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JT-60SA TF coils procured by ENEA: An intermediate assessment
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ARTICLE IN PRESS
FUSION-9213; No. of Pages 4
Fusion Engineering and Design xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
JT-60SA TF coils procured by ENEA: An intermediate assessment Gian Mario Polli a,∗ , Antonio Cucchiaro a , Valter Cocilovo a , Valentina Corato a , Paolo Rossi a , Giovanni Drago b , Paolo Pesenti b , Franco Terzi b , Enrico Di Pietro c , Valerio Tomarchio c a b c
ENEA, C.R. Frascati, Via Enrico Fermi 45, I-000044 Frascati, Italy ASG Superconductors S.p.A., Corso Perrone 73r, I-16152 Genova, Italy JT-60SA European Home Team, 85748 Garching bei Munchen, Germany
h i g h l i g h t s • • • • •
Superconducting magnet manufacturing. In casing insertion. Casing welding. Interface machining. Piping assembly.
a r t i c l e
a b s t r a c t
i n f o
Article history: Received 3 October 2016 Received in revised form 6 March 2017 Accepted 7 March 2017 Available online xxx Keywords: JT-60SA Superconducting tokamak Satellite tokamak program Broader approach
ENEA, in the framework of Broader Approach program for the early realization of fusion with the construction of JT-60SA tokamak, is procuring 9 of the 18 TF coils of JT-60SA magnet system. Within 2016 five coils will be completed and delivered to the cold test facility in Saclay, France, for the final acceptance tests before their shipment to Naka site for the assembly. Manufacturing has been divided in two main production steps: winding pack (WP) manufacturing and integration into casing. All the nine WPs have been already completed on September 2015 and the final integration phase has started in 2015 for the first coil. The integration, in its turn, is composed of six sub-steps: insertion, welding, embedding impregnation, final machining of interface areas, He piping assembly and final acceptance tests. Each of these steps has been already accomplished and two coils have been delivered to Saclay and undergone the cryogenic acceptance tests. This paper provides an overview and intermediate assessment of the contract that ENEA signed with ASG Superconductors for this supply. © 2017 Elsevier B.V. All rights reserved.
1. Introduction In September 2011, ENEA, the Italian Agency for New Technologies, Energy and Sustainable Economic Development, placed a contract to ASG Superconductors in Genoa, for the manufacturing of 9 toroidal field superconducting coils. The first year was devoted to the preparation of the manufacturing drawings, tooling procurement and procedures qualification. In the second year most of the special process have been qualified and the winding of the first double pancake (DP) initiated. The third year was characterized by the completion of the first winding pack (WP) followed by several others and by the conclusion of the qualification activity carried out for
the integration of the WP in the corresponding casing structure. In the fourth year the completion of WP production was accomplished and the first casing set was delivered allowing then the start of the integration phase. In 2016, fifth year of the contract, the first TF coil was shipped to Japan for the assembly in the tokamak hall. In parallel other five coils are in advanced status of manufacture, so much that other four coils will be delivered to the cold test facility in France and then sent to Japan. The contract will be completed in 2017 with the shipping of the remaining coils. The authors have already presented the main goals of the WP manufacturing phase and of the related qualification activity in [1–4], as well as the main issues of the qualification campaign for the integration phase in [5–8]. The present paper deals with the actual issues encountered in the integration, starting from an overview of the different steps of which it is composed: the main
∗ Corresponding author. E-mail address: [email protected] (G.M. Polli). http://dx.doi.org/10.1016/j.fusengdes.2017.03.033 0920-3796/© 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
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Fig. 1. Insertion of the WP inside the casing.
Fig. 2. TF coil in vertical position for the transverse welding of the two casing shells.
results in terms of performances achieved by the coils already completed are also reported.
weight. Once the insertion of the two outer shells of the casing structure have been placed around the WP, about twenty other frames are mounted around the coil to keep it in position while the assembly is rotated vertically to carry out the welding operation.
