42 Comments

  1. You think the grating could get this hot without any melt-through?! We are seeing some serious deformation; no melt-through would mean getting hot enough that gravity alone would have led the grating to plunge.

    It seems to me more likely there was a larger penetration above that place where the grating is deformed and some melt-through occurred there. A small amount of corium going out means it’s likely to have a least partially solidified on the grating (inside the RPV it gets very hot from all the material around it also emitting heat, as soon as it’s out it can evacuate heat much more easily and would drop in temperature very fast, re-solidifying rather easily if it meets a much colder, good heat transmitting material), which would explain the intense radiation remaining. And later after the temperature went down, the corium inside the RPV has solidified again so likely closed the hole through which it went, which explains the small amount of dripping.
    It would be very useful to have a view of the center of that deformed grating area, as well as an analysis of its surface. If there a hole at the center, then the melt-through scenario becomes very likely. Also in the image we see, there could also be some re-solidified corium at some place on the grating, it’s not clear really, but I wonder if we’re not seeing that sort of thing on the other side of the deformation, it looks a bit like there’s some material deposited on top of the grating.

    In any case, I agree that the video and the lack of damage in what we see of the bottom of the RPV are in favor of the scenario of a rather limited amount of melt-through.

    1. About the analysis of the surface, we are able to send robots to mars with spectrometers that can analyse the nature of materials it meets, so I’d hope we can do the same for that reactor.

      1. I read that they had tried probes-but they can’t get far enough into the reactor in time before the media hype overwhelms their components and they self-destruct.

      1. That gap is required for pulling control rod drives out of the reactor…..because they are quite long. We are looking at what us BWR guys call the carousel. It moves around depending on which (we have 185) CRD you are exchanging.

  2. Rod,
    You and Will Davis appear to have reached different conclusions regarding melt-thru. Either way, we’ll know more after they send in the real probe.

      1. I think this is the same likely RVP breach location conclusion predicted by EPRI’s MAAP code runs on Unit 1. Either the CRD nozzel pens or the CRD itself. The MELCOR code runs predict a different failure mode/location.

  3. Most of the articles I have seen on this latest press release have been the usual FUD pushing and fear mongering that is the stock in trade of the FUDdites. Sorry if that offends anyone speaking so frankly, but, to be honest, I’m very, very tired of all the FUD, weeping and wailing and doomsaying.

    For example, 530 Sv/hr, while high, is hardly “astronomical”. Heck, when we were doing destructive PIE of prototype fuel at Idaho Lab and elsewhere, rates in the millions of R/hr were not unheard of. I worked with 60Co sources that yielded exposure rates in the megarad-tissue range on a routine basis. I helped design a neutron-driven prompt gamma source that peaked at close to 10 Mrad-tissue/hr. If there was significant corium drippage, I’m actually surprised that the dose rates are in the range they are (actually on the low side). What they are seeing is a dose rate typical of 1/4th of a PWR fuel assembly unshielded in air after five years of decay. If (note IF) that is all we are seeing then they have had the equivalent of one or less fuel assembly melt through a weak point, probably the CRD penetration or maybe an instrument tube.

    1. From a fifteen year old press release about Sandia’s Gamma Irradiation Facility (GIF):

      “A test can last seconds to months depending on the customer’s gamma needs. Gamma dose rates as low as tens of rads per hour to as high as 300,000 rads per hour can be delivered. (A rad is a unit for measuring absorbed doses of ionizing radiation by a material.)”

      That’s 3000 Gy/hr, right?

      http://www.sandia.gov/media/NewsRel/NR2001/newgif.htm

      1. That is correct, the rad is a generalized unit and you typically have to quote the material you are dealing with, such as rad-silicon, or rad-tissue. I think the Sandia GIF has been re-loaded with 60Co pins so the dose rate now is higher than what was quoted in that older press release.

        1. Cool.

          Point was that 530 Gy/hr is not “whatever scary adjective.” Was it “unimaginable?” “Unprecedented?”

          GIF was DESIGNED for higher dose rates than that, so like Will Davis says, the article that sparked all this is just fear mongering for page views.

          So, is “rad-tissue” a simulated damageable material?

