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Mock-up test results of monoblock-type CFC divertor armor for JT-60SA
Fusion Engineering and Design 84 (2009) 949–952
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Mock-up test results of monoblock-type CFC divertor armor for JT-60SA S. Higashijima ∗ , S. Sakurai, S. Suzuki, K. Yokoyama, Y. Kashiwa, K. Masaki, Y.K. Shibama, M. Takechi, K. Shibanuma, A. Sakasai, M. Matsukawa, M. Kikuchi Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193, Japan
a r t i c l e
i n f o
Article history: Available online 6 May 2009 Keywords: Divertor High heat flux CFC Monoblock JT-60SA
a b s t r a c t The JT-60 Super Advanced (JT-60SA) tokamak project starts under both the Japanese domestic program and the international program “Broader Approach”. The maximum heat flux to JT-60SA divertor is estimated to ∼15 MW/m2 for 100 s. Japan Atomic Energy Agency (JAEA) has developed a divertor armor facing high heat flux in the engineering R&D for ITER, and it is concluded that monoblock-type CFC divertor armor is promising for JT-60SA. The JT-60SA armor consists of CFC monoblocks, a cooling CuCrZr screw-tube, and a thin oxygenfree high conductivity copper (OFHC-Cu) buffer layer between the CFC monoblock and the screw-tube. CFC/OFHC-Cu and OFHC-Cu/CuCrZr joints are essential for the armor, and these interfaces are brazed. Needed improvements from ITER engineering R&D are good CFC/OFHC-Cu and OFHC-Cu/CuCrZr interfaces and suppression of CFC cracking. For these purposes, metalization inside CFC monoblock is applied, and we confirmed again that the mock-up has heat removal capability in excess of ITER requirement. For optimization of the fabrication method and understanding of the production yield, the mock-ups corresponding to quantity produced in one furnace at the same time is also produced, and the half of the mock-ups could remove 15 MW/m2 as required. This paper summarizes the recent progress of design and mock-up test results for JT-60SA divertor armor. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Japanese (JA) government and European (EU) commission established “Broader Approach (BA) Program” toward early realization of fusion energy based on tokamak concept. An upgrading device of JT-60 tokamak with fully superconducting coils (JT-60 Super Advanced, JT-60SA) will be constructed under both the JA domestic program and the international BA program [1–3]. Main mission of JT-60SA is to support and supplement ITER toward DEMO. Scientific researches of JT-60SA in support of ITER are optimization of operational scenarios for ITER, and improved understanding of physics issues of long pulse discharges, and testing of possible modifications before their implementation on ITER. As for the role of the supplementary toward DEMO, main missions in support of DEMO are to explore operational regimes of steady-state advanced high beta operation, and control of power and particle complementary to those being addressed in ITER. JT-60SA is constructed in the present JT-60U torus hall. Many components of the present JT-60U facility including heating and current drive systems and power supply are utilized. The plasma
∗ Corresponding author. Tel.: +81 29 270 7378; fax: +81 29 270 7419. E-mail address: [email protected] (S. Higashijima). 0920-3796/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2009.02.021
major radius is about 3 m, and a break-even-class high-temperature plasma is expected. The divertor geometry is optimized to produce both high triangularity and ITER shape single-null plasmas with one machine. Semi-closed vertical divertor with flatter dome is adopted to keep higher flexibility of plasma shaping capability. The maximum heat flux to JT-60SA divertor is estimated to ∼15 MW/m2 for 100 s [4–6]. The monoblock-type divertor has been developed for ITER in EU [7–8]. At the same time, Japan Atomic Energy Agency (JAEA) has developed divertor armor facing high heat flux in the engineering R&D for ITER [9], and it is concluded that monoblock-type CFC divertor armor are promising for JT60SA. Needed improvements from ITER engineering R&D are good CFC/OFHC-Cu and OFHC-Cu/CuCrZr interfaces and suppression of CFC cracking of the armor. For these purposes, the metalization inside CFC monoblock is applied, and we made some mock-ups and confirmed the performance of the mock-up step by step. Especially, JT-60SA divertor armors are procured previous to ITER’s order and we should develop the armors in order to resolve the problems concerning mass-production. Optimization of fabrication method and understanding of production yield is also explored in the production of the armor corresponding to quantity produced in one furnace at the same time. This paper summarizes the recent progress of design and mock-up test results for JT-60SA divertor armor. In Section 2,
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S. Higashijima et al. / Fusion Engineering and Design 84 (2009) 949–952
Fig. 1. Structure of JT-60SA divertor.
