EVALUATION OF THE RADIOLOGICAL SAFETY OF 192 IR APPARATUS FOR INDUSTRIAL GAMMA RADIOGRAPHY ABSTRACT

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1 2005 International Nuclear Atlantic Conference - INAC 2005 Santos, SP, Brazil, August 28 to September 2, 2005 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: EVALUATION OF THE RADIOLOGICAL SAFETY OF 192 IR APPARATUS FOR INDUSTRIAL GAMMA RADIOGRAPHY Josilto O. Aquino 1, Adriana T. Ramalho 2, Ricardo F. Gutterres 1 1 National Commission of Nuclear Energy (CNEN) Rua General Severiano 90, CEP , Rio de Janeiro, Brazil josilto@cnen.gov.br 2 Institute of Radioprotection and Dosimetry (IRD-CNEN) Av. Salvador Allende, CxP CEP , Rio de Janeiro, Brazil. ABSTRACT Ninety percent of the gamma radiography apparatus operative in Brazil employ 192 Ir sources. The totality of the 11 models of 192 Ir apparatus used in Brazil are portable. The majority of them operate according to category II, i.e. they are panoramic, and have been in continuous usage for more than 20 years. This characteristic, besides the fact that the apparatus are already old-fashioned and worn-out, raises concerns about their radiological safety. After developing a specific methodology for inspection, testing and evaluation of their state of maintenance, almost a hundred 192 Ir apparatus were evaluated. About 20% of them presented some kind of unsafe condition for proper operation. We also studied the 11 models with respect to their compliance with the main safety requirements of three editions of Standards ISO Six models comply with the first edition of ISO 3999, issued in However, five models do not comply even with this first edition of the Standard. None of the 11 models comply with all newest safety requirements of later editions of the Standard. The validity of their type B certificates for transport packages was also evaluated. For one model its certificate has already expired, and for some other models, renewed with restrictions. 1. INTRODUCTION In Brazil, the applications of ionizing radiation in industrial area are performed in about 900 installations, in which around 3,000 radioactive sources are in service [1]. Industrial radiography represents 14% of this total, with 217 X-rays equipments and 287 gamma radiography apparatus. Industrial radiography installations perform their duties in very distinct locations, such as inside shielded enclosures, but most services are carried out on-site, in urban or remote temporary work sites all over the country, by operating organizations that render gamma radiography services to their clients. Industrial radiography is of vital importance in non-destructive testing. It is one of the longest established applications of ionizing radiation, but it is also responsible for roughly half of relevant accidents in nuclear industry, in developed as well as in developing countries, according to the International Atomic Energy Agency [2].

2 Thus, safety and radiological protection in industrial gamma radiography have been receiving especial treatment by regulatory authorities of most Member States. This subject has been extensively approached in an IAEA publication [3]. Gamma radiography apparatus are basically composed of three main components: an exposure container, a control cable and a projection sheath. From the 287 gamma radiography apparatus in use in Brazil, the great majority 90% employ 192 Ir sources, followed by 60 Co and by 75 Se, with 5% each. The Ir apparatus in operation in Brazil have been in continuous usage for more than 20 years, which means that they are old equipments. The totality of the 11 models of 192 Ir apparatus used in Brazil is imported from abroad, as there is no manufacturer in our country. Because of difficulties in the acquisition of spare pieces, these are usually improvised and manufactured informally. Regarding the classification of those 192 Ir exposure containers according to their mobility, they are all portable (class P). Referring to their classification according to the location of the source assembly when the apparatus is in the working position, almost all operate according to category II, i.e., the source assembly is mechanically projected out of the exposure container through a projection sheath. This last characteristic, besides the fact that the apparatus are already old-fashioned, worn-out and probably affected by long usage time, raises concerns about their radiological safety. Category II apparatus represent a worth considering potential risk of overexposing staff members. One aim of the present work was to assess the radiological safety of the 192 Ir apparatus in use in Brazil. A specific methodology for inspection, testing and evaluation of the state of maintenance of the apparatus was developed. The idea is to prevent accidents, as physical failures can lead to overexposure of working staffs. In order to accomplish this, Ir apparatus, from the 11 models in use in Brazil, were studied. Examples of those 11 models are in Fig. 1, according to the seven manufacturers. Figure 1. Examples of the 11 models of 192 Ir apparatus, according to the seven manufacturers.

