence is not assured.
        Steam Cooling is not assured.
        Fuel Melt occurred as this document predicts.

        “So my question is if you are stating that this is a failure of the containment since the reactor is now effectively destroyed?”

        Late operation of the containment vent function (1400 on 3/12) prevented injection from alternate injection systems already aligned.

        Temporary Pumps require the RPV to be depressurized to enable injection to reach the reactor. Reactor Pressure is intentionally lowered by SRV operation to create this condition. Drywell Pressure indication is the lowest Reactor Pressure attainable – the SRVs can’t lower pressure any lower than Drywell Pressure.

        Failing to vent early may have contributed to fuel melt, perhaps unnecessarily.

      2. @Bill Rodgers
        “Containment failure in my viewpoint would be a complete breach of all barriers allowing fuel to migrate unimpeded into the open environment and/or a massive release of radiological material that makes the surrounding area uninhabitable.”

        I’d like to agree with your standard, but as a formerly NRC Licensed Operator – that’s not the way it goes.

        “US NRC General Design Criterion 16 — Containment Design.
        Reactor containment and associated systems shall be provided to establish an essentially leak-tight barrier against the uncontrolled release of radioactivity to the environment and to assure that the containment design conditions important to safety are not exceeded for as long as postulated accident conditions require.”

        “That is no different than a natural gas plant explosion or a coal explosion where the plants are effectively destroyed.”

        Nuclear Power should always be held to a higher standard than Natural Gas or Coal. We make radioactivity. Part of our contract with the public – our Operating License – is a commitment to not release radioactivity in excess of limits.

        I remain convinced that while TEPCO was attempting to obtain permission to vent and lower Drywell Pressure, fuel damage occurred which available injection may have mitigated.
        In the US – no external permission is required – and we would have vented irrespective of release rates to maintain the Drywell below Design Pressure (between 56 and 62 psig, depending on the Mark I). This would have kept leakage below 1.2% per day. And would not have caused the sudden explosive buildup of Hydrogen in the Reactor Building.

        Explosions take away structural integrity, operator access, and equipment functionality – and this may have been a substantial adverse consequence at Fukushima.

        1. There is more in the INPO report regarding this.

          Permission is not required in Japan per se. It is implied through a series of vague policy and cultural norms.

          Had they gone ahead and vented the containments as needed, and legally permitted, it is unlikely they would have succeeded in venting with sufficient time because of the loss of all AC/DC.

        2. The INPO report provides some insight into this.

          In Japan the law allowed the operators to vent the containment. However, it gave them the authority to do this when the rupture disks blow if there is fuel damage. If there is not fuel damage then they can vent earlier prior to exceeding design pressure.

          The policy obfuscates too much, taking away from the operator authority and responsibility of controlling the plant.

          Even had they vented the containments when they could it is doubtful they would have succeeded in preserving their integrity because of the loss of all AC/DC.

        3. Just a nit Rob but GDC 16 does not apply because what happened in Japan was not a ‘postulated accident’ but a beyond design basis event.

          Since Rob was a ‘NRC Licensed Operator’ let me explain that he can be replaced by a more reliable computer for all the expected events. It is the unexpected events that the human mind excels at.

          So Rob after bouncing around for 30 second praying that your family is safe, get to you feet and do your job. Unfortunately you have no way of knowing that a record natural disaster has occurred and it was only going to get worse. If you are lucky your family is still alive. Forget about things like operator access, structural integrity, and functionality.

  3. Rod’s head line is equally wrong.

    Three containments failed at Fukushima. The containment is not designed for long term loss of cooling. They are designed for a large break LOCA which releases a relatively small fraction of fission products and it happens quickly on the order of 10 seconds. For a LOCA, the acceptance criteria is 25 Rem which is below the threshold of causing harm.

    Evacuation is a common mitigation tool for natural disasters and industrial accidents. We do not design our office buildings, schools, and homes to protect us form smoke inhalation; we evacuate until it is safe. I was watching a news report about a chemical fire that required evacuation. The sheriff explained that his county was well prepared for emergencies because they had a nuke plant which funded annual training.

    The big issue I have with Rod is that most of the 20,000 that died because the assumed they were safe. Without knowing the margin of safety, you can not make rational judgments. I am very comfortable with the margin of safety for things we have analyzed like a LOCA. This why loss of decay heat removal capability is one hour reportable to the NRC. It is just a matter of time before before fission products are released and the containment fails because we exceeded the design basis of the plant and know looking at a ‘severe accident’.

    The answer to CBS is that it does not matter if it worse that previously thought because when we projected that we did not know how bad it would be, we got the women and children out of Dodge.