          Rod’s using a Navy “thumb rule” that a Rogoton is a RAD is a REM for gamma radiation. But that was based on a one Curie Co-60 point source at one meter producing one REM per hour. Obviously if it was Cs-137 or Pb-210 or Fe-55 the thumb rule breaks down. But that’s what thumb rules are for. IIRC, it was also used for shallow doses of beta, in that a rad is a REM, but I forget what isotope on which that was based (perhaps just mixed fission products). A Curie of Sr/Y-90 will treat you differently than a Curie of, say, H-3, not to mention the biological processes.

          1. I think the “rad-tissue” designation was to indicate that the dosimetry was tied to the more fundamental unit, which is energy absorbed per unit mass (of whatever). Dealing with REM ties you to the older unit of exposure rate producing a given amount of ionization in air, which is the roentgen, the “r” in “rem”. It gets a bit cumbersome translating from ionization in air to energy deposited in a material.

            The high-energy hot cells at Idaho Lab and other places (like the Battelle Labs at West Jefferson) were designed for (and used with) materials in the megacurie range, which produced contact exposure rates approaching tens of millions of R/hr (yes, roentgens per hour, which is what the dosimetry was calibrated for). Radiochromic dosimeters were the only things that could handle those kind of measurements at the time. Those kinds of exposure rates make the F. Daiichi rates look kind of puny, and certainly not “astronomical” or “unimaginable”, or whatever spurious superlative one might wish to use.

      2. Nice. I’ve just found some papers about food irradiation, up to amount of 30 to 70 thousand Gray, and some people using a Gammacell 220 Excel irradiator for testing the result. It seems that kind of irradiator is present in many facilities for testing.
        I then located a thesis that calibrated irradiation from this at 1.484 Gy/sec, so 5342 Gy/Hour. And the Cobalt 60 source was a bit old so the rate had became slower than what it used to be. It’s likely however that industrial use relies on a higher rate than that, because it’d be very slow to irradiate at high dose.

        Cancer treatements seem to use most of the time typical rates in the range of 100 Gy/hour, or a bit more, but I’m seeing that flash irradiation at much higher rate, up to 200Gy/s locally, is getting used more and more frequently now.

  4. There was a report on the BBC this morning on the explosion at Flamandville, which included extensive comment from John Large, ‘ nuclear industry consultant. ‘ Since he mainly surfaces as a Greenpeace witness anywhere they’re trying to close a reactor, there wasn’t any air showing between his views and theirs.

  5. I still hold to the “no melt-through” mantra, Rod. Some seepage of molten corium? Maybe! But, no catastrophic melt-through. I’m sticking to my guns until…well…let’s see what “scorpion” shows us!

  6. So the plan to remove the corium with shovel and pick-axe is no longer viable…
    What is more relevant for the decommissioning plans is if they can fill the containment with water to use underwater cutting from the refuelling floor.
    Any news regarding the work getting the containments watertight?

    1. Quite fun.

      Yes, there’s no need to worry now from the molten fuel. It will do no harm to anyone in the near future. And yes, we all knew that used&melted nuclear fuel is an extremely nasty, radioactive, harmful thing if it comes close to you. So, not surprising.

      But some day we’ll have to remove it. No shovel and pick-axe, not now and not in the near future. In 300 years time radiation will be far lower (around 1000 times) but, even then, radiation levels will be very high.

      What we’ll do? There’s no easy solution for melted fuel reactors.

      1. Nobody said the job would not be difficult or that it would not take a lot of time. The point is that these stories are pushing the usual FUD when it comes to nuclear energy. Its a one-sided approach that is nothing more than advocacy rather than reporting. This we all know. But every time it pops its ugly head up we should swat it down. I must confess to being somewhat less than enthusiastic spending a good bit of the precious time I have left on this Earth playing whack-a-FUD, but then again, I don’t have the wherewithal to be sailing the South Pacific or playing 18 in the morning and passing away the afternoon at the 19th hole, as much as I’d like to. So, for the moment, whack-a-FUD it is.

        The clean-out of the TMI-2 RPV is a good starting point as reference for dealing with melted and now congealed fuel assemblies. This will be more complex if significant leakage has occurred, but based on the readings at this point it appears the quantities are somewhat less than what might result for a complete burn-through.

      2. New designs incorporate features such as post-accident vessel cooling so that any corium is retained in the vessel. For SMRs, if there is a fuel melt the reactor vessel can be designed to be the shipping container.

