Following up this article about a possible recriticality at Fukushima Daiichi…
In the article, I posted that Iodine 131 was measured at 3 garbage disposal facilities but in December, Iodine 131 was measured at 10 of 12 sewerage disposal plants in Tokyo.
The samples are dehydration sludge, sampled between 12/1 ~ 12/6.
(Source)