    1. Kit – sometimes you confuse me. What are you talking about with regard to the 20,000 people who died? All of them died as a result of the tsunami, not as a result of any event at the nuclear power station. They died from the tsunami because they and their government had made the rational evaluation that living near the coast was worth the very low probability that it would be dangerous.

      Those particular individual lost the bet, but billions of other humans win that bet every single day. Every once in a while a few will lose. That is life on earth, a place where there is only one thing that is 100% certain – we will all die eventually.

      1. If you are confused Rod it is because you are a shallow thinker. When method of doing RCA is to keep asking why, why, why until you know how to prevent the problem. People in Japan where tsunami could occur know to evacuate low lying areas. It is a simple concept assuming adequate warning.

        So why did so many die? Surely some died because they just did not have time. The two killed in the turbine building, they thought they were above the flood level. Surely the inspections they were performing could have been delayed if someone has said, let’s wait until after we know more.

        In the case of evacuating to higher ground is not a matter of costs but a matter of assumption.

        I am not inferring that radiation killed 20,000. That is just an extreme example of making incorrect assumptions. The design of nuke plants is based on certain assumptions. Having an emergency plan is about the unexpected happening. We have to assume that the expected can happen. As soon as that little voice in the back of your head says it can not happen here, hire someone to apply a swift kick in the you know where.

        1. @Kit – like many nukes, you think that using acronyms shows that using acronyms indicates that you are an insider with special knowledge. However, according to NUREG-0544 Rev 4, there are at least four different phrases for which “RCA” is a recognized abbreviation – for the Nuclear Regulatory Commission:
          Radiation Control Agency
          radiological controlled area
          reactor coolant activity
          root cause analysis

          As a not-quite-as-old-as-you guy, I also think of RCA as a formerly dominant producer of electrical devices, mostly radios, but also televisions.

          I presume from the context that you are talking about “root cause analysis”, but wouldn’t it be more useful to simply write that out? Not everyone has a link to NUREG-0544 at their fingertips and not everyone on this thread with something to contribute has a full set of possible acronyms memorized.

          Most of us do not spend our whole lives worrying about low probability events. The most prudent of us probably have a “go box” or bag somewhere in case we need to evacuate, and some who live in areas where the wind is known to pick up now and again may have basements or storm shutters handy. Some of us have some emergency tools, stored water, or generators. However, I am not sure how many people in US coastal cities anywhere in the world are ready and able to get to high ground within 30 minutes of receiving a warning to evacuate. Heck, many people might require 30 minutes just to run to their car, especially if there are thousands of others trying to move in various directions.

          Have you not seen the footage of the wave washing away everything in its path?

  4. An interesting number would be the percentage of radioactive potential that remained sequestered on site after the earthquake and tsunami. I’d suspect there would be more than a few nines.

    Anybody have that number? I think such a number would convey to the general public that the containment essentially worked. If the industry were half intelligent with respect to public relations, they should have had that number ready ASAP.

    If the reciprocal were spun up in the Nuclear countering media, it’d sound quite silly to the general public.

  5. And assuming that the containment did not work. What would be the worse case scenario ? (Plutonium, Uranium and Cesium do not travel very far and tend to remain localized to where the accident occurred).

    Here are some bits from experts on the topic:

    Elmer Lewis: The main concern would be with isolating the soil so that no one was living on it or using farm products from it. Maybe you would remove some of it to an appropriate waste disposal site. Plutonium, uranium and other heavy elements migrate very slowly through soil (i.e. they would stay put).

    Elmer Lewis: It could be considered the initial stage of a China Syndrome. Conceivably the core structure could collapse, the uranium falls onto the bottom of the pressure vessel and onto the concrete below. Again conceivably it could go into the soil below, but it would not penetrate more deeply than several yards. The main danger would still be the radioactivity released to the atmosphere, not what goes into the ground. It might contaminate drinking water for a small area around the plant.

    Jim Smith:
    Radioactive Cs-137 is held in soil for decades (the amount halves every 30 years). It doesn’t spread too far – tiny amounts are spread by the wind and water. As the reactors are now (hopefully) much more stable, the problem for the land system is the radioactivity that is already out there in the soil.

    Again, we should stop worrying. Even if the improbable were to happen, moving 5 KM away from the nuclear plant, as per IAEA directives, is sufficiently safe.

  6. It should be pointed out that this concrete melt “simulation” started out with the assumption that 100% of the fuel in Unit 1 melted through the reactor vessel. Nobody really knows how much, if any, of the fuel left the reactor(s).



    During the height of the crisis, CBS News ran a video segment on the developing story at Fukushima. The reporter was talking about the nuclear reactors, but the video started out by showing a burning natural gas storage facility in Japan.

