Tellurium-129m

Deposition of tellurium-129m was determined from soil samples taken during the period from June 6 to July 8 over an area of 100 km radius around the Fukushima Daiichi NPP. Tellurium-129m, which is a fission product with 33.6 days half-life is as volatile as, and shows similar behaviour to iodine. The highest concentration found was 2.66 m Bq/m2 , 2 km from the plant in the empty town of Okuma. It was pointed out that the observed ratio of tellu — rium-129m to cesium-137 varies with the location of the deposition. The average ratio obtained for the deposition in the north region from the NPP is about 0.19, while it was 0.88 for the coastal area in the south. In southern inland areas, it was 0.23. They may suggest that, between tellurium and cesium, there is a different mechanism or source term, different environ­mental behavior, as well as a different timing of the release. The amount of tellurium-129m released is a few tenths that of iodine-131 (Table 24.3), and its radiological significance was not high compared to iodine and cesium.

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