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IAEA-CN-70/90: The Radiological Incident in Tbilisi

Based on the original text obtained from the International Atomic Energy Agency document "IAEA-TECDOC-1045: Safety of Radiation Sources and Security of radioactive materials," September 1998. This text has been reformatted by CNS for inclusion in the NIS Nuclear Profiles database.

IAEA-CN-70/90

THE RADIOLOGICAL ACCIDENT IN TBILISI

S. ABRAMIDZE, N. KATAMADZE
Centre of Applied Research. Institute of Physics. Georgia
Z. LOMTADZE,
Ministry of Environment. Georgia
R.CRUZ SUAREZ, A.V. BILBAO ALFONSO
International Atomic Energy Agency

ABSTRACT

On 9 October 1997 a facsimile message was received by the IAEA from the Minister of Health of Georgia stating that servicemen of the Lilo Training Detachment of Frontier Troops had developed local radiation induced skin diseases on various parts of their bodies. Details were sent of the medical diagnoses of the nine victims together with information on the radiation sources and dose rates that had caused the exposures. The Georgian Minister Of Health requested the IAEA to assist in the examination and treatment of the patients. An investigation had revealed that several Cs-137, Co-60 radiation sources and some beta emitters had been found and that in some places high dose rates had been detected. The Government of Georgia requested the IAEA to send an emergency team to evaluate the radiological situation at the Lilo Training Center. The present paper is a summary of the finding and lessons to be learned from this situation.

1. THE ACCIDENT

The Lilo Training Detachment of Frontier Troops is located in a remote site about 25 km east of Tbilisi. The Center covers approximately 150,000 square meters. There are three 3 main areas: the living and management area which cover several buildings for soldiers and officers; the living quarters, where some of the officers lived with their families and the empty buildings used for training.

In the past the center was used by Soviet troops for Civil Defense Training. The sources may had been used for calibration of survey equipment and radiological monitoring training in the case of a nuclear accident or nuclear war. The site was transferred to the Georgian Army in 1992. The chronology of the accident is as follow:

April-August 1997: Soldiers from the Lilo Center developed skin bums on several parts of their bodies. From the clinical situation the exposure was fractional and occurred over the course of several months. There is no information on the time and circumstances of when the exposure began.

26 August 1997: A radiation hot spot was discovered at the Lilo Center near the underground shelter. The dose rate was about 45 mGy/h. The measurement was carried out by officers from the Chemical, Radiological and Biological Protection Division of the Georgian Army.

5 September 1997: Second measurement carried out by the same personnel and the representative of the State Sanitary Supervision and Hygiene Standardization to confirm the high radiation levels.

10 September 1997 The Georgian authorities contacted the Center of Applied Research of the Institute of Physics and its Safety and Radiation Protection Department. A Working Group (WG) was established to assess the radiological situation at the site.

2. RADIOLOGICAL ASSESSMENT

The WG started monitoring the area on I I September 1997. The complete lack of information about the sources made their task more difficult. No information was available on the type of radionuclide, chemical and physical form, activity, etc. The survey began close to the underground shelter. On September 12 the exact location of one source was determined but owing to the high dose rate at the location and the lack of a lead container to store the source, no action was taken. On 13 September a source was removed from the pocket of a soldier's winter jacket. and later placed inside lead shielding. The source was a metal cylinder with a diameter of about 6 min and a height of about 12 mm. Additional measurements showed that there was no radioactive contamination at the location.

Slight increase to the background level was determined near to that site. Another source was found at the soccer field located 130 in from the underground shelter and few meters from the official building. In this case the source was approximately 30 cm below the surface. On the same day elevated dose rates were discovered just a few meters from the smoking area. The third source was found 10 cm below the surface. At that stage the WG decide to survey the whole facility and its environs. Detailed measurements were carried out continuously during the following days. A total of 250,000 m² were monitored. Results are as detailed in Table I.

Dose rate at the distance of I in after removing the source from the ground. The value is the result of several measurements at different distances. Two other Cs-137 sources were found, but because they were inside of their lead containers, the dose rate at the surface of the container was very low. A group of about 200 units of night shooting guides containing Ra-226 were also found at different places at the facilities. A Co-60 source at a location 4 was found with very low dose rate.

