Separating Truth from Fiction at Parchin: Neutron Activation Can’t Be Scrubbed Away

Neutrons passing through steel would occasionally collide with a cobalt-59 nucleus, producing easily detectable cobalt-60 if trigger experiments were carried out in the steel chamber at Parchin. (From a Wikimedia Commons illustration of the 1911 Rutherford experiment where alpha particles were sent through a thin gold foil.)

Both Marcy, here,  and b, over at Moon of Alabama, have roundly criticized the cartoon released on Sunday by AP’s George Jahn purporting to depict a chamber at Iran’s Parchin site where various groups accuse Iran of carrying out work aimed at an explosive trigger device for a nuclear weapon. David Albright, working through his Institute for Science and International Security, has been near the forefront in most of these accusations, with one of his accusations coming out in December of 2009 (pdf). As described in his 2009 piece, Albright accuses Iran of attempting to replicate A.Q. Khan’s uranium deuteride (UD3) initiator for a bomb, which “works by the high explosives compressing the nuclear core and the initiator, producing a spurt of neutrons as a result of fusion in D-D reactions. The neutrons flood the core of weapon-grade uranium and initiate the chain reaction.”

Prior to the release of the cartoon, Albright had claimed on May 8 that he had detected activity aimed at “cleansing” the Parchin site.  I debunked that claim the next day, by pointing out that all traces of radioactivity cannot be washed away and that Albright’s claims would mean that the waste water carrying the radioactivity was allowed to drain freely onto the grounds surrounding the building, where the radioactivity could be found without much effort. Albright repeats those claims in Jahn’s article accompanying the cartoon, and he brings in another expert to support his claims that residue from testing a trigger device could be scrubbed:

A cleanup “could involve grinding down the surfaces inside the building, collecting the dust and then washing the area thoroughly,” said David Albright, whose Institute for Science and International Security in Washington looks for signs of nuclear proliferation. “This could be followed with new building materials and paint.

“It could also involve removing any dirt around the building thought to contain contaminants,” Albright said in a statement emailed to selected recipients. “These types of activities could be effective in defeating environmental sampling.”

Fitzpatrick, the other nuclear nonproliferation expert, also said a cleanup could be effective.

“In the past, the IAEA has been able to catch out Iran by going to a building that Iran tried to clean and they still found traces of uranium,” he said. “And Iran learned from that and they learned that ‘boy you have to scrub everything really clean; get down into the drains and grind away any possible residue.”

Earlier in the article, Fitzpatrick (who is  Mark Fitzpatrick, director of the Non-Proliferation and Disarmament Program of the International Institute for Strategic Studies) mentions that Iran is specifically accused of using uranium in the explosives research. Also, the article claims that the equipment associated with the chamber includes “a neutron detection system outside the explosion chamber to measure neutron emissions”.

Albright and Fitzpatrick completely overlook a very important basic aspect of the nuclear physics involved here. If they really are going to claim that uranium is being used and that bursts of neutrons capable of initiating a nuclear reaction are the goal of the experiments, then the neutrons originating from the uranium and from the neutron bursts would result in neutron activation of the steel container itself. Neutron activation occurs when the nucleus of an atom absorbs a neutron, forming a new, radioactive, form of the original atom.

The most common neutron activation product in steel is production of cobalt-60 from the naturally occuring cobalt-59 in the steel. Cobalt-60 has a half-life of over five years and is very easily detected due to the high energy beta and gamma radiation released by it and its decay products. It is critically important to note that this neutron activation occurring within the steel of the container would not be just on the inside surface of the chamber. The collisions of neutrons with cobalt-59 nuclei in the steel would occur throughout the full thickness of the steel, because at the scale of a neutron, the metal atoms comprising the steel are mostly empty space. Thus, the neutrons pass through the steel, only occasionally colliding with a metal nucleus. If the collision is with a cobalt-59 nucleus, then cobalt-60 can be formed as the nucleus absorbs a neutron. (See this helpful tutorial from Florida State University showing the classic 1911 Rutherford, Geiger and Marsden experiment where alpha particles are shot through a gold foil. The concept for neutrons going through steel is essentially the same.)

Neutron activation of steel resulting in cobalt-60 was used in efforts to reconstruct the radiation doses at various locations around the atomic bombs dropped on Japan (pdf). Furthermore, neutron activation of steel in nuclear reactor facilities is a major consideration in the decommissioning of these facilities (pdf).

With those thoughts in mind, we now have tools with which to evaluate subsequent developments surrounding the chamber at Parchin. The claims from Albright and Fitzpatrick appear to be aimed at setting the stage for accusations that Iran carried out trigger research at the facility, even using uranium, but subsequently removed all radioactive traces of that work. Such an accusation could be made after IAEA gaining access to the site but failing to find traces of radioactivity. However, the neutron activation information above would make such an accusation highly dubious, as it would be impossible to remove all traces of neutron activation of the steel from which the chamber is constructed.