requirements, structure, and FEM pre-analysis of divertor armor are explained. Test production and results of high heat flux test using JAEA Electron Beam Irradiation System (JEBIS) [10] of small-size mock-up and full-size mock-ups in Section 3. Finally in Section 4, summary and future plan are presented. 2. Divertor armors Required performances of JT-60SA divertor are (1) handling of 41–50 MW plasma heating power during 100 s, (2) particle control for high density ∼1020 m−3 for long pulse more than 100 s, (3) flexibility in main plasma shape and aspect ratio, (4) capability for maintenance with remote handling system, and (5) flexibility in plasma facing materials for plasma material interaction research toward DEMO [4–6]. Divertor geometry is optimized to produce both high triangularity and ITER shape single-null plasmas with one machine. Semi-closed vertical divertor with flatter dome is adopted to keep higher flexibility of plasma shaping capability. Divertor consists of inner and outer armors where high heat flux is expected, private dome, and inner and outer baffles for medium heat flux region and divertor cassette for remote handling. To maximize flexibility in main plasma shape and aspect ratio, lower and upper divertors are optimized for medium triangularity (ITER-like) configuration and high triangularity configuration, respectively. Design of lower divertor is shown in Fig. 1. Expected heat flux on outer divertor armor using computational simulation reaches to more than 10 MW/m2 for high power heating. Outer divertor armor should have maximum power handling capability within achieved performance in R&D for ITER divertor. According to design requirements, armor performance needs 10,000 cycles of 10 MW/m2 for 100 s and 3000 cycles of 15 MW/m2 for 100 s, and total of 13,000 cycles in normal operation are assumed. Expected heat flux on inner divertor armor is about 10 MW/m2 for high power heating. Armor performance needs 10,000 cycles of 7 MW/m2 for 100 s and 3000 cycles of 10 MW/m2 for 100 s. The JT-60SA armor consists of ten CFC monoblocks (plasma facing component with high heat transfer and high resistance to thermal shock), a cooling CuCrZr screw-tube with high thermal conduction and strong mechanical property, and a thin oxygenfree high conductivity copper (OFHC-Cu) buffer layer between the
Fig. 2. Monoblock-type CFC divertor armor of JT-60SA: (a) overall view and (b) crosssection of the armor.
CFC monoblock and the screw-tube in Fig. 2. CFC monoblocks are directly cooled by the cooling tube, and CFC/OFHC-Cu and OFHCCu/CuCrZr joints are essential for the armor, and these interfaces are brazed. In order to decide the design of the armors, 2D thermal analyses using FEM are performed to determine armor width and thickness and coolant tube type and diameter within a limited total coolant flow. In the analysis condition of CFC monoblock size of 3 cm cubic, cooling tube of M10 screw, and inlet coolant of 40 ◦ C, 2 MPa, 12 m/s, it shows that the maximum temperature of CuCrZr coolant tube is ∼400 ◦ C even for heat flux of 20 MW/m2 . The estimated pressure drop is less than 0.35 MPa. Maximum surface temperature of CFC armor with thickness of 5 mm is less than 1200 ◦ C for incident heat flux of 15 MW/m2 . From the point of view of cost reduction and enough space for tube welding, it is better to reduce the number of the required divertor armors. Therefore, the armor width of 30 mm with M10 screw tube is selected in the inlet condition of 40 ◦ C, 2 MPa and 12 m/s. 3. Mock-up test of the armors In order to develop the armors step by step, the small-size mockups were produced, and then full-size mock-ups corresponding to quantity produced in one furnace at the same time were produced for mass-production in accordance with the results of small size mock-ups. The objectives of small-size mock-ups with three CFC monoblocks are to investigate the acceptable heat flux, property of brazing, and lifetime of the armors, and the producing ability of manufacturers is also checked. CFC/OFHC-Cu and OFHC-Cu/CuCrZr joints are essential for the armor. For improvement of CFC/OFHC-Cu interfaces and suppression of CFC cracking from ITER engineering R&D results, the metalization using metal containing titanium is applied inside CFC monoblock. Fig. 3 shows (a) visible TV image during 1450 cycles, (b) surface temperature at steady state (10 s) during 1450 cycles, and (c) visible TV image after 1450 cycles in the heat cycle test of a small-size mock-up by electron beam irradiation using JEBIS. In the heat cycle test it was repeated that the electron beam corresponding to 15 MW/m2 was injected for 10 s and stopped for 20 s. Time evolution of surface temperature of CFC monoblock indicated the equilibrium state within 10 s in high heat flux test using JEBIS. Direction of fiber lamination of left
S. Higashijima et al. / Fusion Engineering and Design 84 (2009) 949–952
Fig. 3. Heat cycle test (15 MW/m2 × 10 s) of small-size mock-up using JEBIS: (a) visible TV image during 1450 cycles, (b) surface temperature in steady state (10 s) during 1450 cycles, and (c) visible TV image after 1450 cycles. Lines in (c) present direction of fiber lamination of CFC.
