Iran Sanctions Update: Have Senators Actually Read This Bill? - James Fallows - The Atlantic:
(b) several clauses and references that apparently support the "zero enrichment" demand laid down by Benjamin Netanyahu but explicitly not endorsed by the U.S. government. These clauses, with repeated requirements that Iran "terminate" or "dismantle" its "illicit nuclear programs," are ambiguous but can (and presumably would) be read as applying to the entirety of Iran's nuclear infrastructure, peaceful or otherwise. This could mean a demand that Iran give up the right not just to weapons-grade uranium but also to low-level enrichment suitable for power plants and other non-military use.
For the background of the "zero enrichment" policy, see this 2009 paper by Matthew Bunn of Harvard's Belfer Center. He argues (as do many other people who have examined the issue) that the zero-option is theoretically appealing but in reality is completely unacceptable to Iran. Thus its inclusion in any set of "negotiating" points is a way to ensure that the negotiations fail. As Bunn puts it, "Insisting on zero will mean no agreement, leaving the world with the risks of acquiescence [to an Iranian nuclear-weapons program] or military strikes."