Xochitlalpan disaster

Xochitlalpan disaster

Date	4 August 2004
Time	22:11 local time
Location	Xochitlalpan, Aztaco Republic, Zacapican
Type	Nuclear accident
Casualties
Estimated 80,000 affected 5,000 evacuated 71 deaths from radiation sickness

The Xochitlalpan disaster was a major radiological contamination accident which took place in the atomaltepetl of Xochitlalpan in the northern plain of the Aztaco Republic in eastern Zacapican. The incident occurred at the Tequipanco Atomtic Xochitlalpan (TAX) facility, a important nuclear fuel reprocessing plant, when a nuclear waste storage tank suffered an equipment malfunction that caused it to explode and disperse a large amount radioactive material into the environment. The Xochitlalpan disaster represents the worst nuclear disaster in Zacapine history in terms of the amount of radioactive material released into the environment, and the second worst in terms of the number of people affected by the disaster. 71 people, mainly workers at the plant, died from radiation sickness, with many more workers, rescuers and local residents likewise developing acute radiation syndrome but later recovered. Of these, an unknown number would suffer long term negative health effects as a result of their radiation exposure. The total number of persons exposed to the radioactive contaminants as a result of the accident is unknown, with estimates ranging from just 500 people in the immediate area to as many 80,000 across the wider region of northern Aztaco where the contamination is believed to have been spread by the wind. An initial evacuation saw 18,000 local people temporarily displaced, the majority of whom would be allowed to return to their homes by the December 2004 with around 5,000 people from the town of Xochitlalpan itself and other areas of the exclusion zone being subject to a permanent relocation order.

The accident at the Xochitlalpan facility revealed a lax safety protocols and lack of inspections of critical equipment, a condition which was found to have directly contributed to the disaster. An investigation revealed that safety procedures established when the plant was built in 1973 were gradually stripped away or ignored by the later overseers of the facility. Many of the plant workers who were employed at the Xochitlalpan facility in 2004 were found to have bene improperly trained in many safety procedures and in many cases had not been informed of the potential dangers involved. These conditions at the Xochitlalpan facility had been allowed to continue unabated due to a relative lack of regulatory oversight for nuclear fuel processing facilities compared to nuclear power plants, prompting a swath of new legislation implementing tighter rules, more frequent inspections and high level audits of the nuclear safety agencies to ensure accountability. The numerous cases of serious radiation exposure in rescue and cleanup personnel resulted in the creation of a specialized radiological response unit of the CETZ, the Zacapine emergency management agency, to establish a body of specially trained and equipped personnel to handle any future radiological incidents.

Background

The nuclear plant and surrounding town of Xochitlalpan were constructed at once as a single project as part of the nationwide nuclearization initiative which swept through Zacapican in the 1970s. With soaring oil and gas prices and rising public concerns over premature deaths thanks to pollution from coal-fired power plants, dozens of nuclear power plants were slated for construction over the course of 1970s and 1980s as part of this long term plan. In the Aztaco Republic, the main concern was the immense energy demand from the Angatahuaca metropolitan zone on the southern side of the peninsula which would see 13 different coal and natural gas fired power plants decommissioned and replaced with nuclear reactors. New processing plants would also need to be built to handle the spent nuclear fuel produced by these reactors. Both nuclear power plants and the ancillary storage and processing facilities for the nuclear industry were planned to be separated from the pre-existing industrial and population centers for safety purposes, for which a class of specially built calpolli communities called "atomaltepetl" would be established. Xochitlalpan was one such atomaltepetl, the first and largest of the nuclear reprocessing plants and associated calpolli communities to be completed in the Aztaco Republic. The plant, worker's apartments, school, clinics and other infrastructure was largely completed by 1973, although there would be too few qualified plant workers actually living and working in Xochitlalpan to operate the plant at full capacity until 1975.

