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The Criticality Accident in Sarov (Radiation of Uranium)

The Circumstances under Which the Accident Occurred

It was on June 17, 1997, when a physicist who was working at the Nuclear Centre at Sarov, in the Federation of Russia was exposed to severe radiation of uranium. This physicist was the senior technician at this plant. This critical accident took place in an assembly of a highly enriched uranium plant. This technician was rushed to the hospital immediately after the exposure to get proper medical attention. However, it is reported that despite this prompt measure that was taken, the patient died after three days. This exposure caused a high dose of neutron radiation and the damage on this technician was fatal. This skilled technician was overexposed to this radiation and he succumbed to his illness only sixty-six hours after this exposure. The concerted effort by the intensive medical officers to rescue him from this effect was futile. Experts in this field have described this accident as being rare, not only because of the time it took to kill this technician but also because it defied all the medical attention that was given to this man in a timely manner.

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This accident was one of the very first criticality accidents to be reported in this field. Another such accident took place at Tokaimura in Japan two years later in 1999. The IAEA has finally issued reports on these two accidents with the intention of preventing similar accidents in the future. The report is intended to create awareness about such accidents in order to ensure that technicians and other officers working at such plants are protected from any possible harm caused by these radiological substances.

It is reported that this accident occurred on 17 June 1997 in the morning hours when a male technician aged 41 years started his work at the assembly. The reports say that he was 1.80 meters in height and weighed about 81 kilograms. On this fateful morning, the technician is reported to have started to assemble a critical assembly that was consisting of a highly enriched uranium core. It was predominantly copper reflector, and reports have it that it was functioning previously and the technician was very familiar with it, a fact that made him relaxed during this risky process. This accident was considered strange because this technician was very experienced in this field. He had successfully carried out hundreds of criticality experiments before. Therefore, he was considered as one of the most qualified technicians for this task. Given this massive experience and knowledge in this field, it is reported that this technician was dealing with a system he knew so well, and was unlikely for him to experience any problems. This vast experience gave him the confidence to work alone in the experimental hall. This was a complete violation of the laid down requirements of what a technician should do experimental hall.

The reports say that it was at about in the mid morning when the construction of this assembly was in process that a particular component from the reflector slid from the hands of this technician. This component then fell on the lower parts of this assembly. The lower parts of the assembly contained the enriched uranium core because it had just been constructed. According to the set requirements at this assembly, and other assemblies in general, technicians are expected to wear gloves in order to be safe from the assembly’s components while at work. It was at this point that the reports say the criticality point was exceeded. As a result, a sudden flash of light followed by a massive wave of heat emerged from the system. The reports say that this expelled the entire lower part of this assembly downwards into the lower parts of the stand. This technician, being an experienced person in this field, immediately came to the realization that what had just happened was actually criticality accident in this plant. He quickly left this experimental hall. He then managed to close doors leading to other rooms next to the hall.

It is reported that this victim was conscious for a few minutes following the incident, and even said that his exposure to radiation was critical. The radiation protection personnel conducted initial direct radiological survey of this technician immediately. This test confirmed that his body was emitting induced gamma radiation due to presence of radionuclides. The body dose was estimated to be about 10 Gy. This was above the level of 2Gy that needs timely action as per the emergency procedures. His personal dosimeter was immediate taken for assessment. He was then taken to a local hospital where the radiation emergency medical team was had been readied to attend to him. At about one o’clock the same day, it was confirmed that there was form of contamination in the experimental hall except the assembly. The assembly was however, still a criticality state with massive emission of radioactive substances.

It is reported that of the detectors of neutron that were employed in measuring flux of neutron in this hall, those that negligible radioactive substances were only those that were at the furthest distance from the assembly. In order to screen changes in flux of neutron, the experts used another detector just to confirm the amount of radiation. This second check confirmed that flux of neutron was finally relative stability, an indication that there was regulation at the reaction chain. With the help of a periscope, it was possible for these experts to conduct a visual test of this hall enabling them to photograph it for further analysis. The test revealed that this assembly was in the lower part of its stand based on what was captured by photographs. This meant that the team of experts were not be in a position to change its configuration through normal process.

