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Qualification of ITER PF6 helium inlet
Fusion Engineering and Design 134 (2018) 1–4
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Qualification of ITER PF6 helium inlet a,b
a,⁎
a
T a
c
c
Shuangsong Du , Wei Wen , Guang Shen , Jijun Xin , Kevin Smith , Carlo Sborchia , Peter Readmanc, Yuntao Songa, WeiYue Wua, Huan Wua a b c
Institute of Plasma Physics, Chinese Academy of Science, Hefei, China University of Science and Technology of China, Hefei, China Fusion for Energy, Barcelona, Spain
A R T I C LE I N FO
A B S T R A C T
Keywords: PF6 coil Helium inlet Automatic welding Fatigue test
The Poloidal Field (PF) coils are one of the main sub-systems of the ITER magnets. The PF6 coil is being manufactured by the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) as per the Poloidal Field coils cooperation agreement signed between ASIPP and Fusion for Energy (F4E). As one of the critical components, helium inlet locates on the innermost turn and supplies the coil with supercritical helium. During Tokamak operation, the helium inlet will undergo huge cyclic electromagnetic loads and thermal cycling during cooling down and warming up. This paper focus on the main steps of ITER PF6 helium inlet qualification. Helium inlet hole drilling and stainless steel wrapping removal were firstly been carried out. Helium inlet welding with full penetration by automatic welding machine was then performed, followed by leak proof test, non-destructive test, fatigue test and tomography test. At the end, the samples were sectioned for micro and macro inspection. The results show ITER PF6 helium inlet qualification has successfully met the requirements of PF procurement agreement(PA) and was approved by ITER IO.
1. Introduction The ITER PF system consists of 6 solenoidal coils, PF1 to PF6 (as shown in Fig. 1), which serve to shape and stabilize the position of the plasma in the Tokamak. The PF coils are all wound with NbTi conductors, and range in diameter from ∼8 m to ∼ 24 m. ITER PF6 winding pack is composed by stacking of 9 double pancakes. The double pancakes are wound in a “two-in-hand” configuration. Two conductors are wound together to form a pancake layer with winding down from” outside-in” in one layer, and “inside-out” on the other. The two layers are connected by superconducting joint to form a double pancake. Joggling is needed in each layer to accomplish the proper positioning of the conductors during winding, as well as a joggle to make the transition from one layer to the next [1–3]. Each double pancake is supplied with supercritical helium by two inlet parts locate on the innermost turn, in the middle of the vertical joggles, as shown in Fig. 2. Located in the high magnetic field region, the helium inlet will undergo huge cyclic electromagnetic loads and thermal cycling during Tokamak operation [4]. Full penetration weld under monitored welding temperature (below 250 ℃ to avoid strands degradation) is the primary requirement. According to the PA, full size samples to form the
⁎
Corresponding author. E-mail address: [email protected] (W. Wen).
https://doi.org/10.1016/j.fusengdes.2018.06.010 Received 23 April 2018; Received in revised form 2 June 2018; Accepted 12 June 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
helium inlet shall be manufactured fully replicating the production conditions in order to qualify the manufacturing process, before it is applied on the dummy and series double pancakes winding. This paper focus on the main steps of ITER PF6 helium inlet qualification. During qualification process, helium inlet hole drilling and stainless steel wrapping removal were firstly been carried out. Helium inlet welding with full penetration by automatic welding machine was then performed, followed by leak proof test, non-destructive test, fatigue test and tomography test. At the end, the samples were sectioned for micro and macro inspection. 2. Qualification of ITER PF6 helium inlet The requirements of the ITER PF6 helium inlet manufacturing are listed in Table 1. 3 samples were manufactured for the qualification of ITER PF6 helium inlet. The strategies for each sample are as follows: Sample #1: Welding → Visual inspection → Leak test → PT test → Xray test → 5 cool-down cycles at 77 K (thermal shock) → Leak test → Tomography inspection → Sectioning → Visual and microscopic inspections. Sample #2: Welding → Visual inspection → Leak test → PT test → X-
Fusion Engineering and Design 134 (2018) 1–4
S. Du et al.
Fig. 4. Thermocouples planting. Fig. 1. The PF system of ITER magnet.