hand-side monoblock is changed to confirm strength of brazing. Applied two-dimensional CFC has almost the same coefficient of thermal conductivity for two directions of the fiber laminations. Lines in Fig. 3(c) indicate the direction of CFC fiber lamination on the heat receiving surface. The other fiber lamination is the front-back direction in Fig. 3(c). Surface temperature at 15 MW/m2 reaches ∼2000 ◦ C. High temperature regions can be seen in the TV image. This small-size mock-up survives the repeated heat load of 1450 cycles at 15 MW/m2 and 650 cycles at 20 MW/m2 (in excess of
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ITER requirement). In the armor surface slightly eroded regions is seen after the heat cycle test due to sublimation corresponding to high temperature regions. This is mainly due to direction of fiber lamination on left hand-side monoblock, and small defect in brazing was strongly suspected on right hand-side monoblock. Finishing the heat cycle test, the part of high temperature on the right hand-side monoblock was cut. Cross section of the monoblock was investigated, but even small defect in brazing was not found. JEBIS uses the fast-scanned electron beams, and heat flux becomes higher at the both ends than in central region of heated area. In this heat cycle test, higher heat flux area at the right end was not set outside CFC surface of small-size mock-ups, and we therefore concluded that high temperature region was due to characteristics of JEBIS beam profiles. Performance of monoblock CFC armors with improved brazing technique allowing 15 MW/m2 of heat load has been confirmed. In JT-60SA’s procurement of the divertor armors, about ten armors will be produced in the furnace at the same time, that is one-batch-production, to shorten the lead time and keep the procurement schedule. Therefore, in accordance with the results of small-size mock-up test, one-batch-production of full-size mock-ups was explored for mass-production. The objectives of one-batch-production of full-size mock-ups are to optimize the fabrication method and to understand the production yield. In the procurement plan of JT-60SA, about 2000 armors will be produced, and it is impossible to check all the armors using high heat flux load test such as JEBIS because of machine capacity. Therefore, an easy nondestructive inspection is required. One of the representative methods of the nondestructive examination (NDE) is SATIR developed by CEA [11]. JAEA also constructed a thermographic NDE device like SATIR for ITER [12]. Then, other important objective is to find test procedure for acceptance inspection using one-batchproduced mock-ups. In one-batch-production of full-size mock-ups, twelve mockups were produced. On the face of the mock-ups, several random monoblocks have cracks in the radial direction. Some monoblocks also have cracks in the circumferential direction at the ends of the mock-ups, and this suggests that CFC/OFHC-Cu joint is strengthened by the metalization and CFC is cracked as the weak point. Then, all the full-size mock-ups were quickly checked using JEBIS by heat
Fig. 4. (a) Temperature distribution of a full-size mock-up in steady state of 15 MW/m2 using JEBIS. (b) Cycle evolution of the steady-state temperature at three locations of (a) in heat cycle test of 15 MW/m2 .
