Incident with a gamma - irradiation facility in the town of Stamboliyski
The Nuclear Regulatory Agency (NRA) informs you about a severe radiological incident with a gamma - irradiation facility (IRF) in the town of Stamboliyski which resulted in overexposure of persons from the “Gitava” Ltd. personnel.
I. Short description of the incident:
“Gitava” Ltd. possesses a Licence for the use of stationary gamma - irradiation facility “Kalina”, loaded with 12 Sources of Ionising Radiation (SIR) Co-60 (the total activity 421 TBq on 14.06.2011). The SIR are mounted vertically in 3 linear elements (metal cylinders with length-1m and diameter 25mm) placed in a biological shielding (lead container and concrete). The gamma - irradiation facility “Kalina” is constructed under the ground surface and has a panoramic irradiator with biological shielding. The NRA licence is issued for the configuration of the panoramic irradiator with 6 linear elements arranged symmetrically in a circle in protective containers, 3 of the elements are loaded with SIR and the other 3 contain “imitators” – linear metal elements without SIR in them.
On 14.06.2011 during the preparation for loading of new additional sources of ionising radiation (SIR) into gamma - irradiation facility “Kalina” a human error was committed, where instead of an “imitator” from the protective container a linear element was taken out, containing 5 SIR of Co-60 (with total activity 137 TBq at 14.06.2011). As a result of these actions 5 persons from the “Gitava” Ltd. personnel were overexposed. The manipulations with mistakenly extracted highly active liner element, lasted for about 5-10 min. before the liner element was put back into the protective container. According to the estimates of the National Center for Radiobiology and Radiation Protection (NCRRP) and the experts from France the individual absorbed doses, obtained during these manipulations, is above 1 Gy, whereas for one of the overexposed persons the absorbed dose is about 5 Gy. The overexposed 5 persons from the “Gitava” Ltd. personnel undergo medical examination and treatment in the Military Medical Academy (MMA) and “Persie” Hospital in France. 30 days after the incident one of the overexposed persons unexpectedly gets a heart attack and dies. According to the conclusion of the doctors from the MMA his death does not have a direct connection with the exposure dose received during the incident.
A preliminary report for investigation of this incident is prepared by a commission appointed by the Chairman of NRA. The investigation for the clarification of the reasons and circumstances of the incident occurrence continues. In accordance with the “Regulation of the conditions and procedure for notification of the Nuclear Regulatory Agency about events in nuclear facilities and sites with sources of ionising radiation” a report of the commission for investigation, analysis and evaluation of the incident, consisting of the licensee (“Gitava” Ltd) and NRA inspectors is expected.
The preliminary evaluation of the incident on the INES scale of IAEA is – “level 3”
II. Lessons from the incident:
1. Upon carrying out the high radiological risk activities with highly active SIR categories 1,2,and 3 (assembly, dismantling, loading and supplement loading and other risk operations with SIR used in gamma - irradiation facilities, non-destructive testing devices, technology control gages, metrolorgical stands etc.), the licensees shall ensure the necessary means for reliable individual dose control of the pertinent personnel, according to the “Regulation № 32 (07.11.2005) for conditions and order for carrying out individual dose control for persons working with SIR” of the Ministry of Health: individual thermoluminescent and/or film dose meters (TLDM, FDM) and alarm threshold dose meters duplicating the control of TLDM and FDM.
2. During the high radiological risk activities the licensee shall ensure control of the radiation parameters through measurement of the dose rate with stationary and/or portable gages, which are of approved type and have passed the annual metrological check up. At the place, where the activities are carried out, obligatory is the presence of responsible persons, appointed by an order, such as radiation protection officer and/or dosimetrist from the respective sites.
3. The licensees shall organize the preparation and the preliminary plan for the ways and means for carrying out the high radiological risk activities at the respective sites. For this it is necessary:
- to prepare the work programme and the programme for radiation protection upon performing a certain activity, including an emergency plan for actions in case of emergency and unexpected events during work;
- to check the availability and the working condition of the means for the individual dose control and general radiological control necessary for the given activity;
- to perform an exceptional training for persons engaged in performing a certain task and to document it in a journal for instructions;
- when necessary, for specific topics, the licensee shall conduct consultations with external experts of radiation protection;
- to conduct a training of the personnel with an imitation of the situation and the conditions for the forthcoming complex and non standard operations with high radiological risk;
- to forecast the expected exposure doses and to ensure means for radiation protection of the personnel involved in performing a given activity;
- to inform NRA for the planned high radiological risk activities and if necessary, to request a permit in accordance with Act on the Safe Use of Nuclear Energy (ASUNE) if applicable.
4. The non-compliance to the requirements, rules and procedures for radiation protection established in the legislative acts and internal rules leads to radiological incidents. The licensees should constantly and systematically strive to form and keep up the high culture of safety of its personnel.
5. The licensees should review in depth and bring up to date their internal documents (instructions, regulations, procedures, emergency plans, job descriptions, internal orders, programmes) and to outline preventive and corrective measures taking into account the lessons learned from the incident in the town of Stamboliyski and the specifics of their permitted activities with SIR.
6. The licensees shall intensify the internal administrative control on observing the requirements and the rules for radiation protection on their sites, for which they personally bear responsibility according to Art. 16 of ASUNE.
This incident is a lesson for everybody whose work is connected with SIR. Despite the high qualification and the vast practical experience of the “Gitava” Ltd. personnel, due to a human error there occurred a serious incident.
Everybody working with SIR should be extremely careful, cautious and uncompromising and to follow strictly the requirements and the rules of radiation protection and work safety.
According to ASUNE and the Regulation for radiation protection during activities with SIR the licensee and as well as the personnel immediately working with SIR bear the responsibility for safety during activities with SIR.