Financial Tribune- The Arak heavy water production plant has been temporarily shut down partly to ensure that additional production would not breach a curb Iran accepted on its stockpile of the material under the 2015 nuclear deal, a lawmaker said.

Under the landmark agreement with major powers, Iran swapped relief from international sanctions for time-bound constraints on its nuclear program.

The curbs included a call to redesign and reconstruct the Arak reactor and cap the heavy water stocks below 130 tons by selling, diluting or disposing the excess amounts, under certain conditions.

�The JCPOA envisages a 130-ton limit for our heavy water reserves and requires any amount in excess of that to be sold or shipped abroad. When there is no customer, the production of heavy water cannot continue,� Mojtaba Zolnouri told ICANA on Friday.

JCPOA stands for the official title of the deal, namely the Joint Comprehensive Plan of Action.

�So the halt in production is meant to avoid violating the heavy water limit and for maintenance work,� Zolnouri, who heads a Majlis committee on the nuclear activities, added.

Iran�s compliance with the JCPOA is being monitored by the International Atomic Energy Organization, which verified the shutdown on May 16.

In its latest report on June 2, the Vienna-based agency confirmed that Tehran has upheld its end of the action plan.

However, it said Tehran was close to breaching the heavy water cap.

The IAEA report said Iran�s stock of heavy water, a chemical used as a moderator in a type of nuclear reactor that can produce plutonium, reached 128.2 tons, just below a 130-ton limit.

Plutonium can be used as an alternative to uranium for producing atomic bombs.

Iran denies having ever considered developing a nuclear warhead and says its nuclear program is only meant for civilian purposes.

Iran has shipped the surplus to Oman while it looks for prospective buyers.

Start of Modernization Project

Another MP had said earlier this month that the temporary closure of the facility marks the start of the redesigning of the heavy water reactor.

�The repair and maintenance of the heavy water [plant] is the first step in the redesign of the [reactor] structure,� said Hossein Naqavi Hosseini, the spokesperson for Majlis National Security and Foreign Policy Commission.

Tehran, Washington and Beijing released a joint �statement of intent� on Oct. 18, 2015 to announce cooperation on the Arak project and shortly afterward a related document signed by all the parties to the nuclear agreement was published.

The document said the six nation parties to the pact, namely the US, Britain, France, China and Russia plus Germany, are required to contribute to the project through a working group established after consultations with Iran and co-chaired by the US and China.

China is participating in the design and construction of the modernized reactor and, as the primary liaison between the working group and Iran, facilitates communications in the course of the project implementation.

Iran and China signed a deal in late April to go ahead with the joint implementation of the Arak Modernization Project.

�We have been waiting for the Arak deal to take effect � the announcement that the Arak heavy water plant is closed for repair and maintenance shows that the redesign project has become operational,� Naqavi Hosseini added.