OCCUPATIONAL RADIATION PROTECTION OF EMERGENCY WORKERS
THE GOIANIA ACCIDENT
Contents
- Introduction
- The accidentand detection
- The initial response
- The intermediate phase
- References
- Introduction
The objective of this chapter is to describe the radiological accident in Goiania, to describe the occupational radiation protection measures taken to protect the emergency workers, to discuss the strong and weak points of the radiation protection activities and to establish lessons learnt that can be useful in the management of future events.
- The accident and detection
On the 13th of September 1987, a shielded, strongly radioactive 137caesiumsource(50.9 TBq, 1375 Ci, at the time of the accident) was removed from its protective housing in ateletherapy machine in an abandoned clinic in Goiania, Brazil, and subsequently opened. Consequently, many people incurred large doses of radiation, due to bothexternal and internal exposure. Four of the casualties ultimately died and 28 peoplesuffered radiation burns. Residences and public places were contaminated. Thedecontamination necessitated the demolition of seven residences and various otherbuildings, and the removal of the topsoil from large areas. In total about 3500 m3of radioactive waste were generated.
A detailed description of the accident chronology is given in the IAEA report “e The radiological accident in Goiania, IAEA, Vienna, 1988”. Between the 10th and the 13th of September 1987 the teletherapy machine was partially dismantled and the rotating assembly containing the source was removed. On the 18th of September, the rotating assembly was further dissembled and the source container was ruptured, spreading part of the 137Cs in the form of CsCl onto the ground in a garden in the city of Goiania. Later a 1.1 Gy/h dose rate was measured at this place. The blue glow of the CsCl was noted and the source material was thought to be valuable. From the 18th to the 21st of September, the blue powder was distributed to friends and relatives that lived close by or in houses up to 100 km away. By this time all persons who had entered into contact with the source were suffering from various stages of the acute radiation syndrome.
It was suspected that the mysterious powder was causing the sudden and generalized illness and on the 28th of September the remains of the source (around 10% of the original source) wrapped in a cloth bag was taken to the local hospital. The doctor who received the patients and the source was told “This is killing my family”. After a certain time, the doctor became worried about the contents of the bag, and he took the bag and placed it against the outside wall of the hospital courtyard. The external dose of the doctor was later calculated to be around 1.3 Gy. Negligible internal contamination was found as the source was contained by the bag. A number of other persons working in the local hospital (Vigilância Sanitaria) received lower doses.
Figure xx: The remains of the 137Cs teletherapy source wrapped in a cloth bag on a chair in the Vigilância Sanitaria.
On the 29thof September a physicist was contacted and requested to bring a dose rate meter to the hospital to verify the presence of radioactive material. At this point it is considered that the emergency actions began, the physicist being considered the first responder. The physicist correctly chose a very sensitive NaI scintillator detector (full range 30 µGy/h) ideal for locating a lost gamma emitting source, but did not carry a GM based dose rate meter which would allow higher dose rates to be measured. At some distance from the hospital the scintillator was switched on and the needle on the analogue display went to full scale. Thinking that the detector was defect, the physicist returned to the office and chose a second scintillator. When the second scintillator also went off scale near the hospital, the physicist concluded that there was a high dose rate gamma radiation field in and around the hospital.
[Lesson learnt xx: It is necessary to have confidence in the radiation detection equipment. After removing from storage, the equipment should be switched on and passed through a functional test. If no check source is available, the background reading should be noted. If there is no background or if the detector goes off scale, then the detector should be rejected or the batteries changed. Ideally the first responder will be familiar with the dose rate measuring equipment he or she is using.]
While the source location was in progress on the 29th of September the doctor called the fire brigade. The physicist arrived just in time to stop members of the fire brigade from throwing the source into the near-by river.The physicist persuaded the hospital staff to evacuate the premises. The police and fire brigade were called on to maintain the access control.
- The initial response
On the 29th of September the news about the radioactive contamination of Goiania residents spread quickly across the city and its approximately one million inhabitants. In order to regain control the authorities identified those who were most likely to have been contaminated and directed them to the Olympic Stadium (used for football games) for radiation screening and triage. Over the 29th-30thof September, 22 people were identified at the stadium as potentially having been highly exposed. They were put into tents separately from the others.During this period the tents in which people had been housed blew down in a violent storm. This hindered operations and was a foretaste of the adverse weather in which some decontamination work would be done. Only on the 30th of September were the patients subjected to external decontamination through showers; the civil defense personnel thought that the action would contaminate the stadium.
