CRYSTAL GLASS USED FOR X RAY AND GAMMA RADIATION SHIELDING PART TWOTITLE OF THE PAPER

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1 2007 International Nuclear Atlantic Conference - INAC 2007 Santos, SP, Brazil, September 30 to October 5, 2007 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: CRYSTAL GLASS USED FOR X RAY AND GAMMA RADIATION SHIELDING PART TWOTITLE OF THE PAPER Antonio Filho, João 1,2 ; Almeida Jr., Airton T. 1 ; Luiz A. P dos Santos 1 Departamento de Energia Nuclear - Universidade Federal de Pernambuco Av. Prof. Luiz Freire n o 1000, Recife - Brasil jaf@ufpe.br 2 Departamento de Física Universidade Católica de Pernambuco Rua do Príncipe n o 526, Recife- Brasil jaf@unicap.br 3 Centro Regional de Ciências Nucleares CNEN Av. Prof. Luiz Freire s/n, Recife - Brasil ABSTRACT Crystal glass has been widely used as shielding material in gamma radiation sources as well as x-ray generating equipment to replace the plumbiferous glass, in order to minimize exposure to individuals. However, properties of the radiation attenuation of crystal glass commercially available in Brazil, for the different types of energy are not known. For this reason, this work was carried out aiming to determine the radiation attenuation, transmission curves and Half Value Layer. In this work, ten plates of crystal glass, with dimensions of 20cm x 20 cm and range of thicknesses from 0.5 to 2.0 cm, were used. The plates were X-ray irradiated with potential constants of 60, 80, 110, 150 kv and gamma radiation of 60 Co. Analysis in the properties of the 60 Co radiation attenuation of barite plaster and barite concrete commercially available in Brazil were also carried out. The curves of attenuation and of transmission were obtained for crystal glass, barite plaster and barite concrete (mgy/ma.min) at 1 meter as a function of thickness. The thickness equivalent of a half value layer and deci value layer of crystal glass for all types of radiation and energies studied was also determined. 1. INTRODUCTION Crystal glass and the barite plaster and barite concrete has been largely used as shielding material in installations housing gamma radiation sources as well as x-ray generating equipment, in order to minimize exposure to individuals. Crystal glass is a compound of nefetina, sienita, oxalato ferroso, petalita, pirita, nitrato de sódio, selêncio, soda cáustica, sulfato de sódio, óxidos de silício, chumbo, antimônio, cobalto, cuproso, níquel, zinco and the barite plaster and barite concrete are compounds of cement, sand, barium sulfate and water. The knowledge of the physical characteristics crystal glass and the barite such as density, the degree of radiation attenuation and composition, granulometry, plasticity, density, resistance to compression and the degree of radiation attenuation for the different types of barite plaster and barite concrete commercially available in Brazil respectively are very important when dealing with shielding calculations for both medical and industrial

2 installations. This work was carried out aiming to determine the transmission and attenuation factors as well as the thickness equivalent of a half value layer and deci value layer for different X ray energies and gamma radiation of 60 Co. 2 METHODOLOGY The chemistry composition of the crystal glass, the barite plaster and barite concrete are indicated in the table 1 and 2. The samples were prepared in rectangular plate format with dimensions of 30 cm x 30 cm with thicknesses varying from 1cm to 20 cm and exposed to X- ray beams generated by the voltages and 60 Co, as illustrate in table 3, with constant current of 10 ma in a secondary laboratory, with a Pantax type X-ray apparatus. The rate of kerma in air was measured with farmer type dosimeter and ionization chamber of 0.6 cc at a distance of 1 meter from the source of radiation. The thickness above 20 cm were obtained by modifying the components in the conglomeration (e.g. Mixture I one part of cement + two parts of fine sand part of water + three parts of BaSO 4 ). In figures 1, 2 and 3 the attenuation curves are presented in function of the thickness for different compositions of barite plaster traces I; traces II; concrete traces III. Theses curve can be too used to determine the thickness of wall coverings facing the primary and secondary beams in order to conform to the desired level of radiation in a radio diagnostic installation.the table. 3 RESULTS In figures 1, 2 and 3 the attenuation curves are presented in function of the thickness for different compositions of barite plaster traces I; traces II; concrete traces III. Theses curve can be too used to determine the thickness of wall coverings facing the primary and secondary beams in order to conform to the desired level of radiation in a radio diagnostic installation. Tabela 1 Cristal glass característical CRISTAL GLASS THICKNESS (cm) % Ce % other Composition* Crystal glass 0,5 99,5 1,0 2,0 3,0 4,0 * Nefetina, Sienita, Oxalato Ferroso, Petalita, Pirita, Nitrato de Sódio, Selêncio, Soda Cáustica, Sulfato de Sódio, Óxidos de Silício, Chumbo, Antimônio, Cobalto, Cuproso, Níquel, Zinco. Table 2 Composition of barite plaster and concrete Composition of Barite Composition BaSO 4 (g) Cement (g) Sand (g) Water ml) Barite stones(g) Density(g/cm 3 ) Mixture I ± 0.12 Mixture II ± 0.10 Mixture III ± 0.03

