VIENNA — A drawing based on information from inside an Iranian military site shows an explosives-containment chamber of the type needed for nuclear-arms-related tests that U.N. inspectors suspect Tehran has conducted there. Iran denies such testing and has neither confirmed nor denied the existence of such a chamber.

The computer-generated drawing was provided to The Associated Press by an official of a country tracking Iran’s nuclear program who said it proves the structure exists, despite Iran’s refusal to acknowledge it.

That official said the image is based on information from a person who had seen the chamber at the Parchin military site, adding that going into detail would endanger the life of that informant. The official comes from an International Atomic Energy Agency member country that is severely critical of Iran’s assurances that its nuclear activities are peaceful and asserts that they are a springboard for making atomic weapons.

A former senior IAEA official said he thinks the drawing is accurate. Olli Heinonen, until last year the U.N. nuclear agency’s deputy director general in charge of the Iran file, said it was “very similar” to a photo he recently saw that he believes to be the pressure chamber the IAEA suspects is at Parchin.

He said even the colors of the computer-generated drawing matched that of the photo he had but declined to go into the origins of the photo, to protect his source.

Iran-IAEA meeting today

After months of being rebuffed, IAEA and Iranian officials are to meet today in Vienna. The IAEA will renew its attempt to gain access to the chamber, allegedly hidden in a building. Any evidence that Iran is hiding such an explosives-containment tank, and details on how it functions, is significant for IAEA investigations.

Beyond IAEA hopes of progress, the two-day meeting is being closely watched by six powers trying to persuade Iran to make nuclear concessions aimed at reducing fears that it might want to develop atomic arms as a mood-setter for May 23 talks between the six and Iran in Baghdad.

Warnings by Israel that it might attack Iran’s nuclear facilities eased after Iran and the six — the United States, Russia, China, Britain, France and Germany — met last month and agreed there was enough common will for the Baghdad round. But with the Jewish state saying it is determined to stop Iran before it develops the capacity to build nuclear weapons, failure at the Iraq talks could turn such threats into reality.

In Tehran on Sunday, Iran’s top nuclear negotiator said it was up to the Western nations coming to the Baghdad talks to “build trust of the Iranian nation,” adding: “Any kind of miscalculation by the West will block success of the talks.”

Stonewalled for years

The IAEA has been stonewalled by Iran for more than four years in attempts to probe what it says is intelligence from member states strongly suggesting that Iran secretly worked on developing nuclear weapons. It first mentioned the suspected existence of the chamber in a November report that described “a large explosives containment vessel” for experiments on triggering a nuclear explosion, adding that it had satellite images “consistent with this information.”

It did not detail what the images showed. A senior diplomat familiar with the IAEA’s investigation who has also seen the image provided to AP said they revealed a cylinder similar to the image at Parchin.

IAEA chief Yukiya Amano said in March that his agency has “credible information that indicates that Iran engaged in activities relevant to the development of nuclear explosive devices” at the site.

Diplomats told AP that the experiments also appear to have involved a small prototype neutron device used to spark a nuclear explosion — equipment that would be tested only if a country were trying to develop atomic weapons.

Iran has denied conducting such work — and any intentions to build nuclear weapons — but has been less clear on whether the structure where it allegedly took place exists.

The senior diplomat familiar with the IAEA investigations said the Iranians have refused to comment “one way or the other” on that issue to agency experts. Attempts to get Iranian comment were unsuccessful.

Computer-generated image

The official who provided the drawing of the explosives-containment chamber, above, also shared the following information on the chamber:

Origins: Built in the early 2000s by Azar AB Industries Co. in the city of Arak and then transported to Parchin. A senior diplomat familiar with the IAEA investigations and Olli Heinonen, the former senior IAEA official, confirmed this. Company officials did not answer calls for comment.

Volume: 10,600 cubic feet.

Diameter: 15.09 feet.

Length: 61.68 feet.

Time frame: The official said the chamber was used for detonation experiments in 2003, 2005 and 2006. Two officials familiar with the investigations said the first date appeared to be valid but that they had no information of subsequent experiments. The United States thinks Iran stopped working on a concerted nuclear-weapons program at various sites after 2003, while the IAEA suspects Iran is continuing some work but in a much less organized way than before 2003.

The Associated Press