Non-Destructive Testing (NDT) techniques has been applied in the study of antiquities to check and detect the defects such as cracks, porosity, slag inclusion, lack of fusion, lack of penetration in welds, delamination of materials, ... without destroying them. When an X-ray generator is used for these tests, the image quality depends heavily on the ability of X-rays to penetrate through the imaging materials.
Tiểu ban D2: Ứng dụng kỹ thuật hạt nhân công nghiệp lĩnh vực khác Section D2: Application of nuclear techniques in industries and others XÂY DỰNG GIẢN ĐỒ CHIẾU ĐỂ CHỤP CỔ VẬT BẰNG ĐỒNG TRÊN MÁY PHÁT TIA-X RIGAKU–200EGM DEVELOPMENT OF EXPOSURE CHART FOR RIGAKU X-RAY GENERATOR- 200EGM TO DETECT THE DEFECTS INSIDE BRONZE ANTIQUITIES PHAM XUAN HAI, LE VAN NGOC, PHAM QUYNH GIANG Dalat Nuclear Research Institute, No 01 Nguyen Tu Luc Street, Dalat, Lamdong Email: phamxuanhai2007@yahoo.com Abstract: Non-Destructive Testing (NDT) techniques has been applied in the study of antiquities to check and detect the defects such as cracks, porosity, slag inclusion, lack of fusion, lack of penetration in welds, delamination of materials, without destroying them When an X-ray generator is used for these tests, the image quality depends heavily on the ability of X-rays to penetrate through the imaging materials Therefore, it is important to determine the optimal exposure dose and imaging parameters for each type of materials to achieve the best results In this study, we developed the optimal exposure chart for bronze materials on the Rigaku-200EGM X-ray generator The obtained results will be applied in research on defects inside bronze antiquities as well as in NDT research and training in the Training Center at Dalat Nuclear Research Institute Keywords: No-destructive testing, defects inside antiquities, X-ray generator, exposure chart Tóm tắt: Ứng dụng kỹ thuật kiểm tra không phá hủy (Non-Destructive Testing - NDT) kiểm tra phát khuyết tật vết nứt, rỗ xé, ngậm xỉ, không ngấu, không thấu mối hàn, tách lớp vật liệu vật kiểm,… mà không làm tổn hại đến chúng ứng dụng nghiên cứu cổ vật Nếu sử dụng máy phát tia-X kiểm tra chất lượng kiểm tra phụ thuộc nhiều vào khả xuyên sâu tia-X qua vật liệu chụp, để xác định liều chiếu, chế độ chiếu chụp cho loại vật liệu máy chụp quan trọng để có kết tốt Mục tiêu nghiên cứu xây dựng giản đồ chiếu tối ưu vật liệu đồng có chiều dày từ 1mm đến 20mm máy phát tia-X Rigaku-200EGM thử nghiệm xác định khuyết tật hai loại tượng đồng Từ khóa: Kiểm tra khơng phá hủy, khuyết tật bên cổ vật, máy phát tia X, giản đồ chiếu INTRODUCTION In recent years, X-ray radiography has made an important contribution to archeology, which helps us see the interior of an object and identify any invisible cracks or holes Because of its availability, it can help archaeologists and restorers in the historical restoration and preservation and contribute to the dissemination of cultural information The capabilities of an industrial X-ray generator depend on its power, which depends on the maximum voltage of the generator In radiography, the exposure dose of a generator depends on voltage, amperage and exposure time The voltage value determines the strength and weakness of the emitted X-ray beam, which characterizes how deep the X-ray can penetrate through an object The product of the amperage and the exposure time determines the density of the emitted X-ray beam, which characterizes the intensity of the X-ray beam Therefore, an exposure chart is often built and used RIGAKU – 200EGM X-ray generator is donated to the Training Center for teaching and scientific research by Japan To exploit the device effectively, it is very important to build exposure charts for different types of materials according to different voltages Based on the exposure chart, the radiographers can easily select the necessary and optimal conditions for taking an X-ray of different objects Bronze and copper alloys are a common subject in radiography because they are relatively popular materials in welds and castings [1] Therefore, we built the exposure charts for bronze standard samples with the thickness range from 1mm to 20mm and voltages of 70kV, 80kV and 90kV EXPERIMENTAL 2.1 Experiment on RIGAKU X-Ray generator Experiments to build exposure charts to determine the time and voltage suitable for different thicknesses of materials were conducted on the RIGAKU-200EGM X-ray generator using Fuji #100 film in the Training Center at the Nuclear Research Institute Experiments in this study were only conducted in 478 Tuyển tập báo cáo Hội nghị Khoa học Cơng nghệ hạt nhân tồn quốc lần thứ 14 Proceedings of Vietnam conference on nuclear science and technology VINANST-14 the laboratory and arranged based on the single-wall single-image technique