3 Another goal was to assess the radiological safety of the 11 panoramic models of 192 Ir apparatus in use in Brazil. The 11 models were studied with respect to their compliance with the specific basic safety requirements of three editions of the international Standard ISO 3999 [4, 5, 6]. The Brazilian legislation in effect is based upon the first edition of ISO 3999 [4] in what concerns specifications for gamma radiography apparatus. Exposure containers are often designed as transport packages and are tested and certified to type B standards [7]. They must withstand severe impacts, crushing forces, immersion in liquids and heat stress without release of radioactive contents or significant loss of shielding [3]. The competent authority of the manufacturer s nation shall issue an approval certificate stating that the design meets the requirements for type B packages. The certificates are issued with a limited validity, usually 3 to 5 years. Those certificates must then be renewed by the competent authorities of both the manufacturer s nation and the destiny s nation. Thus, another target was to study the validity of the approval certificates for type B packages issued for the 11 models of panoramic 192 Ir apparatus in use in Brazil. 2. METHODOLOGY 2.1. Data Survey Data from the 11 models of 192 Ir apparatus were almost all collected at the headquarters of 14 operating organizations which render gamma radiography services to their clients in Brazil. These organizations generally use 192 Ir apparatus because they are portable and thus easier to travel throughout the country. The present work restricted itself to the study of the 11 models of category II, class P 192 Ir apparatus in usage in Brazil, namely OP-660 (AEA Technology QSA, Inc, 40 North Avenue, Burlington MA 01803, USA); NI-202 (Nucliber S.A., Hierro 9, Madrid, Spain), Iriditron 520 (Automation Industries Corp., P.O. Box 1876, Montrose, Colorado USA), SPEC 2-T (Source Production & Equipment CO., INC., 113 Teal Street, St. Rose, LA 70087, USA), Teletron SU-50 and SU-100 (MDS Nordion 100 International Blvd., Toronto, Ontario, Canada M9W 6J6), Gammamat TI; TI-F and TI-FF (MDS Nordion 100 International Blvd., Toronto, Ontario, Canada M9W 6J6) and Century GI-100 SA and GI-35 (Gamma Industries, AEA Technology QSA, Inc, 40 North Avenue, Burlington MA 01803, USA). Those 11 models totalized 239 apparatus in operation in our country Inspection and Evaluation of the State of Maintenance of Apparatus A specific methodology was developed for inspection, testing and assessment of the state of maintenance of the 192 Ir apparatus. The summarized methodology is presented in Table 1. A visual inspection of the general state of maintenance of the main devices and components of each apparatus was also performed during each evaluation. Through this method, Ir apparatus were evaluated. They belonged to the 14 operating organizations which render gamma radiography services in Brazil.

4 Table 1. Summarized methodology employed for evaluating the state of maintenance of the 192 Ir apparatus Components and accessories Possible faults Tests performed Exposure container Connectors between control cable and source assembly Projection sheath Exposure head Control mechanism Control cable Lock Cracks on the surface; Manufacturer s metallic plate or source information label loose or missing; Loose hook Wear and tear leading to smaller diameter Wrinkles, clogging, ruptures; Excessive bending Ruptures, wrinkles; Wear and tear; Bad connection Wear and tear; Stuck mechanism Frayed cable Damaged key or lock Visual inspection of internal cleanliness; Ambient equivalent dose-rate measurements taken on the surface Test using a specific Go no-go tool Tests with a metallic sphere that must slide smoothly internally Visual inspection Tests of the control mechanism Rubbing a tissue to check for fraying Visual inspection of cleanliness of the lock; Tests of the system 2.3. Conformity with the Main Safety Requirements of Standards ISO 3999 The 11 models were evaluated as belonging to one of three levels of conformity, listed below. This classification depends on whether the models incorporate or not the safety devices required by Standards ISO 3999 [4, 5, 6], concerning category II gamma radiography apparatus. The three levels of conformity are as follow: At the first level of conformity would be included the models which incorporate all the safety devices required by Standards ISO 3999 [5] or [6]. These main requirements are: (a) protective caps; (b) an integral lock with a key that cannot be withdrawn when the container is in the working position, (c) source position indicators clearly recognizable at a distance of 5 m (d) an additional automatic securing mechanism which guarantees that it is not possible to lock the exposure container unless the source assembly is in the secured position, and (e) three attachments must be made in order to release the source assembly from the secured position: between the control cable and the source assembly, between the control cable sheath and the exposure container, and between the projection sheath and the exposure container.

