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Introduction
Nuclear facilities accidents have occurred in some parts of the world, with the most recent one being the Fukushima Daiichi disaster in 2011. These accidents release radioactive contaminants, causing significant damage to the surrounding population’s health and environment. This report examines the Tomsk-7 nuclear accident that occurred on April 6, 1993. It looks into the background, cause, and sequence of the accident, effects on the environment and human health, ethical issues facing such facilities, and lessons learned from the accident.
Background of the reactor/facility/equipment
The Siberian Chemical Enterprise is a part of the nuclear industry in the Russian Federation (Pike, n.d.). The enterprise produces large-scale uranium and plutonium with one of its facilities at Tomsk. Construction of the facility ended in 1953, with stations used to enrich uranium (Pike, n.d.). It also had reactors for electric energy generation, an isotope detachment station, uranium oxide, and hexafluoride production station, and storage facilities for solid and liquid radioactive wastes (International Atomic Energy Agency, 1998). The facility covered an area of 192 , with a supervision area of around 1560 . The location of the site was 16 km from Tomsk, which was the regional capital. Tomsk had over 500,000 inhabitants, with the rural areas sparsely populated by people mainly involved in farming. The government of Russia had maintained secrecy on the existence of the facility.
Due to the activities going on in the facility before the accident, there were records of contamination of air, rivers, and soils from the release of affluent radioactive liquid waste.
The facility at Tomsk was a reprocessing facility. The reprocessing occurred at a structure called Building 201 at the Radiochemical Works site. The reprocessing involved chemically extracting plutonium and uranium from used radioactive fuel elements (“Processing of Used Nuclear Fuel – World Nuclear Association”, 2021). Reprocessing is critical as it recycles nuclear fuel waste. This process reduces the volume and radioactivity of the waste materials (“Nuclear reactor – Growth of nuclear programs”, 2021). The method used at Siberian Chemical Enterprise was the plutonium-uranium extraction process (PUREX). Purex involves dissolving the waste fuel into concentrated nitric acid. The dissolved solution gets added to tributyl phosphate. Tributyl phosphate is a chemical able to form compounds with uranium and plutonium as oil solutions. The oil solution gets physically removed from the acid, and then the tributyl acid got washed out using water to get the elements required.
The Radiochemical Works structure had two reprocessing plants with its vessels located underground and sealed with 2m of concrete walls. One of the sealed vessels referred to as Installation AD-6102/2 is where later the accident would occur. Installation AD 6102/2 was used for preparing the solution to be used for reprocessing. The installation had a volume capacity of 34 covered by stainless steel vessel with a heating system that used steam and a cooling system. The set-up had several sensors installed in it for the control processes. These sensors included a pressure sensor, a thermometer, two-level indicators, flow rate sensors, and a ‘pit open’ alert instrument.
Cause and sequence of the accident
Before the accident, the staff prepared the solution in Installation AD-6102/2 for reprocessing. The acidity level got adjusted to 50 g/L, and they set the temperature to between and , which was the optimal range. The staff undertook procedural measurements to ascertain safety during the preparation process. The values taken included checking the accumulated deposits in the solution and removing them. Following the sediment removal, the personnel checked the concentration the nitric acid used in the reprocessing. Air with a flow rate of got passed through the aqueous solution to ensure the temperature across it was equal and to bubble the nitric acid to dilute the gaseous output.
During the accident, the Installation AD-6102/2 contained several solutions. The first was the nitric acid solution containing plutonium and uranium, extracted during the next cycle. The mixture was highly radioactive and got labeled product 401e. The nitric acid solution was cooled off. A concentrate of uranium was the second solution extracted in the first cycle and got named Product 166. Highly concentrated nitric acid got labeled product 2z. These solutions had over 8750 kg of uranium and around 450 g of plutonium, which was in tune with 0.11Tbq and 0.15 TBq of activities, respectively.
The sequence of the accident
The accident occurred at 12:58 pm on April 6, 1993 (International Atomic Energy Agency, 1998). Five days before the accident, Installation AD-6102/2 got emptied while over 40 of the solution named product 903v and over 73 of solution 422n readied as product 401e for the extraction process. On the day of the accident, 40 of solution 903v and over 73 of 422n got prepared as product 401e for extraction. Thirty minutes before 6:00 am, the operator added 12 of product 166. At 09:30 am, the personnel put in another 7.5 of product 166. At 10:30 am, the personnel added 1.5 nitric acid with a concentration of 14 mol/L for the extraction process. At noon, data relayed from the pressure sensor in the vessel indicated that the pressure had started to rise. At 12:40 pm, when there was a shift change, staff members noticed red smoke rising out of the vent. This smoke color was strange as no processes undertaken contained the production of nitrogen oxides (International Atomic Energy Agency, 1998). Ten minutes later, at 12:50 pm, the plant operators notified the supervising engineer that the pressure was rising. At this point, the pressure sensor now relayed data showing pressure having passed the 2 atm level. The supervising engineer instructed the operators to depressurize Installation AD-6102/2 through the process line of the close-by plant. Five minutes later, at 12:55 pm, the pressure in the steel installation was 5 atm. This pressure was beyond its rated pressure capacity. At 12:58 pm, Installation AD-6102/2 fractured, and seconds later, it exploded.