[Lesson learnt xx: The external decontamination of patients should take priority over environmental contamination considerations. In the case of such an accident the environmental contamination is already orders of magnitude higher than any action caused by personnel decontamination.]
Paramedical team receiving the internally and externally contaminated persons at the Olympic Stadium in Goiania
Standard medical protective clothing was adequate for avoiding contamination of the medical team, no external individual monitoring, dose rate or surface contamination measurement was available for the civil defense teams performing the area evacuation, nor for the medical teams performing the triage and initial medical treatment. The clothes of the patients were placed into plastic bags and separated as active waste, otherwise no other contamination control measures were taken.Some areas of the Olympic Stadium required decontamination.
A monitoring station for members of the public was established at the Olympic Stadium and by February 1988, the total number of persons measured exceeded 125,000, more than 10% of the population of Goiânia.
[Lesson learnt xx: A major population center should have at least 10 active dosimeters available to civil defense workers that can be used immediately in the case of a large scale emergency response.]
- The intermediate phase
On Thursday 1st of October 15 additional radiation protection technicians arrived and by the 3rd of October the emergency infrastructure was more or less complete. The technical radiation protection staff was heavily overburdened due to requests for information from the press and public.
[Lesson learnt xx: The assignment from the beginning of a press officer with subsequent support for public information purposes would have allowed the radiation protection officers to concentrate on occupational radiation protection.]
Many work-fronts requiring occupational radiation protection actions were started almost simultaneously:
a)Radiological surveys of the city and neighboring cities were carried out to identify contaminated areas;
b)Monitoring of the general public at the Olympic Stadium
c)Area decontamination work. There were 7 principal decontamination sites, including the site where the 137Cs source was breached, and a number of minor sites.
d)Medical treatment and decontamination of the patients in the hospitals;
e)Waste management
f)Bioassay measurements
The occupational radiation protection actions, problems and lessons learnt are quite similar for all workfronts, so the information is compiled by technique.
General occupational radiation protection
Organization
In the beginning of the accident the overall organization and assignment of tasks and responsibilities was made on an ad-hoc basis. It required some days before the emergency management structure was defined and informed to all emergency workers. The division of tasks and responsibilities between CNEN, the city of Goiania, the civil defense, the military police, the Health Ministry, the Military among other was developed over time.
[Lessons learnt xx: The response management and teams of the authority dealing with the emergency should be previously defined as part of the emergency planning and preparedness. The assigning of responsibilities in the decision process, from planning to action and evaluation of consequences, should be very clear, and each group should know its function. If possible, teams should be formed with a leader who heads the group in normal working conditions.]
Qualification and training of the emergency workers.
A ward of the General Hospital on the third floor was allocated to the treatment of the patients. When the CNEN medical and radiation protection staff first arrived at the ward in the General Hospital the patients, some in great pain with serious lesions, were sitting together in the back of the ward completely alone. No nurses and doctors from the hospital were present. The reason for this was an unjustified level of radiation phobia felt by the hospital staff. It became clear that there would be no help from the hospital medical or auxiliary staff; no cleaning, no nursing, no security guards, no social or psychological support and so on.
In the case of the area decontamination, Military police, civil defense workers, army soldiers and personnel from building companies were contracted to lend support to the CNEN operations. These workers had no previous training in radiation protection. In the end, some 750 workers were involved, of which some 250 had had previous training in radiation protection.
[Lesson learnt xx: In the case of a large scale accident, it will be necessary to engage the assistance of workers with no experience in radiological work. Indeed, many radiation professionals will find themselves in unfamiliar situations. Intensive training efforts for non-radiation workers should be foreseen in the case of such an accident. Procedures should be written and used in the training program so as to promote good practices.]
Operational working levels
Operational levels for dose rate and surface contamination for evacuation and decontamination, specific activity for waste segregation, radiological release-from-hospital criteria for the patients and others had to be established during the emergency. Operational Levels for occupational doses were set at 1.5 mSv per day, 5.0 mSv per week, 15.0 mSv per month and 30.0 mSv per quarter.
[Lesson learnt xx: It is recommended that the Operational Intervention Levels be established during the emergency planning and preparedness phase. Suitably justified adjustments to the OILs may be made during the emergency on a case-by case basis.]
General support
The occupationally exposed persons working during the Goiania accident were mostly not fully prepared for the work that had to be performed during the emergency phase. Seven day working weeks with long days in hot and humid conditions, a certain isolation from the general public together with the high interest from the press, having to deal with injured and sometimes fatally injured people all added up to the appearance of a number of physical and psychological problems amongst the emergency workers.
