China initiated its nuclear weapon program in 1955 and began to construct its fissile-material production facilities in the late 1950s. China has produced highly enriched uranium (HEU) for weapons at two complexes: Lanzhou gaseous diffusion plant (GDP, also referred as Plant 504) and Heping GDP (the Jinkouhe facility of Plant 814).
In 1958, China started the construction of the Lanzhou plant with advice from Soviet experts. Moscow withdrew all its experts in August 1960, however, forcing China to become self-reliant. On January 14, 1964, the GDP began to produce 90% enriched uranium, which made possible China’s first nuclear test on 16 October 1964.