X RIGAKU equipment was made in Japan with specifications as follows: - Beryllium window ceramic X-ray tube (Beryllium thickness: 1mm) - X-ray filter: Aluminum thickness: mm (replaceable) - X-ray tube output voltage: (70kV-200kV) - The current of X-ray tube: 5mA - Effective target size: 2mm x 2mm The distance between the X-ray tube head and the sample varies from 50cm - 80cm and the radiographing angle is 450 Therefore, we can easily change the voltage, distance, radiographing angle and exposure time to meet the requirements for each sample The X-ray tube is placed in a room with the dimensions of 2.5m x 3.2m and is separated by a 20cm-thick concrete wall to ensure the radiation dose is below the permissible level for the operators in the control room The remaining surrounding walls are also thick enough to ensure radiation protection with the dose rate less than 0.5µSv/h when the X-ray generator is in operation The dose rate at the operating position when the device is off is 0.14µSv/h 2.2 Experimental arrangement for building exposure charts Figure 1: Imaging sample and film Figure 2: Bronze samples for examination To construct the exposure charts, bronze reference samples with different thicknesses were used Each sample was imaged at different voltages The distance between the sample and the tube head was changed to choose the right distance so that the film can achieve a density of 1.5-3.3, a sensitivity of 2% or less, and a high contrast of 0.09-0.16 After choosing the right distance, samples were imaged with different exposure times Film after exposure was processed at the temperature of 20-220C to determine the density In this experiment, films with density D of was selected to build the exposure chart Figure shows the layout of the sample, film and X-ray tube for single-wall, single-image technique Figure shows the bronze samples with the dimensions of 10cmx10cm, thickness from mm to 20 mm [4] 2.3 Results obtained for voltages of 70kV, 80kV and 90kV First, take some X-ray pictures to determine the suitable source-to-film distance (SFD) for the bronze samples with a thickness of 1mm and exposure time of seconds to achieve a density D of This experiment was conducted with the SFD of 50cm, 60cm, 70cm and 80cm Exposure times for each SFD distance were 6s, 12s, 18s and 24s respectively Process the film at the temperature of 20 – 220C and determine the density The results after processing the film are given in Table Table 1: Exposure time, T(s) for bronze samples with different thickness and voltages at the distance of 70 cm to obtain the density ( D) of Voltage 80kV d (mm) 70kV 3.42 4.03 2.67 2.97 479 90kV 1.66 1.92 Tiểu ban D2: Ứng dụng kỹ thuật hạt nhân công nghiệp lĩnh vực khác Section D2: Application of nuclear techniques in industries and others 10 11 12 13 14 15 16 17 18 19 20 4.59 4.95 5.68 6.29 7.30 7.95 9.20 10.19 11.26 12.84 14.88 16.65 18.61 21.45 24.31 27.26 30.67 34.48 3.17 3.81 4.34 4.91 5.50 6.28 7.07 8.11 9.39 10.78 11.47 13.59 15.06 17.45 19.83 22.30 25.69 28.41 2.48 2.81 2.88 3.39 4.07 4.39 5.22 6.04 6.63 7.44 8.43 9.86 10.79 12.89 14.34 16.53 18.56 21.24 From the obtained data, we built the exposure charts in Figure 3, and at the voltages of 70kV, 80kV and 90kV with the distance of 50cm, 60cm, 70cm and 80cm and we obtained the desired density D of 2.The distance of 70cm in agreement with the standards for density, sensitivity and contrast was selected for the next experimental steps Experiment to determine the sensitivity was carried out by imaging samples of different thickness using image quality indicators of the American Society for Testing Materials (ASTM) The measured data on the processed film are shown in Figures 4, and Select the IQI kit suitable for the sample thickness to achieve the best sensitivity less than 2% of the sample thickness according to the radiographic standard Exposure time (s) 100 Sensitivity (%) y = 3.0904e0.1205x R² = 0.999 10 y = 0.013x3 + 0.282x2 - 2.520x + 10.75 R² = 0.981 10 15 Sample thickness (mm) 20 Figure 3: Exposure chart for bronze material at the voltage of 70kV Sample thickness Figure 4: Sensitivity at the voltage of 70kV R² = 0.999 sensitivity (%) Exposure time (s) y = 2.2846e0.1267x y = -0.004x3 + 0.207x2 - 2.818x + 14.80 R² = 0.964 10 15 Sample thickness (mm) 20 Sample thickness(mm) Figure 5: Exposure chart for bronze material at the voltage of 80kV 480 Figure 6: Sensitivity at the voltage of 80kV Tuyển tập báo cáo Hội nghị Khoa học Cơng nghệ hạt nhân tồn quốc lần thứ 14 Proceedings of Vietnam conference on nuclear science and technology VINANST-14 y = 1.5619e0.1309x Sensitivity (%) Exposure time (s) R² = 0.998 y = -0.006x3 + 0.273x2 - 3.837x + 18.89 R² = 0.977 10 15 Sample thickness (mm) 20 Sample thickness (mm) Figure 7: