Atomic artillery shell information declassified by the AEC in 1964 as part of the (not, in the end, successful) prosecution of George John Gessner, an Army deserter who confessed to giving secrets to the USSR.pic.twitter.com/Ok8ZbLyCRC
-
Per RDD-7, it seems like it: https://fas.org/sgp/othergov/doe/rdd-7.html#I16 …
Though the possibility of using Po in an initiator was declassified a few years earlier, per section V.B.3. I don't know if it was released any earlier even without an official declassification action.