2. TF coil integration into casing As already mentioned, the integration is the last phase of the TF manufacturing. It is composed of six steps: i ii iii iv v vi
insertion welding embedding machining piping installation testing
Each step takes in principle about one calendar month for its completion, so that the whole phase should last six months per coil. So far, the one month target has been reached only in some cases, since unpredicted difficulties have always enlarged the duration. The actual time length of the integration is within eight and nine calendar months. In the following subsections the six steps of the manufacturing are presented. 2.1. Insertion The first operation, preliminary to the insertion into the casing, consists in the WP wrapping with a layer of tape release Tedlar© needed to ensure the slippage, during the operating conditions, between WP and case structure and to avoid the ground insulation damage. Layers of glass foils are then applied on the surface of the WP up to 5 mm thickness. This thickness corresponds to the nominal gap between the WP and case considered in the design stage to ensure the insertion. Additional thicknesses of glass cloths and/or fiberglass sheets and G10 are applied to the WP or directly on the inner surface of the casing to compensate for additional gap on finished pieces. The second operation consists in the insertion of the WP in the central core of the insertion tooling. This is a rigid structure with lateral supports able to grasp the WP from the inboard surface and to keep it in the right position during the insertion and the following welding phase. The previous picture (Fig. 1) shows the moment in which the WP, supported by the central core, is positioned in the insertion tooling with the casing legs placed on their carriages for the horizontal insertion. The choice to perform the insertion horizontally, is led by the willing to limit the deformation produced by its own
2.2. Welding The operation that follows is the welding of the casing components. The casing structure (Refs. [9] and [10]) is made in AISI 316L stainless steel for the cryogenic and magnetic properties of this steel. There are two different kinds of components: the outer shells (also referred as curved and straight legs) that provide the larger structural resistance; and the inboard covers that close the WP inside a tubular arrangement. The welding between curved and straight leg, also referred as transverse welding, is the most critical since it is placed in a largely stressed area. The transverse welding is performed with a coil in vertical position, while the welding of the inner covers, along the poloidal direction, to the outer shells is made with the coil in horizontal position, in this way both welding are carried out horizontally. Most of the welding are butt weld full penetration type and are manually accomplished. The following picture (Fig. 2) shows the coil in vertical position for the execution of the transverse welding. One may note the groove for the 50 mm thick welding. The qualification activity granted the setting-up of the welding parameters and the training of the welders and of the NDE personnel. The presence of the WP inside, in addition to making unavailable the inner surface for inspection, imposes a limit on the maximum temperature reached in the process and hence on the welding parameters in the first passes. The welding consists in a first phase with manual TIG technique for the joining of the root and the first filling passes. Then several MIG passes up to 50 mm thickness are carried out. A first UT examination is performed in the mid of the process to check the presence of defects on the root and then it is repeated at the end for the whole thickness. Later the coil is placed horizontally for the insertion and subsequent welding of the covers, so the insertion tooling is freed and ready for another coil. The following picture (Fig. 3) shows a moment of the cover welding. This activity is completed by an UT examination aimed at excluding the presence of defects larger than 5 mm2 . Currently, the welding phase has been successfully achieved on six coils. A critical step, especially in the welding of the first modules, has been the tracking, with laser tracker, of the position of tar-
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
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Fig. 5. Preparation of the module for the resin injection.
Fig. 3. Filling welding of the covers of TFC-02.
Fig. 6. Dimensional survey of the interface areas at the end of the embedding process.
