Odd Things About Natural and Background Radiation

I was reading the Fukushima reports and noted a Cesium 137 level of 150 Becquerel was reported in one area. Norm background is in the 100 Becquerel range. So I was wondering if the Cesium resulted in a total radiation of about 250, the 100 background plus the Cesium measured. I don't know yet, but suppose the total is 250 Becquerel per meter squared. That is high enough to be some what concerned especially if you have young children. Anyway, I left a comment with a scientist guy living in Japan about the report and my questions about the background level of Cesium 137. I was corrected that Cesium 137 does not occur naturally in nature.

I thought the same thing myself, but there is still background Cesium 137 radiation from nuclear weapons tests, Chernobyl and a variety of other nuclear industry sources. Not much, but enough that it can be used to date wines and whiskeys made after 1950 and Chernobyl. Curiosity keep me researching and I stumble across something new to me, a natural nuclear reactor.

So guess what? Cesium 137 does naturally occur in nature. Very, very small amounts, but Cesium 137 and even Plutonium occur in nature. Weird stuff.