It was very necessary to get rid of some parts of this assembly in order to impede reaction. Given the high levels of radiation in the hall, its access was overruled because of the obvious danger it posed. The team of experts dealing with this issue was only left with the alternative of using overhead crane to ensure safety of those involved. This would be done through remote control system. The reports says that any attempt to move an object near this critical assembly could possibly heighten its reactivity making it emit more radiation and heat. This increased the complexity of dealing with this accident. The method that had to be used in disassembling the assembly had to evade any possibility of putting a substantial object close to it. The specialists formed a committee to discuss various approaches that could be used to deal with this critical situation. The committee came up with a number of proposals. Various models were designed by these experts to help investigate some of the promising ideas that were developed. This was done in an experimental hall near this facility, which had a similar critical assembly. The team would make separate calculations to these proposed models in order to ascertain their appropriateness. The models were also tested for their possibility to generate more heat and radiation.

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The team of experts decided to remove from the hall, all nuclear substances that were not utilized in the construction of this assembly. These experts decided to undertake this process with the help of a robot. Upon successful completion of this process, these specialists set forth to alter the configuration of this assembly from a safe position in a remote manner. The team of experts used a robot to suspend suction instrument to hook crane’s overhead to make this process a success. This suction device was connected to a hosepipe. This instrument was then used to wrap uranium core by putting it on the upper part of this assembly. When this was done, it is reported that this assembly’s movement was amplified and this caused a rise in the flux of neutron resulting into a massive increase in temperatures on this assembly and the entire hall. However, this team pressed on with this process. Finally, this suction instrument was activated which then enabled the team of experts to alter assembly’s initial configuration. This stopped the reaction resulting in gradual decrease in emission of neutron to the normal levels. The team then removed this assembly with the help of a crane. It was placed on a stand so that it could be dismantled later. The process of making this assembly safe was finally achieved after one week, at about 1320 hours.

Description of the impact on present and future public health

The critical accident at Aarov has been of great scientific interest because it is rare in nature. This high dosage of ionizing radiation is rare but lethal, and is always caused by exposure to neutrons. Such radiation has been reported to have immediate effect to those they are exposed. In this accident, the medical team of the patient did not have much problem in determining the kind of radiation the patient was exposed to because the accident was already known and prompt measures taken. It is reported that although there was an immediate medical attention given to the patient, the medical team, including the patient, had seen the likely fatal outcome. It was no surprise then when the patient finally passed on. However, it is reported that some sources at VNIIEF’s safety center who wanted to remain anonymous, confirmed that this accident posed no health rise to the 92,000 of this city because it had been contained in a proper manner.

IAEA has been actively involved in the offering swift medical care geared towards saving the victim’s life. IAEA has given out the best health experts help in the management of victim’s health as required by the international bodies regulating radiations. This convention requires that this body provide the ministry of health of this country with various medical help to help the hospitals respond to emergency cases of radiological emissions. In the process of offering the patient a medical attention, it is reported that the patient showed signs of intoxications and distress. The report also shows that the patient developed multiple organ compromise in under 10 hours of post-exposure to the radioactive wave. The incident that led to the death of this nuclear technician is a rare occurrence because of seriousness of the exposure and the symptoms the patient had afterwards. However, this accident also involves a breach in the set policies that defines how technicians at such facilities should conduct their duties irrespective of their position or experience.

The cause of this particular criticality was the amount of uranium that was used. This caused a high level of levels of neutron energy, which came out in form of heat. Various Russian authorities have been blamed for this accident despite the violation of the set protocols by this technician, because these authorities field implementation of relevant policies and ensuring adequate safety of this facility.