    They still have the video available, if you are interested:

  7. In the case of Fukushima, I actually find the notion that the containment “worked”, or accomplished anything at all for that matter, troubling. I can easily imagine the public’s response. “If that’s success (containment working), I’d hate to see what failure looks like.”

    It implies that it’s possible to have a much larger release. I do not believe this. I believe that Fukushima is the absolute largest release that could ever occur for an LWR (especially given that three cores melted down). And I’ve been saying exactly that, in many posts/comments on the web. I basically believe that containment did nothing. It certainly did not do much to limit the release of cesium, the key isotope.

    Am I wrong about this? People are saying that Fukushima released ~10% of what Chernobyl did, and I’ve always believed that due to several fundamental factors, LWR’s are simply incapable of releasing anywhere near what Chernobyl did, containment being only one of those factors.

    Fukushima has a non-flammible core and did not have a massive power excursion. Instead, the heat was less than 1% of rated core power at all times. Chernobyl’s massive power excursion, along with the core being literally on fire, led to a large fraction of the entire core inventory being released into the environment. It also had no containment.

    And now we’re hearing that Fukushima released 10% of what Chernobyl did, even though neither of those two factors were present. It seems to me that containment accomplished nothing, at least for cesium (and iodine).

    Does anyone know what fraction of the total cesium inventory was released off site (including into the ocean)?

    Also, I had said that if the corium had penetrated the down into the soil, it would not have made one iota of difference in terms of the amount of radioactvity released off site. Does anyone disagree? Daniel’s experts seem to agree with me.

    One silver lining argument coming out of this whole thing is that this is literally as bad as it gets in terms of a possible LWR release, and it didn’t cause any deaths (although there is a significant amount of land contamination). Statements or notions that the containment worked, or accomplished anything at all, undermine that argument.

    And unless someone can convince me otherwise, I do not believe it. You may as well have had a reactor with no containment structure at all. Perhaps Kit is right about the main function of contaiment being the prevention of an immediate release due to LOCA (thus allowing time for evacuation).

    1. And now we re hearing that Fukushima released 10% of what Chernobyl did, even though neither of those two factors were present.

      Jim – Well, first of all, that number is just an estimate, but let’s assume that it’s reasonably accurate.

      You’re forgetting that the Chernobyl accident was from one reactor rated at 1000 MWe. The “10%” from Fukushima was from three reactors, plus perhaps a little bit from an additional spent fuel pool. The three reactors together are rated at 2028 MWe. If we include the fourth reactor that was involved in the accident, the rated power is 2812 MWe, almost three times that of Chernobyl.

      Each of those three containments, on average, released about 3% of what the one reactor at Chernobyl did. That’s two orders of magnitude less, and you want to claim that the containments did not accomplish anything at all?!

      The containments did what they were designed to do, but this was a beyond design basis event. I think that it’s a little harsh to be complaining now that the containments are worthless.

      As Kit has pointed out, industrial accidents happen, which is why plans exist to evacuate the local population in such an event. The population along the coast would have needed to have been evacuated anyway because of the tsunami. The greatest danger, from short-lived I-131, has now pretty much passed.

      Why are you so worried about cesium? How many deaths were projected by the Chernobyl Forum due to cesium? (They project 4000 to 9000 due to all sources of radiation; cesium accounts for a fraction of that.) How many people were killed by the tsunami? (Almost 20,000.)

      Now divide the projected effects of Chernobyl by 10 or more. Clearly, to anyone with any sense of perspective, the nuclear incident should be a mere footnote in the story of the destruction caused by the earthquake and tsunami on 3/11.

      Finally, I guess that I should point out to “No-Threshold” Bob that the Chernobyl Forum used the LNT model in their projections of eventual deaths, so I’m not trying to underplay the risks by going against BEIR VII.

      1. You don’t need to convince me that this event is not significant from a (real) public health perspective. Everyone here knows that. What I’m concerned about is the public/politcal reaction, as well as the economic cost.

        Primarily due to cesium, we have a significant (to me, a surprising) amount of land area with dose rates of several Rm/year, which have been declared “uninhabitable”. Around 100,000 people’s lives have been significantly affected, and they’re looking at a cleanup and compensation bill on the order of $100 billion.

        While I know alot of this is due to the (expected) hyping of nuclear problems by the media, people see these consequences as being pretty bad. (Alas, they also probably don’t believe statements from scientists and govt. about the lack of health impacts.)

        Given this, any notion that a significantly higher release is possible under any circumstances will be very troubling to the public. All I’m pointing out is that assertions that containment performed a significant function (i.e., reduced the release by a significant amount) could be very counterproductive, because they suggest that significantly higher releases are possible.

        I continue to believe that Fukushima is about as bad as it gets, in terms of a worst possible LWR event (as I discuss more in my response to Rod below). And the public needs to understand that.

