Isotopic Compositions of 236U and Pu Isotopes in “Black Substances” Collected from Roadsides in Fukushima Prefecture: Fallout from the Fukushima Dai-ichi Nuclear Power Plant Accident

Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan
Vienna Environmental Research Accelerator (VERA) Laboratory, Faculty of Physics, University of Vienna, Währinger Straße 17, A-1090 Vienna, Austria
§ Low Level Radioactivity Laboratory, Kanazawa University, Kanazawa, Ishikawa 923-1224, Japan
Environ. Sci. Technol., 2014, 48 (7), pp 3691–3697
DOI: 10.1021/es405294s
Publication Date (Web): March 6, 2014
Copyright © 2014 American Chemical Society
*Telephone: +81-82-424-7463. Fax: +81-82-424-0735. E-mail:


Abstract Image

Black-colored road dusts were collected in high-radiation areas in Fukushima Prefecture. Measurement of 236U and Pu isotopes and 134,137Cs in samples was performed to confirm whether refractory elements, such as U and Pu, from the fuel core were discharged and to ascertain the extent of fractionation between volatile and refractory elements. The concentrations of 134,137Cs in all samples were exceptionally high, ranging from 0.43 to 17.7 MBq/kg, respectively. 239+240Pu was detected at low levels, ranging from 0.15 to 1.14 Bq/kg, and with high 238Pu/239+240Pu activity ratios of 1.64–2.64. 236U was successfully determined in the range of (0.28 to 6.74) × 10–4 Bq/kg. The observed activity ratios for 236U/239+240Pu were in reasonable agreement with those calculated for the fuel core inventories, indicating that trace amounts of U from the fuel cores were released together with Pu isotopes but without large fractionation. The quantities of U and 239+240Pu emitted to the atmosphere were estimated as 3.9 × 106 Bq (150 g) and 2.3 × 109 Bq (580 mg), respectively. With regard to U, this is the first report to give a quantitative estimation of the amount discharged. Appreciable fractionation between volatile and refractory radionuclides associated with the dispersal/deposition processes with distance from the Fukushima Dai-ichi Nuclear Power Plant was found.

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By Corbett| 8 Comments | Featured, Science


  1. While this proves the initial core melting and dispersal scenarios after the tsunami, the more disturbing fact is that similar deposits seem to be found in and around Tokyo which is unusual for a nuclide release close to the ground as a H2 or vapor explosion would cause. Either these deposits were dispersed gradually over the past years from the “hot zone” around the reactors or else the observed explosions threw debris into higher strata of the atmosphere than originally thought resp. admitted.

  2. Marco Kaltofen, Civil Engineer & Ph.D. Candidate at Worcester Polytechnic Institute (WPI):
    “The sample that we got came from Nagoya in Japan, its 460 kilometers from the accident site. That’s about 300 miles away. […]. The particle we examined was a mixture of fission products from a nuclear reactor and nuclear fuels. We looked at materials like tellurium, radium-226, we saw cesium-134, and -137, cobalt-60, and a whole zoo of isotopes that probably you’ll never hear about on CNN […] 80% by weight of this particle was made up of pure reactor core materials. That tells me that something that came directly from the accident, directly from the core can escape containment and travel a very, very significant distance. […] This material was in the peta-becquerel per kilogram range […] 4 followed by 19 zeroes — that many Bq/kg. That’s a very, very high number.”

    • I read Kaltofen’s paper. The one element he doesn’t detect in his “fuel fragment” is … wait for it … Uranium.

      How odd.

    • John — 4 followed by 19 zeros is 40,000 PBq/Kg, which is 40,000,000 TBq/Kg, or 40,000 TBq/g.

      Compare this to the specific activity of Cs 134 and Cs 137. which is is 44.4 TBq/g and 3.26 TBq/g receptively. BTW the specific activities of U and Pu mentioned in the abstract above are a fraction of Cs. The huge number in the video is completely bogus.

      • Literally a back-of-the-envelope calculation, but 10^19 Bq/kg of activity with each detected particle and gamma ray being in the 1MeV (about 10^-13 joules) range would result in an energy output of about a megawatt of heat from a one-kilo sample or a kilowatt from a one-gram sample. That’s *hot*.

        Cs-134 decay -> 1.6MeV gamma ray.
        Cs-137 decay (two paths) -> average of 1.1MeV gamma ray.
        C0-60 decay -> two gamma rays, total 2.4 MeV

    • Is it possible to determine from this study if the substances being analysed came from an operational reactor core? Is it possible that it came from fuel in the pool, like for instance if the unit 3 explosion threw material from the fuel pool into the air, but the containment remained relatively unharmed.

  3. depleted uranium is being used in oil wells and in weapons created by the usa .contamination is all the government and big business do any more just so they can add another million to their already massive amount of revenue.The saddest part is the ones that can do something about it are so rooted into the capitalist ideas they have been force fed that they could care less about the status of our environment the people of this world need to stand together.

  4. Here is a thought.
    • The core melt was cooled by direct immersion in seawater.
    • The seawater then leaked thru the disrupted containment, thru he buildings and tunnels, directly to the sea.
    • Certain elements can get concentrated in certain sealife which can then be eated by seagulls.
    • Seagulls poop everywhere.

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