Is 20.1 Bq/L I-131 for 3/23 (09:06-18:00) Correct?

Submitted by Anonymous on Sat, 2011-04-09 00:28

The 20.1 Bq/L for I-131 listed for 3/23 is much higher than the day before or the day after (4.65 Bq/L and 7.63 Bq/L respectively). And the closest measurement to 3/23 is the 8.35 Bq/L listed for 3/21-3/22. Is the 3/23 number correct? Isn't that equivalent to 543 pCi/L?

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Yes, the measurement is correct

Submitted by bandstra on Sun, 2011-04-10 22:08.

I just checked our data for 3/22 (the day before) and 3/23, and the count-rate of I-131 is approximately 4 times larger on 3/23 than 3/22.

You can also get this by eyeballing the spectrum for 3/22 and spectrum for 3/23 and looking at the I-131 peak at 364 keV. You can see that the I-131 peak is larger on 3/23 by about a factor of 2, and the acquisition time for 3/23 (26,534 sec) was only half that of 3/22 (54,460 sec). So the rate for I-131 was about a factor of 4 higher, makes the 20.1 Bq/L number plausible.

Now, that being said, it is still unknown how such a spike could have occurred. We have seen in the air filter results that single-day spikes sometimes occur, probably due to the turbulent air transport processes that bring the particulates here. The levels in the rainwater should related somehow to the air concentration, but it will also depend on how the precipitation formed in the cloud. At this point we don't understand enough about this whole process to give a definitive answer.

Mark [BRAWM Team Member]

gosh, they are not always

Submitted by Anonymous (not verified) on Sat, 2011-04-09 10:32.

gosh, they are not always the same, it was raining!
why are you doubting high values? You should doubt the low values. Look at the chernobyl fall out.

Is 20.1 Bq/L I-131 for 3/23 (09:06-18:00) Correct? (rain water)

Submitted by Anonymous (not verified) on Sat, 2011-04-09 10:42.

I doubt *any* number that is significantly different than the trend. The
earlier trend *for rain water* was from 4.65 Bq/L on 3/17 to 4.65 Bq/L on 3/22. With a high of 8.35 Bq/L on 3/21. Then a jump to 20.1 Bq/L on 3/23. Followed by a generally decreasing trend through 3/28. I don't see any low values that seem out of line with the trend over the 11 day period.

Is 20.1 Bq/L I-131 for 3/23 (09:06-18:00) Correct? (rain water)

Submitted by Anonymous (not verified) on Sat, 2011-04-09 10:26.

Sorry, I forgot to state which sampling I was referring to.
I was referring to the rain water sample on 3/23.

http://www.nuc.berkeley.edu/RainWaterSampling