Industrial Radiography Accidents : lessons learned Day 5 – Lecture 7

Aims and Objectives Be familiar with typical industrial radiography accidents Understand specific contributing factors Be aware of lessons learned from past accidents This presentation outlines a selection of industrial radiography accidents and considers the contributory factors.

Contents Case histories described Consequence of each accident Lessons learned

Gamma Site Radiography Lost Source 550 GBq iridium-192 source became detached, fell from guide tube loss was realised after 5 days 78 persons irradiated doses ranged from 11 mSv to 150 mSv Description of accident : Ir-192 source used to examine weld on steel vessel. On completion of the work the winding mechanism was used to returned source to its container. The monitor located at winding position recorded drop in dose rate and radiography assumed the source was back in the container. The equipment was used 5 days later and the resulting radiographs were blank, revealing the source was missing from the container. After a search the source was found near the location it was last used. The investigation found that the source had become detached and fallen from guide tube during dismantling. The noted drop in dose rate occurred when the source became detached from drive cable close to source container which shielded the dose rate monitor from the source. The source was recovered by the RPO. Consequences : 78 persons irradiated 2 persons received a dose of 100-150 mSv 4 persons received a dose of 30-100 mSv 9 persons received a dose of 11-30 mSv 63 persons received a dose of < 11 mSv

Gamma Site Radiography Lost Source Incorrect use of monitor inadequate monitoring Lessons learned : 1. Dose rate monitor not used correctly. The container should have been monitored! 2. Monitoring should also have been carried out when the container was returned to storage location. The missing source would have been noted a lot sooner!

Gamma Site Radiography Defective Equipment 3.2 TBq iridium-192 source jammed in exposed position no emergency equipment no local rules or exposure warnings IAEA assistance in source recovery 7 persons involved in recovery, all doses < 1.0 mSv Description : 1. Site Radiographers using Ir-192 source. The team had no emergency equipment, no pre-exposure or exposure warning signals, no local rules or emergency plans. They did have a dose rate monitor. 2. Source jammed in exposed position. 3. The radiographers secured the area and threw lead sheets over the equipment until dose rate was below 10 Sv/h. 4. The company undertaking the the radiography, contacted the equipment suppliers to assist. The fee quoted by the suppliers was considered unacceptable so the operator contacted the IAEA for assistance. 5. Recovery was difficult : the source could not be returned to the container. Instead drive the source out along the guide tube. The dose rate at 1m from unshielded source was calculated to be 6 mSv/min. it was decided to cut through the drive cable (long handled cutters) and then use long handled tongs to put detached source into spare lead container.

Gamma Site Radiography Defective Equipment guide tube lead container A temporary concrete wall (50 cm ) was built to shield the recovery team. After careful planning and rehearsals the source was recovered. Doses : 7 persons involved. Recorded doses were below 1 mSV.

Gamma Site Radiography Defective Equipment source activity should be optimized- > 1.8 TBq for site work should be justified reasonably foreseeable accidents should be highlighted in prior safety assessments adequate maintenance of ancillary equipment is essential site radiography requires appropriate emergency & ancillary equipment trained personnel adequate supervision Lessons learned : 1. Source activity was unusually high :use of sources > 1.8 TBq should be justified 2. This was a reasonably foreseeable accident. It should have been highlighted in a prior safety assessment and emergency plans should have been developed. 3. Site radiographers should always : - have appropriate emergency equipment - be trained - have local rules and emergency plans - use exposure warnings - be supervised by RPO 4. Condition of equipment should be checked and maintained (guide tubes, cables etc)

X-Ray Site Radiography Localised Exposure Exposure160 kV x-rays No exposure warnings Fingers exposed to primary beam for ~ 10 seconds Localised dose of ~ 60 Sv Description : A radiographer placed his fingers over the window of an x-ray tube (he didn’t know it was generating x-rays). A colleague noticed that the x-ray set was on and they isolated it from power supply. Several days later, the fingers blistered.

X-Ray Site Radiography Localised Exposure periodic checks on safety systems are essential radiation monitoring is essential local rules must be observed personal alarm monitors can lessen the consequences of an accident Contributing factors : The radiographer did not follow the local rules which required isolation of the x-ray set after each exposure and for the use of the radiation monitor when entering the controlled area. Also, the pre-exposure warning signal was hard to hear because it had been taped over t(to reduce the noise level!). And the visual exposure warning light had failed previously and had not been repaired. Doses : By tissue biopsy, it was estimated that the received 60 Sv to the hands.

Gamma Site Radiography Disconnected Source 1100 GBq iridium-192 source became disconnected from the drive cable source picked up by a member of the public and taken home source “lost” from March to June 8 persons died as direct result from exposure to radiation Description :In 1984, 8 members of the public died of over exposure Source became disconnected from drive cable and was not returned to container. Guide tube was disconnected from exposure device and source dropped to the ground.. A passer-by picked it up (tiny metal cylinder marked only with the trefoil symbol) and took it home. The passer-by and 7 relatives died and initially their deaths were assumed to be due to poisoning. Lessons learned: 1. No radiation monitor used to ensure that the source has fully returned to shielded container. The accident would have been prevented the container had been monitored. 2. The passer-by did not recognise the health hazard associated with the source. The source should have better markings to provide a warning.

Radiological Incident in Industrial Radiography February 20th, 1999

Incident Synthesis Location Hydroelectric Construction Site in Yanango. Distance from Lima: 300km (East) District: San Román, Department of Junín. What Happened A non-authorised person unscrewed the screws of the security lock to free the radioactive source of a Gammagraph. No key is needed to remove the source, it can be done with an screwdriver.

