Thursday, March 31, 2011

Fukushima: Ibakari Analysis for March 21st.

I wanted to come back to an dose rate increase in Ibakari that occurred on March 21st at 10:00 am. From here:

According to the TEPCO press release on March 20th, the only event I could find is the cooling of the spent fuel of reactor 2:

Cooling of Spent FuelFrom 3: 05 PM to 5: 20 PM on March 20th, 40 tons of seawater was injected into Unit 2 by TEPCO employees.

On the 22th, at 21:00 JST on March 22, there is a drop, that coincides with a westerly wind. Then the dose rate goes up as the winds comes back to the Ibakari region. So it looks like from the information currently available, the cooling of the pool in reactor 2 and attendant vapor generation might be responsible for this increase in dose rate in Ibakari.


  1. That spike has been attributed to "rain" in sources that I've seen, for example in Daniel Garcia's graph here:

  2. David,
    Thanks for the comment and info. Rain is just the final means by which the radioactive components eventually are deposited in some area ( on some sensors). What is important to understand is how this is transported. In this entry, I am trying to figure out what is the possible source term at the plant that could have triggered this increase in the dose rate. With the help of the Texas A&M computations showing the delayed transport between the plant and some other area, it looks plausible to have this event be the cooling of the spent fuel pool of reactor 2 being the culprit. The cooling must have produced evaporation that eventually fed into the plume. The Texas A&M computation seem to suggest that there is a good fit between the time this event happened and the time is was detected several hours later in Ibakari. If you have any other source of information, I would love to hear about them.