Areva chief executive Luc Oursel announced Monday he had stepped down for health reasons, more than three years after he was appointed to head up the French nuclear giant. "Under these very difficult personal circumstances, and despite my very strong commitment to Areva, I have had no choice but to hand over my responsibilities at the head of the company and have chosen to take a leave of absence in order to pursue treatment," Oursel said in a statement. "I must now fight a personal battle against the illness," he added, without detailing what health problems he suffers from.