Monday, March 21, 2011

Fukushima: New plumes, SPEED measurements and Cs and I measurements in Tokyo.

So far today, there have been reports of produce contamination in he Ibakari prefecture and the fact that two plumes formed and were the reasons for the evacuation of workers at Fukushima. One should note that the detector at Fukushima are not being given in the SPEED network and so we get to see only readings further away from the plume source. As one can see from the report above,  there have an increase in the dose rate on March 21 in the Ikabari prefecture. A similar trend can be found in the detection performed for Cesium 137, Cesium 134, iodine 132 and iodine 131 performed in Tokyo. From the data [1], one can categorize the following days with background level measurements: March 17March 18  March 19,  March 20 while March 15March 16March 21 show much larger contributions. We should remain with an above average contribution for March 22. 

The background levels are estimated by comparing the values to the background values at UCBerkeley. Let us note that these measurements are extracted because each of these elements have a specific gamma signature. Geiger counters being considered for monitoring the plume do not detect the same thing. In particular, in Geiger counters, there is no discrimination in energy.

If we take the measurements of the SPEED network for Hairando (south of Tokyo), the jump seen in the Cesium and Iodine measurement above do not show up on that network's measurement in the same area (Tokyo).

This maybe an issue of wind patterns. One can also regret that while there are a few models looking into the plume displacement over the whole globe, there seems to be scant simulation focused only on Japan.

[1] Source: Department of Health and Welfare, Tokyo

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