A 'production error'?

The IAEA claims to have found uranium that was enriched to 27% - a higher grade than previously seen - near Iran's Fordow underground nuclear facility near the 'holy city' of Qom. As of Friday, the IAEA was attributing the higher grade uranium to a 'production error,' but has asked for clarification. Nuclear bombs require uranium enriched to 90 percent, but much of the effort required to get