As a fuel reprocessing plant, the Tequipanco Atomtic Xochitlalpan facility would take in the spent fuel rods produced at the primary generation reactors across Aztaco and subject the fuel material to a series of chemical processes in order to create recycled uranium and plutonium fuel which could be sent back to the primary generation reactors to be reused. Reprocessing also produces a significant amount of liquid nuclear waste as a byproduct, which in plants such as the TAX facility is stored on site for a time before it can be transported in bulk to long term geological storage facilities. The Xochitlalpan facility stored this waste in a row of six large steel tanks set inside a concrete trench that would theoretically contain any leakage from the tanks. Each of the waste storage tanks could hold between 80 and 90 metric tons of nuclear waste, and used a closed loop water cooling system to dispose of the decay heat generated by the remaining fissile material dissolved in the waste liquid.

Following the catastrophic effects of the Zacatlilco disaster of 1989, regulation and oversight of the nuclear industry was redoubled across Zacapican. However, most of this new oversight was focused on the proper maintenance and usage of nuclear reactors, with little attention being paid towards the ancillary facilities and general nuclear safety outside of the reactor facilities. Some fuel processing facilities in Zacapican, those with a breeder reactor on site, received added regulatory attention, while those which had no reactor such as the Xochitlalpan facility fell into a bureaucratic blind spot with far less scrutiny paid to the daily operations of such facilities. Inspections were generally infrequent, and starting in 1999 Xochitlalpan was allowed to self-audit, further reducing the oversight and accountability of the plant operators to higher bodies within the nuclear industry and the government. This allowed lax attitudes over safety protocol and employee training to set in and go unchallenged, eventually contributing to the failure which caused the disaster.

Disaster

Explosion

The Xochitlalpan disaster began at an unknown time on the 4th of August of 2004 with the failure of a water pump integral to the function of the water cooling loop for Tank 2, the second of the six liquid waste containment vessels at the site. The failed pump caused decay heat to build up inside Tank 2 for a prolonged period, in turn causing the pressure to increase. The walls of the containment vessels were made of steel and rated to withstand high pressures, which would normally afford the plant workers sufficient time to detect the failure and repair the cooling system or otherwise use the waste pumps to relieve the pressure inside the tank. Plant workers indeed detected rising temperatures in Tank 2, but assumed it was due to a failing sensor and took no corrective action. This resulted in the unchecked buildup of pressure as the waste continued to generate decay heat, which would eventually ignite some of the chemical compounds in the waste solution. Without any action taken to alleviate the pressure buildup, the high pressure rating of the vessel would only contribute to the force of the eventual explosion, which to go off around 11 minutes after a new crew of workers arrived to begin the night shift at 22:11 hours.

The explosion completely destroyed Tank 2 and resulted in damage to the adjacent tanks. Each of these tanks, including Tank 2, held their full capacity of 90 tons of liquid waste at the time of the explosion. Large volumes of this nuclear waste was collected in the concrete trench surrounding the storage tanks after the disaster, remaining there for several days exposed to the open air in the immediate aftermath before it could be collected and disposed of. Of much greater consequence were the dozens of tons of radioactive material which was dispersed into the atmosphere as a plume of gasses and vapors released by the explosion and dispersed by the wind. Local residents described the deadly plume as a trail of fast moving clouds in the night sky which glowed green and purple.

Contamination

An estimated 90% of the radioactive material released by the explosion of Tank 2 is thought to have consisted of short lived radioisotopes which would not pose a long term radiological danger. However, the remaining content of the dispersed material, primarily strontium 90, would have a half-life of nearly 30 years, and represented a long term radioactivity hazard in the areas affected that would be reduced to acceptable levels for humans to live and work until several half-life periods had elapsed. Areas of Xochitlalpan and the surrounding landscape were therefore placed under a perpetual exclusion zone until the radioactivity level is determined to be within acceptable parameters, which is not expected to happen before 2150. Due to the direction of the wind at the time of the accident, the plume of contaminants was dispersed away from the coast north of Xochitlalpan and towards the sparsely populated Aztaco highlands, where much of the radioactive material was deposited with negligible to zero radiological contamination being detected either in the ocean or in the highly populated southern edge of Aztaco. It is likely that the wind direction reducing the number of people affected by the radiological contamination. Had the wind been blowing in a different direction at the time, it is possible that the human cost of the disaster could have equaled or exceeded the rate of death, long term illness and displacement exacted by the Zacatlilco disaster 15 years earlier.