    2. @JimHopf

      Don’t forget that Fukushima was a “beyond design basis” event. In that case, the design goal is more along the design goal for the crumple zones on a well built automobile. After a beyond design basis event, they might look horrible and the passengers might be a bit bruised and battered by the exploding air bags (1st hand experience talking here), but the passengers, if they were wearing their seat-belts, have a very good chance of walking away from the pile of twisted steel.

      The pictures from Fukushima remind me a bit of the way my first Jetta (may she rest in peace) looked after I was hit by a 1993 Caprice running a red light, but the cores inside the true containments did not escape into the environment. (I walked away from the accident with nothing worse than a bruised knee from knocking against the steering wheel and some painfully bruised ribs from the air bag.)

      Cs-137 is the long term isotope of interest because it happens to be volatile and water soluble at the temperatures that you might see in a core that is not being actively cooled. It is going to get out if there is any leakage or venting of the containment. I-131 is also volatile, but it is short lived enough to ignore after 80 days.

      There are a lot of other isotopes and other materials that were fully contained. CS and I together only represent a fraction of one percent of the material in a nuclear reactor core. Only in reactor #1 do the calculations show that a significant amount of corium might have left the reactor pressure vessel – the second line of defense after the cladding on the fuel tubes – but even there, the third line of defense held rather nicely and was never in any danger of being breached.

      1. I doubt that the public cares much about the fact that this was a “beyond design basis event”. I understand and appreciate those points (how rare, etc.), but I also understand that fossil fuel use (worldwide) causes more harm than Fukushima (to public health and the environment) every single day. But the public doesn’t understand/appreciate this, and they won’t.

        Anyway, I concur about how the volatiles are the isotopes that will escape a breached containment, and that they therefore will be the main source of environmental impact. That said, I’m surprised about how much got out. I’d been told (by Rockwell, etc..) that even a failed containment would greatly reduce the release of these isotopes, due to plate out and settling effects (inside containment). It seems that a significant fraction of Fukushima’s total Cs inventory was released.

        I understand that there is much more activity in other (non-volatile) isotopes, and that those isotopes did not significantly contribute to the environmental impact, since they remained on site (and largely inside the reactor building). But is this due to any type of containment “success”, or is it due fundamental properties, i.e., the fact that these elements are simply not mobile, and will remain in the corium mass and not be transported by air. I think it would be helpful if we can argue that a significantly larger release is not possible under any circumstances.

        Are there any credible scenarios where significant amounts of these other (non-volatile) isotopes could be transported off site? Is it not true that the physics/chemistry is such that even with a fully melted core, and a gaping hole in containment (the worst conceivable scenario), significant fractions of the non-volatile isotopes would not be transported off site? Finally, would it have mattered (in terms of off-site release) if the corium had gotten all the way through the floor and contacted the soil? I don’t think so.

        The argument I’m trying to make is that containment is useful in that it prevents the immediate release of a large amount of radiation, allowing time to evacuate. But for severe events like Fukushima, where containment is leaking/breached, it actually does not reduce the total amount (eventually) released by all that much. Thus, it can’t get any worse than Fukushima.

        A follow on conclusion is that the hydrogen explosions clearly reduced any benefits from the containment. Such explosions need to be avoided if containment is to do its job and significantly reduce releases to the environment.

    3. “In the case of Fukushima, I actually find the notion that the containment “worked”, or accomplished anything at all for that matter, troubling. I can easily imagine the public’s response. “If that’s success (containment working), I’d hate to see what failure looks like.”

      You’re looking a gift horse in the mouth which the families of lost oil and gas workers and sometimes entire communities around those plants seldom have. Whether by incident or accident or fluke of design the containment held. As “sloppy” the design was, haphazard the human response, as unforeseen the event instigator was, the system nixed Doomsday — if such was even ever in the cards. It also hints that the learning curve from this rare -nature-caused- event will, like TMI, will make a major accident even less likely and more benign in the future. I can’t say that for oil and gas workers whose yearly mortality rates on the job don’t even make the news unless it’s a big Gulf spectacular. I just don’t understand why anti-nukes think a single rare nuclear injury case makes thousands of oil and gas accident victims chopped liver.

      James Greenidge
      Queens NY

  8. It sounds silly, but a lot of people expected (even hoped for!) the TMI/Fukushime melt-through to resemble that blood-acid infinitely dripping down through decks scene in the movie “Alien”, forget “China Syndrome”! (gee, SO much pop culture swings in favor of anti-nuke fear!)

    December 3, 2011 | 1:17 PM

    I almost came out of my chair the other day when I saw this broadcast.

    I’ll bet the program’s sponsors at ANGA were well pleased indeed.”