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fluxes of 5, 10 and 15 MW/m2 × 10 s step by step, and the half of the mock-ups at least removed heat load of 15 MW/m2 as required. In addition, one of the full-size mock-ups was repeated by heat load of 15 MW/m2 shown in Fig. 4. Four CFC monoblocks (no. 1, 2, 5 and 6) in Fig. 4 (a) were tested by 1000 cycles of 15 MW/m2 × 10 s, and two monoblocks (nos. 3 and 4) were tested by 2000 cycles of 15 MW/m2 × 10 s. Surface temperature of CFC were also achieved equilibrium within 10 s in high heat flux test using JEBIS. From visual check, two CFC monoblock (nos. 1 and 10) have the cracks in the circumferential direction. Fig. 4 (b) shows cycle evolution of the steady-state temperature at three typical locations. Location 1, 2 and 3 correspond to the locations existing the crack in the circumferential direction, showing the maximum temperature, and showing the representative at the monoblock receiving 2000 heat cycles, respectively. Injection power of JEBIS changed slightly shot by shot, and the steady-state temperatures of three locations changed corresponding to this. Therefore, we concluded that test part of the mock-up is not affect by heat cycle test. Especially, we confirmed that a monoblock with the cracks in the circumferential direction (monoblock no.1) survived more than 1000 cycles at 15 MW/m2 . This suggests that crack extension of CFC is small by thermal stress. All the mock-ups were already checked before and after heat load test using JAEA’s thermographic NDE device and the analysis is in progress for establishment acceptance criteria for JT-60SA divertor armors. 4. Summary and future plan As JT-60SA divertor armor, the forced-cooled monoblock-type CFC armor was selected because of the high heat flux of about 15 MW/m2 to the divertor, and the design study and R&Ds have been carried out and planned to procure JT-60SA divertor armors. In order to develop the armors step by step, the small-size mock-ups were produced, and then full-size mock-ups were produced at the same time in accordance with the results of small size mock-ups. In the small-size mock-up test, the heat removal capability was confirmed again in excess of ITER requirement. In the full-size mock-up test, it was clear that the half of the mock-ups at least removed high heat flux of 15 MW/m2 as required.
Fine-tuning of metalization and reassess of heat treatment of CuCrZr is necessary for boosting the production yield, especially suppression of the cracks. In addition, decision of procedure of the nondestructive inspection and establishment of acceptance criteria for divertor armors is necessary for the procurement of JT-60SA divertor armors. Acknowledgments We thank Mr. T. Tabata, a student apprentice of JAEA, belonging to Hachinohe Institute of Technology, for his help of heat cycle test. We also thank the Japanese Industry, especially Kawasaki Plant System, Ltd, for their cooperation on the mock-up test. References [1] M. Kikuchi, JA-EU satellite tokamak working group and JT-60SA design team, Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/2-5). [2] T. Fujita, H. Tamai, M. Matsukawa, G. Kurita, J. Bialek, N. Aiba, et al., Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/P7-4). [3] M. Matsukawa, JA-EU satellite tokamak working group and the JT60-SA design team, Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/P7-5). [4] H. Kawashima, S. Sakurai, K. Shimizu, T. Takizuka, H. Tamai, M. Matsukawa, et al., Fusion Eng. Des. 81 (2006) 1613. [5] S. Sakurai, K. Masaki, Y.K. Shibama, H. Tamai, M. Matsukawa, Fusion Eng. Des. 82 (2007) 1767. [6] S. Sakurai, H. Kawashima, S. Higashijima, K. Shimizu, K. Masaki, N. Asakura, et al., J. Nucl. Mater. (PSI-18), in press. [7] M. Merola, W. Dänner, J. Palmer, G. Vielder, C.H. Wu, EU ITER Participating Team, Fusion Eng. Des. 66–68 (2003) 211. [8] M. Merola, W. Dänner, M. Pick, the EU ITER Participating Team, Fusion Eng. Des. 75–79 (2005) 325. [9] K. Ezato, M. Dairaku, M. Taniguchi, K. Sato, S. Suzuki, M. Akiba, et al., Fusion Sci. Technol. 46 (2004) 530. [10] K. Masaki, M. Taniguchi, Y. Miyo, S. Sakurai, K. Sato, K. Ezato, et al., Fusion Eng. Des. 61–62 (2002) 171. [11] A. Durocher, F. Escourbiac, A. Grosman, J. Boscary, M. Merola, F. Cismondi, et al., Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/1-5). [12] K. Yokoyama, S. Suzuki, Presented at the Conference of the Japan Society of Maintenology (in Japanese).
