Presentation on theme: "Overview of Industrial Radiography Sources and Accidents"— Presentation transcript:
1Overview of Industrial Radiography Sources and Accidents Day 5 – Lecture 3
2Objectives To understand:- the applications of industrial radiography the potential for accidents during the use of industrial radiography radiation sources.Mention each topic above placing emphasis on the point that industrial radiography can be a hazardous practice because there is always a potential for serious injury.
3ContentsThe beneficial uses of ionizing radiation as used in industrial radiography practicesThe potential harmful effects due to the lack of and/or effectiveness of an adequate and appropriate radiation safety programThe consequences of radiological accidentsMention each topic above placing emphasis on the point that industrial radiography can be a hazardous practice because there is always a potential for serious injury.
4What is Industrial Radiography? Industrial radiography is:-a process of non-destructive testing for examining the quality of a component or product;most often utilized for quality control of metal fabrication for the oil/gas industry;also used to test a range of other products.Explain the purpose of industrial radiography (Why do the companies carry out industrial radiography ? – What is the benefit ?). Explain some of the common applications but also note that its application is very diverse. Give examples of the common uses and some of the diverse applications (eg underwater radiography, radiography of electronic circuit boards, plus other examples).
5Imaging PrinciplesExplain that industrial radiography involves the use of penetrating gamma or X-radiation to examine materials and parts for imperfections. Using the diagram explain that an x-ray generator or radioactive isotope is used as a source of radiation. Radiation is directed through a part and onto film or other detector. The resulting image or radiograph shows both internal and external features of the part. Possible imperfections are indicated as density changes in the film in the same manner as an medical X-ray can reveal broken bones.
6Overview of Industrial Radiography Equipment Knowledge is required of:-the devices that use ionizing radiation from radiation sources (radioactive substances and x-ray devices) for industrial radiography;the types of radionuclides and activities used;work environments, that may range from clean laboratories to fabrication workshops and mining environments;equipment design and the work procedures that are essential to protect both the radiation worker and the public.Go through the topics above mentioning there is a wide range of equipment types and locations where it may be used. Give examples of the range of isotopes used (Ir-192, Co-60, Se-75 etc).Again highlight the potential for serious injury because industrial radiography relies heavily on the radiographer being vigilant with safety and use of safe working procedures.
7History Roentgen discovers x-rays in 1895 Early x-ray tubes were unreliableVacuum x-ray tube and heated filament (Coolidge-1913)200kVp achieved in 1922Discuss briefly the early times, changes in equipment and standards or protection.In his discovery in 1895, Roentgen found that the x-rays would pass through the tissue of humans leaving the bones and metals visible. One of Roentgen's first experiments late in 1895 was to x-ray the hand of his wife, Bertha. However, it can be argued that the first use of x-rays was for an industrial (not medical) application as Roentgen produced a radiograph of a set of weights in a box to show his colleagues.Prior to 1912, x-rays were used little outside the realms of medicine, and dentistry, though some x-ray images of metals were produced. The main reason that were not used in industrial application before this date was because the x-ray tubes (the source of the X-rays) of that period broke down under the voltages required to produce x-rays of satisfactory penetrating power for industrial purposes. However, that changed in 1913 when high vacuum x-ray tubes with a heated filament as the source of electrons, designed by Coolidge, became available.The high vacuum tubes were an intense and reliable X-ray sources, operating at energies up to 100,000 volts. In 1922, industrial radiography took another step forward with the advent of the 200,000-volt x-ray tube that allowed radiographs of 7-8 cm thick steel parts to be produced in a reasonable amount of time. In 1931, the General Electric Company developed 1,000,000 volt x- ray generators.
8History (cont) 1930s and 1940s 226Ra was used. 60Co and 192Ir after World War IIDiscuss briefly the early times, changes in equipment and standards or protection.Industrial radiography sources used in the 1930s and 1940s were Ra because no other radionuclides were then available of sufficient strength. The capsules used contained approximately 3.7 GBq (0.1 Ci). After World War II, Ir-192 and Co-60 replaced radium.When used, the radioactive source would be placed on one side of the weld or metal casting being "x-rayed," while a sheet of photographic film was placed on the other side. Exposure times were quite long, e.g., one hour to as much as four days. The source was either handled with a long pole ("fish pole") or tied to a cord. The latter method, for example, would allow it to be pulled through a long pipe.In the picture on the left, the source is being removed from its shield ("pig"). The photo on the right shows the source being held at the end of a fish pole. The long exposure time and an unsteady hand often resulted in a blurry x-ray image.
