VIENNA (Reuters) - The U.N. nuclear watchdog is set this week to issue a detailed report with new evidence pointing to suspected research activity in Iran to develop an atomic arms capability, diplomats say.
Western officials and experts believe Iran is making efforts in the three main areas needed for building deliverable nuclear arms -- refining uranium that could be turned into weapons grade fissile material, warhead design work and missile development.
Iran rejects the accusations of military-linked nuclear work as forged and baseless, saying its atomic program is aimed at producing electricity.
This is the part of Iran’s nuclear program that has most worried the West, as obtaining weapons-grade fissile material for the core of a warhead is seen as the most challenging hurdle to overcome in the pursuit of atomic bombs.
Iran already has enough of the material for two nuclear weapons or more, if refined much further from its current low-enriched state, and is steadily amassing more. It says it needs enriched uranium to fuel a network of power plants.
But its decision last year to start refining uranium to 20 percent fissile purity -- up from 3.5 percent usually required for nuclear energy stations -- alarmed the West as it brought it closer to the 90 percent level needed for atomic bombs.
Experts say that having a stockpile of 20 percent uranium would significantly cut the time needed to break out and produce material needed for weapons, if Iran wanted to.
Further stoking Western and Israeli suspicions, Iran is preparing to shift the 20 percent enrichment to an underground bunker near the holy city of Qom, for enhanced protection against any military strikes.
ARE THERE MILITARY LINKS TO IRAN‘S NUCLEAR PROGRAMME?
While the enrichment program has been relatively well documented -- provided Iran does not have undeclared enrichment sites -- any activity in the country aimed at developing a nuclear warhead for a missile would be conducted in secrecy.
If Iran is engaged in such efforts, it would be highly technical and complex scientific work involving neutron physics, high explosives testing and the design of a nuclear payload small enough to fit on a missile.
Diplomats said the IAEA report will shed more light on this aspect of Iran’s program, even though it is not likely to reveal “smoking gun” proof of weaponisation intentions.
The report is expected to give fresh evidence of research and other activities with little other use than arms-related, including studies linked to the development of an atomic bomb trigger and computer modeling of a nuclear weapon.
It will expand on concerns voiced by the IAEA since several years back over Western intelligence allegations that Iran had linked projects to process uranium, test explosives and modify a missile cone for a nuclear payload, the diplomats said.
Earlier this year, the IAEA listed several areas of particular concern regarding possible military dimensions to Iran’s nuclear program.
They included “experiments involving the explosive compression of uranium deuteride to produce a short burst of neutrons” that could set off the fissile chain reaction in a nuclear bomb.
“Every single nuclear weapons program in the world works on this issue,” said Mark Hibbs of the Carnegie Endowment for International Peace. “You have to inject neutrons into the nuclear material to start a fission reaction.”
Other alleged activities listed by the IAEA in a report in May included uranium metallurgy for components relevant to a nuclear device, high explosives testing, and exploding bridgewire detonator (EBW) studies. EBWs use an electrical current to detonate explosive material and are commonly used in nuclear weapons, where an explosion is required to compress the uranium core and help launch the fissile reaction.
“Iran’s experiments involving exploding bridgewire detonators and the simultaneous firing of explosives around a hemispherical shape point to work on nuclear warhead design,” said U.S.-based analyst Peter Crail.
But the IAEA is likely to stop short of saying explicitly that Iran is working to develop nuclear bombs.
“It is important to note that this is R&D (research and development) and not actually work to construct a warhead with nuclear material,” said Crail, of the Arms Control Association, an advocacy and research group.
Iran says it would be a “strategic mistake” to build atomic bombs and that such arms are against Islam.
Britain said earlier this year Iran had carried out covert tests of a missile that could carry a nuclear warhead. Tehran swiftly denied the allegation, saying its missiles cannot carry nuclear payloads.
But the IAEA in May expressed concern about alleged “missile re-entry vehicle redesign activities for a new payload assessed as being nuclear in nature.”
Proliferation expert Mark Fitzpatrick said Iran has a fleet of ballistic missiles under development, the most capable of which has a reach of at least 2,200 km (1,375 miles), potentially far enough to hit Israel and U.S. bases in the Middle East.
Iran has said it conducted a launch in February 2011 that flew into the Indian Ocean. “Iran’s ability to monitor the test flight in the ocean is a new capability,” said Fitzpatrick, a director of the International Institute for Strategic Studies.
The Arms Control Association said Iran was not likely to have a long-range ballistic missile capable of reaching the United States until at least the end of the decade.
“Fitting a nuclear weapon on a ballistic missile is a difficult task that took established nuclear powers such as the United States and the Soviet Union many years to develop,” it said in a paper on Iran’s nuclear program.
Editing by Mark Trevelyan