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Mock-up test results of monoblock-type CFC divertor armor for JT-60SA S. Higashijima ∗ , S. Sakurai, S. Suzuki, K. Yokoyama, Y. Kashiwa, K. Masaki, Y.K. Shibama, M. Takechi, K. Shibanuma, A. Sakasai, M. Matsukawa, M. Kikuchi Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193, Japan
a r t i c l e
i n f o
Article history: Available online 6 May 2009 Keywords: Divertor High heat flux CFC Monoblock JT-60SA
a b s t r a c t The JT-60 Super Advanced (JT-60SA) tokamak project starts under both the Japanese domestic program and the international program “Broader Approach”. The maximum heat flux to JT-60SA divertor is estimated to ∼15 MW/m2 for 100 s. Japan Atomic Energy Agency (JAEA) has developed a divertor armor facing high heat flux in the engineering R&D for ITER, and it is concluded that monoblock-type CFC divertor armor is promising for JT-60SA. The JT-60SA armor consists of CFC monoblocks, a cooling CuCrZr screw-tube, and a thin oxygenfree high conductivity copper (OFHC-Cu) buffer layer between the CFC monoblock and the screw-tube. CFC/OFHC-Cu and OFHC-Cu/CuCrZr joints are essential for the armor, and these interfaces are brazed. Needed improvements from ITER engineering R&D are good CFC/OFHC-Cu and OFHC-Cu/CuCrZr interfaces and suppression of CFC cracking. For these purposes, metalization inside CFC monoblock is applied, and we confirmed again that the mock-up has heat removal capability in excess of ITER requirement. For optimization of the fabrication method and understanding of the production yield, the mock-ups corresponding to quantity produced in one furnace at the same time is also produced, and the half of the mock-ups could remove 15 MW/m2 as required. This paper summarizes the recent progress of design and mock-up test results for JT-60SA divertor armor. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Japanese (JA) government and European (EU) commission established “Broader Approach (BA) Program” toward early realization of fusion energy based on tokamak concept. An upgrading device of JT-60 tokamak with fully superconducting coils (JT-60 Super Advanced, JT-60SA) will be constructed under both the JA domestic program and the international BA program [1–3]. Main mission of JT-60SA is to support and supplement ITER toward DEMO. Scientific researches of JT-60SA in support of ITER are optimization of operational scenarios for ITER, and improved understanding of physics issues of long pulse discharges, and testing of possible modifications before their implementation on ITER. As for the role of the supplementary toward DEMO, main missions in support of DEMO are to explore operational regimes of steady-state advanced high beta operation, and control of power and particle complementary to those being addressed in ITER. JT-60SA is constructed in the present JT-60U torus hall. Many components of the present JT-60U facility including heating and current drive systems and power supply are utilized. The plasma
∗ Corresponding author. Tel.: +81 29 270 7378; fax: +81 29 270 7419. E-mail address: [email protected] (S. Higashijima). 0920-3796/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fusengdes.2009.02.021
major radius is about 3 m, and a break-even-class high-temperature plasma is expected. The divertor geometry is optimized to produce both high triangularity and ITER shape single-null plasmas with one machine. Semi-closed vertical divertor with flatter dome is adopted to keep higher flexibility of plasma shaping capability. The maximum heat flux to JT-60SA divertor is estimated to ∼15 MW/m2 for 100 s [4–6]. The monoblock-type divertor has been developed for ITER in EU [7–8]. At the same time, Japan Atomic Energy Agency (JAEA) has developed divertor armor facing high heat flux in the engineering R&D for ITER [9], and it is concluded that monoblock-type CFC divertor armor are promising for JT60SA. Needed improvements from ITER engineering R&D are good CFC/OFHC-Cu and OFHC-Cu/CuCrZr interfaces and suppression of CFC cracking of the armor. For these purposes, the metalization inside CFC monoblock is applied, and we made some mock-ups and confirmed the performance of the mock-up step by step. Especially, JT-60SA divertor armors are procured previous to ITER’s order and we should develop the armors in order to resolve the problems concerning mass-production. Optimization of fabrication method and understanding of production yield is also explored in the production of the armor corresponding to quantity produced in one furnace at the same time. This paper summarizes the recent progress of design and mock-up test results for JT-60SA divertor armor. In Section 2,
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Fig. 1. Structure of JT-60SA divertor.