    I’m just a lowly one guy, but isn’t there a way for the accumulated intelligence and talents of Atomic Carnival members to get together and form a media rebuttal organ respectable enough to be recognized by the MSM to counterweight these obviously anti-nuclear agenda “spokesmen”? Why are they allowed to lie with murder?

    James Greenidge
    Queens NY

  9. I do know about buildings and I’m puzzled by the design of the Mark 1. When CBS says that the core melted through the first layer and then stopped at the bottom of the 2nd layer of containment, is it possible that some of the hot material overflowed into the torus? Would the torus be encased in concrete too (I can’t tell from the drawing above)? If so I would think the water in the torus would have cooled the hot material and probably explode too with all that steam. Why didn’t GE choose a containment like a pressurized water reactor? I do not understand why they would have 40 feet of concrete on the bottom of the “Jeanne bottle” but then the top of the building is as weak as a high school gymnasium. I will say that the diagram CBS had was inaccurate.

    I would think the torus would be water tight but when TEPCO tried to fill the containment vessel it would never fill up so there must be a leak or a crack. What will they do to contain the melted core now? Can the fill the “bottle” with concrete?

    1. BobinPgh- The following link has the same drawing, but you can click on it for a much larger image. It might help you to understand the construction.


      By “first layer”, I think they mean the concrete at the bottom of the steel dry well (bottle). The 2nd layer might then be the steel dry well itself, I suppose. I doubt any molten fuel would have flowed into the torus.

      It is important to know that this “simulation” starts with the assumption that 100% of the fuel left the reactor. Nobody knows just how much, if any, of the fuel actually left the reactor. See article linked below:

    2. I do not understand why they would have 40 feet of concrete on the bottom of the “Jeanne bottle” but then the top of the building is as weak as a high school gymnasium.

      There’s a very good reason for that. The top of the building is simply the service floor. There’s nothing essential up there. It’s not part of the containment. Thus, if you have some sort of explosion up there, you want the energy to go up and out without any kind of resistance, instead of being reflected or focused downward, where it can hurt the real containment.

      The same kind of logic goes into the design of buildings where explosive material is routinely handled. Once again, if there is an accident, you want the energy of the explosion to be focused in the direction that will do the least amount of damage. Often that direction is straight up.

  10. The report in Japanese at http://www.tepco.co.jp/nu/fukushima-np/images/handouts_111130_09-j.pdf has a diagram on p182 shows the reality – easy enough to understand – about the possible extent of concrete erosion under this analysis – 0.65m. I have no idea how the CBS report managed to get its description of this so wrong.

    But then their images are misleading, and their description of the mess at the plant fails to mention the tsunami, so all in all they get very low marks for communication.

  11. A little friendly reminder. A few miles up the coast from Fukushima Daichi, there is the Daini plant. 6 reactors are still standing. (they have been shut down, but hey who needs electricity.)

    Same earthquake, same tsunami. Design 10 years younger than Daichi.

    Let’s build new plants. Now.

  12. Not too many people are talking about the Fukushima Daini plant that withstood the same earthquake and tsunami.

    Those reactors that were 10 years younger than the design at Fukushima Daichi.

    1. Were the plant buildings inundated like they were at Daichi?

      Coastal features and the defenses (sea walls) that were employed can significantly affect the amount of water that enters the plant. For all we know, Daini was on a bluff, high above the water (like Diablo Canyon is).

      1. Were the plant buildings inundated like they were at Daichi?

        The important difference was that the Daini plants still had off-site power after the earthquake/tsunami. The following link is a plant status report from March 12.

        Also, the tsunami inundation at Daini was not nearly as bad as Daiichi, although there was some flooding at Daini, so they had to use some alternate methods of maintaining water levels and heat removal.

      2. JimHopf

        What is the point of using the phrase. “For all we know, Daini was on a bluff”

        For all we know it is not on a bluff. This is not some kind of conspiracy and mystery about what elevation this other plant is at.

        So please stop using your emotional ignorance to add FUD to a simple question that Google could answer for you quite easily.

        No Daini is not on a bluff. It was inundated by water. Some pumps failed. However backup power was available to keep the plant in a safe condition.

        Daichi has 2 more reactors (that the media also doesn’t talk about). You probably missed that as they didn’t blow up so were not news worthy.

        I’m sorry if my tone is a bit off. There is a reason either consciously or unconsciously why you posed the question you did in the way you did. It was to cast doubt, that the previous poster was hiding something.

        1. I wasn’t suggesting he was hiding something. I was suggesting that he may have jumped to a conclusion, i.e., that the reason Daini didn’t have a maltdown was solely due to superior design.