Fig. 4. Distance between central targets of WP during fabrication.
gets mounted on the WP. Welding, indeed, introduces significant deformation to limit which, in the transversal welding, the welding grooves were prepared with 5 mm of additional material. To evaluate the effect of the deformation induced by the joining process, the following figure (Fig. 4) shows the distance between two reference targets on the equatorial plane of the WP. In the graph, the x axis represents the sub-step of the integration process, while the ordinate axis shows the distance in mm between targets. It is noted that, as long as the module is positioned in the insertion structure (positions 1–6), it does not show significant deformation, when the welding of the covers takes place (positions 7–10) a significant deformation appears that tends to ovalize the original D shape. 2.3. Embedding Once the welding of the covers is completed, it is the time of the embedding impregnation that consists in the filling with epoxy resin of the gap between the casing and the WP in order to make the assembly monolithic. The WP has been already wrapped with glass clothes and the addition of the resin makes the layer able to transfer the electromagnetic forces originated in the WP to the casing structure. The embedding is composed of two substeps: resin injection and curing cycle. The previous picture (Fig. 5) shows the module before the injection of the resin. The resin enters the casing from the bottom and flows inside filling the voids up to the vertical port area where it gets out of the casing. Later the workstation is covered with a rigid structure for the thermal insulation of the chamber and the starting of the curing cycle. The last step, before leaving the embedding workstation, is
the measurement with laser tracker of the twelve targets glued on the WP surface and of the interface surfaces to be machined. The targets on the WP give indication of possible displacements during the embedding and define the reference coordinate system associated to the coil. On the other hand, the measurement of the interface area serves as operative machining instruction for the subsequent machining phase. The previous picture (Fig. 6) shows the result of the dimensional survey carried out at the end of the embedding process. The areas with the arrows are the interface surfaces on the curved leg, where the outer intercoil structure will be placed in the pre-assembly phase of the tokamak. One may observe that the extra-material to be machined, that was nominally 5 mm, presents a non-homogeneous distribution due to the deformation produced by the welding. Cover welding, in particular, tends to squeeze the inboard surface in the toroidal direction as it can be recognized from Fig. 6, where on the outboard the maximum extra-material is 5.27 mm whilst on the inboard it reduces to 1.41 mm due to shrinkage of the cover welding. 2.4. Machining Machining of the interface areas is needed for the final assembly of the coil in the tokamak. It consists of: removal of extra-material in interface surfaces and in the realization of holes for connecting structures in the assembly. Both have to be made with extreme precision in order to ensure a correct assembly of the machine in Naka, therefore, their position and their diameters are controlled either through traditional instruments, reference templates, go-nogo gauges and finally with laser tracker. Previous image (Fig. 7) shows the machining of the wedging surface, inclined 10◦ with respect to the horizontal plane. The following image (Fig. 8) shows the test of the holes for the intercoil structures carried out using a template and three go-no-go
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
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thirteen insulation breakers are mounted at the end of each pipe to separate it electrically from the ground. 2.6. Testing
Fig. 7. Machining of the wedging surfaces.
The end of the TF coil manufacture is achieved with the successful completion of the acceptance tests. There are three different kinds of tests: electrical tests; hydraulic tests; dimensional tests. The electrical tests consist among others in the measurement of the resistance of the WP at room temperature, and of the verification of the insulation in Paschen conditions. The results obtained so far are included in a range of ±1% for the whole set of coils produced thus ensuring the repeatability of the manufacturing process. Concerning the hydraulic tests, the main ones are the flow test of the two He circuits and the pressure and leak test performed on the whole coil to exclude the presence of leaks that may compromise the operation of the coil in the tokamak. Finally the dimensional tests complement those executed at the end of the machining phase and define also the position of the electrical terminations, the position of which has to be corrected due to the deformation produced by the welding operation and due to possible error in the manufacturing. 3. Concluding remarks Two of nine TF coils already passed the cryogenic acceptance tests, other two coils will be tested within 2016 and the rest of the production will be finished within 2017. Although in the manufacturing of the first coils, some unpredicted issues implied some delays with respect to the original schedule, nonetheless, the fabrication rate is constantly increasing due to the set-up of the manufacturing procedure and testing.
Fig. 8. Test of the holes for intercoil structures.