Equipment’s Characteristics Security Lock Radionuclide: Ir1-92 Activity Max: 3.7 TBq

Equipment’s Characteristics With a screwdriver, the safety lock can be removed and so the source is accessible

Chronology Welder 4:00 pm: A worker (welder) finds the source of gammagraphy (Ir-192) abandoned in a water pipe. He puts it in the back pocket of his trousers. He works for six hours with the source in his pocket and his assistant nearby 10:00 pm: He leaves work, takes a bus and travels home (he felt little pain in his right leg). During his return, he travelled for 30 minutes with 15 people. He thinks that the red skin is due to an insect sting. His wife sat on the trousers for 10 minutes to feed their baby. Two kids slept nearby. 11:00 pm: The welder, takes the trousers off the room.

Chronology Operator 10:30 pm: The operator makes a gammagraphy. The radiation detector doesn’t detect any readings. He assumes the equipment is not working well and stop to have dinner. 00:00 am: He enters the water pipe, checks the gammagraphy equipment and finds the no screws nor radioactive source. They start looking for the source. 1:00 am: They find the welder in his house (February 21st). He gets out with the source in his hands. The operator hits the welders hand, throws the source to the street and puts a stone to cover it. The source is recovered and secured in a container with iron walls 2” thick.

Chronology What was done? Initially, the welder was hospitalised in the Cancer Centre of Lima. He was then sent to the Military Hospital “Precy de Claart” Grave Burns Treatment Centre in France.

Consequences Overradiation: 1 Person Exposed: 18 People 16 Days After the incident 3/8/99 Effects on Leg (70 days after the incident 5/3/99) Effects on Leg (13:00pm 2/21/99)

Consequences Leg Amputation (10/18/99) Severe Infection 12/14/99

What Went Wrong? Organisation - Procedures were not implemented. - Absence of Safety Culture in the Company’s Management. - Source inspection and measures were inadequate. - Lack of training and qualification of the operators. NATIONAL AUTHORITIES ESTABLISH: The evaluation of the authorisations and inspections should be developed by an experienced and trained team.

Gilan Accident Chronology July 1996, Gilan Industrial radiography at the power plant 185 GBq Ir-192 source Source fall into trench surrounded by a 1 m concrete wall situated 600 km north of Tehran. As the source was shielded by the concrete, its loss was not detected by the radiography team when they finished work and they assumed that it had been safely returned to its container, as usual.

Gilan Accident Chronology K.Z. plant worker was climbing up a ladder when he noticed a shiny metallic object He picked it up and put it in pocket At around 09:30 he started to experience dizziness, nausea, lethargy and a burning feeling in his chest. Believing that the object was a possible cause of his symptoms, he put it back K.Z.,, came from a rural village and was unable to read. Over the next 1.5 h, K.Z. reportedly removed the source from his pocket to inspect it and then returned it to the pocket on a number of occasions.

Gilan Accident Chronology At around 09:00, the radiographers observed that the source was not visible in the channel of its holder A search was immediately initiated and the source was found in the trench at approximately 10:00. It was recovered and placed in a shielded container, and the Site Manager and the Radiation Protection Officer were informed.

Gilan Accident Chronology At 13:00, K.Z. told his colleagues that he was feeling weak and lethargic and he mentioned the strange shiny object that he had found and then put back in the trench. The Site Manager was informed, and after consulting the Radiation Protection Officer he notified the Atomic Energy Organization of Iran (AEOI), who advised him to send K.Z. to a doctor to have blood samples taken. Management at the plant arranged medical examinations of all personnel suspected of having been exposed, as required by the Radiation Protection Act of the Islamic Republic of Iran. A team of AEOI inspectors was assembled and travelled to Gilan to investigate the accident. On arrival at the plant, the inspection team reviewed the circumstances of the accident and recommended repeat blood checks of all 600 personnel.

Gilan Accident Consequences Erythema on the right side of his chest extending to the upper abdomen. Chest lesion continued to expand Blistering Estimated whole body dose of about 4.5 Gy The team sent 55 workers and blood samples of all the plant employees to the AEOI’s Medical Service in Tehran for detailed medical and haematological examination. The blood test results (of about 3000 samples altogether in the month after the accident) were reviewed by the AEOI’s medical adviser, who reported that all samples were normal except K.Z.’s. The 55 workers examined in Tehran showed no pathological symptoms or signs that could be associated with exposure to ionizing radiation. Over the next 16 days, the chest lesion continued to expand with ever deepening erythema, which progressed to dry desquamation starting at the nipple and eventually to moist desquamation extending over an area of 30 cm × 15 cm with early epidermal necrotic change. Erythema had also developed on the medial side of his elbow (right antecubital fossa), and by 2 August 1996 erythema with early blistering had appeared on the palm of his left hand. The patient was transferred to Paris for medical treatment, grafting

TYPICAL CAUSES OF ACCIDENTS FAILURE TO USE SURVEY METER LACK OF REGULATORY CONTROL EQUIPMENT FAILURE POOR OR NO TRAINING ACCIDENT NOT FOLLOWING SAFETY POCEDURES NO SAFETY PROGRAM

Lessons learned : Summary Adherence to established safety procedures would have prevented most accidents Safety may be compromised if regulatory controls are not in place Systematic audits by management help to ensure that level of knowledge and performance of radiographers is maintained A poor safety culture can result in degradation of safety systems and procedures Deficient training is contributory in the majority of accidents