Exposure chart for bronze material at the voltage of 90kV Figure 8: Sensitivity at the voltage of 90kV 100 70kV 80kv 90kV Exposure time (s) Phim : Fuji# 100 Màn tăng cường : Màn chì 0.03 mm 10 10 Sample thickness (mm) 15 20 Figure 9: Exposure chart for bronze material at the voltage of 70 kV, 80 kV, and 90 kV, SFD = 70 cm The results of exposure time, sample thickness and voltage obtained at a fixed distance between the film and the X-ray tube head are in agreement with the technical documentation of the generator in particular and the radiographic method in general From the obtained charts, the radiographers can easily determine the time, distance and voltage for the bronze samples to be imaged with different thicknes when using Fuji #100 film Figure 10: X ray image of 2mm-thick bronze sample at the voltage of 70kV; SFD = 70cm Figure 11: X ray image of 2mm-thick bronze sample at the voltage of 70kV; SFD = 70cm 481 Tiểu ban D2: Ứng dụng kỹ thuật hạt nhân công nghiệp lĩnh vực khác Section D2: Application of nuclear techniques in industries and others Figure 12A: Antique bronze statue Figure 12B: X ray image of a bronze statue Figure 13A: Antique bronze statue Figure 13B: X ray image of a bronze statue From the built-in exposure chart, tests were conducted to determine the defects inside two types of bronze statues (Figure 12A and 13A) as well as the uniformity of the specimen (Figure 12B and 13B) From the Figure 12B, we can see that the density of the statue is uniform and there are no defects inside the statue From Figure 13B, it can be seen that the different density of the statue means non-uniform thickness The head of the statue is thicker than the body; the body of the statue has cracks and porosities inside 2.4 Assessment of radiation dose and safety To ensure radiation protection during the experiment, the dose rate distribution was checked and evaluated during the operation We used the Aloka TCS 172 dosimeter to measure the dose rate in the generator area The values of dose rates at different positions on the walls in room shown in Figure 14 have been checked when the generator in operation at the maximum voltage of 200kV: Figure 14: Diagram for dose rate (µSv/h) at different positions on the wall in room No1 when the X-ray generator is in operation at the maximum voltage of 200kV The obtained data on radiation dose rate inside and outside the X-ray room is quite low compared to current Vietnamese standards for radiation protection, which is less than 0.5 μSv/h The dose is 0.24 μSv/h at the operating seat 2.5 Discussion The obtained results of exposure time, sample thickness and voltage at fixed distance between film and tube head are in agreement with the technical documentation of X-ray generator in particular and the X-ray radiography method in general Based on the results, the radiographers can easily determine the time, distance and voltage value to be applied to the bronze samples to be imaged with different thickness when using Fuji #100 film The obtained exposure charts has been practically applied to check the bronze statues to determine their defects and homogeneity as shown in Figure 12A Based on the interpretation of the processed film, we can see that the statue has an uneven thickness and the head of the statue is thicker than the body There are cracks and porosities in the body of the statue The results give us an accurate assessment of the quality of the statue From Figure 13A, we can see that the density of the statue is uniform and there are no defects inside 482 Tuyển tập báo cáo Hội nghị Khoa học Công nghệ hạt nhân toàn quốc lần thứ 14 Proceedings of Vietnam conference on nuclear science and technology VINANST-14 CONCLUSION The suitable exposure charts (time, voltage and distance) for bronze samples with thickness from 1mm to 20mm using RIGAKU–200EGM generator and Fuji film #100 is obtained in this study The charts also help students and trainees easily choose the optimal exposure conditions when practicing radiography In the future, we will build exposure charts at higher voltages for thicker bronze samples to be able to exploit the device more and more effectively in training, research and development REFERENCES [1] Baldev Raj, T Jayakumar, M Thavasimuthu (1997) Practical nondestructive testing Narosa Publishing house – NewDelhi Madras Bombay Calcutta Lodon [2] Đao Quang Long, Nguyen Quang Hai (1998) Material testing by level radiographic technique Vienna, IAEA technical document [3] Norikazu OOKA, Toshihiro OHBA (2007) Radiography testing 1th VAEC-JAEA Joint Training Course on Application of Nuclecar Technique in Industry and Environment [4] Training Center, Nuclear Research Institute (2019) Experiment on industrical radiography, lecture and experimental guidance 483