requirements, structure, and FEM pre-analysis of divertor armor are explained. Test production and results of high heat flux test using JAEA Electron Beam Irradiation System (JEBIS) [10] of small-size mock-up and full-size mock-ups in Section 3. Finally in Section 4, summary and future plan are presented. 2. Divertor armors Required performances of JT-60SA divertor are (1) handling of 41–50 MW plasma heating power during 100 s, (2) particle control for high density ∼1020 m−3 for long pulse more than 100 s, (3) flexibility in main plasma shape and aspect ratio, (4) capability for maintenance with remote handling system, and (5) flexibility in plasma facing materials for plasma material interaction research toward DEMO [4–6]. Divertor geometry is optimized to produce both high triangularity and ITER shape single-null plasmas with one machine. Semi-closed vertical divertor with flatter dome is adopted to keep higher flexibility of plasma shaping capability. Divertor consists of inner and outer armors where high heat flux is expected, private dome, and inner and outer baffles for medium heat flux region and divertor cassette for remote handling. To maximize flexibility in main plasma shape and aspect ratio, lower and upper divertors are optimized for medium triangularity (ITER-like) configuration and high triangularity configuration, respectively. Design of lower divertor is shown in Fig. 1. Expected heat flux on outer divertor armor using computational simulation reaches to more than 10 MW/m2 for high power heating. Outer divertor armor should have maximum power handling capability within achieved performance in R&D for ITER divertor. According to design requirements, armor performance needs 10,000 cycles of 10 MW/m2 for 100 s and 3000 cycles of 15 MW/m2 for 100 s, and total of 13,000 cycles in normal operation are assumed. Expected heat flux on inner divertor armor is about 10 MW/m2 for high power heating. Armor performance needs 10,000 cycles of 7 MW/m2 for 100 s and 3000 cycles of 10 MW/m2 for 100 s. The JT-60SA armor consists of ten CFC monoblocks (plasma facing component with high heat transfer and high resistance to thermal shock), a cooling CuCrZr screw-tube with high thermal conduction and strong mechanical property, and a thin oxygenfree high conductivity copper (OFHC-Cu) buffer layer between the
Fig. 2. Monoblock-type CFC divertor armor of JT-60SA: (a) overall view and (b) crosssection of the armor.
CFC monoblock and the screw-tube in Fig. 2. CFC monoblocks are directly cooled by the cooling tube, and CFC/OFHC-Cu and OFHCCu/CuCrZr joints are essential for the armor, and these interfaces are brazed. In order to decide the design of the armors, 2D thermal analyses using FEM are performed to determine armor width and thickness and coolant tube type and diameter within a limited total coolant flow. In the analysis condition of CFC monoblock size of 3 cm cubic, cooling tube of M10 screw, and inlet coolant of 40 ◦ C, 2 MPa, 12 m/s, it shows that the maximum temperature of CuCrZr coolant tube is ∼400 ◦ C even for heat flux of 20 MW/m2 . The estimated pressure drop is less than 0.35 MPa. Maximum surface temperature of CFC armor with thickness of 5 mm is less than 1200 ◦ C for incident heat flux of 15 MW/m2 . From the point of view of cost reduction and enough space for tube welding, it is better to reduce the number of the required divertor armors. Therefore, the armor width of 30 mm with M10 screw tube is selected in the inlet condition of 40 ◦ C, 2 MPa and 12 m/s. 3. Mock-up test of the armors In order to develop the armors step by step, the small-size mockups were produced, and then full-size mock-ups corresponding to quantity produced in one furnace at the same time were produced for mass-production in accordance with the results of small size mock-ups. The objectives of small-size mock-ups with three CFC monoblocks are to investigate the acceptable heat flux, property of brazing, and lifetime of the armors, and the producing ability of manufacturers is also checked. CFC/OFHC-Cu and OFHC-Cu/CuCrZr joints are essential for the armor. For improvement of CFC/OFHC-Cu interfaces and suppression of CFC cracking from ITER engineering R&D results, the metalization using metal containing titanium is applied inside CFC monoblock. Fig. 3 shows (a) visible TV image during 1450 cycles, (b) surface temperature at steady state (10 s) during 1450 cycles, and (c) visible TV image after 1450 cycles in the heat cycle test of a small-size mock-up by electron beam irradiation using JEBIS. In the heat cycle test it was repeated that the electron beam corresponding to 15 MW/m2 was injected for 10 s and stopped for 20 s. Time evolution of surface temperature of CFC monoblock indicated the equilibrium state within 10 s in high heat flux test using JEBIS. Direction of fiber lamination of left
S. Higashijima et al. / Fusion Engineering and Design 84 (2009) 949–952
Fig. 3. Heat cycle test (15 MW/m2 × 10 s) of small-size mock-up using JEBIS: (a) visible TV image during 1450 cycles, (b) surface temperature in steady state (10 s) during 1450 cycles, and (c) visible TV image after 1450 cycles. Lines in (c) present direction of fiber lamination of CFC.