9Types of Industrial Radiography Equipment Commongamma source projectorsdirectional x-raypanoramic x-rayx-ray crawlersgamma crawlerscrawler control sourcesUncommonbetatronlinear acceleratorneutron radiographytorch devicesfluoroscopyExplain that the a range of equipment types used for industrial radiography has grown, each with there own advantages and disadvantages that influence what equipment the radiographer may use for any particular application. Discus some of the different potential radiation hazards that they present.Discuss briefly the primary types used and that they may never encounter some types of equipment but they should nevertheless be aware of their existence and application.
10X-ray Equipment Has three main components:- x-ray tube assembly; x-ray control panel;high tension (HT) cables.Discuss the main components of the equipmentDiscuss application of the different types of equipment presented in the slide (directional, panoramic and CP x-ray devices).The potential for serious injury when using x-ray equipment is very apparent when one considers the dose rate that x-ray equipment can produce.As an a Rigaku 250EGS2 250 kVp directional x-ray unit operating at 250 kVp and 5 mA produced a dose rate in air of approximately 1.2 Gy/min at 30 cm (with 2 mm Al filter). With only the 1mm Be window the dose rate was approximately 10.6 Gy/min at 30 cm.[Source: Radiation Health Branch, Department of Health Western Australia]
11Betatron Special Considerations survey meters with appropriate responseoperator trainingshieldingDiscuss that application to import and use uncommon equipment may be encountered for a special project that requires the particular advantages it has to offer.Discuss the proposal to use the betatron and the special considerations that it warrants (who would operate it, additional shielding , distance, calibrated survey meter ?).
12Gamma crawler equipment Special applicationson-shore pipelinesoff-shore pipelines (on a barge)remotely controlled with a separate ‘control’ source, typically 137Cs.Discus the main elements and purpose of the crawler equipment and where they may typically be used (onshore and offshore). Briefly discuss the potential accidents with this type of equipment and how vigilant operation is required.
13Radioactive Sources and some properties The range of HVLs and TVLs demonstrates the range of radiation energies emitted by the listed nuclides. The highest energy gamma radiation in this table is emitted by Co-60. Ideally, the choice of nuclide for industrial radiography depends on the nature of the material being radiographed. However, practical issues of cost, half life, containment (weight) and shielding make Ir-192 the most commonly used source.
14Projector-type radiography equipment Discuss briefly the principle of operation. Survey, connection, checking connection, set up item to be radiographed, crank out to expose, survey, crank in to shield, survey , lock off between exposures, diss-assembly and stowage, survey etc.Discuss briefly why this is the main type of design used throughout the world.Discuss briefly the main problems with this type of equipment if adequate procedures are not in place and followed.
15Source containersSource containers must comply with recognized standards to ensure that exposures to users and the public are kept As Low As Reasonable Achievable.Discuss briefly that equipment design standards play a major role in limiting accidents that may cause serious harm. Highlight that poor operational procedures and safety programs are probably the major contributor to accidents involving industrial radiography equipment.Discuss briefly the incident involving the gamma projector in the slide. The gamma projector came from a industrial radiography practice that experienced a severe fire. Despite the whole building being destroyed by the fire, the container remained intact and did not loose any shielding. It can no longer be used for radiography.The shielding of source containers must remain intact following any credible accident or incident. The shielding of this container (right) remained intact following a severe fire at the licensed premises.
16FluoroscopyReal-time radiography is a well-established method of NDT having applications in automotive, aerospace, pressure vessel, electronic, and munition industries, among others. The use of RTR is increasing due to a reduction in the cost of the equipment and resolution of issues such as the protecting and storing digital images.Perhaps the main advantage of RTR is the increased inspection speed. There are however, disadvantages such as set up costs and image resolution that make the method unlikely to replace film radiography just yet.In the above picture, RTR is used inside a shielded and interlocked cabinet. The radiation safety advantages of this configuration are very clear. Perhaps in the not to distance future it will become an affordable widespread method but radiography will still be required in field locations where the advantages of shielded and interlocked cabinets can not be put to use.
