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 there is already achieved once it reaches 20 percent concentration, shortening the time needed for any nuclear weapons "break-out."

One source said the higher level detected was believed to be within variation of the usual activity at the Fordow facility - where Iran is refining uranium to a fissile concentration of 20 percent - making clear it was not a big difference.

"It is not up there... towards nuclear weapons capability," the diplomat said. It could simply be a "production error" but the UN nuclear watchdog had asked Iran to clarify the issue.

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Another diplomatic source said he had also heard of the find but it was unclear whether it would be included in an IAEA report due to be released to member states later on Friday. IAEA regularly inspects Fordow and other Iranian nuclear sites.

What if it was an error in the other direction and the concentration was actually supposed to be higher? What could go wrong?