hand-side monoblock is changed to confirm strength of brazing. Applied two-dimensional CFC has almost the same coefficient of thermal conductivity for two directions of the fiber laminations. Lines in Fig. 3(c) indicate the direction of CFC fiber lamination on the heat receiving surface. The other fiber lamination is the front-back direction in Fig. 3(c). Surface temperature at 15 MW/m2 reaches ∼2000 ◦ C. High temperature regions can be seen in the TV image. This small-size mock-up survives the repeated heat load of 1450 cycles at 15 MW/m2 and 650 cycles at 20 MW/m2 (in excess of
951
ITER requirement). In the armor surface slightly eroded regions is seen after the heat cycle test due to sublimation corresponding to high temperature regions. This is mainly due to direction of fiber lamination on left hand-side monoblock, and small defect in brazing was strongly suspected on right hand-side monoblock. Finishing the heat cycle test, the part of high temperature on the right hand-side monoblock was cut. Cross section of the monoblock was investigated, but even small defect in brazing was not found. JEBIS uses the fast-scanned electron beams, and heat flux becomes higher at the both ends than in central region of heated area. In this heat cycle test, higher heat flux area at the right end was not set outside CFC surface of small-size mock-ups, and we therefore concluded that high temperature region was due to characteristics of JEBIS beam profiles. Performance of monoblock CFC armors with improved brazing technique allowing 15 MW/m2 of heat load has been confirmed. In JT-60SA’s procurement of the divertor armors, about ten armors will be produced in the furnace at the same time, that is one-batch-production, to shorten the lead time and keep the procurement schedule. Therefore, in accordance with the results of small-size mock-up test, one-batch-production of full-size mock-ups was explored for mass-production. The objectives of one-batch-production of full-size mock-ups are to optimize the fabrication method and to understand the production yield. In the procurement plan of JT-60SA, about 2000 armors will be produced, and it is impossible to check all the armors using high heat flux load test such as JEBIS because of machine capacity. Therefore, an easy nondestructive inspection is required. One of the representative methods of the nondestructive examination (NDE) is SATIR developed by CEA [11]. JAEA also constructed a thermographic NDE device like SATIR for ITER [12]. Then, other important objective is to find test procedure for acceptance inspection using one-batchproduced mock-ups. In one-batch-production of full-size mock-ups, twelve mockups were produced. On the face of the mock-ups, several random monoblocks have cracks in the radial direction. Some monoblocks also have cracks in the circumferential direction at the ends of the mock-ups, and this suggests that CFC/OFHC-Cu joint is strengthened by the metalization and CFC is cracked as the weak point. Then, all the full-size mock-ups were quickly checked using JEBIS by heat
Fig. 4. (a) Temperature distribution of a full-size mock-up in steady state of 15 MW/m2 using JEBIS. (b) Cycle evolution of the steady-state temperature at three locations of (a) in heat cycle test of 15 MW/m2 .
