Because you have a cycle of ~14 days of darkness and light on the moon so solar will need a backup. Batteries are an option but 14 days worth of storage for a

Because you have a cycle of ~14 days of darkness and light on the moon so solar will need a backup. Batteries are an option but 14 days worth of storage for a lunar base is probably asking a bit too much. Also nuclear provides another benefit on the moon - heat which you’ll definitely need during those 14 days of darkness.