The complex in the above Google Maps image used to be (and probably continues to be) a major target of U.S. reconnaissance programs. It was also the subject of the photographic interpretation report titled Probable Atomic Energy Complex Under Construction Near Chih-Chin-Hsia, China, Top Secret, published in 1964. (Chih-Chin-Hsia [赤金峽] is not far from Yu-Men [玉門] of Gansu [甘肅] Province.) The following image, extracted from the report, was very likely taken on a U-2 mission. It is not so different from how it looks today.
The report contains a detailed analysis of this complex, including the following drawing (click on drawing for a larger version). You may want to zoom in the Google image on area identified as Section I in the drawing. You will see that there are two smoke stacks now.
If you zoom out on the Google image, you will see that this complex is literally located in the middle of nowhere. I must wonder how the Americans located this complex forty years ago. How many people have spent how many days on locating it? It is also unimaginable for me how they determined its functions relying on images.
An earlier version of the report mentioned above can found here. It might have been based on CORONA satellite images because the resolution was poorer.