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fluxes of 5, 10 and 15 MW/m2 × 10 s step by step, and the half of the mock-ups at least removed heat load of 15 MW/m2 as required. In addition, one of the full-size mock-ups was repeated by heat load of 15 MW/m2 shown in Fig. 4. Four CFC monoblocks (no. 1, 2, 5 and 6) in Fig. 4 (a) were tested by 1000 cycles of 15 MW/m2 × 10 s, and two monoblocks (nos. 3 and 4) were tested by 2000 cycles of 15 MW/m2 × 10 s. Surface temperature of CFC were also achieved equilibrium within 10 s in high heat flux test using JEBIS. From visual check, two CFC monoblock (nos. 1 and 10) have the cracks in the circumferential direction. Fig. 4 (b) shows cycle evolution of the steady-state temperature at three typical locations. Location 1, 2 and 3 correspond to the locations existing the crack in the circumferential direction, showing the maximum temperature, and showing the representative at the monoblock receiving 2000 heat cycles, respectively. Injection power of JEBIS changed slightly shot by shot, and the steady-state temperatures of three locations changed corresponding to this. Therefore, we concluded that test part of the mock-up is not affect by heat cycle test. Especially, we confirmed that a monoblock with the cracks in the circumferential direction (monoblock no.1) survived more than 1000 cycles at 15 MW/m2 . This suggests that crack extension of CFC is small by thermal stress. All the mock-ups were already checked before and after heat load test using JAEA’s thermographic NDE device and the analysis is in progress for establishment acceptance criteria for JT-60SA divertor armors. 4. Summary and future plan As JT-60SA divertor armor, the forced-cooled monoblock-type CFC armor was selected because of the high heat flux of about 15 MW/m2 to the divertor, and the design study and R&Ds have been carried out and planned to procure JT-60SA divertor armors. In order to develop the armors step by step, the small-size mock-ups were produced, and then full-size mock-ups were produced at the same time in accordance with the results of small size mock-ups. In the small-size mock-up test, the heat removal capability was confirmed again in excess of ITER requirement. In the full-size mock-up test, it was clear that the half of the mock-ups at least removed high heat flux of 15 MW/m2 as required.
Fine-tuning of metalization and reassess of heat treatment of CuCrZr is necessary for boosting the production yield, especially suppression of the cracks. In addition, decision of procedure of the nondestructive inspection and establishment of acceptance criteria for divertor armors is necessary for the procurement of JT-60SA divertor armors. Acknowledgments We thank Mr. T. Tabata, a student apprentice of JAEA, belonging to Hachinohe Institute of Technology, for his help of heat cycle test. We also thank the Japanese Industry, especially Kawasaki Plant System, Ltd, for their cooperation on the mock-up test. References [1] M. Kikuchi, JA-EU satellite tokamak working group and JT-60SA design team, Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/2-5). [2] T. Fujita, H. Tamai, M. Matsukawa, G. Kurita, J. Bialek, N. Aiba, et al., Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/P7-4). [3] M. Matsukawa, JA-EU satellite tokamak working group and the JT60-SA design team, Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/P7-5). [4] H. Kawashima, S. Sakurai, K. Shimizu, T. Takizuka, H. Tamai, M. Matsukawa, et al., Fusion Eng. Des. 81 (2006) 1613. [5] S. Sakurai, K. Masaki, Y.K. Shibama, H. Tamai, M. Matsukawa, Fusion Eng. Des. 82 (2007) 1767. [6] S. Sakurai, H. Kawashima, S. Higashijima, K. Shimizu, K. Masaki, N. Asakura, et al., J. Nucl. Mater. (PSI-18), in press. [7] M. Merola, W. Dänner, J. Palmer, G. Vielder, C.H. Wu, EU ITER Participating Team, Fusion Eng. Des. 66–68 (2003) 211. [8] M. Merola, W. Dänner, M. Pick, the EU ITER Participating Team, Fusion Eng. Des. 75–79 (2005) 325. [9] K. Ezato, M. Dairaku, M. Taniguchi, K. Sato, S. Suzuki, M. Akiba, et al., Fusion Sci. Technol. 46 (2004) 530. [10] K. Masaki, M. Taniguchi, Y. Miyo, S. Sakurai, K. Sato, K. Ezato, et al., Fusion Eng. Des. 61–62 (2002) 171. [11] A. Durocher, F. Escourbiac, A. Grosman, J. Boscary, M. Merola, F. Cismondi, et al., Proceedings of 21st International Conference on Fusion Energy 2006, Chengdu, IAEA, Vienna, 2006 (CD-ROM file FT/1-5). [12] K. Yokoyama, S. Suzuki, Presented at the Conference of the Japan Society of Maintenology (in Japanese).