Sunday, April 8, 2012

Science Council of Japan: 250 Millisievert External Radiation Exposure in 30 Years Possible in #Fukushima Without Continued Decontamination

That seem like a lot, but come to think about it, 250 divided by 30 equals 8.33. At this point, average 8.33 millisieverts per year exposure in parts of Fukushima, particularly near Fukushima I Nuclear Power Plant, seems almost reasonable.

Anyway, here's Yomiuri reporting on one of several report issued on April 9, 2012 by the Science Council of Japan:


Risk of dying from cancer will increase unless decontamination continues after residents return


The Science Council of Japan's estimate shows that unless decontamination is carried out for a certain period of time after the residents return to the areas surrounding Fukushima I Nuclear Power Plant, the cumulative radiation exposure in 30 years may exceed 100 millisieverts. The estimate was published on April 9. The area surrounding the plant is highly contaminated with radioactive materials. When the cumulative radiation exposure reaches 100 millisieverts, the risk of dying from cancer goes up by 0.5%.


The Council calculated different scenarios for cumulative radiation exposure levels for 30 years, taking into account the amount of radiation exposure before the evacuation, annual radiation exposure levels on return, and decontamination after the return of the residents.


The result shows that if the residents return when the annual radiation exposure levels drop to 20 millisieverts and if no decontamination is done afterwards, the residents may be exposed to nearly 250 millisieverts in 30 years, even with the attenuation of radioactivity.

Oops. The Japanese national government's guideline to return the residents to the areas inside the no-entry zone and the planned evacuation zone is that the annual radiation exposure levels drop down to 20 millisieverts. Judging from the decontamination work that has been done inside the zones and outside, it doesn't look like there will be on-going decontamination.

The original 53-page report by the Science Council of Japan is titled (my translation) "To take a first new step toward dealing with radioactivity - take action based on the scientific probe of facts". The radiation exposure for the residents who return to their homes in the evacuation zones is discussed from page 15 to page 20 in the report.

The average background (natural) external radiation exposure in Japan before the Fukushima nuclear accident was about 0.6 millisievert per year. In 30 years, the cumulative external radiation would have been 18 millisieverts.


Chibaguy said...

This clinical trial will take decades to manifest results. Until then no need for additional nukes even those using thorium as these reactors do not exist. There is no evidence on hand that can back up what Japan is forcing on the citizens. Until we have such evidence as sad as it may be no need to advance bomb making technology. I rest my case for Japan at least.

Anonymous said...

On April 7 @ 12:32 a link was posted to an EPA NSCEP doc.
Table 1-3
site specific incidence risk per unit dose

Looking at that table might suggest women stop racing for the cure and start racing to eliminate one of the causes.

pat b said...

8.33 mSv external radiation, but what's the internal Rad numbers.

So far we've been seeing 3-4X internal to External, and I believe that ratio will increase.

the internal radiation dose and the effects on children will magnify.

Fukushima province is only for the old, who can try and fight the reactors.

Anonymous said...

@pat b, where have you seen a 3-4 ratio for internal to external exposure? Are you getting thyroid dose messed up with full body dose?

About the article, I never understood why the Japanese still mention 20 mSv as the criterion for resettlement. Surely they must understand that 20 mSv per year in April, when the extended evacuation zone was established, and 20 mSv per year at this point or some years in the future would result in very different accumulated exposures in the long run.

When they measured radiation levels in April to determine the evacuation zone outside of the 20 Km radius, there were still contributions from Iodine-131, Telluriums and other short lived isotopes. Apart from that, there was a very high contribution from Cesium-134, which would decay year by year at a faster rate than cesium-137, thus reducing its contribution to the air dose rate. In short, areas that were 20 mSv/year last April would probably be between 10-15 mSv now and would be under 5 mSv/year 10 years from now.

However, this is not the case for areas where 20 mSv/year are measured now, and specially it won't be the case for areas were the same yearly dose is measured in the future. This is because that accumulated dose would be the result of a higher contribution by Cs-137, which has a longer half-life, thus the decrease in yearly dose would be much slower and the accumulated dose after 30 years would be much higher.

arevamirpal::laprimavera said...

@anon at 3:52PM, I sort of remember seeing the graph made from the data from Norway (could be Sweden) after Chernobyl, showing the percentages of internal radiation exposure from food and inhalation and the external radiation exposure. I'll try to look for it again, but internal radiation was much larger than external in that graph.

Anonymous said...

lolo, what's the # that JP people accept liability for annual radiation exposure, like X ms/yr->in exchange for the JP gov releasing the REAL radiation #s

Anonymous said...

THE MSV'S are from mox that blew through the air and is allover everything.

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