The Arak heavy water reactor, designed to replace the 40 year old Tehran Research Reactor, is way behind schedule. Iran had not planned upon needing to refuel the TRR. They are producing small amounts of the slightly less than 20% enriched Uranium needed for fuel, but have not yet developed the ability to manufacture the fuel plates needed by the TRR. The squeeze is on. The TRR is about burned out. Fuel replacement is mandatory and Iran is not capable of supplying it. Russia and China have made it clear that the sanctions will happen unless Iran gets in full compliance with the IAEA.
Middle East quartet reportedly set to meet during UN General Assembly (dpa)
from the article: Iran to give UN better access to nuclear sites, say diplomats