      3. And in any case, worrying does no good. Better to take a rational and logical approach to the problem, spend some time coming up with a solution and plan, then getting down to work. Certainly if worrying does no good, spreading FUD does even less. I have little respect for those who would provoke fear rather than promote understanding.

  7. Scary headlines are a dime-a-dozen.
    “EnviroNews” is one of the worst perpetrators, with their “ALERT: New Radiation Readings in Fukushima Reactor 2 Are ‘Unimaginable,’ Lethal in 1 Min.”

    How about “EnviroNews ALERT: Radiation Level at Ivanpah Solar Plant “Unimaginable”, Lethal in ~1 second.”
    ( Air temperatures at Ivanpah Solar can reach 1,000 degrees Fahrenheit [540 °C] — frying thousands of birds alive, every year )

    Or how about “EnviroNews ALERT: We know enough to stay out of hot reactors; Meanwhile many kids die needlessly being left in hot cars.”

    A graphic meme containing the above (with thanks to friends who helped with the text) :
    https://www.facebook.com/493843777362196/photos/a.493867307359843.1073741828.493843777362196/1256087541137812/

    See also https://youtu.be/XNDWN8KDVSM — “One Decision” (Child Safety Film – Vehicular Heatstroke)

    1. @Jaro

      It’s easy to ignore fringe “click bait” sites. They are roughly equivalent to ants. Whacking isn’t effective enough to be worth the effort.

      It’s only when outlets like the Washington Post that I bother to whack the mole.

  8. The clean up costs are said to run into $200bn. That seems pretty steep.

    Just wondering if someone would like to express a view of what would of happened at Fukushima if it’d had a corium catcher, and how this would have affected the clean up costs?

    1. I thinkthat cost is dominated by compensation payments and off site decontamination work.

      Investments in prevention would have been much more worthwhile than a core catcher. We do not know yet how much corium reached the containment floor but the rpv bottom with all the CRD mechanism is probably more difficult to clean up anyway. Core catchers seem a waste of effort, much better to provide RPV bottom emergency cooling.

  9. Thank you for combating this instance of “Fake News” Rod:

    “Fake news is killing people’s minds, says Apple boss Tim Cook ”

    “Made-up news reports trying to promote a particular agenda gained huge traction on social media in the US during the election.” ( http://www.telegraph.co.uk/technology/2017/02/10/fake-news-killing-peoples-minds-says-apple-boss-tim-cook/ )

    I think this is incorrect, we’ve always had to deal with politics, advocacy journalism, then in more extreme cases propaganda and yellow journalism – AKA “fake news,” to some degree, its just become more extreme, more prevalent in social media and is therefore more obvious and easy to spot.

    If you look at it from the nuclear power “controversy”, and take advantage of the perspective this situation has to offer – its perpetually been a issue.

    1. @John T. Tucker

      I’m not sure I would apply the trendy label of “fake news” in this instance. Nearly all of the reports I’ve seen on this high radiation measurement provide the real numbers supplied as the result of real investigation activity. They simply do it in the wrong context and without adequate explanation of what the numbers actually mean.

      1. I would Rod, not that I like it or agree with it or the scope of its current use, its just whats out there and whether I like it or not is irrelevant.

        That at best unnecessary term is in itself interesting when placed with the social media phenomena. The worst thing you can be is a “fake person.” In professional circles the worst is a poser or “fake.” I would argue the term was basically created and propagated by professional media to deride independent / blogger sources. If so Its backfired of course.

        But really considering everything moving in these spheres (media, energy advocacy and advertising, social media, activism) its something im interested in and a reaction I probably should have seen coming.

  10. Terrorism is essentially the use of fear to accomplish political ends. I hold reports like the one Rod here criticises so aptly, to be a class of terrorism.
    Stuff like that is killing people who die from the effects of air pollution, let alone those who will drown or starve from ocean levels rising and die in hurricanes whose violence grows with the higher humidity over slightly warmer oceans.

    1. @Albert Rogers

      I tend to agree with your definition. By that standard, many government figures in the U.S. resort to terrorism to attempt to achieve their goals for spending, controlling other people’s freedoms and aggregating power to themselves.

  11. Obviously it’s not confirmed if the grating melted or not.

    One possibility…..we all need to remember unit 2’s RCIC system ran for 70 hours.