[Lesson learnt xx: When setting up teams of emergency workers, it should be borne in mind that there is a need to foresee a back-up team to relieve the first team deployed. Psychological and medical support should be made available locally.]
Individual monitoring
Individual monitoring for external radiation
In the area decontamination work-field the highest dose rates could exceed 1 Sv/h. The highest dose rate near the interned patients was measured ataround 3 mSv/h. External individual monitoring was obligatory in all work areas where 137Cs was present. Film dosimeters for the effective dose, TLD ring dosimeters for extremities and Quartz Fiber Dosimeters (QFDs) were used. A few electronic dosimeters were also available. The QFDs were used for day to day planning. The disadvantages of the QFDs are the uncertainty in the measurement, difficulty in recording the initial and final doses after a work task and the problem of high ambienthumidity causing them tobe easily discharged if care was not taken with the end caps.
[Lessons learnt xx: QFDs should not be used for emergency operations unless there is no other option. Electronic personal dosimeters with alarm and visual display are recommended.]
Radiological surveys over skin lesions gave dose rates as high as 15 mSv/h, and a survey of a six-year-old girl showed an average dose rate of 3 mSv/h in skin contact. Dose rates as high as 1 mSv/h were measured on the surface of urine sample. In the area decontamination activities, localized dose rates as high as 1.2 Sv/h were measured. The records of 755 emergency workers in the period from 30 September to 21 December 1987 show that 68% of the workers received doses of less than 1 mSv and no-one received a dose higher than 16 mSv.
In some work fronts the exchange frequency of the film dosimeters was too short. Exchanging the dosimeters with a minimum detection level of 0.2 mSv every day would imply in a possible “missed dose” of 2 mSv over 10 days.
[Lessons learnt xx: establish the dosimeter exchange frequency to be not longer than a month but for a period of time where the recorded dose will be at least 1 mSv. In areas where the dose rate may increase rapidly, active dosimeters with alarms must be worn.]
The film dosimeters were worn at times without any protection against contamination. A low activity of 137Cs contamination on the outer case of the dosimeter may cause a spurious relatively high dose to be evaluated and registered. This effect may be seen and corrected for when using film dosimetry, but not when TLD or other dosimetric system is used.
[Lessons learnt xx: Ensure that all dosimeters are placed in a plastic outer protective covering before entering a contaminated area.]
Except in laboratory conditions, such as in the bioanalysis laboratories where some of the urine samples measured around 1 mSv/h, it was found that the use of ring dosimeters was not very practical, and the information recovered from the ring dosimeters was not very useful for ongoing radiation protection work in the field.
Records and form filling have to be reduced to a minimum during emergency work. The data base for doses maintained by the IRD external dosimetry laboratories requires extensive personal records of the users, name, date of birth, address, etc. To expedite matters and to cope with dosimeter exchange periods shorter than a month, a specific data base was designed for use during the accident. The personal data was reduced to name, employer and the social security number.
Individual monitoring for internal radiation
194 emergency workers were monitored for internal contamination in IRD's whole body counter. Of these, 38 people had 137Cs body burdens that exceeded the minimum detectable activity (74 Bq in a counting time of 30 minutes) The highest level of internal activity was 2.0 ± 0.3 kBq, corresponding to a committed dose equivalent of about 10 µSv. The great majority of persons with internally deposited activity worked in the area decontamination.
Dose evaluation through cytogenetic dosimetry
In the first few weeks of the emergency, 129 cytogenetic analyses were performed at the IRD/CNEN. This demand overburdened the laboratory that is used to analyzing around one or two analyses per month.
[Lessons learnt xx: A network of cytogenetic laboratories should be maintained that can accept a sudden peak in the demand for cytogenetic analysis.]
Workplace monitoring
Dose rate measurements
The dose rate measuring equipment used during the emergency was mainly lent by other installations for the duration of the emergency. 18 types of equipment are listed in the paper [Becker]. The scales of the equipment read in the units of R/h, Sv/h and even C kg-1/h. Considering that many of the emergency workers had never made extensive dose rate surveys before, the variety of scales only added to the confusion.
[Lesson learnt xx: For emergency work, standardize the dose rate measuring quantity in H*(10) calibrated in Sv/h].
Ionization chambers, proportional counters and Geiger-Mueller (GM) detectors were used. It was found that for quick response times, reliability, ruggedness, adaptability to high temperatures and humidity, either the GM detector or the proportional counter represent the best choice.