– Is Radiogenic lead hidden or missed ? (Fukushima Diary, Jan. 4, 2012):
Following up this article http://fukushima-diary.com/2012/01/fukushima-news-8400-bq-kg-lead-210-measured-sample-yokohama/
At first, a Japanese lab (Isotope research institute) measured Strontium-90 from the sample.
However Yokohama city government asserted it has nothing to do with Fukushima and the lab released this report after the announcement.
On the report, they mention pb-210.• ?????3M ?? RadDisk-Sr ?????????????????????
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• ????????????????????????????????????
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• ????????????????????????????????????
?????????Pb212,214 ??????????????????????
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• ????????????????????ICP-MS ????????????
??????? Sr90 ???
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• ????? ???????????????????????????????Pb-212,214 ??????????????????????????? ???
??Pb-210 ???????????????????????????????
??????????????? ????????????????????
????Pb-212, Pb-214 ????????????????????????????????????????
• ICP-MS: ????????????????????ICP-MS ???????
?? ?????????? Sr, Pb, Ba ??????? ??????????
????????????????????????? Sr90 ????????
??Sr90 ??????
?????????????????????? Pb-210 ????????????
Pb-210 ????????????????????????????????????
? Pb-210 ???????????? 20-40 Bq/kg ????????????????
?????????? Pb-210 ????????????Pb-210 ??????????
??????????? ???????????????????????????
??????????????????????????????????????<Translate and Summary>
The measurement was done by using 3M’s RadDisk-Sr, which catches Strontium selectively, but it can catch lead and calcium as well because the ionic radius is close to strontium.
In order to make it accurate, additional measurements were done to see pb-212 and 214 but they both were less than the measurable amount.
However, pb-210 is so low energy spectrum that germanium semiconductor detector can’t measure it.
The possibility therefore remains that pb-210 is caught by the disk, but it’s known that pb-210 is only 20 ~ 40 Bq/Kg in soil as environmental radioactivity.
In conclusion, the high reading is not caused by pb-210 but is affected by strontium.
Probably no one has ever thought no less than 8,400 Bq/Kg of pb-210 exists in the roof of a normal apartment.