The Iranians would have been utterly stupid to have accepted such an arrangement, because of course there was no guarantee at all that Iran would ever get any reactor fuel out of it — just as Iran has not received an ounce of enriched uranium from the French enrichment facility in which it invested a billion of dollars.
When the Iranians didn’t accept this arrangement, the opponents of the deal in the West (who naturally don’t want to see any peaceful resolution of the standoff with Iran) were naturally quick to declare the negotiations at an end and Obama’s approach to Iran as a failure.