The explosion
After the explosion, the alert network, which monitored the radiation levels, was activated, prompting the staff members to wear the breathing equipment hanged close-by. All personnel were immediately assembled in a safe area and got apprised of the situation. Within a few minutes, the fire brigade had arrived to put out the ensuing fire. Personnel who had no urgent got instructed to leave the affected site. No personnel onsite or by the fire brigade was injured. After the accident, the Government of Russia requested the International Atomic Energy Agency (IAEA) to help with the investigations. The IAEA experts and investigators started the inquiry.
Because of the high radiation levels and unstable structure due to the explosion, it became hard to access the building. However, from a distance, investigators could see that the buildings were significantly damaged. In some sections, the explosion destroyed the concrete ceiling and walls. A visual examination concerning how much of the radioactive solution had escaped to the environment from the room containing installation AD6102/2 could not occur. The IAEA came up with a publication titled The Radiological Accident in The Reprocessing Plant at Tomsk.
Cause of Accident
The investigators found the absence of compressed air required for a rigorous mixture of the solutions as the most likely cause of the accident. Sensor data from the plant showed that there was no compressed air was used in the solution. This data contradicted the chief operator who claimed that they used compressed air before the accident. Due to that data, the investigators considered that the accident was a result of human error (International Atomic Energy Agency, 1998).
Investigators also found that when the nitric acid was being added into the solution to alter the acidity level, there was inadequate compressed air for rigorously mixing. These conditions may have resulted in the solution layering, as shown in figure 1 above. This layering caused nitration and oxidation of the organic layer by nitric acid. The investigators assumed the reactions happened due to the presence of nitric acid in the top layer. That assumption was because the pressure rise occurred more than an hour after the acid solution got added into the solution.
Nitric acid is known to oxidize the organic substance. This oxidation leads to the generation of gases and heat due to the exothermic nature of the process. The production of gases caused a buildup of pressure over time. The pressure buildup was because the control mechanism to eject air was over-stretched while efforts to depressurize it using vessels close by also failed. As a consequence, the pressure in the installation rose to 5 atm, causing it to fracture. The explosion was due to the oxidation process and the high-temperature condition of around (International Atomic Energy Agency, 1998).
Health effects
The residents of Nadezhda and Georgievka were most at risk for contamination as radioactive snow continued to fall days after the accident creating hotspots with a radiation level of up to 30 µGy/h, 100 times higher than the acceptable level [nuclearrisk.org]. Soil samples measured after the accident contained radioisotopes such as Strontium-90 and Cesium-137, known to cause leukemia and genetic defects in newborns if inhaled.
Investigators found that over 1,940 personnel got exposed to radiation. Also exposed to radiation were twenty members of the fire brigade who came to put out the fire. Figure 2 below shows the various ways the body could be exposed to radiation (International Atomic Energy Agency, 1998).
Environmental effects
After the accident, the government set up seventeen survey teams from Tomsk-7 and the Tomsk Region to start the environmental assessment. The survey teams used plans previously set up as a playbook in case such situations occurred. Beta and alpha activity concentration and external dose rate were the parameters measured (International Atomic Energy Agency, 1998). The surveyors sent the samples to the lab for analysis. The Hydrometeorological Services, a department in the Russian Federation, undertook investigations using the tools at their disposal. The service took hourly measurements in Tomsk and three other regions close-by. These regions included Kemerovo, Novosibirsk, and Krasnoyarsk. All data taken got relayed to the Commission on Emergencies of the Tomsk-7 and Tomsk regions. Due to the swift response undertaken by the commission had established:
- Up to 20km northeast of the accident location, the dose rate was between 0.6 and 0.15µGy/h.
- The main road between Samus and Tomsk had radioactive materials and hence required restricted access.
- In Georgieva, the level of contamination didn’t require crucial protective measures.
The figure 2 below shows a basic map of the Tomsk Region (International Atomic Energy Agency, 1998).
Air Contamination
From measurements between April 6 and April 8, 1993, only Niobium-95 got detected in the air as other radionuclides were below the threshold level (Porfiriev, 1994). The level of Niobium-95 rose from before the accident to after the accident. However, by April 19, the concentration level on Niobium-95 had fallen below the threshold level.
Water Contamination
Water samples, with volumes between 0.5 L and 3 L, were taken from Tom, Pesechka, and Samuska rivers. The samples underwent gamma spectrometry to measure the level of contamination. Pesechka river and Samuska river samples had contamination below. This level was below the minimum detectable level of equipment used. Tom river was found to have a concentration of beta activity in the samples but had returned to an acceptable level by April 18.
Forest Contamination
The investigators found the forested areas had contamination of radionuclides from the accident. Soils samples taken had high levels of radioactive contamination with radioisotopes such as strontium-90 and cesium-137.
Ethical issues
The ethical issues behind nuclear energy facilities have always been a point of concern. The concern is the weighing of the benefits versus the danger posed. The moral issues brought to the fore include.
Impact on local population’s health
Local populations around nuclear facilities face the risk of health problems of exposure to low-level radioactivity over the long term (Xiang) as these facilities leak.