It is reported that the Russian authorities had more than 3,400 firefighters who were charged with the responsibility of keeping fire from possibly spreading to other parts of town. The authorities severally stated that wildfires did not pose any threat to nuclear facilities. They announced that they had successfully eliminated all the explosive and radioactive materials from this site. However, reports say that the authorities later returned these radioactive materials

Suggested of steps that can be taken avert such an accident in future

Radiation safety

This accident proved that it is not enough to avoid accident by simply developing policies and control measures for the engineers who are working in such environment. It is important for the leadership to foster a culture within the organization that will help in developing a positive attitude of self-protection and protection of others within such a plant. This culture will also discourage complacency. It is also important for the management of this facility to prepare and implement relevant policies that will enhance safety of everyone within the plant. The policies should categorically specify responsibilities of all the relevant officers including that of the managers.

It is important to have detailed safety assessments procedure in such plants as this in order to verify the possible degree of accidents that can possibly occur and to come up with procedures that can lessen consequences they come with or just prevent their occurrence in totality. It is complex to prevent any possible breach of the set procedures as stated in the policies. For this reason, areas where such serious accidents can occur should have effective engineering controls. Given the risk associated critical assembly experiments, it would be better if the process were automated.

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It is important to have technicians undergo regular training on radiation protection in order to keep them alert on hazards they face when undertaking their duties, and the need to follow procedures.

Accident dosimetry

When a radiation accident has occurred, it is important to retain any materials such as clothes or objects that could be used in assessing doses, because this helps the medical team when offering treatment to a person exposed to radiation. Anyone working in such an environment should know the importance of retaining such materials.

When an accident in such a plant takes place, it is important to take a record of all details such as the location of the victim at the specific time of such accident.

Clear instruction should be given to staff on how to handle or label materials after the accident. Orientation of items or samples should be stressed when giving such instructions.

In order to have an accurate evaluating of doses neutron, it is necessary to have detailed data of induced activity and then use it to make comparison with a referenced data. Health experts say that evaluating of victim’s blood helps in giving an estimate of the radiation’s dose, while evaluating of actuation in the tissues of hair gives information on the possible spatial spread of these doses.

The medical community

It is important to ensure that there are a number of medical specialists when managing victims of radiation because there are always chances that various organs such as skin, lung, and the envious system among others will be damaged during this accident. Managing a radiation patient can be a complex process because the response of the organ systems may differ, a fact that is said to bring a series of various radiation disorders. For this reason, it is important for authorities to ensure that hospitals that are supposed to manage such patients have well-trained and medical personnel to deal with the situation.

Although delayed prodromal symptoms may be an indication that the exposure is expressly lethal, this accident ascertained that high radiation doses could possibly result into clinical signs at very early stages. For this reason, it is important to note that prodromal symptoms can be considered as reliable only when assessing severity of the exposure based on positive indications. Absence of these early prodromal signs cannot be construed to mean a less severe accident. This particular case has clearly established the possible effect of radiation on various organ systems of a person. It illustrates that an individual’s ability to live when exposed to serious radiological emissions depends on his or her blood quality.

It is important to note that interstitial pneumonitis would develop if the doses were above eight. This may result into the death of the victim after a period of about one year. In this particular case, the serious injury on the lungs and oedema was experienced instantly during this massive exposure of the radiological emissions. When one has a high exposure to radiation, his or her survival will always be based on the ability of the affected body tissues to respond to medication. When various tissues and organs are exposed in varying levels of radiological emission, it becomes very complex to ascertain the exact cause of death. In this particular accident, the patient developed mild gastrointestinal radiation syndrome, which was fatal, especially due to the high dosage in the abdominal tissues and organs. This particular case shows that if an individual has an exposure to high radiation levels, which kill the cells extensively, cytogenetic dosimetry may not be appropriate the dosage that will be estimated from the process would not be accurate. This is so because any form of cell damage or its death makes white blood cells to be eliminated from blood of the victim. This makes it very complex to find out the true culture of the white blood cells in order to assist in dose assessment.

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