Acknowledgments This research was supported under the Italian Electricity System Research Fund (Fondo per la Ricerca di Sistema) of the Italian Economic Development Ministry within PAR 2015. References
Fig. 9. View of piping in the inboard side of the curved leg.
gauges. Holes position is afterwards measured with laser tracker to simplify the assembly operations. 2.5. Piping installation The last manufacturing phase regards the installation of the piping for the circulation of He inside the WP and the casing (Fig. 9). Two different circuits are realized one for cooling the casing structure and one to keep the WP in superconducting state. The circuit for the casing cooling is directly welded onto the casing whilst the WP circuit is kept insulated from the casing. Finally a set of
[1] A. Cucchiaro, et al., Manufacturing of the first toroidal field coil for the JT-60SA magnet system, in: 2013 IEEE 25th Symposium on Fusion Engineering, SOFE 2013, 2013, art. no. 6635462. [2] V. Cocilovo, et al., Qualification process and quality control planning for JT-60-SA Toroidal Field coils construction, in: 2013 IEEE 25th Symposium on Fusion Engineering, SOFE 2013, 2013, art. no. 6635458. [3] A. Cucchiaro, et al., Qualification and preparatory activities for the manufacturing of 9 TF coils of the JT-60SA magnet, Fusion Eng. Des. 88 (9–10) (2013) 1605–1608. [4] A. Cucchiaro, et al., First Italian JT-60SA TF coil winding pack preliminary insertion into casing, (2016), in: Proceedings – Symposium on Fusion Engineering, 2016-May, 2016, art. no. 7482356. [5] S. Davis, et al., Status of the JT-60SA magnet system, (2016), in: Proceedings – Symposium on Fusion Engineering, 2016-May, 2016, art. no. 7482274. [6] Y. Koide, et al., JT-60SA superconducting magnet system, Nucl. Fusion 55 (8) (2015), art. no. 086001. [7] K. Yoshida, et al., Construction status of the superconducting magnet system for JT-60SA, IEEE Trans. Appli. Superconduct. 26 (4) (2016), art. no. 7372427. [8] G.M. Polli, et al., Validation of special processes for the integration activities of the JT-60SA TF coils manufactured in Italy, Fusion Eng. Des. 98–99 (2015) 1131–1134. [9] P. Rossi, et al., Manufacturing of the casing components for the JT-60SA toroidal field coils, IEEE Trans. Appl. Supercond. 26 (4) (2016), art.7405305. [10] P. Rossi, et al., Technical aspects and manufacturing methods for JT-60SA toroidal field coil casings, Fusion Eng. Des. 89 (7–8) (2014) 965–969.
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
ARTICLE IN PRESS
FUSION-9213; No. of Pages 4
Fusion Engineering and Design xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
JT-60SA TF coils procured by ENEA: An intermediate assessment Gian Mario Polli a,∗ , Antonio Cucchiaro a , Valter Cocilovo a , Valentina Corato a , Paolo Rossi a , Giovanni Drago b , Paolo Pesenti b , Franco Terzi b , Enrico Di Pietro c , Valerio Tomarchio c a b c
ENEA, C.R. Frascati, Via Enrico Fermi 45, I-000044 Frascati, Italy ASG Superconductors S.p.A., Corso Perrone 73r, I-16152 Genova, Italy JT-60SA European Home Team, 85748 Garching bei Munchen, Germany
h i g h l i g h t s • • • • •
Superconducting magnet manufacturing. In casing insertion. Casing welding. Interface machining. Piping assembly.