5 At the second level of conformity would be included the models which comply only with the requirements of the first edition of Standard ISO 3999 [4], and thus are in compliance with the Brazilian legislation in effect [8], as the latter was based on the former. The main safety requirements are simpler: (a) protective caps, (b) an integral lock with a key that cannot be withdrawn when the container is in the working position and (c) source position indicators, no mention of distances. At the third level of conformity would be included the models which do not comply with the requirements of any edition of the Standards ISO 3999 [5, 5, 6], and thus are not in compliance with the Brazilian legislation in effect [8] Analysis of Approval Certificates for Transport Packages Type B certificates for the 11 models of apparatus were analyzed, including issue date, revisions, expiry date and any reference relating to the obligation of an extraordinary special packaging or overpack. The IAEA publication Packtram [9] was consulted, and data about the certificates was also collected at the headquarters of the 14 operating organizations that render gamma radiography services. 3. RESULTS 3.1. Evaluation of the State of Maintenance of Apparatus Almost 20% of the 97 inspected apparatus demonstrated evidence of some kind of unsafe condition for proper operation. The total number of problems observed was 20, in Ir apparatus evaluated. At the exposure containers, 17 problems were observed: eight apparatus with poor state of maintenance (five Iriditron 520 and three NI-202); four with damaged lock (two Gammamat TI-F; one Teletron SU-100 and one NI-202, the latter also with the exposure container cracked); two apparatus with the source label loose or missing (one OP-660 and one Teletron SU-100); one with loose metallic plate (OP-660) and one with erosion of internal shielding (Iriditron 520). At the projection sheaths, three problems were observed: two apparatus with ruptured sheaths (two NI-202) and one with ruptured exposure head (Iriditron 520). No faults were observed at the control mechanisms and cables Compliance with the Main Requirements of Standards ISO 3999 The 11 models were evaluated as belonging to one out of three levels of conformity, as previously described. Details of the evaluation of the 11 models regarding their compliance with three specific editions of Standards ISO 3999 [4, 5, 6], and also with the Brazilian legislation having legal efficacy [8], are presented in Tables 2, 3 and 4. At the first level of compliance were included the models which comply with the safety requirements of Standards ISO 3999 [5] or ISO [6]. None of the 11 models could be included at this level. At the second level of compliance were included the models which comply only with the requirements of ISO 3999 [4], and consequently with the Brazilian legislation in effect [8]. Six models Gammamat (TI; TI-F; TI-FF), OP-660 and Teletron (SU-50; SU-100) were included at this level, which represents 70% of the 239 apparatus in use in Brazil.

6 Table 2. Evaluation of the 11 models of 192 Ir apparatus regarding three editions of Standards ISO Ir models Requirements of ISO 3999 [4] and Brazilian legislation [8] Protective caps (front and back) Source position indicator Integral lock with key Additional requirements of ISO 3999 [5, 6] Additional lock Three needed connections Automatic securing mechanism Source position indicator clearly visible at 5 m Gammamat (TI, TI-F, TI-FF) Y Y Y S N N Y OP-660 Y Y Y S N N N Teletron (SU-50, SU-100) Y Y Y S Y N N Century (GI-100 SA, GI-35) Y N Y N N N N Iriditron 520 Y N Y N N N N NI-202 Y N Y N N N N SPEC 2-T Y N Y N N N N Y = yes; N = no Table 3. Summary of models which comply or not with Standards ISO 3999 Models ISO 3999 [4] and Brazilian legislation [8] ISO 3999 [5] or ISO [6] Gammamat (TI; TI-F; TI-FF) Y N OP-660 Y N Teletron (SU 50; SU 100) Y N NI-202 N N SPEC-2T N N Iriditron 520 N N Century (GI-100 SA; GI-35) N N Y = yes; N = no Table 4. Evaluation of 11 models according to three levels of radiological security First level: Models complying with Standards ISO 3999 [5, 6] None Second level: Models complying with Brazilian legislation [8] Gammamat (TI, TI-F, TI-FF) OP-660 Teletron (SU 50, SU 100) Third level: Models not complying with Brazilian legislation [8] Century (GI-100 SA, GI-35) SPEC-2T Iriditron 520 NI-202

7 At the third level of compliance were included the models which do not comply with ISO 3999 [4], and consequently neither with the Brazilian legislation having legal efficacy [8]. Five models Century (GI-100 SA; GI-35), SPEC 2-T, Iriditron 520 and NI-202 were included at this level, which represents 30% of the 239 apparatus of 192 Ir in usage in Brazil Analysis of Certificates for Type B Packages The regulatory authorities of the manufacturer s nation and also of destiny s nation shall periodically revalidate certificates for transport packages. The Brazilian regulatory authority (CNEN, National Commission of Nuclear Energy) does not issue certificates for transport packages, neither revalidates the already existing ones. Thus, the validity of type B approval certificates issued by the manufacturer s nation for the 11 models of apparatus was analyzed. The certificates are listed in Table 5. Table 5. Models with their respective Type B certificates for transport package Model Certificate Number of revalidation Validity (dd/mm/yyyy) Additional requirement Iriditron 520 USA/9007/B Expired Century GI-100 SA USA/6717/B (U) 13 30/11/2003 a Y b Century GI-35 USA/6717/B (U) 13 30/11/2003 a Y b NI-202 c E/001/B (U) 12 31/12/2004 Y b SPEC-2T USA/9056/B (U) 11 30/04/2005 Y b Gammamat TI D/2011/B (U) /12/2006 N Gammamat TI-F D/2012/B (U) /12/2006 N Gammamat TI-FF D/2013/B (U) /12/2006 N Teletron SU 50 D/2022/B (U) /01/2007 N Teletron SU 100 D/2023/B (U) /01/2007 N OP-660 d USA/9283/B (U) /06/2008 Y b Y = yes; N = no; a Certificate not renewed; b Special packaging (overpack); c Named ENI-202 because of the overpack; d Named OPL-660 because of the overpack and new certificate. For the model Iriditron 520, the certificate has already expired. This represents 17% of the 239 apparatus in usage in Brazil. For models Century (GI-100 SA; GI-35), their certificates had not been renewed yet.

