He had a clearance through a contractor to inspect welds: https://www.washingtonpost.com/world/europe/brussels-attacks-stoke-fears-about-security-of-belgian-nuc

He had a clearance through a contractor to inspect welds: https://www.washingtonpost.com/world/europe/brussels-attacks-stoke-fears-about-security-of-belgian-nuclear-facilities/2016/03/25/7e370148-f295-11e5-a61f-e9c95c06edca_story.html?utm_term=.c412eca26c11 https://www.washingtonpost.com/world/europe/brussels-attacks... I don't know the specifics of this particular plant's security procedures, but it's unlikely he was in a position to do any significant damage to the plant, and his clearance process was likely much less involved than would be for someone who is in a position to do real damage.