a r t i c l e
a b s t r a c t
i n f o
Article history: Received 3 October 2016 Received in revised form 6 March 2017 Accepted 7 March 2017 Available online xxx Keywords: JT-60SA Superconducting tokamak Satellite tokamak program Broader approach
ENEA, in the framework of Broader Approach program for the early realization of fusion with the construction of JT-60SA tokamak, is procuring 9 of the 18 TF coils of JT-60SA magnet system. Within 2016 five coils will be completed and delivered to the cold test facility in Saclay, France, for the final acceptance tests before their shipment to Naka site for the assembly. Manufacturing has been divided in two main production steps: winding pack (WP) manufacturing and integration into casing. All the nine WPs have been already completed on September 2015 and the final integration phase has started in 2015 for the first coil. The integration, in its turn, is composed of six sub-steps: insertion, welding, embedding impregnation, final machining of interface areas, He piping assembly and final acceptance tests. Each of these steps has been already accomplished and two coils have been delivered to Saclay and undergone the cryogenic acceptance tests. This paper provides an overview and intermediate assessment of the contract that ENEA signed with ASG Superconductors for this supply. © 2017 Elsevier B.V. All rights reserved.
1. Introduction In September 2011, ENEA, the Italian Agency for New Technologies, Energy and Sustainable Economic Development, placed a contract to ASG Superconductors in Genoa, for the manufacturing of 9 toroidal field superconducting coils. The first year was devoted to the preparation of the manufacturing drawings, tooling procurement and procedures qualification. In the second year most of the special process have been qualified and the winding of the first double pancake (DP) initiated. The third year was characterized by the completion of the first winding pack (WP) followed by several others and by the conclusion of the qualification activity carried out for
the integration of the WP in the corresponding casing structure. In the fourth year the completion of WP production was accomplished and the first casing set was delivered allowing then the start of the integration phase. In 2016, fifth year of the contract, the first TF coil was shipped to Japan for the assembly in the tokamak hall. In parallel other five coils are in advanced status of manufacture, so much that other four coils will be delivered to the cold test facility in France and then sent to Japan. The contract will be completed in 2017 with the shipping of the remaining coils. The authors have already presented the main goals of the WP manufacturing phase and of the related qualification activity in [1–4], as well as the main issues of the qualification campaign for the integration phase in [5–8]. The present paper deals with the actual issues encountered in the integration, starting from an overview of the different steps of which it is composed: the main
∗ Corresponding author. E-mail address: [email protected] (G.M. Polli). http://dx.doi.org/10.1016/j.fusengdes.2017.03.033 0920-3796/© 2017 Elsevier B.V. All rights reserved.
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
G Model FUSION-9213; No. of Pages 4
ARTICLE IN PRESS G.M. Polli et al. / Fusion Engineering and Design xxx (2017) xxx–xxx
2
Fig. 1. Insertion of the WP inside the casing.
Fig. 2. TF coil in vertical position for the transverse welding of the two casing shells.
results in terms of performances achieved by the coils already completed are also reported.
weight. Once the insertion of the two outer shells of the casing structure have been placed around the WP, about twenty other frames are mounted around the coil to keep it in position while the assembly is rotated vertically to carry out the welding operation.
