Complex sentence: The French Commissariat à l'énergie atomique (CEA) studied the area, as did Alusuisse in the 1970s, which only came to conduct small scale mining.
Split into simpler sentences: The French Commissariat à l'énergie atomique (CEA) studied the area. The same did Alusuisse in the 1970s, which only came to conduct small scale mining.