Discussion: (D) Adequacy of Radioassay Techniques; Alternate Assay Methods Panel: I. J. Russell, moderator; G. A. Cowan L. B. Lockhart, J. P. Friend, M. I. Kalkstein Col, Russell: I should like to start by making some personal observations concerning the adequacy of radioassay techniques. I think we are in pretty good shape. and do it with pretty good precision. One can analyze for almost any nuclide produced in bomb debris I think what is needed, is a little better understanding of how to treat data from a given laboratory satisfactorily in relation to those obtained from another laboratory. art has by no means been reached. Let me give you a couple of examples of what Imean. This state of the Three tungsten isotopes of interest were produced in the Hardtack series, and most people have concerned themselves only with one or two of the three. It is possible, if one looks at all three and knows production ratios of the individual sources, to arrive at some conclusions concerning how much of a given source is in one's sample. This has been done by only one laboratory; it is very unfortunate that samples have not been looked at from this point of view by others and substantiated or questioned as appropriate. Then, one could say that, given shots A, B, and C as principal producers of tungsten, source A is 18 times source B and about 1.2 times source C, valuable information. This is Sources A and C had about the same yield; source B had a very high yield, a yield that would, according to the figures Dr. Martell just presented, have put the cloud at an extremely high altitude indeed above U-2 sampling capabilities. It leads one to question, as unambiguous, the attribution of such things as the transient increase in Strontium 90 to the downward excursion of Teak and/or Orange. Dr. Friend's graph that this represented something of the order of 30 percent increase. I noted from Cerium 144 produced in a high-yield shot is not going to be distinguishable, by very small differences in half-life or in detonation time, from the Cerium 144 produced by Teak and/or Orange. Mind you, these data were presented not on the basis of Rhodium 102, but on the character of the ratio per se. Practically everybody has looked at Strontium 90, Strontium 89, and Cerium 144. It is nice to know one's numbers have a good relative-absolute sense such that from the Strontium 89, for example, you can say there are so many fissions attributable to a given source. If the fissions based on a Cerium 144 source represent a significantly larger number than those inferred from Strontium 89, one can subtract to get excess Cerium 144 fissions which now have to be Hardtack and things prior to Hardtack. To do.this, however, one has to be on an absolute-relative basis and believe that the sub- traction of two numbers close to each other can give significant results. somebody else's data, done this. feet. I have, taking the liberty of using And for 1959, a rather peculiar feature is observed between 40, 000 and 65, 000 The ratio of atoms of Rhodium 102 corrected to time of production, assuming time of production was Orange, to fissions attributable to anything earlier than the Soviet series, decreases with time. Rhodium 102 to Cerium 144 fissions are decreasing with time, and this ratio has a value which is 2 percent of the production ratio in Orange, if one can believe the number for Rhodium 102 production that Dr. Cowan has quoted. 87