My longest and most loyal Israel-friend, Ira K., wants me to write an easier version of my last article describing the actual Bibi Iranian Nuke Red-Line. Ira worked so hard with me on opposing the US Troops in the Golan Heights issue 18 years ago, so, I couldn't refuse Ira anything.
So here goes, first working backwards:
Step One: You need 35 kilograms (kg) of weapons-grade 90% U235 uranium metal (U235) to make a gun-type Hiroshima atomic bomb-
This time let’s work backwards from enough uranium weapons-grade material for one gun-type Hiroshima-type bomb or one "Significant Quantity" of weapons-grade uranium. Iran would need about 30 kg of weapons-grade uranium metal, composed of 90% 'good' U235 and 10% 'bad' U238, for one Significant Quantity of weapons-grade uranium. ('Good' as I'm using it here means 'good' for an atomic bomb.)
So, working backwards, if you need about 30 kg of 90% uranium weapons-grade metal, you really should start the enrichment process aiming for about 35 kg of 90% weapons-grade uranium metal, because there is always some loss in the enrichment process. Hence, the enrichment process would target to achieve about 35 kg of 90% U235 weapons-grade uranium for one bomb.
Step Two: 35 kg of weapons-grade 90% U235 contains about 32 kg of pure 'good' 100% U235-
To make the calculation easier, ask yourself, how much pure 'good' 100% U235 you need, if you need 35 kg of 90% U235 for one bomb? Since the 235 uranium is 90% of the weapons-grade uranium metal, you multiply 35 kg times 90% (35 kgs x .9 = 31.5 kg) and you get about 31.5 kg of pure 'good' U235 that’s needed to make one Hiroshima-type bomb. (Remember the little extra is from a small loss factor in the enrichment process. So if you only aim for 31.5 kg you'll get a little less - or about 28 kg - due to predictable small loss factors in the enrichment process.)
Step Three: 31.5 kg of 'good' U235 and 128.5 kg of 'bad' U238 make a uranium mixture totaling 160 kg, comprised of 20% 'good' U235 and 80% 'bad' U238-
Now, if it takes 31.5 kg of pure ‘good’ U235 for one bomb, then you need about 160 kg of the uranium mixture of 20% good/80% bad uranium to be able to enrich out the 31.5 kg of pure ‘good’ U235. This is because 160 kg times 20% equals 32. (160 kg x .2 = 32 kg) This means the total weight of the mixture of 31.5 kg of 'good' U235 and 128.5 kg of 'bad' U238 uranium comes to a total of about 160 kg of the mixture of the two isotopes of U235 and U238. This 160 kg uranium mixture is by definition 20% 'good' U235 and 80% 'bad' U238.
Step Four: Add 80 kg of fluoride to the 160 kg of the 20%good/80% bad uranium mixture and you get 240 kg of uranium hexafluoride (UF6) gas-
Now, you take 160 kg of the combined 20%good/80%bad uranium and add fluoride to it to make UF6. The amount of kilograms of the element fluoride it takes to make UF6 gas is about 80 kg of fluoride when there is 160 kg of 20% good/80% bad uranium mixture. Thus, the total combined weight of the fluoride added to the weight of the mixed 20%good/80%bad uranium mixture is a grand total of 240 kg of UF6 gas.
So, now we have done the math and established that you need about 240 kg of UF6 gas (comprised of 20% ‘good’ U235) in order to make a Hiroshima-type bomb. From here, let’s move forward in the enrichment process to get to an Iranian-made bomb that would be ready to use.
Then, working forwards:
Step One: It takes two or three weeks to enrich 20% 'good' U235 UF6 gas to 90% 'good' U235 UF6 gas-
Once the Iranians have stockpiled 240 kg of UF6 gas of 20% 'good' U235 concentration, it would take the Iranians less than a month to enrich the 20% UF6 gas to 90% 'good' U235 UF6 gas.
Step Two: Chemically decouple the uranium from the fluoride in the 90% UF6 gas, and you get 35 kg of weapons-grade 90% 'good’ U235 metal-
So, the Iranians, in a simple chemical procedure, could decouple the uranium from the fluoride which is in the UF6 gas, and get 35 kg of uranium weapons-grade metal that would be composed of 90% 'good' U235 and 10% 'bad' U238. With the new centrifuges Iran claims to have installed, this would take even less time.
Step Three: Put the weapons-grade 90% U235 into a gun-type bomb assembly-
With 1940's technology, US scientists were so certain their U235 gun-type bomb design would work, they didn't even test it before they dropped it on Hiroshima. With 2010 technology and North Korean bomb-building experience, the Iranians could already have the actual bomb mechanism ready to be loaded with the 30 kg of weapons-grade 90% U235.
Conclusion: Hence working backwards, if the Iranians were able to stockpile 240 kg of 20% UF6, then Iran could quickly enrich that stockpile and arm one nuclear bomb in less than a month. Therefore, 240 kg of 20% U235 UF6 gas is Bibi's Red-Line.
The Problem: Bibi's Red-Line leaves only 2-4 weeks to plan and execute an attack against Iran. So, by the time the world has figured out Iran crossed the Red-Line, it would very likely be too late to attack Iran.
In reality, Bibi's Red-Line leaves no time to plan and launch an effective attack. Once the Iranians have 240 kg of UF6 20% 'good' U235, the Iranians could make a mad dash for an atomic bomb. Since the inspectors inspect the centrifuges for uranium content only every 3 months, nobody would even know for as long as two months. By then the Iranians could have dispersed the enriched 90% U235 UF6 gas to a completely different location, untouchable by an allied attack. So, the Iranians could very well have crossed the finish line and enriched a bomb's worth of weapons-grade uranium and moved it to a variety of other special locations for secure storage to assemble a bomb.
Houston, we have a problem. If Obama doesn't recognize Bibi's Red-Line, or his Red-Line is weaker than Bibi's, then Obama is, by definition, ceding Iran as a nuclear-weapons state.