3 Table 3 - Quality specification of the X- ray and 60 Co ISO quality Effective energy kilovolt Inherent filtration mm Al Additional filtration 1ª CSR mm Cu 2ªCSR mm Cu W60 45 kev 60 kv ,297mm Cu W80 57 kev 80 kv ,507mm Cu W kev 110 kv ,988mm Cu W kev 150 kv ,030mm Sn Co 1250 kev Tabela 4 Half value layer and deci value layer for different X ray energies and gamma radiation of 60 Co. RESULT LITERATURE RESULT barite plaster concrete cristal glass hvl (cm) - mixture tvl (cm) - mixture tensão hvl (cm) tvl (cm) hvl (cm) tvl (cm) 1,91 1,95 2,26 1,91 1,95 2,26 g/cm 3 g/cm 3 g/cm 3 g/cm 3 g/cm 3 g/cm 3 Tensão I II III I II III 2,35 g/cm 3 2,08 g/cm 3 60 kv 0,36 0,35 0,35 1,20 1,20 1,20 50 kv 0,43 1,50 0,79 2,50 80 kv 0,61 0,60 0,57 2,00 2,00 1,90 70 kv 0,84 2,80 1,20 3, kv 0,93 0,94 0,86 3,10 3,10 2, kv 1,60 5,30 1,30 4, kv 1,50 1,50 1,40 5,00 5,10 4, kv 2,24 7,40 1,80 6,10 60 Co 6,70 6,90 5,90 22,30 22,90 19,80 60 Co 6,90 20,60 5,60 18,70 Figure 1 - Attenuation curves obtained for crystal Glass X-ray irradiated with potential constants of 60, 80, 110, 150 kv and density of ρ = 2,08 g/cm 3 respectively.

4 Figure 2 - Attenuation curves obtained for barite plaster X-ray and crystal glass, irradiated with 60 Co, with density of 1.95 g/cm 3 and 2.05 g/cm 3 respectively. Figure 3 Transmission curves obtained for barite plaster X-ray and crystal glass, irradiated with 60 Co, with density of 1.95 g/cm 3 and 2.05 g/cm 3 respectively.

5 Figure 4 Transmission curves obtained for crystal glass X-ray irradiated with potential constants of 60, 80, 110, 150 kv, and density of 2,05 g/cm 3. 4 CONCLUSIONS According to the results presented in the work, it can be concluded that: - The attenuation and transmission curves, and thicknesses of the semi and deci-reduced layers are rare for the barite plaster, barite concrete and crystal glass types of materials studied, although their use permits the dimensioning of the armor covering for external x- radiation whit precision and safety without elevating the cost of protection; - The dimensioning and wall coverings against external X-radiations and 60 Co carried out by the equivalent thickness method, overestimates the valve of the armour covering thicknesses, resulting in an elevation in the cost of protection and a structural overloading of the installation building..

6 REFERENCES 1. ANTONIO FILHO, J. et al., Physical Characteristics of barite plaster Used X-Ray Shielding Part One, IN 11 TH INTERNATIONAL CONGRESS OF THE INTERNATIONAL RADIATION PROTECTION ASSOCIATION, 2004, Madrid. IRPA - Send editorial S.A.; Electronic CD. 2. DOUGLAS J. SIMPKIN, General solutions to the shielding of medical X and γ ray by the NCRP report 49 methods, Health Physics, V. 52, n.4, p , JAEGER, R.G.; BLIZARD, E. P.; CHILTON, A. B.; GROTENHUIS, M.; HÖNIG, A.; JAEGER, T.H. A; EISENLOHR, H. H. Engineering Compendium on Radiation Shielding, Springer-Verlag, New York, NATIONAL COUNCIL ON RADIATION PROTECTION AND MEASUREMENT, REPORT 49: Structural Shielding Design and Evaluation for medical use of x rays of energies up to 10 MeV, CEMBER H. Introduction to Health Physics, USA: Pergamon Press, FALCÃO, B. Materiais de construção. Ed. Livro Técnico S.A., Rio de Janeiro, ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, Procedimento de preparo, aplicação e manutenção de paredes e tetos com argamassas e materiais. NBR 7222, Rio de Janeiro, ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS, Método de ensaio de confecção e cura de corpos de prova cilíndricos e prismáticos. NBR 5738, Rio de Janeiro, ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. Ensaio de compressão de corpos de prova cilíndricos e prismátic, NBR 5739, Rio de Janeiro, BLACK, G. R. Methods of Soil Analysis, Madison, EMBRAPA. CENTRO NACIONAL DE PESQUISA DE SOLOS. Manual de métodos de análise de solo, Rio de Janeiro, INTERNATIONAL ORGANIZATION FOR STANDARDIZATION. X and gamma reference radiations for calibrating dosimeters and dose rate meters and determining their response as a function of photon energy, part 1: Radiation characteristics and production methods. ISO , Vienna, 1996.