The arxiv blog just featured a paper that appeared on arxiv that points to an analysis of the plume that landed at the University of Washington in Seattle. The paper is at the end of this entry. A good summary is here, from the text:
Finally, there are a huge number of possible breakdown products from nuclear fission in a reactor and yet the Seattle team found evidence of only three fission product elements--iodine, cesium and tellurium. "This points to a specifific process of release into the atmosphere," they say.
Cesium Iodide is highly soluble in water. So these guys speculate that what they're seeing is the result of contaminated steam being released into the atmosphere. "Chernobyl debris, conversely, showed a much broader spectrum of elements, reflecting the direct dispersal of active fuel elements," they say.
If one checks the Texas A&M predictions, arrival in Seattle on March 17-18 can be assumed thanks to this map that assumes ejection around 12 GMT on March 13th (or 21 JST March 13th)
This would correspond to an event in Unit 3 according to this map.
The folks at University of Washington ought to be looking at the Texas A&M simulations to see if and when they are going to catch up elements of the plumes.
Unit 3 is still a concern today as an analysis of the water outside of the secondary containment has shown elements such as Technetium-99m (Thanks David).
To see if the plume contains some of these elements, we ought to be looking at the smoke that left unit 3. As per TEPCO's report:
At approximately 4:00 pm, March 21st, light gray smoke was confirmed arising from the floor roof of the Unit 3 building. On March 22nd, the color of smoke changed to somewhat white and it is slowly dissipating.-At approximately 10:45 pm on March 22nd, the light in the main control room was turned on.-At around 4:20 pm on March 23rd, our staff confirmed light black smoke belching from the Unit 3 building. At approximately 11:30 pm on March 23rd and 4:50 am on March 24th, our employee found no signs of smoke.
If one converts these dates from JST to GMT, we have:
7:00 am GMT March 21st: light gray smoke
7:20 am March 23rd: light black smoke
A simulation for the March 21st event was performed for 6:00 am and it shows that plume hitting Seattle tomorrow.
A simulation for the second event does not seem as conclusive.
The paper: Arrival time and magnitude of airborne fission products from the Fukushima, Japan, reactor incident as measured in Seattle, WA, USA by J. Diaz Leon, J. Kaspar, A. Knecht, M. L. Miller, R. G. H. Robertson, A. G. Schubert. The abstract reads:
We report results of air monitoring started due to the recent natural catastrophe on March 11, 2011 in Japan and the severe ensuing damage to the Fukushima nuclear reactor complex. On March 17-18, 2011 we detected the first arrival of the airborne fission products 131-I, 132-I, 132-Te, 134-Cs, and 137-Cs in Seattle, WA, USA, by identifying their characteristic gamma rays using a germanium detector. The highest detected activity to date is less than 32 mBq/m^3 of 131-I.