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Monday, November 29, 2021
MEXICO CITY, Apr 18 2011 (IPS) - Mexico needs to take urgent steps to tighten oversight of the storage, handling and disposal of radioactive materials that can threaten the lives and health of its population, experts warn.
“The materials must be stored safely under strict security conditions, and radiological safety must be properly monitored,” the head of the Mexican Society of Radiology and Imaging (SMRI)’s School of Radiology Technicians, Fernando Cruz, told IPS. “There are many regulations that need to be reviewed,” he said.
Accidents recorded over the past 25 years testify to the fact that better governmental control is needed. In 2008, Tubos de Acero de México (TAMSA), the country’s main manufacturer of steel pipes, inadvertently melted down some Caesium-137, a source of highly penetrating radiation, in a factory in the southeastern state of Veracruz.
The incident was reported by Zinc Nacional, a company that buys steel dust and recovers the zinc it contains. An 80-ton load of scrap metal from TAMSA activated the company’s radiation detectors, and Zinc Nacional promptly sent it straight back.
The National Commission for Nuclear Safety and Safeguards (CNSNS), the agency of the Energy Secretariat (Ministry) responsible for monitoring all uses of nuclear and radioactive materials and other sources of ionising radiation, was informed on Jun. 29, 2008 that TAMSA had melted radioactive material in its foundry, and carried out an inspection nine days later.
Alejandro Cortés, a CNSNS employee, presented details of the incident at the International Conference on Control and Management of Inadvertent Radioactive Material in Scrap Metal, held at Tarragona, Spain, in February 2009.
In recent years, CNSNS’s Radiation Security Office has issued nearly 1,900 permits for possession and use of radioactive materials, some of which may be stored and transported in “open” fashion (without protective containers) while some must be “sealed” in shielded containers, usually made of lead or tungsten and up to several centimetres thick.
Among the main “open” sources used in Mexico are Iodine-125 and -131, Thallium-201, Phosphorus-32, Carbon-14, Technetium-99m, Gallium-67 and Hydrogen-3, most of them for medical uses. The main “sealed” sources purchased from abroad are Cobalt-60, Iridium-192 and Americium-241/Beryllium for therapeutic and industrial purposes. At least 22 companies are authorised to buy and transport radioactive materials.
The TAMSA accident is reminiscent of the case of iron bars contaminated with Cobalt-60 that occurred in the mid-1980s in Ciudad Juárez, on the border with the United States, with consequences that endure to this day.
In 1977 the private Medical Specialties Hospital in Ciudad Juárez illegally obtained a radiotherapy unit containing Cobalt-60 that was acquired as contraband from a U.S. supplier. The core of radioactive Cobalt-60 in a radiotherapy unit produces highly penetrating radiation. Suitably shielded and directed, a beam of radiation from the Cobalt-60 can be used to kill, for example, cancer cells in a patient’s body.
In 1983, two hospital employees sold the ageing radiotherapy unit, still containing Cobalt-60, as scrap to Yonke Fénix, which sold it on to the now defunct state-owned Aceros de Chihuahua (Chihuahua Steel Company).
This company and others like it used the contaminated scrap to make iron reinforcing bars that were subsequently used in buildings in 16 of Mexico’s 32 states. CNSNS estimated that at least 6,608 tons of radioactive reinforcing rods were manufactured.
In 1985, CNSNS identified 17,636 buildings, including shopping centres and public buildings, 1,276 of which had higher than natural background levels of radiation. More than 800 buildings were demolished due to unacceptable radioactive contamination.
But Agustín Horcasitas, a former production manager at Aceros de Chihuahua, said in his 1999 book about the disaster, titled “El gran engaño” (The Great Deceit), that approximately 10,000 tons of the iron bars were never recovered.
More than 5,000 tons of the contaminated material lie buried in a “nuclear cemetery” in Samalayuca, in the northern state of Chihuahua, 70 kilometres from the U.S. border.
Some 4,000 people suffered exposure to radiation, without harmful effects on health being found at the time, according to the CNSNS report. But years later the Mexican press reported that at least three people who had spent time in close proximity to the radioactive bars have died of degenerative diseases, and unknown numbers of people are suffering from similar illnesses.
“Radioactive waste is not being tracked, so no one knows where it ends up,” Bernardo Salas, head of the Laboratory for Radiological Analysis of Environmental Samples, at the Faculty of Sciences at the state National Autonomous University of Mexico (UNAM), told IPS.
Regulations under article 27 of the constitution cover all aspects related to nuclear energy, while there are at least six additional sets of regulations for the design of installations, storage of radioactive waste and permitted radiation exposure levels for workers.
But the number of site inspections carried out by CNSNS at nuclear facilities has declined from 30 in 2000 to 23 in 2009 and only 13 in the first half of last year.
More than 7,733 people work with sources of ionising radiation, according to CNSNS, which in the last few years has investigated 42 cases of exposure to radiation higher than the maximum permissible levels. In the incident with contaminated steel dust in Veracruz, 83 people were exposed to radiation, but at levels below those regarded as hazardous.
In November 2002, six people at the Nuclear Medicine Unit of the Specialties Hospital of the state “Siglo XXI” National Medical Centre became acutely ill when they drank coffee poisoned with Iodine-131. A co-worker at the hospital had deliberately added the radioactive material to the coffee.
At the annual congress of the Mexican Radiation Safety Society (SMSR), Hermenegildo Maldonado, a senior official with CNSNS, recommended updating the legal framework, creating theoretical and practical examinations for personnel working with radioactive materials and modernising radiation safety training.
CNSNS has proposed a protocol for monitoring and dealing with radioactive material inadvertently present in scrap metal, in cooperation with steel producers, but this has not been adopted.
“Hundreds of medical and industrial radioactive sources are abandoned, stolen, or lost each year, constituting both a safety and security concern,” wrote Duyeon Kim, deputy head of the Washington-based non-governmental Centre for Arms Control and Non-Proliferation, in the March edition of the Bulletin of the Atomic Scientists.
In her article, she proposed: “The threat of radiation leaks or loss of control over radioactive materials caused by nature, internal system failures, or malicious intent” should be included in the discussions at the Nuclear Security Summit to be held in Seoul in 2012.
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