Iran Fact File: Analysis of Iranian Breakout Calculations

      A report recently published by quasi-official Iranian website NuclearEnergy.ir claims Tehran would need at least 18 months to produce enough enriched uranium for one bomb. But that timeline differs drastically from the U.S. estimate of two months because of questionable methodology, according to Iran Fact File, a project of the James Martin Center for Nonproliferation Studies. Ferenc Dalnoki Veress notes that the Iranian report “ignores the risk of clandestine nuclear facilities, such as centrifuge plants, conversion plants and hot cells,” which factor in to Western estimates of Iran’s breakout time. The following are excerpts from Iran Fact File’s response to the Iranian article.

 
URANIUM PROGRAM
 
Issue 1
“Iran is also constructing a heavy water research reactor. The nascent reactor in Arak, known as the IR-40, has a capacity of 40 Mega-watt (MW) and is designed to meet Iran’s need for radioisotopes, material test and other neutron therapy and neutron studies. The United States and its allies claim that this reactor can produce weapon-grade plutonium. Although plutonium is an inherent element of any reactor of any type, Iran has declared repeatedly that it does not need the IR-40’s plutonium in any shape or form.” (NuclearEnergy.ir)
 
            It is true that every reactor can make the “element” plutonium, but not every reactor is well suited for producing weapons grade plutonium. In fact, ordinary light water reactors tend to produce reactor grade plutonium when the fuel is removed not weapons grade plutonium. Weapons grade plutonium is much easier to use in a bomb than reactor grade plutonium, although, it must be said that they are both dangerous. Simple, back-of-the-envelope estimates and calculations that are more elaborate, predict approximately 8-10 kg of weapons grade plutonium produced per year from the IR-40 reactor. The type of reactor that Iran has chosen to build is exactly the type of reactor that is of concern for weapons grade production.
 
Issue 2
“Enriching uranium above 90 percent U-235: although Iran now has the required technology and infrastructure for enrichment of uranium, Iran’s current centrifuge machines are not capable of directly enriching uranium from natural U-235 concentration (or even up to 5 percent) to above 90 percent.” (NuclearEnergy.ir)
 
            The wording in the article is troublesome. Iran is certainly capable to enrich uranium to 90% enrichment. Say 25 kg of 90% enriched uranium is the goal. You can think of this as a final destination on a long road. A centrifuge is like a vehicle to get to the final goal. You can decide to stop at the 5% milestone or you can continue on along the road to get to 90% final destination. The same vehicle is used either way.
 
Issue 3
“Assuming the highest estimate of Iranian separative work unit (SWU) capacity, the required time for producing 6,000 SWU will be 6.6 months. But a very obvious and underlying principle has been neglected here . The theoretical critical mass is not reachable even within that timeframe for any non-nuclear weapon states which does not have the expertise. There is some loss and waste of material in the process of learning. Moreover, any chemical conversion and transformation process has its inherent loss in the form of solid and liquid waste as well as in-process holdup. Thus, as a rule of thumb, there is a need for more than 6,000 SWU of HEU as raw material for diversion.” (NuclearEnergy.ir)
 
            No underlying principle has been neglected. The 25 kg Significant Quantity (SQ) already takes into account processing losses etc. Many analysts suggest that the 25 kg SQ rule is too high. It is NOT the minimum amount that you would need to have to make a nuclear bomb, and it is NOT the critical mass. You could make as much as two 10 kt bombs with that much HEU for a nuclear weapon newcomer country.
 
PLUTONIUM PROGRAM
Issue 1
“There is no significant amount of plutonium in Iran. Thus, the claimed breakout in this manner is tied to the commissioning of the IR-40 reactor, which is planned for 2015. However, even after commissioning, the reactor must work for many months to irradiate the fuel for production of plutonium. In this regard, the first step, which is to produce the required fissile material, would take at least 2 years after the commissioning of the IR-40. ”
 
            I am not sure it would take 2 years. However, commissioning the reactor as a violation of safeguards would bring back sanctions and would make a start of the reactor very difficult for Iran. Regardless of Iran’s stated intentions, there is once again a valid concern because of historic precedents: the first nuclear weapon of many countries (Soviet Union, UK, France, India, DPRK (probably)) have been with plutonium. [10] While at the moment Iran may not have ill intentions, it is hard to predict the future.
 
Issue 2 and Issue 3
The irradiated fuel assemblies comprise different high radioactive materials, which cannot be contacted or worked with except via special facilities called “hot cells.”
Iran has no “hot cell”, which is needed for plutonium extraction and further processes. Construction of such a facility would require at least 4 to 5 years, and the commissioning and the operation would require another 1 to 2 years.
 
            It is true that Iran would need to have a hot cell and a reprocessing facility to extract the plutonium. However, I think 5 years as an estimation seems too long. Iran’s intentions have to be questioned, because of previous declarations that Iran planned to construct a hot cell for the IR-40. See para 44 and GOV/2003/75:
            "In its letter of 21 October 2003, Iran acknowledged that two hot cells had been foreseen for this project. However, according to the information provided in that letter, neither the design nor detailed information about the dimensions or the actual layout of the hot cells was available yet, since they did not know the characteristics of the manipulators and shielded windows which they could procure. On 1 November 2003, Iran confirmed that it had tentative plans to construct at the Arak site yet another building with hot cells for the production of radioisotopes. Iran has agreed to submit the relevant preliminary design information with respect to that building in due course."
 
            See also para 74 (Annex) in GOV/2003/75:
 
            In its letter of 21 October 2003, Iran acknowledged that two hot cells had been foreseen for this project. However, according to the information provided in that letter, neither the design nor detailed information about the dimensions or the actual layout of the hot cells were available at the present time, since they did not know the characteristics of the manipulators and shielded windows for the hot cells which they could procure. Iran indicated in that letter that manipulators would be needed for: 4 hot cells for the production of medical radioisotopes, 2 hot cells for the production of Co-60 and Ir-192 sources, 3 hot cells for waste processing, and 10 back-up manipulators. The 21 October 2003 letter included a drawing of a building which Iran said would contain hot cells for the production of isotopes. In the meeting on 1 November 2003, upon further Agency inquiry, Iran confirmed that there were tentative plans to construct at the Arak site an additional building with hot cells for the production of radioisotopes. Iran stated that that first building was to contain hot cells for the production of “short lived” isotopes, and that it intended to construct the other building to produce “long lived” radioisotopes. Iran agreed to provide preliminary design information for the second building.
 
            Clearly, there was interest in 2003 for a hot cell that could be used to produce “long-lived” isotopes. Many analysts have taken this these long-lived isotopes to refer to plutonium. Now, hot cells are used for peaceful purposes, but some analysts are concerned that there may be clandestine facilities which could be used to extract plutonium, in batch form, smaller quantities in smaller labs that would pose less risk.
 
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