[Reactor4] Exposure dose to remove the lid of PCV4 was 7.8 timers higher than new fuel from SFP4

Tepco removed the lid of PCV4 on 8/10/2012. It’s supposed to be a part of the entire removal process of spent fuel assemblies in SFP4, but Tepco did not announce more specific reason to remove it.

They are to remove the lid of RPV4 by early October.

The exposure dose of the workers was remarkable. 36 workers were involved and the highest reading of the exposure dose was 0.39 mSv for 15 minutes work. It’s 1.56 mSv/h.

Tepco estimated the exposure dose would be 0.8 mSv/d, which is only 0.03 mSv/h.

The actual exposure dose was 52 times higher than estimated.

Also, when they removed the new fuel from SFP4 in July, the highest exposure dose was 0.62 mSv for 3 hours work, which is 0.20 mSv/h. (cf. [Reactor4] Photos and videos to take out the new fuel assemblies)

The exposure dose to remove the lid of PCV4 was 7.8 times higher than the one to remove the new fuel assemblies from SFP4. [Link]

The graph is below to compare. By the way, according to Tepco’s announcement, there was no fuel in PCV4 supposedly.


[Reactor4] Exposure dose to remove the lid of PCV4 was 52 timers higher than new fuel from SFP4


[Reactor4] Exposure dose to remove the lid of PCV4 was 52 timers higher than new fuel from SFP4 2


↓ Tepco’s handout about the removal of PCV4 lid. [Link]


[Reactor4] Exposure dose to remove the lid of PCV4 was 52 timers higher than new fuel from SFP4 7


[Reactor4] Exposure dose to remove the lid of PCV4 was 52 timers higher than new fuel from SFP4 8


↓Video released by Tepco [Link]

  1. I thought TEPCO claimed that this ‘lid’ was sitting beside the Spent fuel pool and not over it… since last summer. High readings would then indicate that Fukushima is spewing like never before!
    Please clarify, Iori.

  2. That lid is a piece of history.

    It should be cleaned up and put in a museum.

    If it cannot be cleaned so well, it should go on the front lawn of the Diet building to serve as a reminder to all who enter.

  3. So if it was empty…what the hell was the black rod they pulled out of the vessel with the giant crane and whipped down by the dome?

  4. so all those people on the ground was to insure
    the view of the HITACHI/GE ad banner was centered

    one would think its bad publicity

    why did they do this now
    airing out the reator?

    I mean, why?

  5. Best guess is the building section underneath the dome is collapsing faster than they thought. Perhaps they are removing weight? The northern section of the building is leaning into the southern section with the sfp. No matter what’s happened to the rods now, a building break-up could dump them.

  6. FUKUSHIMA DIARY FR – [Réacteur4] La dose d’exposition au retrait du couvercle du PCV4 était 7,8 fois plus forte que le combustible neuf de la SFP4
    Par Mochizuki, le 13 août 2012 · 6 Commentaires

    Tepco a enlevé le couvercle du PCV4 (= Primary Containment Vessel of reactor 4 = enceinte primaire du réacteur 4) le 10 août 2012. C’est supposé faire partie du processus de retrait total des assemblages de combustibles usagés de la SFP4 (= Spend Fuel Pool of the reactor 4 = piscine des combustibles usagés du réacteur 4) mais Tepco n’a pas annoncé de raison plus spécifique à ce retrait.

    Ils vont enlever le couvercle du RPV4 (= Reactor Primary Vessel of #4 = Enceinte primaire du réacteur 4) début octobre.

    La dose d’exposition des travailleurs a été remarquable. 36 travailleurs ont participé à l’opération et la plus haute lecture a été 0,39 mSv pour 15 minutes de travail. C’est du 1,56 mSv/h.

    Tepco a estimé que la dose d’exposition devait être de l’ordre de 0,8 mSv/jour, ce qui revient à 0,03 mSv/h seulement.

    La dose effective rencontrée a été 52 fois plus haute que celle estimée.

    De plus, quand ils ont retiré le combustible neuf de la SFP4 en juillet, la plus haute exposition était à 0,62 mSv en 3 heures de travail, soit 0,20 mSv/h. (cf. http://fukushima-diary.com/2012/07/reactor4-photos-and-videos-to-take-out-the-new-fuel-assemblies/ )

    La dose d’exposition pour retirer le couvercle du PCV4 a été 7,8 fois plus haute que celle rencontrée en retirant les combustibles neufs de la SFP4. [Lien : http://www.meti.go.jp/earthquake/nuclear/pdf/120730/120730_01z.pdf%5D

    Le graphique ci-dessous fait la comparaison. Au passage, selon les communiqués de Tepco, il ne devait soi-disant pas y avoir de combustible dans le PCV4.


