Of interest today is the peak observed on March 24th (California time = GMT - 9). If one checks the Texas A&M maps, it looks like there is a possibility to connect this peak to a source term around March 20th at around midnight (GMT) or a little bit before.
The TEPCO press release for that time frame show something new that day among other things:
Cooling of spent fuel pools At approximately 8:21 am, March 20th, water discharge to Unit 4 by fire engine has started with the cooperation of Self-Defense Forces.Or because the graph shows counting performed for the whole day in California (as opposed to actual time period) another later event:
Cooling of Spent Fuel From 3: 05 PM to 5: 20 PM on March 20th, 40 tons of seawater was injected into Unit 2 by TEPCO employees.
The finding seems consistent with any of two source terms occurring at
- 8:31 AM on March 20th, or about midnight March 20th (GMT) and,
- 3:05PM/5:20PM on March 20th or about (6:00AM GMT March 20th).
The detection in California has occurred around March 24th (PST) or about March 24th/March 25th (GMT).
Hence it becomes difficult to delineate which of the two source terms was effectively detected at Berkeley. Now let us watch the Tokyo measurements. it shows a start at about 8:00 am March 21st (JST)
which seems consistent with reactor #4 pool cooldown. The second peak seems connected to the reactor #2 cooldown but it could also be connected to the smoke observed on top of unit 3 (March 21), however that would seem unlikely since according to TEPCO environmental readings remained at the same level when the fumes occurred. Once the cooldown is obtained and stable, there is no expectation of further release to the environment. The expectation is now that the radiation measurements should continue decreasing (irrespective of whether the winds are westerly).