Category Archives: Japan

Fukushima residents exposed to far less radiation than thought

by Katherine Kornei
Published in Science
23 Jan 2017

Citizen science usually isn’t this personal. In 2011, roughly 65,000 Japanese citizens living near the crippled Fukushima Daiichi Nuclear Power Plant started measuring their own radiation exposure in the wake of the Tōhoku earthquake and tsunami. That’s because no one, not even experts, knew how accurate the traditional method of estimating dosage—taking readings from aircraft hundreds of meters above the ground—really was. Now, in a first-of-its-kind study, scientists analyzing the thousands of citizen readings have come to a surprising conclusion: The airborne observations in this region of Japan overestimated the true radiation level by a factor of four.

Continue reading Fukushima residents exposed to far less radiation than thought

Radioactive Refuges

by Ashley Braun
Originally in Hakai Magazine
Published: 16 Jan 2017

A heavily-exploited Japanese fish found sanctuary after the 2011 Fukushima earthquake.

You won’t catch any three-eyed mutant fish off the coast of Japan these days, but in the wake of the 2011 earthquake and tsunami you also won’t have a problem finding flounder, the latest species to suddenly flourish in a nuclear disaster zone after humans have been pushed away.

link to full article here.

Aftershock rattles Japan’s Fukushima region

A Mw 6.9 aftershock shook the Iwaki region of the coast of Japan on November 22, 2016. Considered an aftershock, since it was within 2 rupture lengths of the  2011 Great East Japan earthquake that itself ruptured a 300 km stretch of seafloor, this is just the latest shaker of the hundreds of quakes >Mw 4 that have occurred since March 11th, 5 years ago. While on the human timescale, there has been enough time for many structures to be rebuilt and life to return to normal for many, geologically speaking the M9 quake is still reasonably fresh. While aftershocks DO get more spaced out in time since the main shock, they do not necessarily become weaker and so this is unlikely to be the last tremor of this magnitude in the area. Continue reading Aftershock rattles Japan’s Fukushima region

Open Access Review of Fukushima Radionuclide Source Term, Fate and Impact in Pacific

Fig1Buesseleretal2017.png
Schematic of Fukushima Daiichi sources of 137-Cs from Buesseler et al. (in press). Atmospheric fallout (1) and direct ocean discharges (2) represent total petabecquerels (PBq = 10^15 Bq) released in the first month of the meltdowns. Groundwater fluxes (3) and river runoff (4) are approximate ranges for the first year in terabecquerels (TBq = 10^12 Bq), a unit 1,000 times smaller than the PBq used for fallout and direct discharge. Details on source term estimates can be found in the paper (http://www.annualreviews.org/doi/abs/10.1146/annurev-marine-010816-060733). (Buesseler et al. 2017)

by Jay T Cullen

The purpose of this post is to bring to the attention of readers here a review of the available measurements and science based investigations of the Fukushima Daiichi Nuclear Power Plant (FDNPP) and its impact on the Pacific Ocean ecosystem and public health. This post is part of an ongoing effort to summarize scientifically rigorous information about the disaster for interested readers. The new paper is a product of a working group on radioactivity in the ocean convened by the Scientific Committee on Ocean Research (SCOR) an international non-governmental non-profit organization. I highly recommend this paper for anyone who wishes to better understand what the international scientific community has found about the marine release, fate and impact of FDNPP-derived radionuclides in the marine environment.  The working group was made up of 10 experts from 9 different countries, including Japan, and published the open access paper in Annual Reviews.  The main findings of the review were as follows:

  • The amount of 137Cs released from the plant was ~50-fold less than the fall out from nuclear weapons testing in the 20th century and ~5-fold lower than that released from Chernobyl in 1986. Total releases from Fukushima are similar to the discharges of 137Cs from the nuclear fuel reprocessing plant Sellafield in the UK
  • Initial releases in the weeks to months after the disaster which began on March 11, 2011 dwarf those from aggregated ongoing releases from the plant site
  • The majority of radionuclide releases ended up in the Pacific Ocean with most deposition and input occurring close to the FDNPP
  • Current range of estimates of the total 137Cs ocean source term are 15-25 PBq (PBq = 1015 Becquerel where a Bq is one nuclear decay event per second). While many other radionuclides were released from FDNPP, the most likely isotopes to represent a health risk to the marine ecosystem and public are those of Cs given their longer half-lives for radioactive decay (134Cs = ~2 yrs; 137Cs = ~30 yrs) and higher relative abundance compared to other isotopes of concern in the FDNPP source term
  • Because Cs is very soluble it rapidly dispersed in the ocean after the disaster given mixing, transport and dilution by ocean currents.  Peak levels of 137Cs occurred close to the plant in 2011 where activity concentrations near FDNPP was tens of millions of times higher than before the accident. By 2014 137Cs concentrations in the central North Pacific was about six times the remaining weapons testing fallout and about 2-3 times higher than prior fallout levels in the northeast Pacific near to North America. Most of the fallout remains concentrated in the top few hundred meters of the ocean. Measurements being made by the Fukushima InFORM project indicate that maximum 137Cs levels off the North American coast are likely to occur this year before declining to levels associated with background nuclear weapon testing before the accident by about the end of this decade
  • There are unlikely to be measurable effects on marine life with the exception of coastal areas very close to FDNPP immediately after the disaster. Monitoring of fish species in Fukushima Prefecture show that about 50% of samples in coastal waters had radiocesium levels above the Japanese 100 Bq kg-1 limit, but that by 2015 this had dropped to less than 1% measuring over the limit. High levels continue to be found in fish around and in the FDNPP port
  • Given levels in seawater and marine organisms measurable impacts to human health through contact with the ocean and the consumption of seafoods are very unlikely

There are many informative graphics and moderately technical summaries of available studies found in the new paper.  The authors highlight the difficulty of monitoring radionuclides in the ocean  given the dynamic nature of the sea and logistical challenges presented by the temporal and spatial scales and low levels of FDNPP derived contamination going forward.  In addition to providing ongoing assessments of risk to the environment from the disaster it is likely that useful information about ocean circulation will be obtained through continued monitoring efforts.

Most radioactive caesium fallout on Tokyo from Fukushima accident was concentrated in glass microparticles

by Goldschmidt Conference
Originally published by EurekAlert
26 June 2016

New research shows that most of the radioactive fallout which landed on downtown Tokyo a few days after the Fukushima accident was concentrated and deposited in non-soluble glass microparticles, as a type of ‘glassy soot’. This meant that most of the radioactive material was not dissolved in rain and running water, and probably stayed in the environment until removed by direct washing or physical removal. The particles also concentrated the radioactive caesium (Cs), meaning that in some cases dose effects of the fallout are still unclear. These results are announced at the Goldschmidt geochemistry conference in Yokohama, Japan. Continue reading Most radioactive caesium fallout on Tokyo from Fukushima accident was concentrated in glass microparticles