3. SOURCE RECOVERY AND TEMPORARY STORAGE

The sources are temporarily stored at the Lilo site next to the scrapyard. The first six sources are inside the lead shielding provided by the Institute of Physics. The rest of the sources are inside their lead containers found at the site. The physical protection of the source is assured by the Detachment of Frontier Troops. The storage room is locked, clearly identified and security surveillance is maintained during the whole day.

4. THE IAEA MISSION

The IAEA team made a radiological monitoring survey in the internal and external areas of the Lilo Center. All the green areas and various buildings were surveyed. The values correspond to the background levels. The surface contamination measurements show no contamination at all at the site. Additional tasks to collect and process the information on the sources provided by the Georgian WG and to assess the adequacy of the storage of the sources, were accomplished.

The temporary storage room was very carefully monitored. The dose rate values at the outside surface of the walls of the room are similar to levels due to natural background level of radiation. All containers were measured at the surface. At 3.5 in from the group of sources the dose rate is at the level of background radiation.

5. INDIVIDUAL DOSE ASSESSMENT

Estimates of internal doses for the patients has not proved necessary in this accident since all the radiological surveys made at the sites show that none of the sources were damaged or leaking radioactive material and the environment was also free of radioactive contamination.

Following many radiological accidents dose estimates based upon radiological information on the sources involved, ambient dose rates and a reconstruction of the sequence of events can provide valuable information for the initial screening of the irradiated persons as well as estimation of the doses they may have received. For the Georgian accident this has not proved possible since there is insufficient information available on the relevant parameters contributing to the irradiation of the persons involved. The dates and times of irradiation are not known, neither are the specific sources producing the irradiations or the exposures geometries. The patients have also not been willing to discuss the circumstances surrounding their exposure. Because of these problems in reconstructing the many scenarios assessment of the external doses received have not been made. Inspite of this, theoretical calculations have been made based upon doses calculated from the largest sources activity and assuming simplified irradiation geometry. For a limited number of irradiation geometries exposure time have been estimated to produce the observed clinical injuries.

6. LESSONS TO BE LEARNED

The review of radiological accident is a mechanism for feeding back experiences into the relevant system of control, in order to help lessen the likelihood of accidents in the future and to be better prepared for those that do occur. Such reviews add to the fund of knowledge, and also illustrate and emphasize principles and criteria, which, however, are usually already well known. This is reflected in the observations and recommendations that follow, which derive from the review of the radiological accident in Tbilisi , Georgia but not necessarily from the specific circumstances of the accident.

Lack of documentation relating to the plant suggested that there had been only limited contact between the former sources owner and the current operating institutions, this was possibly due to changes in organizations and their responsibilities in the former USSR republics. The absence of official data on the presence of radioactive sources at the territory of Lilo training center caused partly the delay of identification of the radiological accident. Also the lack of routine environmental monitoring at a national level made impossible the early detection of the emergency.

Although after the identification of radioactive emergency the necessary actions were taken promptly, the absence of appropriate emergency response plan created additional difficulties. The lack of up-to-date equipment, adequate training of the staff and financial resources made the situation very difficult. The necessity of multilevel system of emergency response and preparedness is evident. The national emergency plan would consist of clear distribution of responsibilities, particularly naming the unit dealing with in-field actions. Such unit, as well as the source of emergency funding, must be designated by law or special regulation at a national level.

The lack of appropriate medical experience regarding the radioactivity-originated diseases caused the long period between the hospitalization of victims and verification of final diagnosis. The country-level measures for the wide dissemination of information for physicians aiming to deliver them at least a minimum knowledge in symptoms of radioactivecaused diseases are needed. At least one well- equipped medical team with trained staff should be designated by the national emergency plan for the prompt reaction in case of identification of radiological emergency.

International cooperation has facilitated significantly both of the treatment of persons injured and the initiation of the actions necessary for the avoidance of such accidents in future. A permanent contact with international organizations, particularly IAEA and WHO, and the clear understanding of possible ways, mechanisms and schemes of international cooperation by relevant national authorities would be a significant factor of decrease the risk and scale of possible accidents.

Appropriate international organizations should consider having ready for use radiological equipment available. Should also consider having a set of radiological equipment at hand ready to be shipped and an emergency preparedness group formed by in-house staff . Personnel using instruments should be trained to be able to obtain a clear indication of dose rate response, for a wide range of doses; and to know the most suitable equipment in different conditions and its calibration factors. Instrumentation should be capable of being adjusted to withstand field conditions, so that it can be used in high humidity, high temperatures and unstable environmental conditions and altitude variations.

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