    ↓ plaquette de Tepco sur le retrait du couvercle du PCV4. [http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120810_01-e.pdf]
    (2 copies d’écran)

    ↓Vidéo publiée par Tepco [Lien : http://photo.tepco.co.jp/en/date/2012/201208-e/120810-01e.html%5D

  7. I agree with Kathryn. The stability of the building must be dire enough to push the removal process ahead of schedule. Like Gundersen said, if the fuel pool looses water due to a crack and the fuel rods are exposed to the air, it would create a fire and release more Cesium into our atmosphere (more than ALL the bombs ever exploded since the 1940’s). Frightening.

  8. Thanks Kathryn
    Feel kinda dumb,
    just noticed the big 52 tons written on the pcv

    Im sure with the condition of the building
    thats the message, besides the ad

    something is just not right

    its trash
    just put it on the ground with a remote quick disconnect
    no people on the ground even needed

    I think they wanted something out of there
    and that lid may go back on.
    The timeline of years to stop the radiation volcano
    will pretty much have the same effect as a collapse.

  9. The yellow containment lid has been sitting in its normal storage position while the empty reactor was being retro fitted. The fuel assemblies (2) were removed from the spent fuel pond (I’m still trying to figure out why the fuel assemblies were not placed in a cask before removal but what do I know?).

    What caused the yellow lid to read more contamination than the removed unused fuel assemblies, I’m sure, has more to do with the assemblies being kept underwater and the yellow lid exposed fallout in the open air. Both the yellow lid and (2) unused assemblies had contamination readings way higher than in typical working conditions.

    The reactor lid and steam dryer should be next up for removal as they are just large paperweights now.

    1. cool, you may not be here but
      you sound like you have a clue

      lets see, been a year and a half
      at this pace
      chances are good
      anything they remove
      will have a even higher rad reading

      This work seems to be centered around taking apart
      one of four heavely damaged
      radiation spewing reactor buildings.

      maybe I can answer your ?

      I’m still trying to figure out why the fuel assemblies were not placed in a cask before removal

      With the amount of radiation spewing from the area
      Why bother
      thats the only part of what they did so far that makes sence

      They havent gotten to the stage of stoping or at least containing
      exposure to the air, land or sea yet.

      Only leak they seem to prevent is info about the true condition
      And they had a nice dog and pony show removing the fuel assy’s and lid
      but the other paperweights just sit there
      maybe awaiting new banners

      Seems to me the lid and dryer could have been off by now
      if it is weight they are concerned about

      they know that northern japan has had an earthquake
      just about everyday this month,
      with an noticable increase in intensity today

      It seems they know
      that whatever they do short of containment
      in the end, wont really matter

      1. “Roger that” t-evans,

        If plucking unused assemblies out of pool #4 is so easy, why don’t yank somemore out?

        Units 1,2 & 3 will kill humans and robots with their uncontrolled radiation releases so stalling for time is the name of the game for TEPCO and the Japanese government…they only need to wait about 100 years before they can approach the melted cores. As soon as they find out where they are.

  10. Just throwing this out there…

    why not dump some of th efuel back in the reactor and put the lid back on?? Shorter distance and the fuel can not get hot enough enymore to actually melt the reactor. Also drop the control rods in there and keep it all stable. That takes quick care of one load. This reactor was empty at the time of the accident right? RIGHT??? or is there something else they aren’t saying..

    1. The structure of the building of unit4 is in a very bad condition. The building is in such a bad shape that it could collapse really soon. They need to remove weight to make it more stable (that’s also why they removed the whole upper section of the building). If the building would collapse and SFP4 would leak all the fuel rods would start to burn and release ridiculously high amounts of radioactive material. Trust me, you wouldn’t want that, no matter where you live on this planet, you wouldn’t be safe

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This website updates the latest news about the Fukushima nuclear plant and also archives the past news from 2011. Because it's always updated and added live, articles, categories and the tags are not necessarily fitted in the latest format.
I am the writer of this website. About page remains in 2014. This is because my memory about 311 was clearer than now, 2023, and I think it can have a historical value. Now I'm living in Romania with 3 cats as an independent data scientist.
Actually, nothing has progressed in the plant since 2011. We still don't even know what is going on inside. They must keep cooling the crippled reactors by water, but additionally groundwater keeps flowing into the reactor buildings from the broken parts. This is why highly contaminated water is always produced more than it can circulate. Tepco is planning to officially discharge this water to the Pacific but Tritium is still remaining in it. They dilute this with seawater so that it is legally safe, but scientifically the same amount of radioactive tritium is contained. They say it is safe to discharge, but none of them have drunk it.