Effect on the environment
Due to the risks of an accident such as the Tomsk-7 accident, the harm to the environment could be catastrophic (Blandford & May, n.d.). The Tomsk-7 accident scrutiny showed various radionuclides in the rivers, soils, and air. There is also the risk of leaks from such facilities as there is no permanent way to store nuclear wastes posing a danger to the environment (Porfiriev, 1996). It poses the question of whether nuclear energy is worth it at the expense of the surrounding habitat.
Violation of safety protocols
With investigations to other nuclear facilities, nuclear energy agencies admitting falsifying data to suppress safety risks.
Lessons learned by the nuclear society from this accident
Lesson from the cause of the accident
The problem was the lack of compressed air in Installation AD-6102/2, required to ensure a rigorous mixture of the solutions that indicated human error as the cause. As such, plant managers need to ensure that procedures are in place to ascertain the safety and the smooth flow of activities. The course of action also needs to be updated as equipment in the plant is updated. The employees need regular training to keep them up to date on the operational procedures. There is a need to double-check all undertaken processes as this could mean a tragedy, happening or not (Taebi, 2015).
Lessons from Infrastructure
Plant managers need to ensure that the structures and facilities can cope with the daily running and emergencies such as the accident. It is also critical that exposure to the environment, personnel, and the surrounding population gets regularly measured so that measures get taken as soon as possible to rectify any issues.
The investigators found no means to measure the levels of beta activity. This finding meant they could not measure the amount of plutonium intake by the personnel exposed to radiation. Had it been a more dangerous accident, it would have had more damaging consequences on the personnel.
Managements were encouraged to use all equipment at their disposal to continuously measure and check the effects of their activities to ensure its suitable for both emergency and typical situations.
Education
It is critical to continuously train the local population around such facilities on measures they should undertake in case of such accidents to ensure they can protect themselves.
It is also critical to train the local population on the importance of such facilities and the role such facilities play in society to alleviate stress and anxiety caused to the local population.
Lessons learned by you from this accident
- The swift response from the fire brigade and the nuclear agencies was impressive as they formed survey teams immediately to check on the extent of contamination
- Organizations such as the International Atomic Energy Agency (IAEA) need to enforce strict procedural guidelines by regularly inspecting nuclear facilities to guarantee compliance and avert accidents.
- IAEA and other regulatory agencies should ensure that the staff working in nuclear facilities get trained to avert accidents caused by neglect or human error.
- There need to come up with procedures that would ascertain double-checking of plant operations to prevent human errors.
- Local populations around nuclear facilities need to be educated and equipped with protective components that they would in case of such accidents in the future
- Need for developing technology tools to ensure staff members follow all procedures in operating a nuclear facility to prevent such accidents in the future.
Conclusion
Tomsk-7 nuclear accident is an example of the danger posed by nuclear facilities. The explosion had ramifications on the local population, the environment, and facility employees. The contamination meant that the communities surrounding the facility comprised of farmers had to abandon their economic activity as their land and crops were contaminated. It posed an immense risk as some of the radionuclides released are known to cause leukemia and deformities in newborns when inhaled.
These risks pose the ethical question of whether nuclear facilities are worth the risk as they pose a grave danger to society in case of an accident such as the Tomsk-7.
Investigations concluded the cause of the accident was the lack of compressed air in Installation AD-6102/2, which resulted in a sequence of events that caused the explosion. The lack of compressed air in the vessel got attributed to human error in following the laid-down procedures. Due to such a case, there is a need to implement systems in such critical facilities to ensure the personnel follows the laid down procedures and double-check to avoid such accidents.
However, the recommendations given by the investigators will surely help avoid another nuclear accident in the future.
References
Blandford, E., & May, M. Lessons Learned from “Lessons Learned”: The Evolution of Nuclear Power Safety after Accidents and Near-Accidents | American Academy of Arts and Sciences. Amacad.org. Web.
EnvJust, J. (2020). Explosion at nuclear facility, Seversk (Tomsk-7), Russia | EJAtlas.
Environmental Justice Atlas. 2021, Web.
International Atomic Energy Agency. (1998). The Radiological Accident in The Reprocessing Plant at Tomsk. Vienna: IAEA.
Nuclear reactor – Growth of nuclear programs. Encyclopedia Britannica. (2021). Web.
Pike, J. Tomsk-7. Globalsecurity.org. Web.
Porfiriev, B. (1996). Environmental aftermath of the radiation accident at Tomsk-7. Environmental Management, 20(1), 25-33. Web.
Porfiriev, B. (1994). Radiation Accident at Tomsk-7: A System Analysis Case Study. Udspace.udel.edu. Web.
Processing of Used Nuclear Fuel – World Nuclear Association. World-nuclear.org. (2021). Web.
Taebi, B., & Roeser, S. (Eds.). (2015). The Ethics of Nuclear Energy. Cambridge University Press.
Xiang, H., & Zhu, Y. (2011). The Ethics Issues of Nuclear Energy: Hard Lessons Learned from Chernobyl and Fukushima. Online Journal Of Health Ethics, 7. Web.
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