          My guess is that he’s probably mostly right. However, the local wave height, as well as the local ground accelerations, for a given earthquake and tsunami, are very site specific, and can vary widely for different locations. The height of the seawall, and the height of the ground over the water are also important.

          Pete’s link above seems to suggest that the ground acceleration and amount of inundation was indeed significantly less at Daini.

          All that said, I don’t doubt that more modern designs are (would be) much more resistant to the problems that occurred at Daichi.

  13. A bit off topic, but I think worth mentioning.

    The Francis Crick Prize Lecture to be given at the Royal Society on Wed Dec 7th is about DNA repair. It will be given by Dr Simon Boulton from Cancer Research UK.

    The time is 6.30 London time.

    The lecture can be watched live at royalsociety.org/live

    This topic is highly relevant to the question of how dangerous low levels of radiation are to health.

  14. To be clear, I have never thought it is possible to kill someone off site as a result of a problem at LWR with a containment building. If you bussed school children to site and withheld drinking water, the death toll could be higher.

    Evacuation was a prudent precaution because maybe the models are wrong. I would have allowed volunteers to return wearing protective clothing to tend to domestic animals like dairy cows that must be milked daily. Irrational fear trumps cruelty to animals. Since dairy cows can walk away slowly it is sad that they were not allowed to.

    Of course none of this compared to abortions because of irrational fear.

    On the other hand, the radiation hazard to site workers and emergency responders is real.

  15. Thanks for the answer, but what I cannot understand is: Is there some reason why a boiling water reactor could not be placed in a concrete dome like a PWR? It seems like if that were the case, there would not be the hydrogen explosions and all that debris, which is probably one reason why it will take 30 years to clean the place up because it is such a mess. After all, didn’t the NRC want to outlaw the Mark 1 but that would be the “end of nuclear power”? To be truthful, the Mark II doesn’t look much different just round rather than square and larger. I believe we will still see nuclear power but I can’t imagine anyone would buy a GE brand reactor anymore.

    As for the evacuation, would it not have been possible to allow people to go there for maybe a day to take care of the animals and pick up their pets? That would have been much more humane without much risk.

    1. Yes, example of Mark III double containments for BWRs include Grand Gulf, Clinton, and Cofrentes Nuclear Power Plant. The following link has a nice picture.

      For the record Bobin, Mark I and II containment have a concrete dome. They are just surrounded by an industrial building.

      I think what you want to outlaw is floods, tornadoes, hurricanes, and earth quakes. Natural disasters do make a mess. The safest place to be in a natural disaster is working at a nuke plant. No one is hurt from radiation and we can clean up the mess later. The mess is relatively small at the nuke plant.

  16. Isar I is an example for a BWR installed in a spherical containment. However, the spent fuel pool is still outside the containment inside the RB.

  17. I guess I am asking why the Mark 1 is the way it is and why not like a PWR containment building? The New York Times said it was “easier and cheaper to build” and thus implies it is “cheap”. You are right in that we do not hear about the 5 and 6 reactors at Fukushima. But is it possible the maybe the reactors are not as bad off but the electrical part of the plant is so damaged it might not be economical to repair them? Also, it seems that the Daini plant was not hit as badly, will it start up again?

  18. @Cal Abel

    “Even had they vented the containments when they could it is doubtful they would have succeeded in preserving their integrity because of the loss of all AC/DC”

    Venting the Drywell / Torus earlier may have allowed Reactor Pressure to be lowered sufficiently to achieve injection with the Temporary Pump.
    Aligning alternate injection sources is required by Emergency Operating Procedures and Severe Accident Guidelines – this always includes lowering Reactor Pressure sufficiently to enable injection, or lowering Drywell Pressure sufficiently to enable flooding.

    Page 11 of the INPO Report…
    “The decision to complete evacuations before venting containment, and the subsequent equipment and radiological challenges encountered as operators attempted to establish a vent path, delayed injection of water into the Unit 1 reactor. At approximately 0230 on March 12, as Unit 1 depressurized, pressure in the reactor and in containment equalized at approximately 122 psia (0.84 MPa abs). This pressure is above the discharge pressure of the station fire pumps and fire engines. Once pressure had equalized, further reductions in reactor pressure were not possible until containment pressure had lowered. As a result, little to no injection was achieved until after the containment was vented successfully, which occurred at approximately 1430 on March 12.
    High containment pressures in Unit 1 contributed to the amount of time Unit 1 did not have adequate core cooling.”

