Iran needs at least 180 kg of near-20% U-235 gas for a two-step nuclear breakout, as explained in the ISIS report of 8 Oct 2012. The 180 kg breakout uses only the centrifuge cascades at Natanz, and would take 1.7 months. It starts with a stockpile of 180 kg of near-20% U-235 gas, and enriches it in two steps: to 60% and then to just over 90%.

134.9 — As of the last IAEA report (16 Nov 2012), Iran had 134.9 kg of near-20% U-235 gas.
+ 2.5 — The Natanz facility produces 5 kg of gas per month, which adds 2.5 kg for the last half of Nov 2012.
+ 5.0 — The Fordow facility had half of its centrifuges installed and either enriching or ready to begin enrichment as of mid Nov 2012. At half capacity, Fordow produces 10 kg of 20% U-235 gas per month. Running at half capacity for half a month adds 5 kg. Full capacity would be 20 kg/month.
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142.4 kg total as of 01 Dec 2012

Assuming the Fordow facility reached its full enrichment capability by 1 Dec 2012, Fordow would add 20 kg of U-235 gas per month to Iran’s stockpile of 20% gas. The Natanz facility has four cascades, arranged in tandem, tasked with producing 20% gas, adding another 5 kg per month. So the total is 25 more kg per month, which is 12.5 kg per half month and about 0.8 kg per day. The increase in the gas stockpile would then be as follows:

01 Dec 2012 — 142.4 kg
15 Dec 2012 — 154.9 kg
01 Jan 2013 — 167.4 kg
15 Jan 2013 — 179.9 kg
01 Feb 2013 — 192.4 kg
15 Feb 2013 — 204.9 kg
01 Mar 2013 — 217.4 kg
15 Mar 2013 — 229.9 kg
01 Apr 2013 — 242.4 kg
15 Apr 2013 — 254.9 kg

The most relevant breakout points are then:

1.7 month breakout (180 kg) — 16 Jan 2013
1.4 month breakout (190 kg) — 30 Jan 2013
1.3 month breakout (200 kg) — 11 Feb 2013
1.0 month breakout (240 kg) — 29 Mar 2013
0.9 month breakout (250 kg) — 09 Apr 2013

On or about 16 Jan 2013, Iran may have sufficient 20% uranium gas for a nuclear breakout of 1.7 months. By the end of January, the time needed for a breakout drops to about 1.4 months. By late March or early April, Iran would have the capability to breakout in one month or less.

Unless Israel or the U.S. undertake a military strike on Iran’s nuclear facilities very soon, Iran will obtain nuclear weapons in 2013.

See my previous articles on this topic:
When will Iran have enough 20% Uranium for a Breakout?
Background Information on Iran’s Nuclear Program
Iran’s Evolving Breakout Potential: How Bad Is It?
Reasons why Iran will nuke New York City, not Israel
Nuke Map — possible location of Iran’s attack on U.S.

by
Ronald L. Conte Jr.
Roman Catholic theologian and
translator of the Catholic Public Domain Version of the Bible.