Worst radiation plume over Japanese land
"The smaller cyclone over Honshu developed rapidly on 15 March, and the FD-NPP plume got caught in its circulation system. It was transported to the south at 18:00 UTC on 14 March, to the southwest six hours later, and back to the north and finally east from about 06:00 UTC on 15 March. The plume covered large parts of centraleastern Honshu and crossed over Tokyo and other major population centers before it left Japan towards the northeast around 18:00UTC on 15 March."
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"The highest release rates occurred on 14 March, when hydrogen explosions occurred in reactor units 3 and 4 and, presumably, unit 2. We also find unexpectedly high 137Cs emissions from 16-19 March, which suddenly dropped by orders of magnitude when spraying of water on the spent-fuel pool of unit 4 started. Thus, we believe that these high emissions are related to the degraded fuel in the spent-fuel pool of unit 4, and this result would also confirm that the spraying was an effective countermeasure at least in this case. [...]
The winds transported the FD-NPP emissions towards the Pacific Ocean most of the time, while Japan was affected only occasionally. While this seemed like a relatively fortunate situation for Japan during the accident event, a different picture emerges from our detailed analysis. Exactly during and following the period of the highest 137Cs emission rates on 14 and 15 March, the FD-NPP plume was advected towards Japan and affected large areas in the east of Honshu Island. The advection towards Japan was triggered by a developing cyclone, which produced precipitation on 15 March, leading to the deposition of large fractions of the airborne 137Cs over Japanese land."
http://enenews.com/just-published-worst-radiation-plume-from-fukushima-was-blown-over-tokyo-on-march-14-15-this-was-the-main-deposition-event-over-japan-for-the-entire-disaster
(..)
"The highest release rates occurred on 14 March, when hydrogen explosions occurred in reactor units 3 and 4 and, presumably, unit 2. We also find unexpectedly high 137Cs emissions from 16-19 March, which suddenly dropped by orders of magnitude when spraying of water on the spent-fuel pool of unit 4 started. Thus, we believe that these high emissions are related to the degraded fuel in the spent-fuel pool of unit 4, and this result would also confirm that the spraying was an effective countermeasure at least in this case. [...]
The winds transported the FD-NPP emissions towards the Pacific Ocean most of the time, while Japan was affected only occasionally. While this seemed like a relatively fortunate situation for Japan during the accident event, a different picture emerges from our detailed analysis. Exactly during and following the period of the highest 137Cs emission rates on 14 and 15 March, the FD-NPP plume was advected towards Japan and affected large areas in the east of Honshu Island. The advection towards Japan was triggered by a developing cyclone, which produced precipitation on 15 March, leading to the deposition of large fractions of the airborne 137Cs over Japanese land."
http://enenews.com/just-published-worst-radiation-plume-from-fukushima-was-blown-over-tokyo-on-march-14-15-this-was-the-main-deposition-event-over-japan-for-the-entire-disaster