17Industrial Radiography Accidents 48 industrial radiography accidents1 were reported to the US Nuclear Regulatory Commission between 1971 and1980.Severe injuries and a number of deaths have since been reported and investigated.Discuss the above material.Footnote 1 - involving overexposure greater than 5 rems to the whole body or 75 rems to a part of the body. (Ref: NUREG/BR-0024). Many accidents may go unreported because those responsible fear the legal consequences.Highlight some of the more well known recent industrial radiography accidents. February 1999 Peru a 192Ir industrial radiography source was picked up by a welder resulting in sever burns to his buttock.July 2000 Cairo a 192Ir industrial radiography source was stolen resulting in the death of a man and his son. Eight people face up to life in prison.Highlight that it is likely a large number of less severe accidents go unreported.1involving doses greater than 50 mGy to the whole body or 750 mGy to a part of the body. (Ref: NUREG/BR-0024). Many accidents may go unreported because those responsible fear the legal consequences.
18Industrial Radiography Accidents (cont) IAEA Safety Report Lessons Learned from Accidents in Industrial Radiography. Series No.7:-43 cases; 9 involving the public or other non-radiation workers.
19Industrial Radiography Accidents (cont) Severe injuries to a non-radiation worker resulting from the radiography worker failing to use a survey meter to confirm the source had been returned to the shielded container.Day 15The Radiological Incident in Gilan IAEA Report 2002During the night of 23–24 July 1996, industrial radiography was undertaken at the Gilan combined cycle fossil fuel power plant, situated 600 km north of Tehran. Welds on a boiler and pipes located at a height of 6 m above the plant floor were radiographed with a 185 GBq 192Ir source. At the end of the shift, at around 03:00 on 24 July 1996, the iridium source became detached from its drive cable, reportedly due to failure of the lock on the radiography container. This resulted in the source falling 6 m into a trench which was surrounded by a 1 m high wall made of concrete blocks. 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.K.Z. was climbing up a ladder carrying heat insulation material when he noticed a shiny metallic object (the 192Ir source) lying in the trench. Once down the ladder, he picked up the source and put it in the right breast pocket of his coveralls. 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. 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 in the trench and then went to the workers’ rest room.Relate this type of injury to actual accidents that have happened, primarily through poor operator training, failure to use survey meters and other warning devices.185 GBq 192Ir in shirt pocket for 90 minutesestimated skin dose of 30 Gy; whole body as 2-5 Gy
20Industrial Radiography Accidents (cont) Poor source security leading to severe injuries and death137Cs industrial radiography source; Argentina 1968A number of deaths have resulted from the radiation doses received following prolonged exposure to industrial radiography sources.The above picture follows an accident in 1968 (May 3 - 4) where a worker carries Cs-137 radiography source in his pockets; Buenos Aires (Argentina).The man latter had both legs amputated.
21Industrial Radiography Accidents (cont) Poor source security leading to severe injuries and deathDoses17000 Gy (localized)1 - 8 Gy (internal organs)0.6 Gy (head)A number of deaths have resulted from the radiation doses received following prolonged exposure to industrial radiography sources.The above picture follows an accident in 1968 (May 3 - 4) where a worker carries Cs-137 radiography source in his pockets; Buenos Aires (Argentina).The man latter had both legs amputated.137Cs industrial radiography source; Argentina 1968
22Industrial Radiography Accidents (cont) Yanango, Peru 19991.37 TBq 192Ir.2 days after accident; blister on upper thigh.The above picture follows an accident in Peru on 21 February The worker carries Ir-192 radiography source in his rear pocket for several hours.The source, in the man’s pocket, was taken on a bus to his home where his wife and children were also exposed. The wife sat on the man’s trousers with the source in it for between 5 to 10 minutes while breastfeeding a baby.
23Industrial Radiography Accidents (cont) Source not properly secured. Loss not apparent for 6 hours.The above picture follows an accident in 1999 () where a welder carries Ir-192 radiography source in his rear trouser pocket; dose near contact leads to amputation of one leg; Yanango (Peru). IAEAA 1.37 TBq 192Ir was “lost” from its shielded container. The source was picked up by an employee at the site where radiography was taking place and carried in his pocket for several hours. Some 5 hours later he experienced pain in the back of his right thigh. His wife later noted reddening of the skin. She was also exposed when she sat on his jeans (which contained the source) for 5‑10 mins while breastfeeding. Two other children were within 2 – 3 metres of the source for around 2 hours.The loss of the source was not apparent to the industrial radiographer until some 6 hours after it was picked up by the employee when a series of routine exposures resulted in unexposed films. The skin dose (at 1 cm) to the employee’s leg was estimated at around 10 kGy. His right leg was later amputated at the hip and the anal sphincter and basal part of the scrotum were resected. His wife developed an ulcerative lesion on the lower back.Although the cause of the “loss” of the source remains unknown, it is clear that the industrial radiographer failed to ensure the security of the source container and failed to properly use the radiation survey devices available to him.This type of incident has been reported elsewhere and could occur in any country. Prevention depends solely on appropriate training and strict observance of prescribed safety procedures by the industrial radiographer.Also relate accidents in Iran 1996, Morocco 1984 Algeria and more recently in Egypt 2000 etc.Skin dose at 1cm estimated at 10 kGy; right leg amputated. The worker’s wife and two children were also exposed.
