Iran's primary nuclear enrichment facility in Natanz has continued to operate since 2007, despite sanctions by UN Security Council.

VOA: standard.2009.10.24

This was very successful and it was an enrichment.

这个实验很成功,也是一次改进。

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I do a program called "BRYTE", which is Brown Refugee Youth Tutoring Enrichment,

我参加的一个项目叫“BRYTE”，是布朗青年难民辅导计划的简称，

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However,Iranian President Mahmoud Ahmadinejad said earlier this week that Iran will not stop the enrichment drive, and considers the matter closed.

VOA: standard.2009.09.11

That deal would commit Iran to shipping about 75 percent of its lightly enriched stockpile of uranium to Russia for further enrichment.

VOA: standard.2009.10.21

In April,the P5+1 offered Iran a revised package of incentives for it to halt uranium enrichment and return to negotiations over its nuclear program.

VOA: standard.2009.09.11

The plan calls for Iran to send uranium abroad for enrichment, but Tehran countered with conditions to what was presented as a take-it-or-leave-it proposition.

VOA: standard.2009.11.15

"Last September,the world learned that Iran had secretly built another uranium-enrichment facility at Qom, in clear violation of Security Council resolutions and Iran's IAEA obligations."

VOA: standard.2010.06.09

Officials say the Vienna talks will focus on possibly sending Iran's uranium overseas for enrichment.

VOA: standard.2009.10.04

The plan follows months of deadlock over Iran's nuclear program and the recent discovery of a previously unknown nuclear-enrichment plant near the Iranian city of Qom.

VOA: standard.2009.10.19

Republicans and Democrats expressed identical concerns that by engaging in negotiations, Iran may be playing for time in an effort to move ahead with weapons-related enrichment.

VOA: standard.2009.10.28

Uranium enrichment is the process used to make fuel for nuclear power plants, but when extended it can also produce fissile material for an atomic bomb.

VOA: standard.2009.11.28

U.S.officials say Iran's uranium enrichment program is weapons-related, despite Tehran's expression of peaceful intent.

VOA: standard.2010.05.14

The North also said it had reached the final stage of a uranium enrichment program, possibly creating a second process by which it can build nuclear arms.

VOA: standard.2009.09.06

The fact that if Tehran surrendered most of the uranium it has been processing at its Natanz enrichment facility it would ease worries that its effort is weapons related.

VOA: standard.2009.10.24

The threshold for weapons is 90 percent enrichment."

VOA: standard.2009.10.19

Despite better atmospherics in their relationship since the start of the Obama administration, the two sides have not resolved differences over Georgia, European missile defense and ways to prompt Iran to end uranium enrichment.

VOA: standard.2009.05.07

Iran's military exercises, which started Sunday and have included test launches of short and medium-range missiles as well, come just days after the disclosure that Tehran is building a new uranium enrichment plant.

VOA: standard.2009.09.28

The P5+1 last year presented Iran with a revised offer of incentives for it to halt a uranium enrichment effort U.S.and European officials believe is weapons-related and return to negotiations on its nuclear program.

VOA: standard.2009.06.24

But we're not going to wait forever,". Kelly said preparations have been made for a visit Sunday by IAEA inspectors to the partially-underground enrichment facility near the city of Qom that Iran recently acknowledged it has been secretly building.

VOA: standard.2009.10.24

With Iran now facing intensified pressure to provide a complete account of all of its enrichment and any weapons-related activities, revelation of the new enrichment facility reinforced the determination of U.S.lawmakers to move ahead with tougher sanctions.

VOA: standard.2009.09.25

On the Iran nuclear issue, Lavrov said while Moscow opposes harsh additional U.N.sanctions against Tehran, it does support,and is applying, "robust" political pressure to get Iran to return to negotiations with the major powers on its enrichment program.

VOA: standard.2009.05.07

Iran has sent mixed signals about its response to the plan, under which much of the low-enriched uranium Iran has produced in its controversial enrichment program would be shipped abroad for processing, a step that would ease Western concerns about Iran's nuclear intentions.

VOA: standard.2009.11.09

The comments from the State Department came after Iran failed to provide a final response Friday to a proposal brokered by the United Nations nuclear watchdog agency under which Tehran would ship abroad much of the low-enriched uranium it has produced in an enrichment effort that has drawn international concern.

VOA: standard.2009.10.24

lead author Matthew During of Ohio State University, described what happened after just three weeks, "And what was surprising to us was that the animals in the enriched environment, the cancers are 40 percent smaller" "When we moved that enrichment to six weeks,now, the cancers were approximately a dramatic effect,and not only that, but 17 percent of those animals had no tumors whatsoever."

VOA: standard.2010.07.14