Ciudad Juárez cobalt-60 contamination incident
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The Ciudad Juarez cobalt-60 contamination incident was a radioactive contamination incident that occurred in 1984 in Ciudad Juarez, Mexico originating from a radiation therapy unit illegally purchased by a private medical company and subsequently dismantled for lack of personnel to operate it. The radioactive material ended up in a junkyard, where it was smelted with other metals and produced about six thousand tons of contaminated rebar, which were distributed in 15 Mexican states and several cities in the United States. It is estimated that four thousand people were exposed to radiation as a result of this incident.
Accident events
Events
In November 1977, the Centro Médico de Especialidades, a private hospital in Ciudad Juárez, Chihuahua, purchased a radiotherapy unit that utilized cobalt-60, which it introduced to Mexico without complying with current regulations. The equipment was kept in storage for almost six years, because the hospital lacked qualified personnel to operate it.[1] Vicente Sotelo Alardin, then an employee of the medical center, dismantled the unit on December 6, 1983 to sell it as scrap metal at the Fénix junkyard at the request of the hospital's maintenance manager. Sotelo had disassembled the head of the radioactive unit and extracted a cylinder containing the cobalt-60 source. He then loaded the material into his truck, where he drilled into the cylinder, causing some cobalt-60 granules to spill into the vehicle. The truck, now contaminated by the cobalt-60, subsequently suffered a mechanical failure upon Sotelo's return from the junkyard and remained immobile near his home in Ciudad Juarez for 40 days.[1]
Meanwhile, at the junkyard, the use of electromagnets for handling the scrap caused the cobalt-60 granules to spread throughout the yard. The fine granules were attracted to the magnetic fields of the other electromagnetic cranes in the yard and eventually mixed in with other metals. This radioactive scrap was sent to two foundries: Aceros de Chihuahua (Achisa), a construction rebar factory in the state capital; and Falcon, a manufacturer of table bases. It is estimated that, by January 1984, these had already been exported to the United States and the interior of Mexico.[1]
Detection of radioactive material
On January 16, 1984, a radiation detector at the Los Alamos National Laboratory, located in New Mexico, United States, detected the presence of radioactivity in the vicinity. The detector went off because a truck carrying rebar produced by Achisa had taken an accidental detour and passed near the laboratory. U.S. authorities realized that the rebar triggered the alert and swiftly notified Mexico's National Nuclear Safety and Safeguards Commission (CNSNS) on January 18. CNSNS confirmed a wide dispersion of radioactive material had occurred and ordered Achisa to suspend the distribution of manufactured rebar until it was verified that it was not contaminated. Mexican authorities also proceeded to close the junkyard.[1]
On January 26, 1984, CNSNS personnel detected an abandoned truck emitting radiation levels of up to a thousand roentgens per hour. Since the vehicle was in a densely populated area, it was towed by a crane to El Chamizal Park. Having discovered the vehicle, CNSNS was able to track down Vicente Sotelo, who confirmed ownership and clarified that he worked at the Specialty Medical Center.
Upon further investigation, the CNSNS concluded that, in addition to the Fénix junkyard, Achisa, and Falcon, three other companies had received contaminated material: Fundival, located in Gómez Palacio; Alumetales, in Monterrey; and Duracero, in San Luis Potosí. It was estimated that the contaminated material had made its way into 30,000 table bases and 6,600 tons of rebar.[1]
Aftermath
Recovery and cleanup of radioactive material
Decontamination began on January 20, 1984, two days after CNSNS was notified by U.S. authorities. Between February 8 and April 14, work was carried out to locate and isolate contaminated material in the Fénix junkyard. Decontamination work was also carried out at the Achisa and Falcon during this period, in addition to tracking shipments with contaminated rebar that had been dispatched to 15 Mexican states.
CNSNS managed to recover 2360 tons of unused rebar, in addition to visiting over 17,000 construction sites and determining that 814 structures would need to be demolished.[2] CNSNS also managed to recover all of the 30,000 contaminated table bases, in addition to about 90% of the thousand tons of contaminated rebar that had been exported to the United States[3]. However, by June 1984, over a thousand tons of contaminated rebar remained unaccounted for, having been shipped to the states of Chihuahua, Sonora, Sinaloa, Baja California, Baja California Sur, Coahuila, Nuevo León, San Luis Potosí, Guanajuato, Jalisco, Zacatecas, Tamaulipas, Querétaro, Durango, and Hidalgo.[4]
The work of retrieving the radioactive rebar was more complicated in these states. 434 tons of rebar were identified in Sonora, scattered throughout the state, including in the capital Hermosillo. 80 tons of rebar had been shipped to Hidalgo and distributed among nine municipalities there, while 42 tons were recovered from the cities of Zacatecas and Fresnillo in Zacatecas. In those states, hundreds of fences and homes built with contaminated material had to be demolished.[3]
Storage of radioactive material
In February 1984, the CNSNS identified a site in the Samalayuca desert for the construction of a "cemetery" facility known as La Piedrera to house the radioactive material, where the rebar collected in Chihuahua was eventually stored in September 1984. Material collected in other areas was stored at facilities in Maquixco, Mexico State (70 tons) and Mexicali, Baja California (115 tons).[4]
According to CNSNS figures, 2930 tons of contaminated rebar, 1738 tons of contaminated unprocessed metal, 200 tons of metal table bases, 1950 tons of contaminated scrap, 860 tons of containers with other contaminated material, and 29191 tons of contaminated soil, slag, and plaster were stored in La Piedrera.[4]
In 2001, a report by El Universal charged that 110 tons of radioactive waste from the Ciudad Juárez incident had been kept outdoors. The material had been stored in the Sierra de Nombre de Dios between 1985 and 1998, and then transferred to Samalayuca, where it was deposited without proper shielding.[5] In 2004, an analysis by the National Autonomous University of Mexico revealed that radiation levels in Samalayuca were still alarmingly high and heavily criticized the fact that the waste had been stored without adequate containment measures.[4]
Population exposure
According to the 1985 CNSNS report, about four thousand people were exposed to cobalt-60 radiation as a result of the incident. It is estimated that almost 80 percent of people received a dose less than 500 mrem (equivalent to 0.005 Sv); 18 percent, between 0.5 and 25 rems (0.005 - 0.25 Sv); and only two percent (about 80 people) received doses greater than 25 rems (0.25 Sv). Of these, five people received a dose between 300 and 700 rems (3 - 7 Sv). CNSNS also examined Vicente Sotelo's neighbors, determining that three of them had received a dose above 100 rems (1 Sv).[6]
See also
References
- ^ a b c d e "México ha exportado 6.000 toneladas de acero contaminado por radiactividad". El País (in Spanish). 1984-05-03. ISSN 1134-6582. Retrieved 2022-02-05.
- ^ "MEXICO: Recurring Risks from Radioactive Materials". Inter Press Service. 2011-04-18. Retrieved 2022-02-05.
- ^ a b "Chernobyl en México: El accidente de radiación más grande". FolkU (in Mexican Spanish). 2020-06-29. Retrieved 2022-02-05.
- ^ a b c d "Energía y contaminación nuclear en México – Rebelion" (in Spanish). Retrieved 2022-02-05.
- ^ "Mantienen a cielo abierto 110 ton de basura radiactiva". El Universal (in Spanish). Retrieved 2022-02-05.
- ^ Isabel Carrasco Cara Chards, Maria (July 2, 2021). "The Mexican Chernobyl, The Biggest Nuclear Accident In The American Continent". Cultura Colectiva. Retrieved February 5, 2022.
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