2. TF coil integration into casing As already mentioned, the integration is the last phase of the TF manufacturing. It is composed of six steps: i ii iii iv v vi
insertion welding embedding machining piping installation testing
Each step takes in principle about one calendar month for its completion, so that the whole phase should last six months per coil. So far, the one month target has been reached only in some cases, since unpredicted difficulties have always enlarged the duration. The actual time length of the integration is within eight and nine calendar months. In the following subsections the six steps of the manufacturing are presented. 2.1. Insertion The first operation, preliminary to the insertion into the casing, consists in the WP wrapping with a layer of tape release Tedlar© needed to ensure the slippage, during the operating conditions, between WP and case structure and to avoid the ground insulation damage. Layers of glass foils are then applied on the surface of the WP up to 5 mm thickness. This thickness corresponds to the nominal gap between the WP and case considered in the design stage to ensure the insertion. Additional thicknesses of glass cloths and/or fiberglass sheets and G10 are applied to the WP or directly on the inner surface of the casing to compensate for additional gap on finished pieces. The second operation consists in the insertion of the WP in the central core of the insertion tooling. This is a rigid structure with lateral supports able to grasp the WP from the inboard surface and to keep it in the right position during the insertion and the following welding phase. The previous picture (Fig. 1) shows the moment in which the WP, supported by the central core, is positioned in the insertion tooling with the casing legs placed on their carriages for the horizontal insertion. The choice to perform the insertion horizontally, is led by the willing to limit the deformation produced by its own
2.2. Welding The operation that follows is the welding of the casing components. The casing structure (Refs. [9] and [10]) is made in AISI 316L stainless steel for the cryogenic and magnetic properties of this steel. There are two different kinds of components: the outer shells (also referred as curved and straight legs) that provide the larger structural resistance; and the inboard covers that close the WP inside a tubular arrangement. The welding between curved and straight leg, also referred as transverse welding, is the most critical since it is placed in a largely stressed area. The transverse welding is performed with a coil in vertical position, while the welding of the inner covers, along the poloidal direction, to the outer shells is made with the coil in horizontal position, in this way both welding are carried out horizontally. Most of the welding are butt weld full penetration type and are manually accomplished. The following picture (Fig. 2) shows the coil in vertical position for the execution of the transverse welding. One may note the groove for the 50 mm thick welding. The qualification activity granted the setting-up of the welding parameters and the training of the welders and of the NDE personnel. The presence of the WP inside, in addition to making unavailable the inner surface for inspection, imposes a limit on the maximum temperature reached in the process and hence on the welding parameters in the first passes. The welding consists in a first phase with manual TIG technique for the joining of the root and the first filling passes. Then several MIG passes up to 50 mm thickness are carried out. A first UT examination is performed in the mid of the process to check the presence of defects on the root and then it is repeated at the end for the whole thickness. Later the coil is placed horizontally for the insertion and subsequent welding of the covers, so the insertion tooling is freed and ready for another coil. The following picture (Fig. 3) shows a moment of the cover welding. This activity is completed by an UT examination aimed at excluding the presence of defects larger than 5 mm2 . Currently, the welding phase has been successfully achieved on six coils. A critical step, especially in the welding of the first modules, has been the tracking, with laser tracker, of the position of tar-
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
G Model FUSION-9213; No. of Pages 4
ARTICLE IN PRESS G.M. Polli et al. / Fusion Engineering and Design xxx (2017) xxx–xxx
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Fig. 5. Preparation of the module for the resin injection.
Fig. 3. Filling welding of the covers of TFC-02.
Fig. 6. Dimensional survey of the interface areas at the end of the embedding process.
Fig. 4. Distance between central targets of WP during fabrication.
gets mounted on the WP. Welding, indeed, introduces significant deformation to limit which, in the transversal welding, the welding grooves were prepared with 5 mm of additional material. To evaluate the effect of the deformation induced by the joining process, the following figure (Fig. 4) shows the distance between two reference targets on the equatorial plane of the WP. In the graph, the x axis represents the sub-step of the integration process, while the ordinate axis shows the distance in mm between targets. It is noted that, as long as the module is positioned in the insertion structure (positions 1–6), it does not show significant deformation, when the welding of the covers takes place (positions 7–10) a significant deformation appears that tends to ovalize the original D shape. 2.3. Embedding Once the welding of the covers is completed, it is the time of the embedding impregnation that consists in the filling with epoxy resin of the gap between the casing and the WP in order to make the assembly monolithic. The WP has been already wrapped with glass clothes and the addition of the resin makes the layer able to transfer the electromagnetic forces originated in the WP to the casing structure. The embedding is composed of two substeps: resin injection and curing cycle. The previous picture (Fig. 5) shows the module before the injection of the resin. The resin enters the casing from the bottom and flows inside filling the voids up to the vertical port area where it gets out of the casing. Later the workstation is covered with a rigid structure for the thermal insulation of the chamber and the starting of the curing cycle. The last step, before leaving the embedding workstation, is