On the other hand, should Iran remove the chamber, then that would be suggestive that they were unable to remove neutron activation evidence and thus unable to hide evidence of trigger research. Further, analysis of the metal itself, if access to the chamber is granted, would be very informative about Iran’s intentions when the chamber was constructed.

The AP cartoon article claims the chamber was constructed in the early 2000’s by Azar AB Industries. It is doubtful that this Iranian company has experience working with steel intended for nuclear uses. The cobalt concentration in the steel used for this chamber should be compared to the cobalt concentration in other steel materials produced by Azar AB Industries, because steel intended for use in nuclear activities is intentionally engineered to be low in cobalt content:

Due to the ability of cobalt to absorb neutrons, severe restrictions are placed on its concentration in steels destined for atomic energy applications. Levels of 0.01 and 0.005% Co maximum and lower are commonly listed by the N.R.C.

If the chamber was constructed of steel that is artificially low in cobalt content, then that would suggest that Iran intended the chamber to be used in trigger device development. On the other hand, if no evidence of neutron activation is found upon analysis of the chamber and if it is found to be comprised of steel no different in cobalt content from other steel produced by Azar AB Industries, that would be very strong evidence that the chamber had always been intended for nanodiamond work and no trigger work involving uranium was carried out.

Update: It seems relevant to note how far neutrons can penetrate in steel. The illustration above for the Rutherford experiment is for a very thin foil of gold. Penetration of neutrons into steel depends on the speed at which the neutrons are travelling. The ability of radiation to penetrate into an object is measured as the half-value layer, which is the thickness of the material that is needed to stop half of the radiation that is incident on it. For neutrons, we have this for passage through steel or iron:

10-100 keV neutrons = 0.36 cm

100-500 keV neutrons = 2.73 cm

1 MeV neutrons = 3.45 cm

The neutrons emitted in uranium decay are in the 250-560 keV range, so up to one fourth of neutrons emitted by uranium would travel as far as 5 cm, or two inches, into the steel of the chamber walls. I have not seen an estimate of the chamber wall thickness, but this rough calculation should suffice to demonstrate that virtually the entire thickness of the chamber walls would be subject to neutron activation.


9 replies
  1. Duncan Hare says:

    The tank may be low cobalt steel to avoid detection.

    There is other steel around, reinforcing, roof trusses, possibly sheet metal, all of which is susceptible to neutron adsorption.

    The walls of a steel tank is not going to contain or adsorb all the neutrons. The neutrons pass through the continent vessel, and irradiate the surrounding structure (ask any nuclear plant operator).

    The effects of neutron flux cannot be removed, hidden nor concealed. If it could then Hanford and Oak Ridge would be theme parks and places for vacations.

  2. orionATL says:

    no,no, jim. you title is all wrong.

    we’re not “separating truth from fiction” here; we’re looking for the few tiny grains of truth that exist in a sand pile of israeli-generated lies. i’d guess finding higgs boson has a higher probability of success.

  3. jerryy says:

    Even the non-tech public does not have to get very far into the nuts and bolts of nuclear physics to see that Albright’s claim is bunk.

    Keep in mind that folks have been tracing the radioactive water discharged from Japan’s reactors after that tragedy. Water that was discharged into the ocean, the very, very big ocean. If that big ocean did not dilute the radioactivity to lower than traceable amounts, how can some person with essentially ‘a scrub brush and a water hose’ going to remove traces from the buildings?

  4. rugger9 says:

    Duncan is quite correct about the shielding. Keep in mind that the reactor compartments are typically shielded with water or plastic as well as high-Z metals, the former for neutrons [since the energy loss is greater the closer the masses match, otherwise it pinballs], the latter for gamma radiation. The article also doesn’t discuss fission products. FWIW, Co-60 has two very high energy gammas in its decay sequence, not just one.

    Also, since neutrons decay into protons [hydrogen] some embrittlement is likely as well for the vessels and support structures, a known effect of hydrogen in its various isotopes on metals.

  5. orionATL says:

    thanks for that update.

    at parchin david albright’s gotcha boys were pointing to water, clearly implying some sort of “ordinary” scrubbing activity intended to fit into an ordinary teevee viewer/newspaper reader’s everyday experience.

    while traveling around town today, i was thinking – this is an atomic-level event. “scrubbing” in the normal use, i.e., not “scrubbing” the towers of electricity generating plants, involves doing some sort of cleaning to a surface “layer” – of your skylight, car windshield, driveway, skin, etc.

    but i’d guess that ordinary scrubbing can’t alter atomic level changes caused by radiation unless those changes are limited to a layer a few atoms thick, a “skin”.

    this update suggests one would have to “scrub” 2 inches of steel to remove traces of radiation.

    my non-specialist’s knowledge was limited to thinking that neutrons can travel effortlessly thru almost all materials.

    i don’t know about “naturally” occurring cobalt in steel, but i do know from my experience that cobalt-altered steel is used in drills which are in turn used for drilling into very hard metal, like stainless steel.

    if one were trying to scrub 2 inches off of cobalt steel, it seems unlikely one would use water at any pressure or velocity.

    david albright is a physicist.

    he would understand a lot more about these matters than i.

    so how did he and his organization reach his transparently false conclusion?

    was it money?

    was it ideology?

    was it tribalism?

    was it albright’sheimer?

    or was it sound physics?

    i kept thinking today, in this regard, of hungarian physicist edward teller.

