IR-40 is an Iranian 40 megawatt (thermal) heavy water reactor under construction near Arak. The International Atomic Energy Agency (IAEA) was informed on May 5, 2003 that construction would begin in June 2004. Iran announced that the reactor will begin nuclear operation in 2014.
Iran's leadership decided to begin designing the reactor in the 1980s. The basic design was completed in 2002. The current Iranian research reactor, Tehran Research Reactor, is nearing the end of its operational life having been in use since 1967.
The reactor was originally going to be constructed at a location in Esfahan, though after the designs were completed Iran decided to build instead at its present location near Arak. In August 2006, mixed reports came out about when the reactor would go into operation, one stating that the plant would start up in 2009, while another reported that operation would be postponed until 2011. Reportedly, the Russian firm Nikiet assisted with portions of the design. 
Press reports indicate that Iranian President Mahmoud Ahmadinejad visited the reactor in June 2013, on the occasion of the reactor vessel installation which is the final precursor prior to commencement of operation.
Role in Iran's nuclear program
Iran states that the reactor will only be used for research and development, medical and industrial isotope production. On June 16, 2010 Iran announced plans to fabricate fuel for the Tehran Research Reactor by September 2011 and to build a new 20 MW reactor for radioisotope production within five years.
There are some proliferation concerns about the reactor's ability to produce enough plutonium for several nuclear weapons each year. However the IAEA has reported that it found no indication of ongoing reprocessing activities, required to extract plutonium from the spent fuel. In full operation, it is expected that the reactor will produce from 10 kilograms (22 lb) to 12 kilograms (26 lb) of plutonium a year within its spent nuclear fuel.
Natural-uranium fueled heavy-water reactors were originally designed for producing weapons-grade plutonium usable for construction of nuclear weapons. Analysis suggests that Iran could extract 8–10 kilograms of high purity Pu-239 annually from fuel irradiated in IR-40. This, according to the IAEA, is sufficient weapons-grade material to produce 1 to 2 nuclear weapons annually. Iran has denied access to the IR-40 for design information verification, despite the IAEA's right to conduct such verification.
As a result of concerns that this plutonium would support weapons development, former IAEA Deputy Director-General for Safeguards, Olli Heinonen, proposed a reactor redesign to a reactor using slightly enriched uranium fuel rather than natural uranium. Use of enriched uranium fuel combined with extended operations would reduce the reactor's ability to produce weapons-grade plutonium.
Iran has indicated they do not intend to reprocess IR-40 spent fuel to recover weapons-grade plutonium, nor operate under a low burnup regime that could produce weapons-grade plutonium. Originally a hot cell facility at the Arak site was planned, described as capable of handling irradiated fuel and targets (such as targets for production of medical radioisotopes) from the IR-40, but in 2004 plans for hot cells at Arak were removed. However some proliferation experts have expressed concern that once sufficient fuel has been irradiated Iran may modify this facility or build a separate reprocessing facility to recover weapons-grade plutonium.
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