Lia radiological accident
42°46′56″N 42°00′43″E / 42.78222°N 42.01194°E
The Lia radiological accident began on December 2, 2001, with the discovery of two orphan radiation sources near the Enguri Dam in Tsalenjikha District in the country of Georgia. Three villagers from Lia were unknowingly exposed. All three men were injured, one of whom eventually died. The accident was a result of unlabeled radioisotope thermoelectric generator (RTG) cores which had been improperly dismantled and left behind from the Soviet era. The International Atomic Energy Agency (IAEA) led recovery operations and organized medical care.
Source of the radioactive material
In the early 1980s, a series of radio relays were built to connect the Enguri Dam with the Hudoni Dam, which was under construction. The relays were in remote territory with no reliable access to electricity, and thus were powered with a series of eight radioisotope thermoelectric generators (RTGs) manufactured in 1983. Each RTG was a Beta-M type powered by strontium-90, and contained some 1295–1480 TBq of radioactivity. However, the Hudoni dam's construction was stopped as Georgian independence from the Soviet Union drew near. The stations and their RTGs were abandoned and eventually dismantled. The RTGs became lost at this time. Two were rediscovered in 1998, leading to no injuries. Two more were found in 1999, and again led to no injuries or significant radiation exposure. Two more were rediscovered in 2001, which led to the accident. The other two sources remain unaccounted for. The sources were not marked, and had been removed from the rest of the generator housing. They were heavy for their size, weighing 8–10 kg (18–22 lb) despite being only 10 cm × 15 cm (3.9 in × 5.9 in). Upon their recovery, it was determined the radiation emitted at the surface of the sources was 4.6 Sieverts (Sv) per hour. A fully absorbed whole-body dose of 5 Sv has a 50% chance of death. The original dose output at the time of their construction would have been much higher, but said output had decreased 40% since their construction due to radioactive decay. The actual dose received per hour would be lower unless physically touching the source, as radiation decreases with distance according to the inverse-square law.[1]
The accident
Three men from Lia (later designated as patients 1-DN, 2-MG, and 3-MB by the
Aftermath
Medical
Two days after exposure, on December 4, patient 2-MG visited a local doctor but did not mention the mysterious heating source, and the doctor assumed he was drunk. The resulting treatment however did clear up the symptoms. On December 15, patient 1-DN and 2-MG developed burning and itching on the small of their backs, where the radiation source had been closest. Patient 1-DN lost his voice as well, but did not seek care at that time. The wife of patient 3-MB and the brother of patient 2-MG learned that all three men were ill with similar symptoms, including increasing
Doses
Radiation doses were estimated in several different ways, but it was clear that Patient 2-MG received the greatest dose.[1] Below, doses are measured in grays. A whole-body dose of 10 Gy is 99% fatal, a dose of 6 Gy is 50% fatal with treatment, and a dose of 2 Gy is 5% fatal with treatment.[2] Localized doses, especially where the patients suffered radiation ulcers, may have been much higher. Patient 1-DN, despite a survivable whole-body dose of between 2.8 and 5.4 Gy, received 21-37 Gy to his shoulder, which eventually killed him. In the chart below, there is some uncertainty in the measurements. The calibration curve method is from an assumed exposure time, distance, and rate. This is close to the doses determined by the measurements of chromosome aberrations taken from blood samples analyzed by the Georgia Cytogenetics Laboratory. Also included are doses calculated by the Dolphin method, which uses a slightly different detector.[1][3] No other people in the area were found to have been exposed.[1]
Source of estimate | Patient | ||
---|---|---|---|
1-DN | 2-MG | 3-MB | |
Calculated, calibration curve | 3.1 | 4.4 | 1.3 |
Calculated, Dolphin method | 5.4 | 5.7 | 1.9 |
Measured, Georgia Cytogenetics Laboratory | 2.8 | 3.3 | 1.2 |
Measured, Georgia Cytogenetics Dolphin Method | 3.0 | 4.3 | 2.3 |
Source recovery
The day after the hospitalization, Georgian authorities attempted to find the suspected radiation sources, but bad weather prevented them from reaching the site. On December 29 they tried again and ascertained the exact location, also shooting video footage. On January 4, 2002, the Georgian government appealed to the IAEA for help. A first attempt at recovering the sources was made two days later, but failed again due to weather. A fact-finding mission was led to determine how to best recover the sources, and their nature. The containers were extremely well built, which prevented the loss of radioactive material under all but the most extreme conditions. They had survived being abandoned in the woods for over a decade and had released no radioactive material. The radiation hazard was localized only, due to escaping ionizing radiation. For this reason, the IAEA had intended to wait until the spring thaw to recover the sources, but concerns by residents led the Georgian government to push for an early recovery. A tactically difficult recovery mission was successfully carried out on February 2–3, 2002.[1]
The recovery mission faced numerous challenges, with winter weather being chief among them. The village of
Analysis
The IAEA's final report concluded that the proximate cause of the accident was that the sources were unmarked and unlabeled, and thus their danger could not be known. It also chastised the illegal abandonment of the sources to begin with. The report stressed the importance of basic knowledge of radiation injuries by clinicians and called for increased programs to make them aware of the signs of radiation overexposure. The initial clinician who treated patient 2-MG did not accurately assess the injury (partly due to 2-MG's failure to mention the orphan source), thus delaying proper treatment for almost three weeks.[1]
Between the fall of the Soviet Union and 2006, the IAEA had recovered some 300 orphan sources in Georgia, many lost from former industrial and military sites abandoned in the economic collapse after the Soviet breakup.[5]
References
- ^ OCLC 900016880.
- ^ "Radiation Exposure and Contamination—Injuries; Poisoning". Merck Manuals Professional Edition. Retrieved 2021-06-03.
- PMID 31452629.
- S2CID 2760372.
- ^ "Radioactive Sources Recovered in Georgia". IAEA. 2006-07-27. Retrieved 2021-06-04.