The Castle Yankee thermonuclear test was the first bomb to use enriched Lithium-6 isotope , up to perhaps 40 % enrichment ( the earlier Castle Bravo test had used the same enriched lithium combination but was not weaponised i.e. was not built as a deployable bomb ) . The device tested was called the '' ' Runt II ' '' design ; it was reportedly very similar to the Runt design tested in Castle Romeo , other than the enrichment level
Castle Bravo
Castle Bravo
Mark 24 nuclear bomb