LIBBY (continued) In that case you get not only this beta ray, but that be ray. Two for each disintegration. That's one way of do it, the other procedure is te not bother to separate the strontium at all, but just te take the yttrium daughter of the sample. ont I sort of parsonnally favor the second, f being a little bit sore easy. However, which ever way you do it, it is possible to take a ton of sample and con¢ sider detecting the strontium in it with something like 50% efficiency, because of this daughter relationship, For exaanle, we can take the yield of the material fros a 20 kiloton bosb. 20 kiloton bowb equals 1 kilograa of fissionable material. That's about four acles, The strontiua comes in about at 5% fission yield, 20 we have about k over 20 and about .2 or 1/5 woles of strontius”, That is about 1023 gr90 atous yield. If we get a unifors distribution of a 20 kiloton bomb over the earth's surf we therefore get about 20,000 Sestons per square centimeter for a 20 kiloten boab. Kow the 20 year life means we have to have 15 million Sr’? atoas -- means that you have one disintegration per ainute. As the average lifetine of Sr?? is 15 aillioa minutes. Ye will have froa this 20,000 over 15 million ag the disintegrations per sinute per square centineter. Since we can detect a minimus something like 1 dpm without working too hard, I zean ons disintegration per alnute, it means that we're ae f