24Consequences of Accidents Severe deterministic effectsdeath, loss of limbs, erythemaIncreased stochastic riskfatal cancerEnvironmental contaminationSocial & economic consequencesDiscuss in summary the above points as have been illustrated in the previous slides.
25Causes of Accidents Causes identified as contributing to accidents: Lack of or inadequate regulatory frameworkauthorizationinspectionenforcementLack of or inadequate safety culturemanagementquality controltraining and qualifications of workers
26Causes of Accidents (cont) Regulatory control lacking or inadequateFailure to use survey meterEquipment failureInadequate or lack of trainingACCIDENTDiscuss the above typical causes of accidents. Each has the potential to result in dangerous situation. However, as will be learnt later during this week, some of the above factors can be managed while others are outside the scope of management because they are not necessarily recognised as a problem.Safety procedures not followedLack of safety program
27Causes of Accidents (cont) Regulatory control lacking or inadequateACCIDENTDiscuss the features that may be representative of a lack of regulatory control giving examples of the possible consequences.The Regulatory Authority has inadequate:-authorization processes;field inspections;inspection follow up.
28Inadequate or lack of training Causes of Accidents (cont)Inadequate or lack of trainingACCIDENTDiscuss that many accidents have been a result of poor or no training.Lack of training (and ongoing training) results in:-unqualified and poorly instructed workers;poor or no understanding of emergency procedures
29Causes of Accidents (cont) A lack of safety program within an industrial radiography company may also be associated with insufficient regulatory control.No safety programinadequate managementlack of safety cultureLack of safety program
30Safety procedures not followed Causes of Accidents (cont)Safety procedures not followed indicates:-lack of safety cultureinadequate supervisionlack of trainingACCIDENTOne of the more serious factors that may lead to accidents is failing to follow safety procedures – particularly failing to make sufficient and proper radiation surveys. Accidents that result from this case can often result in serious injuries because there can often be a time lag before it is recognised that an accident has occurred..Safety procedures not followed
31Causes of Accidents (cont) Equipment failureACCIDENTEquipment failure indicates:-lack of manufacturer’s recommended maintenance;poor use of equipment;equipment being used beyond design limitsEquipment failure can lead to accidents but if properly managed they can be controlled before the accident becomes serious.Example, a common ‘equipment failure’ involves a source holder becoming detached from the control cable. This is often the result of wear of the couplings and can result in the source being unconnected in an exposed position. Source retrieval can be accomplished safely provided a safety plan is adopted and followed.
32Causes of Accidents (cont) Failure to use survey meterACCIDENTFailure to use survey meter indicates-insufficient and/or non-functioning meters;inadequate user safety training;hurrying to complete the work (employer pressure);lack of safety culture.Explain that accidents involving failure to use survey meters can have serious consequences because the operator is unaware whether the source is in a shielded condition or not and therefore, does not necessarily know where the source is located.
33} Safe use of Radiation Sources Radiation Sources: are widely used; provide substantial benefits; butcan cause harmful effects (injury or death).Safe operation requires:training;SAFETY CULTURE}maintenance;control.
34Safe use of Radiation Sources (cont) the RISKSBENEFITSshould outweigh
35ReferencesIAEA, International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, Safety Series No. 115, Vienna (1996).IAEA, Organization and Implementation of a National Regulatory Infrastructure Governing Protection against Ionizing Radiation and the Safety of Radiation Sources, IAEA-TECDOC-1067, Vienna (1999).IAEA, Lessons learned from accidents in industrial radiography, (reports in) Safety Reports Series.IAEA, Accident reports.
36ExerciseConsider the following industrial radiography equipment; portable x-ray; fixed x-ray; fixed gamma; portable gamma.Which has the greatest potential to cause serious harm to the user and to the public?Why?Course participants should be able to recognise the higher risk in use of that portable gamma radiography equipment.The higher risk are associated with the field use of the equipment where public access may be possible, the design which often involves the source leaving a shielded position and the high reliance of operator following safe procedures.