Fig. 5. Automatic welding machine.
Fig. 2. Two-in-hand winding configuration.
Table 1 ITER PF6 helium inlet requirement. Item
Requirement
Temperature control Weld joint
Cable temperature shall remain below 250 °C
Leak rate Fatigue test
Full penetration (ISO 5817_B level) < 10−9 Pa*m3*s−1, under 3 MPa 77 K, strain range 9.5 × 10−5–9.5 × 10−4 during 600,000 cycles or 1.9 × 10−4–1.9 × 10−3 during 30,000 cycles.
Fig. 6. Temperature curve of welding.
Tomography inspection. Among them, Sample #3 is a backup of sample #2, in case sample #2 failed during fatigue test. If sample #2 survived in fatigue test, no tomography inspection and following tests will be performed on Sample #3. Sample #1 was bent to the internal radius of the double pancake, simulating geometry of the turn. Samples #2 and #3 were straight. All the manufacturing of the above qualification samples started with helium inlet hole drilling by a portable milling machine and stainless steel wrapping manual removal, shown in Fig. 3. The clearance of the hole root is vital to reduce the stress concentration and pressure drop. Welding temperature measurement on the cable was required on sample #1. To do this operation, 6 thermocouples were planted from the back, as shown in Fig. 4. The thermocouple joints were planted under the weld in the point of the highest temperature during welding.
Fig. 3. Helium inlet hole drilling and wrap removal.
ray test → 5 cool-down cycles at 77 K (thermal shock) → Leak test → Fatigue test at 77 K → Leak test. Sample #3: Welding → Visual inspection → Leak test → PT test → Xray test → 5 cool-down cycles at 77 K (thermal shock) → Leak test → Tomography inspection → Fatigue test at 77 K → Leak test → 2
Fusion Engineering and Design 134 (2018) 1–4
S. Du et al.
Fig. 7. 7 layers of helium inlet weld joint. Fig. 10. Tomography test in CERN.
Fig. 8. Visually check of first layer welding.
Fig. 11. Sample #1 macro inspection.
Fig. 12. Sample #1 micro inspection.
surface, leak test(N/A for sample #1), PT and x-ray test were been performed. The leak rate was one order lower than the requirement. For the full penetration and coverage of x-ray, 12 shots were taken, as shown in Fig. 9. After x-ray test, thermal shock test and leak test again, sample #1 was sent to CERN for tomography test. No non-acceptable defects were observed in the weld volume as shown in Fig. 10. Sample #1 was ultimately sectioned for macro and micro inspection, as shown in Figs. 11 and 12. Sample #2 was sent to SWIP in Chengdu for fatigue test. Before cool-down to 77 K, 8 strain gages were installed on the test sample((as shown in Fig. 13). Fatigue test was performed with a cyclic longitudinal strain of 9.5 × 10−5–9.5 × 10−4 during 600,000 cycles. The cycle frequency was 5 Hz. The test took 3 days and the sample survived (shown in Figs. 14 and 15).
Fig. 9. 12 shots for x-ray test.
The holes of thermocouples were then sealed with heat-resistant tapes. For the sake of more efficiency and reliable than manual welding, helium inlet was welded with an automatic welding machine, shown in Fig. 5. Active cooling was applied by fixing a pair of water circulated copper plate around the conductor. While helium inlet welding, temperature on the cable was continuously monitored and recorded, the temperature was below 250℃ in the entire welding process, as shown in Fig. 6. The welding joint included 7 layers, as shown in Fig. 7. Each layer contained 6 passed along the perimeter direction. The first layer welding was crucial in regard to full penetration. Thus, the welding quality was visually checked and recorded (shown in Fig. 8) by endoscope after each pass welding in the first layer. When helium inlet welding was finished, visual inspection on the
3. Conclusion The qualification of ITER PF6 helium inlet was successfully accomplished by ASIPP. During welding, the temperature was below the requirement of 250 ℃. The 3
