Surface deposition of 131-I as reported in Fig. 15 of Katata et al. (2015)
The purpose of this short diary is to discuss the surplus of misinformation on the environmental impact of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) disaster present in the public domain. The diary is part of an ongoing effort to mobilize useful and accurate information about the disaster with respect to the likely impacts on the health of the North Pacific and residents of western North America. Energy News has a history of misrepresenting or misunderstanding the scientific literature in its presentation of information specific to Fukushima. A recent report on a study estimating the atmospheric source term for Fukushima is no exception. It used to be that within a few hours of such misinformation posting we could be sure to see it show up on Kos but luckily we have been spared it recently. Below the fold I outline how this misinformation is packaged as an example of the sort of poor reporting and knowledge mobilization that the Fukushima disaster begets.
The article that is the subject of the Energy News report was recently published in the peer-reviewed, open access journal Atmospheric Chemistry and Physics by Katata and colleagues.
According to the Energy News headline and emphasis placed in reporting about the paper we should all be very scared.
Headline about Katata et al. (2015) Atmos.Chem.Phys.Discuss.
One would take away that the study had found:
- Atmospheric releases from Fukushima were much higher than previously reported
- Dangerous levels of radioactive fallout from the atmosphere occurred in North America following the FDNPP meltdowns in 2011
- The red color used in figures in the paper has some intrinsic meaning that is independent of the scale bar
If one actually reads the paper, understands it or approaches a summary with an intent other than to misrepresent its findings you take away the following information.
What they did
Katata et al. (2015) estimated the atmospheric releases during the accident over time by combining environmental monitoring data with both atmospheric and ocean model simulations. They used WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) to model atmospheric radionuclide inventories and dispersion, and for the ocean the SEA-GEARN-FDM model (see paper for details of how the models work).
What they found
Major releases of radionuclides directly to the atmosphere due to the FDNPP accident occurred in the following intervals in March 2011:
- the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1
- the morning of 13 March after the venting event at Unit 3
- midnight of 14 March when the SRV (Safely Relief Valve) at Unit 2 was opened three times
- the morning and night of 15 March, and the morning of 16 March
The simulations measured the highest radioactive contamination at the site between March 15 to 16 related complicated interactions among rainfall, plume movements, and the temporal variation of release rates associated with reactor pressure changes in Units 2 and 3 and the documented hydrogen explosions.
Looking at the match between the observational data and the models they determine a new source term for Iodine-131 (131-I half life ~8 days) and Cesium-137 (137-Cs half life ~30 yr) that is reported in the table from the study shown below:
Table 8 from Katata et al. (2015) showing various source term estimates for Fukushima for 137-Cs and 131-I.
They estimate a source term of 151 PBq (PBq = PetaBecquerel = 1015 Bq) for 131-I and 14.5 PBq for 137-Cs. Neither of these estimates are markedly higher than previously published source terms based on modeling and measurements.
Indeed, best estimates of a recently released report by the Science Council of Japan that compared simulation results from nine regional atmospheric models, six global atmospheric models and eleven ocean models with monitoring data to better constrain the amount of radioactivity released from Fukushima at the height of the accident reported atmospheric source term for 137-Cs to be 19.4 +/- 3.0 PBq. The Katata et al. (2015) study is actually lower than the existing consensus value.
Energy News completely misunderstands and misinterprets the study and misleads its readers.
Atmospheric fallout in North America
Of course the results of the Katata et al. (2015) study do nothing to change what the scientific community has learned about the levels of atmospheric fallout measured from Fukushima in North America. Fallout levels in rain and air were about a factor of 10 lower after Fukushima than what was measured following the Chernobyl disaster in 1986. You can read about the levels measured in air, rain, kelp, mushrooms and soil in the following diaries previously published at this site:
Looking For Fukushima Contamination in Mushrooms and Soil of Western North America
Peak Concentrations of Radioactive Iodine From Fukushima in North American Rain Water and Seaweed
Fukushima Fallout Radionuclides in Air, Rain and Food from San Francisco Bay Area
Neither the levels delivered in 1986 nor the fallout resulting from Fukushima in 2011 represent a danger to the public in North America according to health physicists.
Conclusion
Science and risk communication is a difficult task. There exists a tremendous amount of misinformation on the internet about just about any topic one can conceive of. The Fukushima disaster is a great example of how much misinformation is inadvertently and sometimes purposefully spread. This short diary is another example of why friends don't let friends read Energy News. They do this all time and it would take a full time effort to debunk their ham-handed science communication efforts.