Radioactive Borders (part 4)

 

Tales from the Nuclear Age

Copyright © 2012 by Charles Glassmire

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Feb. 22, 2012

Radioactive Borders (part 4)

 

          On July 20, 2010, radiation inspector Enzo Montagna detected a shipping container on the dock near Genoa Italy emitting a life-threatening level of high radiation. The container manifest showed nothing irregular. Emergency personnel were summoned and it was decided to isolate the box by surrounding it with other shipping containers moved in by crane. Now the box sits quarantined on the Voltri dock surrounded by a barricade of stone and water-filled shipping containers; the radioactive source still remains unidentified.

          Additional surveying around the container determines the hottest spot to be in the center of the long side of the container and about 2 feet above ground(1). This exact center location is suspicious, for if someone were trying to hide a source, they would likely bury it at the middle of the container so as to be difficult to reach. It also suggests the container was NOT meddled with during transit. The remainder of the contents is 18 tons of copper wire, old radiators and other scrap metal. To place a source at the middle, 9 tons of metal would first need to be removed.

          Now there is time to direct attention to identifying the source. Many decaying radioisotopes give off a spectrum of gamma rays. This radiation is similar to visible light, but much more energetic in damaging human cells. If an isotope is present in its pure form, each one gives off gammas with a characteristic energy, wavelength and frequency. If there is a mixture of isotopes present, the problem becomes more complex. If the spectrum of the gamma field can be measured, it might be possible to identify the isotope in question.

          A very expensive scintillation counter is brought in – known as a pulse height analyzer. It should be able to measure the energy of the emitted gammas and hopefully classify the isotope. The gamma field is subsequently scanned and the data printed out. Two clear peaks appear at energy levels of 1.17 Million Electron Volts (Mev) and 1.33 Mev. These peaks identify the offender as Cobalt 60. The data is distinct from natural background radiation, and there seem to be no other isotopes present.

          How did such an active isotope get into this shipping container? Perhaps by accident? Not likely. The handler would probably be dead by now. An RDD? (Radiological Dispersion Device – dirty bomb)? This is a possibility. Cobalt 60 has a 5 year half life. It would linger in a dispersed area for a very long time – rendering the real estate unusable. Some observers object that it is a solid very hard metal, and difficult to “blow up”. A determined user however, could first machine it into a powdered form, then mix it with a common explosive.

          Cobalt 60 is fairly readily available especially around medical facilities. This is its most common use. Cobalt 60 is not found in nature. It must be created in a high flux nuclear reactor by irradiating the natural form, which is Cobalt 59. Normally the radioactive 60Co is then extracted for use in medical devices which emit intense radiation for treatments utilizing cancer therapy and other medical applications. There is also some use in industry for radiography of pipe metal welds, food irradiation etc. Cobalt 60 decays to a stable Nickel, and about 12.5% of the Cobalt isotope disappears each year.

          But if the origin of this material was medical or industrial, why would someone anonymously put it into a shipping container? The obvious answer is for terrorism purposes. But there are better sources to steal if one intends a dirty bomb. Perhaps the answer lies elsewhere.

          By United States law, 60Co sources are tracked carefully after manufacture, each one being assigned a serial number, and transport is required to use shipping containers weighing tons and tested to survive fire and crashes. This is not necessarily the case in foreign countries. For example, when the Soviet Union manufactured their nuclear weapons, each weapon was not issued a serial number. This makes it very difficult to track the devices. When Senator Lugar visited a few years ago, he found warehouses full of unnumbered bombs secured by underpaid guards, or padlocks and chain fences, and sometimes not guarded at all. We hope none have been sold clandestinely.

          Since the Cobalt eventually loses its potency (5.27 year half life) this raises a problem for the owner of the isotope. Eventually it becomes ineffective. So what to do with the source after its life expires?  Disposal turns out to be an expensive proposition. Until recently, The Department of Energy operated the Yucca Mountain repository in Nevada for safe deposit of nuclear waste materials. After an investment of billions, President Obama, at the urging of Harry Reid, closed the facility.

          Currently, the worldwide installed base of Cobalt 60 is estimated to be 260 million curies (a unit of radioactivity), disbursed to 170 gamma facilities(2). In the U.S., high-activity sources are uniquely numbered and tracked “cradle to grave”. In addition, the irradiator pays substantial upfront financial guarantees to cover anticipated disposal costs(2). Sometimes sources may be returned to the manufacturer, who mixes the depleted metal with newly activated to get a mix with appropriate strength. Disposal with shipping and fees of just one high level Cobalt source can cost the owner upwards of $130,000 (3). How much easier to avoid such costs in a less regulated foreign country, by just throwing the source in the garbage?

          On the dock at Voltri, alarm grows. The Stevedores are now refusing to handle or go near the container. The union blames port authorities for the week of unattended irradiation of passers-by. For 5 days in August 2010 the union strikes for 2 hours each day.  TV begins quoting local outrage. Painted signs begin to appear on the dock.   Genoese officials post signs   “Danger – Ionizing Radiation …

 (to be continued …)

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(1) “Mystery Box”, Andrew Curry, Wired Magazine, Nov. 2011.

(2) “Cost-Benefit Analysis for Potential Alternative Technologies for Category 1 and 2 Radioactive Sources”, ICF Incorporated, L.L.C., August 31, 2009.

(3) “Radiation Source Use and Replacement”, http://www.nap.edu/openbook.php?record_id=11976&page=27.

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