  6. P J Evans says:

    Teller was a hawk (given his history, I’d be surprised if he hadn’t been one), but I’ve never heard anyone describe him as a fool. Or as stupid. Albright seems to be aiming for at least one of those descriptors.

  7. orionATL says:

    edward teller was an extraordinarily capable scientist;

    he was also a political fool.

    from miss wiki:

    ” … US Government work and political advocacy

    After the Oppenheimer controversy, Teller became ostracized by much of the scientific community, but was still quite welcome in the government and military science circles. Along with his traditional advocacy for nuclear energy development, a strong nuclear arsenal, and a vigorous nuclear testing program, he had helped to develop nuclear reactor safety standards as the chair of the Reactor Safeguard Committee of the AEC in the late 1940s,[35] and later headed an effort at General Atomics which designed research reactors in which a nuclear meltdown would be impossible (the TRIGA).[36]

    During the 1960s, Teller argued vigorously against the proposed nuclear test ban, testifying before Congress as well as on television.Teller promoted increased defense spending to counter the perceived Soviet missile threat. He was a signatory to the 1958 report by the military sub-panel of the Rockefeller Brothers funded Special Studies Project, which called for a $3 billion annual increase in America’s military budget.[37]

    … He was a tireless advocate of a strong nuclear program and argued for continued testing and development—in fact, he stepped down from the directorship of Livermore so that he could better lobby against the proposed test ban.[38] He testified against the test ban both before Congress as well as on television…

    Nuclear technology and Israel

    For some twenty years, Teller advised Israel on nuclear matters in general, and on the building of a hydrogen bomb in particular.[45] In 1952, Teller and Oppenheimer had a long meeting with David Ben-Gurion in Tel Aviv, telling him that the best way to accumulate plutonium was to burn natural uranium in a nuclear reactor. Starting in 1964, a connection between Teller and Israel was made by the physicist Yuval Neeman, who had similar political views. Between 1964 and 1967, Teller visited Israel six times, lecturing at Tel Aviv University, and advising the chiefs of Israel’s scientific-security circle as well as prime ministers and cabinet members. At each of his talks with members of the Israeli security establishment’s highest levels he would make them swear that they would never be tempted into signing the Nuclear Non-Proliferation Treaty. In 1967 when the Israeli program was nearing completion, Teller informed Neeman that he was going to tell the CIA that Israel had built nuclear weapons and explain that it was justified by the background of the Six-Day War. After Neeman cleared it with Prime Minister Levi Eshkol, Teller briefed the head of the CIA’s Office of Science and Technology, Carl Duckett. It took a year for Teller to convince the CIA that had obtained nuclear capability; the information then went through CIA Director Richard Helms and then to the US president. Teller also persuaded them to end the American attempts to inspect the Negev Nuclear Research Center in Dimona…

    Strategic Defense Initiative

    Teller became a major lobbying force of the Strategic Defense Initiative to President Ronald Reagan in the 1980s.In the 1980s, Teller began a strong campaign for what was later called the Strategic Defense Initiative (SDI), derided by critics as “Star Wars,” the concept of using ground and satellite-based lasers, particle beams and missiles to destroy incoming Soviet ICBMs. Teller lobbied with government agencies—and got the approval of President Ronald Reagan—for a plan to develop a system using elaborate satellites which used atomic weapons to fire X-ray lasers at incoming missiles— as part of a broader scientific research program into defenses against nuclear weapons. Scandal erupted when Teller (and his associate Lowell Wood) were accused of deliberately overselling the program and perhaps had encouraged the dismissal of a laboratory director (Roy Woodruff) who had attempted to correct the error.[47] His claims led to a joke which circulated in the scientific community, that a new unit of unfounded optimism was designated as the teller; one teller was so large that most events had to be measured in nanotellers or picotellers. Many prominent scientists argued that the system was futile. Bethe, along with IBM physicist Richard Garwin and Cornell University colleague Kurt Gottfried, wrote an article in Scientific American which analyzed the system and concluded that any putative enemy could disable such a system by the use of suitable decoys. The project’s funding was eventually scaled back.[citation needed]…’

    just a little background on a truely distinguished intellect who proved to be an utter fool when discussing the social applications of his equations.

    david albright, by contrast, is in no way so intellectually distinguished, but trods the same path of inept political “commentary” as did teller.

  8. orionATL says:

    @P J Evans:

    our comments crossed.

    i get your point.

    teller was a brilliant and imaginative physicist as I’ve just noted.

    i think he was a fool as a political thinker – and intellectually dishonest to boot.

    intellectual competence in a single individual is rarely distributed across a range of subjects – it certainly was not in teller’s case. it happened to have been so distributed in oppenheimer’s case.

    in the foolishly fearful climate of the time, however, the fool who lied won out.

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