the measurement with laser tracker of the twelve targets glued on the WP surface and of the interface surfaces to be machined. The targets on the WP give indication of possible displacements during the embedding and define the reference coordinate system associated to the coil. On the other hand, the measurement of the interface area serves as operative machining instruction for the subsequent machining phase. The previous picture (Fig. 6) shows the result of the dimensional survey carried out at the end of the embedding process. The areas with the arrows are the interface surfaces on the curved leg, where the outer intercoil structure will be placed in the pre-assembly phase of the tokamak. One may observe that the extra-material to be machined, that was nominally 5 mm, presents a non-homogeneous distribution due to the deformation produced by the welding. Cover welding, in particular, tends to squeeze the inboard surface in the toroidal direction as it can be recognized from Fig. 6, where on the outboard the maximum extra-material is 5.27 mm whilst on the inboard it reduces to 1.41 mm due to shrinkage of the cover welding. 2.4. Machining Machining of the interface areas is needed for the final assembly of the coil in the tokamak. It consists of: removal of extra-material in interface surfaces and in the realization of holes for connecting structures in the assembly. Both have to be made with extreme precision in order to ensure a correct assembly of the machine in Naka, therefore, their position and their diameters are controlled either through traditional instruments, reference templates, go-nogo gauges and finally with laser tracker. Previous image (Fig. 7) shows the machining of the wedging surface, inclined 10◦ with respect to the horizontal plane. The following image (Fig. 8) shows the test of the holes for the intercoil structures carried out using a template and three go-no-go
Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033
G Model FUSION-9213; No. of Pages 4
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4
thirteen insulation breakers are mounted at the end of each pipe to separate it electrically from the ground. 2.6. Testing
Fig. 7. Machining of the wedging surfaces.
The end of the TF coil manufacture is achieved with the successful completion of the acceptance tests. There are three different kinds of tests: electrical tests; hydraulic tests; dimensional tests. The electrical tests consist among others in the measurement of the resistance of the WP at room temperature, and of the verification of the insulation in Paschen conditions. The results obtained so far are included in a range of ±1% for the whole set of coils produced thus ensuring the repeatability of the manufacturing process. Concerning the hydraulic tests, the main ones are the flow test of the two He circuits and the pressure and leak test performed on the whole coil to exclude the presence of leaks that may compromise the operation of the coil in the tokamak. Finally the dimensional tests complement those executed at the end of the machining phase and define also the position of the electrical terminations, the position of which has to be corrected due to the deformation produced by the welding operation and due to possible error in the manufacturing. 3. Concluding remarks Two of nine TF coils already passed the cryogenic acceptance tests, other two coils will be tested within 2016 and the rest of the production will be finished within 2017. Although in the manufacturing of the first coils, some unpredicted issues implied some delays with respect to the original schedule, nonetheless, the fabrication rate is constantly increasing due to the set-up of the manufacturing procedure and testing.
Fig. 8. Test of the holes for intercoil structures.
Acknowledgments This research was supported under the Italian Electricity System Research Fund (Fondo per la Ricerca di Sistema) of the Italian Economic Development Ministry within PAR 2015. References
Fig. 9. View of piping in the inboard side of the curved leg.
gauges. Holes position is afterwards measured with laser tracker to simplify the assembly operations. 2.5. Piping installation The last manufacturing phase regards the installation of the piping for the circulation of He inside the WP and the casing (Fig. 9). Two different circuits are realized one for cooling the casing structure and one to keep the WP in superconducting state. The circuit for the casing cooling is directly welded onto the casing whilst the WP circuit is kept insulated from the casing. Finally a set of
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Please cite this article in press as: G.M. Polli, et al., JT-60SA TF coils procured by ENEA: An intermediate assessment, Fusion Eng. Des. (2017), http://dx.doi.org/10.1016/j.fusengdes.2017.03.033