Radiation Sickness

Nearly all of the plant workers along with many residents of the nearby town were immediately exposed to high level radioactive contamination. Symptoms of radiation sickness were readily apparent, yet many workers did not initially recognize the nature of their symptoms due to a lack of training. Fortunately, the medical staff of the local clinics in the town of Xochitlalpan were far better trained in nuclear safety and radiation sickness, and were among the first to respond to the disaster along with a fire brigade dispatched to contain a low level fire at the plant. As the scope of the disaster became apparent, specialized medical assistance was dispatched with large numbers of patients displaying signs of radiation sickness being directed to major regional hospitals. Anticipating that these nearby facilities would be overwhelmed, the Aztaco Republican Guard and the National Army dispatched medical companies under the direction of the CETZ disaster response team to establish field treatment centers in the areas closest to the affected area to treat hundreds and even thousands of evacuees showing signs of radiation sickness at varying levels of severity. By August 14th, 70 people would due from acute radiation syndrome, the majority being plant workers of the night shift who were immediately exposed by the accident, and several others being members of the fire brigade and medical rescue personnel from Xochitlalpan who responded to the disaster. The last person to die from ARS as a result of the disaster was a worker involved in the cleanup of the contamination around the plant, who was suffered a severe exposure and died on September 2nd, bringing the final direct death toll to 71. The true number of those whose lives would later be cut short by radiogenic illnesses such as cancer later in life because of exposure from the Xochitlalpan disaster is unknown, while estimates range from 140 to as high as 22,000.

Aftermath

Evacuation

The general evacuation of the town of Xochitlalpan was ordered to begin in the morning of August 5th. Due to the short notice of the order, few vehicles were available for the mass evacuation of the thousands of residents. Instead, the initial response team of the CETZ seized the public busses of the city and surrounding districts to transport the people away from the dangerous zone. Even with such measures, there were not enough vehicles to transport everyone at once, thanks in some measure to the tendency of the evacuees to bring too many personal belongings on the evacuation vehicles, slowing down the rate of the evacuation. Nevertheless, progress was steady and only increased as the hours of the 5th of August passed and further resources arrived to assist with the disaster response. By the end of the day, vehicles from the Angatahuaca metro area were arriving under the direction of CETZ to assist with the evacuation. They would be sorely needed, as on August 6th and again on August 14th, the evacuation zone would be expanded and many thousands more people would need to be relocated, including some of the initial Xochitlalpan evacuees which had been moved to an area that fell within the August 14th expanded evacuation zone. The majority of the 18,000 people evacuated from the region were directed to disaster relief shelters in Amegatlan and other suburbs of Angatahuaca, where many of the 5,000 subject to permanent relocation would settle over the following years.

Cleanup

In order to prevent the spread of contamination, the CETZ ordered forces of the Aztaco Republican Guard to immediately enforce the seizure of crops and livestock in the agricultural regions of the northern Aztaco, even those which were not within the immediate path of the radiological contamination. Crops were to be buried and livestock were to be slaughtered and buried along with the crops, in order to prevent any radiological contamination of the food supply. Large tracts of land were likewise ordered to be subjected to auto-burial, in which the topsoil containing the radioactive contamination would be dug up and buried under itself so as to contain the radioactive particles under the surface where they could not be blown by the wind any further. An adhesive solution was sprayed on buildings and streets in the Xochitlalpan area to likewise prevent radioactive material on such surfaces to be spread by the wind or washed away by rain.