Fusion Engineering and Design 134 (2018) 1–4
S. Du et al.
pressure of 3 MPa. The weld undergone PT test, x-ray test and tomography test did not show any sign of defect, which well met the standard of ISO 5817_B level. The test sample also survived in fatigue test under 77 K. The manufacturing procedures were developed, finalized and approved by ITER IO, which was then effectively applied on the dummy and series double pancakes winding. Disclaimer The work leading to this publication has been funded by Fusion for Energy under the Polodial Field Coils Cooperation Agreement of PF6. This publication reflects the views only of the authors, and Fusion for Energy cannot be held responsible for any use which may be made of the information contained therein. Acknowledgments The author and co-authors were grateful for the strong collaboration and support from ASIPP, F4E and ITER IO, and would also in debt of CERN for tomography test, SWIP for fatigue test, company of Hefei Juneng electro physics high-tech development Co. Ltd for non-destructive test.
Fig. 13. Sample #2 and strain gages installation.
References [1] Shuangsong Du, Wei Wen, Jin Chen, Weiyue Wu, Yuntao Song, Guang Shen, ITER PF6 double pancakes winding line, Fusion Eng. Des. 116 (2017) pp10–16. [2] Jie Xu, Wei Wen, Jin Chen, Weiyue Wu, ITER PF6 double pancakes winding line multi-axis automatic controlling system, Fusion Eng. Des. 121 (2017) pp124–129. [3] S.A. Egorov, A.A. Mednikov, I.Y. Rodin, A.V. Pugachev, Winding shop of the PF1 coil double pancakes, IEEE Trans. Appl. Supercond. 21 (3) (2011) 1974–1977. [4] A.G. Kazantsev, M.G. Kakhadze, K.A. Soin, I.Y. Rodin, S.N. Nasluzov, Fatigue strength of PF-1 coil helium inlet with weld defects, Procedia Struct. Intergr. 2 (2016) 3562–3568.
Fig. 14. Sample #2 after fatigue test.
Fig. 15. Sample #2 fatigue cycles.
leak rate was one order less than 10−9 Pa*m3*s−1, under helium
4
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Qualification of ITER PF6 helium inlet a,b
a,⁎
a
T a
c
c
Shuangsong Du , Wei Wen , Guang Shen , Jijun Xin , Kevin Smith , Carlo Sborchia , Peter Readmanc, Yuntao Songa, WeiYue Wua, Huan Wua a b c
Institute of Plasma Physics, Chinese Academy of Science, Hefei, China University of Science and Technology of China, Hefei, China Fusion for Energy, Barcelona, Spain
A R T I C LE I N FO
A B S T R A C T
Keywords: PF6 coil Helium inlet Automatic welding Fatigue test
The Poloidal Field (PF) coils are one of the main sub-systems of the ITER magnets. The PF6 coil is being manufactured by the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) as per the Poloidal Field coils cooperation agreement signed between ASIPP and Fusion for Energy (F4E). As one of the critical components, helium inlet locates on the innermost turn and supplies the coil with supercritical helium. During Tokamak operation, the helium inlet will undergo huge cyclic electromagnetic loads and thermal cycling during cooling down and warming up. This paper focus on the main steps of ITER PF6 helium inlet qualification. Helium inlet hole drilling and stainless steel wrapping removal were firstly been carried out. Helium inlet welding with full penetration by automatic welding machine was then performed, followed by leak proof test, non-destructive test, fatigue test and tomography test. At the end, the samples were sectioned for micro and macro inspection. The results show ITER PF6 helium inlet qualification has successfully met the requirements of PF procurement agreement(PA) and was approved by ITER IO.