    RCIC is a terry turbine driven aux feed pump. It runs around 600 gpm. It uses reactor steam as it’s supply source, and discharges into the suppression pool. The pump takes a suction from the suppression pool and injects to the reactor. There is a sidestream oil cooler that uses pump discharge as it’s cooling source.

    With no decay heat removal in service, the pool heats up and boils. RCIC now is pumping boiling water through its oil cooler. This whole time the containment is heating up both from a temperature and pressure perspective. The containment clearly exceeded the HCTL (Heat Capacity Temperature Limit) of the suppression pool, which is a measure of the pool’s capability to absorb heat from a LOCA, rupture, or emergency blowdown. If you exceed HCTL, then you will likely exceed the containment maximum temperature limit during one of those events. Similarly the pressure suppression pressure (PSP) was clearly exceeded, which protects the drywell and suppression pool from over-pressure conditions during a LOCA, rupture, or emergency blowdown.

    So after 70 hours (well over the 8-12 hour RCIC mission time), RCIC finally failed. The containment was already well past its energy limits several hours later when RPV breach would have occurred. Operators were trying to open a safety relief valve to lower pressure, but were not fully depressurized.

    Would could have happened, is the core boiled off, fuel relocated, melted the bottom head just enough to cause a rupture, and the reactor water cleanup bottom head drain or one of the other bottom head penetrations, drytubes, control rod drive penetrations, etc, failed, and the high pressure release caused the grating to fail. It’s also possible a partial melt did occur and was quickly resolidified as pressure dropped and fire pumps started injecting.

    This might make sense, as unit 2 had a loud explosion noise coming from the containment/suppression pool, and could explain the grating damage.

    Obviously until the next robot, we won’t know for sure.

    1. Molten fuel hitting the concrete at the Drywell Floor does make quite a blast from what I’ve read. MCCI also releases Carbon Monoxide and Hydrogen are produced as the concrete decomposes ablates. If the TEPCO account is factual, it seems to me that MDRIR was quickly re-established which should limit core migration. The RWCU Bottom Head Drain is right above where the floor grating hole is pictured, I was hoping for a better pan up image to see the Instrument Guide Tubes for TIPs or dry tubes for LPRMs, SRMs and IRMs. One would think the TIP indexer could provide a series of ports to conduct a fiber optic to various regions below the RPV. First inserting a cutter tool “x” feet in, spin it until the tube is cut. Insert a piston and hydraulically force it to the break site. With a severed tube, you have a port to a known location under the RPV. No robot electronics, just fiber optic boroscope cable. ***but then again – they didn’t invite me*** So I’ll siddown and shuddup.

      1. Haha

        For those who aren’t familiar with GE terminology. MDRIR is the minimum debris retention injection rate. In laymens terms, it is a curve showing the minimum amount of water you must inject X number of hours after shutdown to ensure the bottom head doesn’t breach. Reestablishing MDRIR after the breach should prevent further core melt and relocation, even though the Severe Accident Guidelines don’t mandate it at that point.

        1. I don’t know if you have EPG SAG Rev 3, but SAGs do reference MDRIR to arrest core migration in the Containment.

          Mark 1 designs also have Severe Accident Management Water Addition (SAWA) and Severe Accident Water Management (SAWM) to put a minimum of water level onto the Drywell Floor without flooding out the Torus Vents. SAWA / SAWM protects the containment and maintains Torus Vent capability.

          SAWA intent is to arrest migration towards the lower radius of the Drywell to Torus Vent Pipes. The lowest permissible SAWA Flow for Containment Injection is the applicable MDRIR.

          I helped BWROG and NEI close the last 3 Tier 2 and 3 Fukushima Issues at the ACRS Fukushima Subcommittee Meeting in February 2016.
          These were Hydrogen Control, Venting, and Severe Accident Instrumentation issues associated with Mark 1s.
          Hatch had just implemented Rev 3, so it was the example design.

          1. I’m an SRO at Clinton. We still rush to Minimum Debris Submergence Level after a breach. no SAWA for us.

    1. We aren’t directly related! He’s a good guy though. I’ve been at Clinton a while now and people still ask if he’s my Dad.

  12. I’m better at BWRs than genealogy.
    And I wasn’t that good of an operator, ask the old guys on your crew.

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