Can the US, NATO, or Israel stop Iran's nuclear weapons program by bombing? Most assume we can, but can we? Probably not. Iran has constructed it key uranium enrichment facilities underground to protect them from bombs. When the US developed a huge bunker buster bomb capable of destroying the Natanz facility located 90 feet underground. Iran countered by building a second facility near Qom--the Fordow facility buried 300 feet under a mountain. Iran claims its Fordow facility is impregnable, even to the US's new 30,000-pound massive ordnance penetrator, or MOP, known, the biggest "bunker-busting bomb" in the world.

Policmic and other sources reported, according to a former Iranian intelligence official, a massive explosion rocked Iran's Fordow nuclear facility at 11:30 a.m. local time on Monday, January 21st destroying huge parts of the installation and trapping as many as 240 personnel deep underground. There are reports that several North Korean technicians were in the chamber when the explosion occurred.

Iran denies the reports, and the White House has bought the denial. Understandable, since it fits Obama's narrative. The London Times did not buy the White House's story and reported the explosion.

Later reports say that 40 people, including 2 North Koreans, were killed. At the time of the explosions, the source said, 203 Iranian scientists and technicians along with 16 North Koreans had been logged in at the site, though the initial report listed 240 people.

It was reported reported on February 25th that high levels of radiation had been reported and the death toll had risen to 76; 17 high-ranking officers, including majors and colonels had been arrested; and Maj. Ali Montazernia, a member of the security forces in charge at Fordow had been summarily executed. According to a source in the security forces protecting Fordow, many of the personnel, who arrived after the explosion to assist with the cleanup at the site, had been taken to a military hospital suffering from headache, nausea and vomiting--classical symptoms of high-level radiation exposure.

Was Fordow sabotaged? Or was it an accident? Iran claims it was sabotage. Understandable, for Iran can once again claim it was victimized and thus avoiding any hint of incompetence. Actually Iran has to claim sabotage; otherwise questions would have to be asked about the level of enrichment of the uranium being processed.

It's an accepted fact that Iran is using centrifuges to enrich uranium, which it claims will be used to make fuel rods and plates for nuclear power reactors. There is no doubt that some of the enriched uranium will indeed be used for that purpose, however the real concern is what amount will be used to fabricate nuclear weapons.

To understand that concern, one must have a grasp of technology. Uranium is an element, and elements are building blocks for all things; and like most elements, uranium has several forms known as isotopes. Isotopes of uranium all have 92 protons but different numbers of neutrons. U-238, uranium's most common isotope, contains 92 protons and 146 neutrons (92+146 = 238), while U-235 has 92 protons and 143 neutrons.

Uranium ore is shipped for processing from Iran's mines as uranium oxide, yellow cake, containing 0.7 % U-235 atoms. U-235 atoms are the isotopes best suited for creating a chain reaction. To build a nuclear reactor or a nuclear bomb, it is necessary to increase the percentage of U-235.

Iran employs an enrichment technology based upon spinning tubes, centrifuges. Yellow cake is converted into a highly corrosive gas that is fed into the spinning centrifuge. The U-238 atom is slightly heaver (the mass of 3 neutrons) and moves to the wall of the centrifuge tube, leaving the lighter U-235 atoms in the center. The gas in the center is drawn out and fed into the next centrifuge. Each pass through a centrifuge increased the percentage of U-235 atoms by a tiny amount. Thousands of passes are required to reach a 5 % concentration. Many more thousands of passes are required to reach a 20% concentration required for a special type of nuclear reactor. Continuing the process for thousands of more passes will achieve a 90% concentration, bomb grade highly enriched uranium. The difference between uranium enriched for nuclear reactor fuel and uranium enriched for an atomic bomb is the number of times the uranium gas is passed through a centrifuge.

The under ground centrifuge facility at Natanz enriches uranium to 5% U-235, and Iran admits that the Fordow facility enriched to 20%. It takes less time to enrich from 20% to 90% that it does to enrich from 0.7% to 20%. Was Iran enriching from 20% to 90% when the explosion occurred?

A nuclear reactor requires a continuous chain reaction. An atom of U-235 captures a neutron and then fissions, splits, creating two new elements (atoms know as daughter products) and releasing neutrons. The total weight of the neutrons and the two new atoms is less than the U-235 atom's weight. What happened to the missing weight (mass)? It was transformed into energy according to Einstein's equation E=mc2. In a nuclear reactor the fissions are controlled so that one fission produces another fission--a steady-state fission chain reaction. An atomic bomb reaction requires an ever-increasing fission chain reaction--a super critical chain reaction, where one produces two, two produce four, four produce eight, continuing until a nuclear detonation occurs and the remaining U-235 atoms are blown apart stopping the chain reactions.

Each fission occurs in about one billionth of a second, so things happen faster than the human mind can follow. Chain reactions are controlled in a nuclear reactor by control rods that absorb neutrons. A controlled nuclear reaction is referred to as a critical chain reaction.

In an atomic bomb the chain reaction begins when the U-235 is configured so that a super critical reaction, an increasing chain reaction, occurs. This configuration is referred to as the geometry. In an atomic bomb, explosives are used to move the U-235 from a non-critical geometry into a super critical geometry. Sounds simple enough, but the science and engineering required to do so are very complicated.

In a perfect world there are no accidents, but as we know, we do not live in a perfect world. My first job included dealing with nuclear accidents. For example dropping a radioactive source, spilling a radioactive solution, a scattered radioactive isotope (if deliberate it would be a dirty bomb), or a criticality accident--an accidental chain reaction.

U-235 can be accidentally placed in a critical geometry. It has happened. U-235 fission products, the two atoms created when the U-235 atom splits, are radioactive. In an accident (excluding a reactor melt down), the critical reaction does not last very long, but a tremendous amount of heat is generated in a few billionths of a second. This is what I think happed in the Iranian underground centrifuge chamber at Fordow on January 21, 2013.

Iran was installing their new, highly efficient IR-2m centrifuges--centrifuges not fully proven. Iran is in a hurry to enrich uranium and haste causes accidents. As discussed above, uranium gas is fed into the centrifuge so that U-235 atoms are concentrated along the centerline of the spinning tube. As the concentration of U-235 atoms increases from 0.7% toward 90% the chance of creating a critical geometry increases, which is what I speculate cause the Fordow accident.

Assuming that a criticality event occurred in one centrifuge, the massive heat release would cause the gas in the spinning tube to expand, exploding the tube and filling the area with a highly corrosive and radioactive gas. The fissions would release neutrons and gamma radiation, and the released neutrons could trigger a similar reaction in a nearby centrifuge. The result would be a toxic, radioactive chamber nearly impossible to clean up. If this is what occurred, sealing the chamber is the best solution: a solution that would allow Iran to save face and hide the cause of the accident.

Iran refused to allow IAEC inspection of Fordow after the accident, and all talk about installing the new centrifuges has shifted to Natanz. If there was a criticality accident underground at Fordow, then Iran can gain an advantage by agreeing to close Fordow in return for more concessions from the West. This scenario falls in line with the Obama administration's fantasy that Iran is not seeking a nuclear weapon.

Like Benghazi it is doubtful that we will ever learn the truth.