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.
Comments or questions? Contact Kenley Butler at
MIIS CNS: Kenley.Butler@miis.edu
