What motivated the USSR to assist China with the development of Nuclear Weapons?
Why would the USSR want China to have this technology during the 1950s and early 1960s? What did they get out of this transfer of technology?
As part of its 1957 "Great Leap Forward," program, China's undertook to ship "surplus" food to the Soviet Union in exchange for help in "industrial" development, especially its nuclear program. That's because one of Khruschev's main concerns during his tenure was agricultural reform, which was grounded in his desire to see Soviet citizens, "live better," or at least "eat better."
That wasn't a good idea because it turned out that China needed the food itself. That happened because Chinese commune leaders on quotas reported production greater than actually achieved, leading Mao to believe that he had a "surplus" for export.
I bring my answer from politics section since this question is really closer to history. Maybe somebody can add up some valuable extra data to my sources:
I found this link on the subject: http://www.sinodefence.com/strategic/organisation/programme.asp
I read from other sources (sorry, I don't remember them now) as well that USSR primary target was nuclear power. In the beginning China was strong ally for USSR, and in the 60's their diplomatic relationship became cooler. So for the 50's USSR assisted them as an ally to enforce the communist block and of course increase their own power by an ally. After Stalin's death under Khruschev this relation decayed slowly, and became hostile for sure during the Sino-Soviet border conflict.
I am guessing the soviets' primary target as the nuclear power generation was the main goal, and they didn't really mind if the chinese people make bomb as well. But as I know it wasn't a goal. The propaganda was about peaceful use of nuclear power.