Project 639

639
639 thermonuclear test, 3.3 megatons
Information
Country	China
Test site	Lop Nur Test Base
Period	June 17, 1967
Number of tests	1
Test type	Atmospheric
Device type	Two-stage thermonuclear bomb
Max. yield	3.3 megatons of TNT (14 PJ)
Test chronology
← 596L 7th test →

639 was the codename for China's first full-scale test of a two-staged thermonuclear device, on 17 June 1967, yielding 3.3 megatons of TNT. It followed the first two-stage thermonuclear test, at a smaller 122 kt yield, in December 1966. It was the sixth nuclear test that was carried out by the People's Republic of China, and represented the completion of the "second bomb" i.e. thermonuclear bomb component of the "Two Bombs, One Satellite" program. With these two tests, China became the fourth nation to develop thermonuclear weapons, following the US, USSR, and UK.