    1. Unit 1 timeline (abbreviated)
      1537 loss of all AC after 2nd tsunami
      1818 placed isolation condenser in service
      1825 removed isolation condenser from service (likely due to concerns over brittle fracture prevention due to the high CDR observed earlier)
      2119 water level 8″ above TAF (likely accurate indication and with water over the fuel no/minimal core damage. Also no data to establish a water loss rate which is going to be the rate of water leaving through the relief valves)
      2151 reactor building access loss due to high dose rates (indication of first fuel damage core is likely partially uncovered causing the fuel damage)
      2200 water level jumps to 21.7″ above TAF (this is indication of reactor vessel depressurization and we are seeing flashing in the reference legs)
      0230 Containment reaches 122 psia
      0245 Reactor pressure decreased to 116 psia
      (the report does not say this but having lived through reference leg flashing during transients and rapid plant cool downs any water level is going to be erroneous until the reference legs are force fed)
      0419 The containment vessel pressure drops to 113 psia
      (this would indicate the containment began to leak at this point as pressure was being relieved and is probably contributed to the read levels later in the torus and in general to the workers. This established the path for hydrogen to possibly enter the reactor building later.)
      0514 onsite dose rates are noticed (this is when the operators think the containment failed)
      0900 order given to vent unit 1
      1430 Unit 1 effectively vented (page 11and 20) due to rupture disc failure. Not due to operator action
      1536 explosion

      I am at a loss to explain how without power and more specifically control air how the operators would be able to protect the plant and prevent containment failure. As Kit will be sure to point out I never operated a BWR (I’m SMR PWR all the way) so I may have missed something in my analysis. I also couldn’t find the containment design pressure through this reading. I imagine that design pressure is around 60 psia. It also looks like the rupture discs are more of a hinderance than help…

      1. @Cal Abel
        “I am at a loss to explain how without power and more specifically control air how the operators would be able to protect the plant and prevent containment failure”

        Injection stops core damage, or at least arrest fuel migration if Minimum Debris Retention Injection Rate is achieved.

        It isn’t much, a few hundred gpm would have done it at this point.

        Containment Failure is prevented by limiting max temperature and pressure achieved, optimally keeping both below Design Temperature.

        The Containment Vent Path is capable of removing ALL Decay Heat in a BWR long term.

        That’s a crucial concept in our EOP philosophy.

        As I said earlier, EARLIER Containment Venting BEFORE Core Damage occurred (no high radiation conditions restricting access) allows RPV Depressurization to a sufficiently low value that the Temporary Pump aligned would have PREVENTED Core Damage.

        That means NO Fission Product release from the cladding, NO Hydrogen generation at all – injected water steaming off through SRVs, and a boiling Suppression Pool ultimately steaming Decay Heat out the Containment Vent.

        The Rupture Disk enables the Hardened Vent Path for this purpose.
        Hardened Vent Path was established to prevent busting Normal vent Path ducts inside the RB during Severe Accidents.

        Normal Vent Path is through the Standby Gas Treatment Train (RB Emergency Exhaust Filter Train)which only handles ~ 2 psig of pressure.

        Regarding Kit’s opinion that Containment Criteria doesn’t apply to accident situations beyond design, my position is;
        1) The public deserves better service than a Control Room crew evacuating a site. I have posted earlier that operators could have vented early and AVOIDED fuel damage at Fukushima.
        I do not fear for anybody’s family in light of Fukushima.
        2) MELCOR models from the 90s established the consequences of sustained SBO. US BWROG EOPs and SAGs used this prediction to establish our strategies – Containment Venting of Decay Heat is not a new invention.

        Pages 27 – 29 this document

        Feeding the reactor generates steam, which flows through the SRVs to the Torus. Ultimately the Torus will boil, and steam will be vented through either Torus or Drywell vents and no significant radiological release results

        3)It is possible to vent a BWR Containment with a flashlight, an SCBA Bottle , a regulator and tubing applied to the associated Vent Valve diaphragm. The SCBA can be used “unregulated” to bust the rupture diaphragm if necessary before opening the Vent Valve. No AC or DC Power is required. A pressure gage can be installed on the same vent piping to read Drywell or Torus Pressure. This is already a commonly used contingency procedures.

        3) These folks lacked guidance, permission, or a clue – and evidently dangerous combinations of these.

        1. Thank you for the elucidation.

          I would not be so quick to say they didn’t have a clue. They lacked a good bit of information that we have the hindsight of having at our disposal. It is unfortunate that the policy constraints and social constraints prevented them from having the responsibility to operate the plant. The policy short fall is the fault of the government for not providing them with clear enough words to operate the plant at all times. I think we agree on that point.

          What would pressure have been in the torus and containment at 2151, which is around when they started melting the fuel?

          They were not able to get even few hundred GPM. They had 1300 gal by 0830. It wasn’t until 0245 that they reached that point where RPV pressure was low enough to have any flow. What other medium/high head sources do they have w/o AC

          I ran some numbers a while back, an early intentional depresurization will cause a loss of RPV water inventory of about 30%. This feature is not on existing BWRs? but on ESBWR? as a means to provide rapid core cooling with low head sources.

