Of course my book presents Walter Zinn’s 1951 experimental breeder reactor as a key event, but one of its purposes was to confirm the very presence of such reactors, namely that they “breed” fissile material. That is, for every atom of uranium-235 (or other fissile material) consumed inside the reactor, another atom of plutonium (or other fissile material) is produced, almost as if by magic.
I found an Argonne press release from April, 1953, in which the laboratory describes in detail, over four pages, how Zinn’s breeder’s extracted fuel was analyzed (not easy, very radioactive) over the previous six months. The press release talks about the point of the exercise being to determine if the reactor did in fact “breed.” It states that a breeder does breed if its “conversion ratio” exceeds 1.0. I was flabbergasted to read that the conclusion of the presser was, effectively, “having told you what the point of all this was, we’re not going to reveal the punchline”:
The values of the conversion ratio found in this work will not be made public at this time.
Furney, L. C. 1953. Furney to Young, Apr. 24, 1953. “Reading File, April 24, 1953,” Box 79, Laboratory Director’s Reading File, 1949-1957, RG 326, NARA-GL, Chicago, Illinois.