Iran said Wednesday it had introduced a new generation of uranium-enrichment centrifuges which would refine the radioactive material more efficiently, with the country’s nuclear chief Ali Akbar Salehi saying the new IR-8 model had already been tested, though it was not yet being fed with uranium gas.

“These centrifuges have undergone mechanical tests, but we haven’t yet injected gas into them as it requires a relevant permission by the president,” Salehi said in comments relayed by Iran’s Fars new agency.

Anticipating consternation in the world over Tehran’s continued enrichment efforts, Salehi insisted that development and use of new centrifuge models was well within the country’s rights as part of the interim nuclear deal with world powers signed last November.

Iran says the uranium is needed to fuel its nuclear facilities, which it insists are for peaceful purposes only. The newer centrifuges, it contends, will allow it to meet national needs more efficiently. But such efficiency may not be looked upon favorably by Western nations, who fear that uranium enriched to a high level could be used to build nuclear weapons.

Iran currently has nearly 19,000 centrifuges, including 10,000 of the so-called first generation being used to enrich uranium. Some 1,000 second generation machines, three to five times more powerful, have been installed but are not in service. Under the November deal, Iran cannot increase the number of its centrifuges.

Former Israeli Ambassador to the US Michael Oren has warned that Iran was continuing to develop its centrifuges, and that more sophisticated models would enable it to speed more quickly to nuclear weapons if it chose to try to break out to the bomb. “If the talks break down,” he told The Times of Israel earlier this year, “and you [the Iranians] quickly install your additional 9,000 centrifuges, among them the IR2s, which really give you [the equivalent of] about 24,000 centrifuges. And you have a stockpile [of enriched uranium]. And maybe you’ve done some research and development, that actually gives you some [centrifuges] closer to an IR3, which has an even higher rate of accumulation than the IR2s, how long is it going to take you [to break out]?”

Salehi also said Wednesday that workers have begun redesigning Iran’s nearly completed Arak heavy water reactor to limit the amount of plutonium it can make as part of the interim deal.

As originally designed, the reactor at Arak could have produced substantial amounts of plutonium, material that can be used as the fissile core of a nuclear weapon. Iran has offered to redesign it to produce only a fifth of the plutonium it could have made. However, the West has asked Iran to totally replace the Arak reactor with one that would be able to make only minuscule amounts of plutonium.

Iran's Arak heavy water reactor (photo credit: Hamid Foroutan/ISNA/AFP)

Iran’s Arak heavy water reactor (photo credit: Hamid Foroutan/ISNA/AFP)

Iran has opposed that, saying a heavy water reactor is needed to produce medical radioisotopes while a light water reactor, like the one Iran has at Bushehr, is used to generate electricity.

The Arak reactor remains one of the sticking points between the Islamic Republic and world powers as they try to negotiate a permanent deal over Iran’s contested nuclear program. Last year, they struck an interim deal that saw Iran agree to limit its uranium enrichment in return for the easing of some economic sanctions. Negotiators now face a November deadline to come to a final deal.

AP contributed to this report.