8 For the models Century (GI-100 SA; GI-35), NI-202, SPEC-2T and OP-660, the certificates have been revalidated with extra exigencies by the competent authority of the manufacturer s nation. This represents 59% of the 239 apparatus. The main exigency is of a special packaging, i.e., an overpack with specified dimensions, with internal filling for absorbing mechanical shocks. For the models Gammamat (TI, TI-F; TI-FF) and Teletron (SU 50; SU 100), their certificates were approved by the manufacturer s nations without any extra exigencies. This represents 24% of the 239 apparatus studied at the present work. 4. CONCLUSIONS Almost 20% of the 97 inspected apparatus demonstrated evidence of some kind of unsafe condition for proper operation. The operating organizations that render gamma radiography services in Brazil should establish a programme for preventive and corrective maintenance of the apparatus, similar to the methodology presented at this work. Only the models Gammamat (TI, TI-F; TI-FF), OP-660 and Teletron (SU 50; SU 100) incorporate the basic safety devices required by the Brazilian legislation in effect [8], which is based on the specifications of the first edition of the international Standard ISO 3999 [4]. This represents 70% of the Ir apparatus in usage in Brazil. The models Century (GI-100 SA; GI-35), SPEC-2T, Iriditron 520 and NI-202 do not even incorporate all the basic safety devices specified by ISO 3999 [4]. Thus, they also do not comply with the Brazilian legislation in effect [8], being considered improper for safe use. This represents 30% of the 239 apparatus. None of the 11 models in usage in Brazil comply with all newer requirements of the latest editions of Standards ISO 3999 [5, 6]. It is worth mentioning that this same situation of non-conformity may be occurring abroad, particularly in other nations from Latin America. The Brazilian regulatory authorities (CNEN - National Commission of Nuclear Energy and ABNT - Brazilian Association for Standardization) should bring up to date the national specific legislation, in order to adjust it to the newer requirements of ISO [6]. After doing so, CNEN should progressively remove from service and circulation those apparatus that do not comply with the national legislation that will be in effect. To achieve this, CNEN could progressively reduce the maximum activity that can be loaded in the models improper for safe use. In the first year this reduction could be of 50% and, from this on, the reduction could be of 20%, every other year. This would make impracticable the use of such inappropriate models. ACKNOWLEDGEMENTS The authors are grateful to all of those who, direct or indirectly, collaborated to this work.

9 REFERENCES 1. Aquino, J.O., Avaliação das condições de segurança radiológica de irradiadores portáteis panorâmicos de gamagrafia industrial utilizados no Brasil, Master s dissertation, Instituto de Radioproteção e Dosimetria, IRD/CNEN, Rio de Janeiro, Brazil, 100 p (2003). 2. IAEA (International Atomic Energy Agency), Lessons learned from accidents in industrial radiography, Safety Report Series No. 7, STI/PUB/1058, Vienna, 57 p (1998). 3. IAEA (International Atomic Energy Agency), Radiation protection and safety in industrial radiography, Safety Report Series No. 13, STI/PUB/1066, Vienna, 61 p (1999). 4. ISO (International Organization for Standardization), Apparatus for gamma radiography Specification, International Standard ISO 3999, first edition, Switzerland, 28 p (1977). 5. ISO (International Organization for Standardization), Apparatus for industrial gamma radiography Design and test criteria, International Standard ISO 3999, revision of first edition, Switzerland, 29 p (1997). 6. ISO (International Organization for Standardization), Apparatus for industrial gamma radiography. Part 1: Specifications for performance, design and tests. International Standard ISO , Switzerland, 31 p (2000). 7. IAEA (International Atomic Energy Agency), Regulations for the safe transport of radioactive material 1996 Edition (Revised) Requirements, Safety Standards Series TS-R-1 (ST-1, Rev.), STI/PUB/1098, Vienna, 220 p (2000). 8. ABNT (Associação Brasileira de Normas Técnicas), Equipamento de Radiografia Gama Especificação, NBR 8670, Brasil (1984). 9. IAEA (International Atomic Energy Agency), Directory of national competent authorities' approval certificates for package design, special form material and shipment of radioactive material, IAEA-TECDOC-1302, Vienna, 113 p (2002).