The move was seemingly designed to intensify pressure on Europe to find an effective way around US sanctions that block Tehran’s oil sales abroad.
Starting up the Arak heavy water reactor’s secondary circuit doesn’t violate Iran’s 2015 nuclear deal with world powers. But it does inch Tehran’s programme closer towards weapons-grade levels.
Ali Akbar Salehi explained to state TV that the secondary circuit transfers heat to the reactor’s cooling system. He said the entire reactor system will go online in 2021.
Heavy water helps cool reactors, producing plutonium as a byproduct that can potentially be used in nuclear weapons. Iran insists its nuclear programme is for peaceful purposes.
Britain is helping Iran redesign the Arak reactor to limit the amount of plutonium it produces. London has filled the role left after the US unilaterally withdrew from the nuclear deal last year.
Tehran has slowly stepped up violations of the nuclear deal to pressure world powers to provide more incentives to make up for the US withdrawal from the deal. American economic sanctions are having a crushing effect on Iran’s economy.
On Sunday, Adm. Ali Shamkhani of Iran’s Supreme National Security Council warned that his country will take another step in lowering its commitment to the deal, if Europe does not implement its commitments.
The International Atomic Energy Agency, the UN’s nuclear watchdog, said last month that Iran breached another limit of the nuclear deal by stockpiling more heavy water than the accord allowed.
Also in November, Washington renewed sanctions waivers that allow Russia and other European nations to conduct civilian nuclear cooperation with Iran, specifically the redesign work to continue at the Arak reactor and at the Fordo uranium enrichment facility. Both sites are monitored by the IAEA.
Iranian state media said technicians switched on a secondary circuit at Arak, a plant built to produce the heavy water used as a moderator to slow down reactions in the core of nuclear reactors.
“Today we are … starting a noteworthy section of the reactor,” the head of Iran’s atomic agency, Ali Akbar Salehi, said in remarks broadcast live on state TV.
“The Arak heavy water nuclear reactor … consists of two circuits,” Mehr said.
“The first circuit is tasked with removing heat from the heart of the reactor, and the secondary circuit is responsible for transferring the heat from the first circuit to cooling towers and finally to the outside environment,” Mehr added.
Iran agreed to shut down the reactor at Arak, — about 250 km southwest of Tehran — under the 2015 deal. The foreign powers that signed the pact said the plant could eventually have produced plutonium, which can also be used in atom bombs.
But Iran was allowed to produce a limited amount of heavy water and Tehran has been working on redesigning the reactor. Tehran says it will make isotopes for medical and agricultural use.
The control room of the reactor, named Khondab, will take about five to six months to build and the remaining systems will be completed in about one year, Salehi told a news conference at the site.