Atmospheric dose of reactor4 pool area is nearly 0.1 mSv/h / Reaches the annual dose limit only within 200 hours

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Following up this article.. NRA “Radiation dose is too high in reactor4 spent fuel pool area” → Tepco covered lead plate over the crane [URL]


The radiation dose on the “stand” above reactor4 pool is 90 μSv/h, according to NRA (Nuclear Regulation Authority).

The annual dose limit of workers is 20 mSv. The total exposure dose of fuel removing workers will reach this annual limit only within 200 hours.

Tepco is to keep removing the fuel until the end of this year.


However, Tepco announced they will not release the exposure dose data of the workers. The reason is not announced either.

(cf, Tepco not to announce the total exposure dose of workers for reactor4 pool fuel removing [URL])



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Français :

La radioactivité ambiante frise les 0,1 mSv/h à la piscine du réacteur 4 : c’est la dose annuelle en moins de 200 heures
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Article lié : La NRA “La radioactivité est trop forte autour de la piscine du réacteur 4″ → Tepco a recouvert de plaques de plomb ce qui est au-dessus de la grue

La radioactivité ambiante sur le “stand” au-dessus de la piscine du réacteur 4 est de 90 μSv/h, selon la NRA (Nuclear Regulation Authority).
La dose annuelle maximale admissible pour les travailleurs est de 20 mSv. La dose d’exposition totale des travailleurs du chantier de retrait des combustibles atteint cette limite en 200 heures seulement.
Tepco va continuer le retrait des combustibles jusqu’à la fin de l’année.

Or, Tepco a annoncé qu’ils n’allaient plus publier les doses reçues par les travailleurs. Ils n’en donnent aucune justification non plus. (cf. Tepco ne publiera pas l’exposition totale des travailleurs du retrait des combustibles de la piscine du réacteur 4)

Note : Si vous êtes de la grande presse internationale, ne lisez pas ce site sans avoir préalablement pris contact avec moi.

  1. that does not include internal absorption (inhaling the some of the vapours of the stuff for example).

  2. 1mSv per year is high range estimate threshold for human beings based on Chenobyl research, although, even Low Dose Radiation can cause symptoms ranging from depression to aggression to fatigue. Also, what radionuclides are involved. If there are alpha nuclides, even a very small dose will cause havoc if ingested…

  3. According to yesterday’s Asahi Shimbun NRA officials found high levels of radiation emitted from cobalt-60 ‘that was apparently mixed with shavings produced when workers cut into reactor components inside the [#4 spent fuel pool].

    Can anyone suggest what components the workers might have been cutting into? Is this an oblique reference to the spent fuel rods?

    1. Induced Radiation in Structural Steel

      http www epa gov/ (radiation/radionuclides/cobalt) html

      Where do cobalt and cobalt-60 come from?

      Non radioactive cobalt occurs naturally in various minerals, and has been used for thousands of years to impart blue color to ceramic and glass. The radionuclide, cobalt-60, is produced for commercial use in linear accelerators. It is also produced as a by-product of nuclear reactor operations, when structural materials, such as steel, are exposed to neutron radiation.

    2. Gamma Cam Photos of Structural Steel near the FDU-3 nuclear explosion are hot, presumably with Cobalt-60 among the isotopes. The radiation levels were described as ‘Death In Seconds’ in the media. However you might make it a couple of minutes.

      How does cobalt-60 change in the environment?

      Cobalt-60 undergoes radioactive decay with the emission of beta particles and strong gamma radiation. It ultimately decays to non radioactive nickel. The half-life of cobalt-60 is 5.27 years. This is short enough to make isolation a useful treatment strategy for contaminated areas. In some cases, simply waiting 10 to 20 years allows for sufficient decay to make the site acceptable for use again.

      1. Well if we go out 7 half lifes, the radiation will be about 1%, so things that
        would kill you in minutes, will kill you in a few hours and those things that
        kill in hours will kill you in a few weeks.

        If the Japanese can get the fuel out of the fuel pools and maintain the
        water into a ghost fleet of tankers for 100 years, maybe the problem can
        become more tractable, but,we are talking some 40 years for the cobalt
        to drop off a bit and to closer to 120 for the tritium.

        1. Several Problems

          Four items represent Global Concerns: These are

          1) Spent Fuel (water cool for 40 years, then dry cask)

          2) Secure and Stabilize the Corium slugs

          3) Reduce the radioactive water, CONTAMINATION & flow to the Pacific Ocean.

          4) Secure and contain the 3 meltdown reactors.

          Your tanker fleet, could reasonably store the Post-ALPS-Water, with the remaining Tritium (tritiated water) for about 50 years, and then SAFELY sink the fleet.

          The highly radioactive structural steel, induced by neutron flux, from the FDU-3 atomic explosion; can be safely stored in a steel and concrete bunker.

          Japan has LOTS of other problems, such as a LOOMING leukemia epidemic.


          Bill Duff

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About this site

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.


February 2014