1. Introduction The ITER PF system consists of 6 solenoidal coils, PF1 to PF6 (as shown in Fig. 1), which serve to shape and stabilize the position of the plasma in the Tokamak. The PF coils are all wound with NbTi conductors, and range in diameter from ∼8 m to ∼ 24 m. ITER PF6 winding pack is composed by stacking of 9 double pancakes. The double pancakes are wound in a “two-in-hand” configuration. Two conductors are wound together to form a pancake layer with winding down from” outside-in” in one layer, and “inside-out” on the other. The two layers are connected by superconducting joint to form a double pancake. Joggling is needed in each layer to accomplish the proper positioning of the conductors during winding, as well as a joggle to make the transition from one layer to the next [1–3]. Each double pancake is supplied with supercritical helium by two inlet parts locate on the innermost turn, in the middle of the vertical joggles, as shown in Fig. 2. Located in the high magnetic field region, the helium inlet will undergo huge cyclic electromagnetic loads and thermal cycling during Tokamak operation [4]. Full penetration weld under monitored welding temperature (below 250 ℃ to avoid strands degradation) is the primary requirement. According to the PA, full size samples to form the
⁎
Corresponding author. E-mail address: [email protected] (W. Wen).
https://doi.org/10.1016/j.fusengdes.2018.06.010 Received 23 April 2018; Received in revised form 2 June 2018; Accepted 12 June 2018 0920-3796/ © 2018 Elsevier B.V. All rights reserved.
helium inlet shall be manufactured fully replicating the production conditions in order to qualify the manufacturing process, before it is applied on the dummy and series double pancakes winding. This paper focus on the main steps of ITER PF6 helium inlet qualification. During qualification process, helium inlet hole drilling and stainless steel wrapping removal were firstly been carried out. Helium inlet welding with full penetration by automatic welding machine was then performed, followed by leak proof test, non-destructive test, fatigue test and tomography test. At the end, the samples were sectioned for micro and macro inspection. 2. Qualification of ITER PF6 helium inlet The requirements of the ITER PF6 helium inlet manufacturing are listed in Table 1. 3 samples were manufactured for the qualification of ITER PF6 helium inlet. The strategies for each sample are as follows: Sample #1: Welding → Visual inspection → Leak test → PT test → Xray test → 5 cool-down cycles at 77 K (thermal shock) → Leak test → Tomography inspection → Sectioning → Visual and microscopic inspections. Sample #2: Welding → Visual inspection → Leak test → PT test → X-
Fusion Engineering and Design 134 (2018) 1–4
S. Du et al.
Fig. 4. Thermocouples planting. Fig. 1. The PF system of ITER magnet.
Fig. 5. Automatic welding machine.
Fig. 2. Two-in-hand winding configuration.
Table 1 ITER PF6 helium inlet requirement. Item
Requirement
Temperature control Weld joint
Cable temperature shall remain below 250 °C
Leak rate Fatigue test
Full penetration (ISO 5817_B level) < 10−9 Pa*m3*s−1, under 3 MPa 77 K, strain range 9.5 × 10−5–9.5 × 10−4 during 600,000 cycles or 1.9 × 10−4–1.9 × 10−3 during 30,000 cycles.
Fig. 6. Temperature curve of welding.
Tomography inspection. Among them, Sample #3 is a backup of sample #2, in case sample #2 failed during fatigue test. If sample #2 survived in fatigue test, no tomography inspection and following tests will be performed on Sample #3. Sample #1 was bent to the internal radius of the double pancake, simulating geometry of the turn. Samples #2 and #3 were straight. All the manufacturing of the above qualification samples started with helium inlet hole drilling by a portable milling machine and stainless steel wrapping manual removal, shown in Fig. 3. The clearance of the hole root is vital to reduce the stress concentration and pressure drop. Welding temperature measurement on the cable was required on sample #1. To do this operation, 6 thermocouples were planted from the back, as shown in Fig. 4. The thermocouple joints were planted under the weld in the point of the highest temperature during welding.
Fig. 3. Helium inlet hole drilling and wrap removal.
ray test → 5 cool-down cycles at 77 K (thermal shock) → Leak test → Fatigue test at 77 K → Leak test. Sample #3: Welding → Visual inspection → Leak test → PT test → Xray test → 5 cool-down cycles at 77 K (thermal shock) → Leak test → Tomography inspection → Fatigue test at 77 K → Leak test → 2
Fusion Engineering and Design 134 (2018) 1–4
S. Du et al.
Fig. 7. 7 layers of helium inlet weld joint. Fig. 10. Tomography test in CERN.