          I hear once you go boilers you never go back. I’m staying with PWR’s for a while longer, thank you very much.

        2. The document was a great read. Thank you for posting it.

          In those EOP’s, do they assume that the torus is vented as well to prevent a long term pressure build up?

  19. @Cal Abel

    2151 3/11 Drywell (and Torus Pressure) was about 200 kPa, roughly 15 psig.

    On a lowering Reactor Water level due to any initiator, BWRs have three important level decision points.

    Top of Active Fuel – This is the terminus of “Assured Core Cooling by Submersion”. After this point, Level will drop faster because fuel accounts for substantial volume below this level. Clad temperatures are rising.

    Minimum Steam Cooling Water Level WITH Injection. This generally is about 25 inches below TAF. at this point, the submerged portion of the core is generating adequate Steam Flow (through open SRVs) to cool the exposed fuel, limiting clad temperature to 1500 F.

    Minimum Steam Cooling Water Level WITH ZERO Injection. This generally is about 40 inches below TAF. at this point, the submerged portion of the core is generating adequate Steam Flow (through open SRVs) to cool the exposed fuel, limiting clad temperature to 1800 F. (This occurred at Fukushima)

    The correct action at MSCRWL (Zero Injection)is to Emergency Depressurize by opening SRVs.
    Again, this takes no AC/DC power, we have portable generators with rectifiers to provide the ED function in an SBO.

    You are correct that ED costs substantial inventory. Inventory no longer cools the core during ED, water flashing to steam cools the core as pressure drops. Latent heat of vaporization is absorbed by water boiling SUBSTANTIALLY reducing clad temperature during ED. As reactor pressure lowers, the Fire Truck or Temporary Fire Pump should have been aligned and running and will commence injection. Initially steam cooling, then submerging the core without substantial fuel damage.

    Regarding Torus Venting – the Torus is always the preferred path for Containment Venting. Aerosols are scrubbed of Iodine and Particulates by the quenching action of downcomers or SRV tailpipes in the Torus. It is OK (but dirtier) to Vent the Drywell. Torus Pressure is relieved through Torus to Drywell Vacuum Breakers, and BOTH will show lowering Presssure no matter which path is used.

    In an extended SBO – feed and bleed is all you have.
    Its also all that’s needed. Drywell Pressure, and Reactor Pressure are the obstacles.
    Operators must know EVERY method of opening SRVs.
    Operators ust know EVERY method of venting the Containment.

    As an aside – Japanese plants have only ONE licensee per crew. This installs a single point failure vulnerability in the decision / execution process. US Plants have multiple SROs and ROs per unit.

    1. It seems from our experience with western reactor accidents that the large break LOCA is not the risk we should be concerned about. WASH 1400 suggests this with small leaks (TMI). I don’t recall it looking at massive common mode failures (Fukushima).

      I had an idea of modifying the RWST’s to serve as a suppression pool and fission product trap for acting as a continuous containment vent filter. There is posting on this elsewhere on this blog.

      I do not think e earthquake without additional information was a sufficient condition to initiate ED. The Tsunami on the other hand shifted the environment to warrant that shift from protecting fuel integrity (long term operability) to sacrificing design margin and the plant to protect the operators and the public.

      A single licensed operator may actually be warranted. It is how the Navy operates (EOOW) is the only one with the license issued by NR. It does not alleviate the responsibility of the subordinate watch standers to do their best. I had plenty of non licensed operators who were smarter and more knowledgable that my EOOWs. Each individual was accountable to do their best, but the buck stopped with the EOOW.

      Just because somebody has a license does not improve their ability. It does however ensure legal accountability. A structure that allows people to be accountable for their mistakes ensures they will do their best. This is perhaps why we have o have so many licensed operators in the US. From observing both structures (Navy and commercial US). The one where everyone is accountable to do their best gives the best performance at the lowest cost to the consumer.

  20. I was a Navy Reactor Operator in my youth.
    There is no comparison between the complexity of a large commercial BWR or PWR and a Navy S5W, S8G, or A4W reactor plant.

    Please read about the Japanese handling of Shika Criticality on Page 9.


    An eight year cover up. The Samurai swept that one under the rug. I’ve seen enough of that.

    When decisions are solely focused on a single person, the career aspirations of the sole decision maker has been known to taint the quality of decisions made. This is also true in the US Navy in my experience.

    Single failures occur. In hardware, in human performance – all require a backup.

    In my 35 years, I have lost MANY ex officers in NRC License Operator Training due to technical deficiencies and even a few integrity issues.

    I’m not buying the pitch.

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