Former Fukushima Daiichi Worker: My best guess is explosion had to blow lid off pressure vessel at Reactor 1

Published: August 2nd, 2012 at 4:31 pm ET


Chris Canine has 15 years experience as a Health Physics Technician, Chemist and Radiation Safety Instructor. He has worked at over 20 plants throughout the United States, Japan and Mexico — including Fukushima #1 and #2 in the late 1970’s.

August 1, 2012 comment on ‘Tepco planning to float a balloon inside Reactor 1 in early August — Inspecting top floor with spent fuel pool

Tepco is basically saying that the refueling floor is still too radioactively hot for any human to enter. There was no fire in that spent fuel pool, and we never heard that it was like unit #3 and blew the lid off the pressure vessel. So why are radiation levels so high? During normal operations there is little radiation on the refueling floor because there is really nothing there. The fuel in the pool is under water with no dose on the surface, and the reactor is buried under cement and steel.

My best guess is that the hydrogen explosion had to blow the lid off this reactor also. With radioactive gasses and particulates coming out of the reactor the cover was put on the building to limit the releases out onto the site. But as the cover kept in a lot of this radioactive material the refueling floor is so contaminated that it is no longer a place where humans can work or even walk through.

Find the answer why they put a cover on only this building and that will tell you the condition of this unit.

More from comment thread

This whole fiasco is some sort of giant jigsaw puzzle. Tepco will not tell the truth or explain what is really going on so you need to get the information you can and try to make the pieces fit.

The fuel pools are still there as is most of the highly damaged reactors. When any of them fall down all the people of Japan will be running to the exits as quickly as possible-we will definitely know when that happens.

Published: August 2nd, 2012 at 4:31 pm ET


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  1. Molten fuel bore a hole at bottom of Containment Vessel at Reactor No. 1– Pressure Vessel is “completely broken” says Kyoto U. nuclear professor May 17, 2011
  2. Explosion Danger at Reactor No. 1? Worker says hydrogen levels over 4% in pipe leading to Containment Vessel — Mainichi: “Danger of explosion” if over 4% September 23, 2011
  3. *NEW Dec. 1 Yomiuri* Gov’t Study: Reactor pressure vessel may be “tilted” after corium melted through concrete floor up to 200 cm deep November 30, 2011
  4. TEPCO admits “multiple holes” found in bottom of No. 1 reactor’s pressure vessel May 13, 2011
  5. Quake, not tsunami, may have caused damage that led to meltdown — Within 16 hours, No. 1 reactor core melted and made a hole in pressure vessel May 15, 2011

16 comments to Former Fukushima Daiichi Worker: My best guess is explosion had to blow lid off pressure vessel at Reactor 1

  • iso-tope iso-tope

    ahh finally some truth… and it didn't come from IneptCo. This makes alot of sense, and as to why this building only was covered and so quickly…

  • dosdos dosdos

    I doubt it physically blew the lid off, but as Gunderson explained, it probably stressed the securing bolts so badly that it leaked profusely around the seal of the cap.

  • Time Is Short Time Is Short

    "The fuel pools are still there…" Riiight.

    Sounds like a 'limited hangout':

    Mike would be so upset over this.

    • A 'limited hangout' is a public relations or propaganda technique that involves the release of previously hidden information in order to prevent a greater exposure of more important details.

      Perhaps they want us to forget about a possible puddle of molten corium that might not stay in one place. Perhaps this reactor melted thru first? Perhaps the molten corium spattered like a drop of water on a hot skillet? The only thing we know for sure is that T3PC0 knows and isn't telling.

  • eatliesndie eatliesndie

    Well, it's anyone's guess, I guess.

  • Replacant Replacant

    Disinformation in full force too bad they cant put the same effort into protecting the public as they do their liability. Really at this point Tepco is done so why cant the Japanese government ask for the nuclear industry at large to help clean up this mess?

    Of course the big answer is there isnt any technology that can take that much radiation, most likely the robots they would want use cant even operate in the reactor 1 building as the robots would fail.

  • MaidenHeaven MaidenHeaven

    Tokyo Electric Power Co. said one of the reactor cores at its stricken Fukushima Dai-Ichi nuclear plant is more seriously damaged than previously thought, setting back the utility’s plan to resolve the crisis.

    Fuel rods in the core of the No. 1 reactor are fully exposed, with the water level 1 meter (3.3 feet) below the base of the fuel assembly, Junichi Matsumoto, a general manager at the utility known as Tepco, told reporters at a briefing in Tokyo. Melted fuel has dropped to the bottom of the pressure vessel and is still being cooled, Matsumoto said.

    Japan is trying to contain the worst nuclear disaster since Chernobyl after a quake and tsunami two months ago knocked out power and cooling systems at the Fukushima station. While authorities have previously suspected a partial meltdown at unit 1, high radiation levels had prevented workers from entering the building to check the damage until last week.

    “What this means is this is probably going to be a much more difficult cleanup than they originally planned for,” said Paul Padley, a particle physicist at Rice University in Houston. The government and Tepco “have consistently appeared to be underestimating the severity of the situation.”

  • mark_eric

    Sounds like a lot of contradictory information to me. Refueling floor is too radioactive for humans, reactor #1 too radioactive for engineers to enter, yet engineers entered to see the tops of the melted fuel rods. They need to float a balloon up to find out the condition of the top of the reactor, yet as already stated, they've told us that the top of fuel rods are exposed and melted down.

    Considering the state of #3 and #4, I have always thought it strange that only #1 got the cover. I guess I always assumed that the cover was purely cosmetic, and if any of the reactors needed an SEP Field Generator* #3 and #4 do.

    * (

    • Radio VicFromOregon

      @mark_eric, Reactor 1 was always in the worse shape, and the venting of ionized radiation, though far less than during the explosion, was fairly constant, so i think that is why they covered Reactor 1 – to direct the steam through a scrubber before it released into the air. All those contradictory statements drvie me nuts! There is a lot of guessing taken as fact by the media then written and published.

  • BreadAndButter BreadAndButter

    GO chrisk9! 🙂

  • patb2009

    here's my take, and it's a nickel take.

    Rac one went first and badly, so it began boiling and generating hydrogen when rod temps exceeded 800F. so you had big Hydrogen pressure bubble, leaking out of the RV then out of the CV into the secondary containment.

    That big secondary finally had a hydrogen explosion, and the shock wave shattered the containment top deck. that was easily a 2-300 PSI overpressure and it busted up all the refueling floor and deck lids.

    then subsequently as the core melted down, it began dripping onto water pooled in the basement.
    that created little steam bursts that blew corium all over the place including the floor deck.
    the rest of the corium consolidated and burned it's way out the bottom, headed to Africa.

    Or, they are lying and the SFP 1 burned and tossed fuel all over the floor deck.

    Tepco is a bunch of psychopathic liars, so, who knows.

    Japan is done, apparently US Govt predictions are that the fertility rate will hit 0.75 children per woman in japan within a decade and 50% of those kids will be unhealthy. so within a generation japan could be a country of 10 million people.

    • PhilipUpNorth philipupnorth

      patb2009: Corium burned out the bottom of Reactor1. You are right, right, and right again. Great analysis.