The 27-year-old Duane Arnold Nuclear Power Plant near Palo is running out of room for its spent uranium fuel.Spent fuel rods have always been stored underwater in a large pool inside the plant. Alliant Energy officials say the pool will be full by 2003, and they’ve obtained government approval to store bundles of nuclear waste in special steel-and-concrete containers which will eventually be placed in a new storage facility that will be built on plant property. Construction on the new storage facility will start next year.