Fig. 8. Visually check of first layer welding.
Fig. 11. Sample #1 macro inspection.
Fig. 12. Sample #1 micro inspection.
surface, leak test(N/A for sample #1), PT and x-ray test were been performed. The leak rate was one order lower than the requirement. For the full penetration and coverage of x-ray, 12 shots were taken, as shown in Fig. 9. After x-ray test, thermal shock test and leak test again, sample #1 was sent to CERN for tomography test. No non-acceptable defects were observed in the weld volume as shown in Fig. 10. Sample #1 was ultimately sectioned for macro and micro inspection, as shown in Figs. 11 and 12. Sample #2 was sent to SWIP in Chengdu for fatigue test. Before cool-down to 77 K, 8 strain gages were installed on the test sample((as shown in Fig. 13). Fatigue test was performed with a cyclic longitudinal strain of 9.5 × 10−5–9.5 × 10−4 during 600,000 cycles. The cycle frequency was 5 Hz. The test took 3 days and the sample survived (shown in Figs. 14 and 15).
Fig. 9. 12 shots for x-ray test.
The holes of thermocouples were then sealed with heat-resistant tapes. For the sake of more efficiency and reliable than manual welding, helium inlet was welded with an automatic welding machine, shown in Fig. 5. Active cooling was applied by fixing a pair of water circulated copper plate around the conductor. While helium inlet welding, temperature on the cable was continuously monitored and recorded, the temperature was below 250℃ in the entire welding process, as shown in Fig. 6. The welding joint included 7 layers, as shown in Fig. 7. Each layer contained 6 passed along the perimeter direction. The first layer welding was crucial in regard to full penetration. Thus, the welding quality was visually checked and recorded (shown in Fig. 8) by endoscope after each pass welding in the first layer. When helium inlet welding was finished, visual inspection on the
3. Conclusion The qualification of ITER PF6 helium inlet was successfully accomplished by ASIPP. During welding, the temperature was below the requirement of 250 ℃. The 3
Fusion Engineering and Design 134 (2018) 1–4
S. Du et al.
pressure of 3 MPa. The weld undergone PT test, x-ray test and tomography test did not show any sign of defect, which well met the standard of ISO 5817_B level. The test sample also survived in fatigue test under 77 K. The manufacturing procedures were developed, finalized and approved by ITER IO, which was then effectively applied on the dummy and series double pancakes winding. Disclaimer The work leading to this publication has been funded by Fusion for Energy under the Polodial Field Coils Cooperation Agreement of PF6. This publication reflects the views only of the authors, and Fusion for Energy cannot be held responsible for any use which may be made of the information contained therein. Acknowledgments The author and co-authors were grateful for the strong collaboration and support from ASIPP, F4E and ITER IO, and would also in debt of CERN for tomography test, SWIP for fatigue test, company of Hefei Juneng electro physics high-tech development Co. Ltd for non-destructive test.
Fig. 13. Sample #2 and strain gages installation.
References [1] Shuangsong Du, Wei Wen, Jin Chen, Weiyue Wu, Yuntao Song, Guang Shen, ITER PF6 double pancakes winding line, Fusion Eng. Des. 116 (2017) pp10–16. [2] Jie Xu, Wei Wen, Jin Chen, Weiyue Wu, ITER PF6 double pancakes winding line multi-axis automatic controlling system, Fusion Eng. Des. 121 (2017) pp124–129. [3] S.A. Egorov, A.A. Mednikov, I.Y. Rodin, A.V. Pugachev, Winding shop of the PF1 coil double pancakes, IEEE Trans. Appl. Supercond. 21 (3) (2011) 1974–1977. [4] A.G. Kazantsev, M.G. Kakhadze, K.A. Soin, I.Y. Rodin, S.N. Nasluzov, Fatigue strength of PF-1 coil helium inlet with weld defects, Procedia Struct. Intergr. 2 (2016) 3562–3568.
Fig. 14. Sample #2 after fatigue test.
Fig. 15. Sample #2 fatigue cycles.
leak rate was one order less than 10−9 Pa*m3*s−1, under helium
4