lunedì 30 aprile 2012

Nuclear Plants, Radiation and Food in Japan - updates

Currently in English, Italian translation will follow. 

Power Production

No electricity is generated from nuclear plants in Japan. All but one reactors are down, officially for maintenance. Whether they will be reactivated is still debated. Oki reactors are now less likely to be put back on line, pending the complaints by local government and some still unclear safety issues.

As of now, both Kanto and Kansai (that are on different grids) are consuming about 80% of the full power production. If this figures are correct, there is the clear possibility to have scheduled black-outs this summer, especially if it will be warmer than last year. The situation might be more critical for Kansai  which had a larger nuclear-produced energy fraction and that last summer had still the nuclear power plants online. 

Environmental radiation in case of no decontamination
in 10 and 20 years from now

Environmental radiation

Outside the exclusion zone, Japan has  an average  lower environmental radiation than Italy.  
Recent simulations show that - in absence of any decontamination - the Fukushima expelled Cesium will leave the exclusion zone unsafe for more than 10 years. This is hardly surprising given the 30 years half-life of Cesium 137. Decontamination strategies are under study, either by removing the ground, by letting radiation penetrate deepen in the soil in case of hot spots, or by physically separating the radioactive material from the rest. A truck from Toshiba has been set up to demonstrate the principle. The first method seems more expensive but is much more reasonable,  provided that all the material is stored around the site of the now destroyed power plant. The truck option would be the cleanest one, but cost of the procedure and the possibility of large scale production are not clear. 

Is there radiation in food in Japan?

A vegetable wholesaler has been found relabeling the origin of Fukushima cucumbers in other prefectures. He was just scolded, no fine or charges. The cucumbers were not dangerous in themselves, since it still is below the new limit of 100Bq/kg for Cesium, but the lack of legislation is worrying. This new lower limit (previously was 500Bq/kg) is causing a lot of trouble to fruit and vegetable companies, since the value is extremely low too meet. .  All food (and our body) contains radioactive material: as a reference it is worth remembering that bananas  have 125 Bq/kg of  Potassium 40 (even though it is expelled faster from the huma. body).

Left and right: radiation data of Coop food products

All are below the new limit of 100Bq/Kg (mentioned in the top page). The food with highest radiation content are Shiitake mushrooms. Note that Germanium detectors have an higher resolution than those of NaI  and can distinguish between the isotopes of Cs134 and Cs137. 
The total amount of radiation in Ge-measured products is the sum of the two isotopes. Cs134 has a shorter half-life, two years, compared to the 30years of Cesium 137, so it is expected that Cs134 content will be negligible by next year.

Rate of disappearance of Cesium from human body
from here