- Email: [email protected]
Design of the ITER EC upper launcher nuclear shielding
Fusion Engineering and Design xxx (xxxx) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of the ITER EC upper launcher nuclear shielding ⁎
P. Spaeha,b, , G. Aielloa,b, N. Casald, M. Gagliardie, J. Pachecoe, T. Scherera,b, S. Schrecka,b, D. Straussa,b, B. Weinhorsta,c a
Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany Institute for Applied Materials, Germany Institute for Neutron Physics and Reactor Technology, Germany d ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067St., Paul Lez Durance Cedex, France e F4E, Fusion for Energy, Joint Undertaking, Barcelona, Spain b c
A R T I C LE I N FO
A B S T R A C T
Keywords: ITER ECRH Upper port plug Neutronics Shielding
ITER will be equipped with four EC (Electron Cyclotron) Upper Launchers (UL) of 8 MW microwave power each with the aim to counteract plasma instabilities during operation. These launcher antennas will be installed into four upper ports of the ITER vacuum vessel. Beside their functional purpose the port plugs which are the structural system of the launchers, have to provide as much shielding as possible in order to protect adjacent components from neutrons and photons and to minimize the shutdown dose rate in the port interspace and the port cell, being located further back in the ITER Tokamak building. Thus appropriate shielding blocks shall be installed at proper positions inside the plug. In addition several structural components will be dressed up geometrically in order to provide maximum shielding capability. This paper presents the general design of the shielding elements and their technical integration into the EC Upper Launcher.
1. Introduction In four of the upper ports of ITER, Electron Cyclotron launchers will be installed for heating and plasma stabilization [1]. The inner volume of the launchers is characterized by a relatively open structure which is unavoidable since the propagation of the microwave beams shall not interfere with any structural components. Thus it is essential to fill all remaining volumes with shielding components to guarantee the compliance of the launchers with the neutronic design requirements. That is why the EC Upper Launchers will be armed with five major shielding elements, of which two will be installed into the plasma-facing Blanket Shield Module (BSM Shields), two further ones in the front area of the launcher main structure (Internal Shields) and the fifth one in its rear part (Auxiliary Shield). Further shielding capability will be added by extending regular components of the launcher towards its inner volume. Some of these shielding components must be equipped with suitable internal cooling structures in order to dissipate heat loads from neutrons and photons and stray radiation from the microwave beams as well. The cooling passages of the shield blocks shall be integrated into the general PHTS cooling circuit of the structural system of the EC UL. Further design requirements concern stable fastening and structural integrity to sustain substantial mechanical loads from plasma
⁎
disruptions, an acceptable pressure drop inside the cooling systems and proper steel/water ratio for optimum shielding performance. 2. Motivation During the ITER CCB-233 (Configuration Control Board) sessions, radiation maps were presented and the EC Upper Launchers were identified to contribute on high radiation streaming towards the upper cryostat area [2] and thus cause relevant heating of the PFC (Poloidal Field Coils), being located above the upper ports. As a consequence a shielding improvement task was performed. It started with a survey of the composition of the EC launcher and identification of potential areas for additional shielding [3]. Then several runs of MCNP analyses have been made to investigate the effectiveness of adding the contemplated shielding elements. Having assessed the feasibility of integrating shield blocks at the specified locations, the mechanical design of these shielding components has started. 3. Shielding optimization To get the optimization task started a cutaway drawing of the CAD model of the EC UL was used to identify potential zones for additional
Corresponding author. E-mail address: [email protected] (P. Spaeh).
https://doi.org/10.1016/j.fusengdes.2019.01.036 Received 8 October 2018; Received in revised form 19 December 2018; Accepted 8 January 2019 0920-3796/ © 2019 Published by Elsevier B.V.
Please cite this article as: Spaeh, P., Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2019.01.036
Fusion Engineering and Design xxx (xxxx) xxx–xxx
P. Spaeh et al.
Fig. 1. Potential shielding enhancement zones.
components and the shielding elements. All structural components of the launcher are made from stainless steel 316 L(N)-IG. The total length of the Launcher is around 5.60 m and the total weight sums up to ca. 19,000 kg. For integration and manufacturing reasons, the BSM top- and bottom shields are designed as individual components to be fastened into the BSM structure. Also the internal backpack shield block is designed as an individual part for installation reasons. All shield components being situated in the area where nuclear heat loads higher than 0.05 MW/m³ occur, require active water cooling which is why these are equipped with cooling water channels. In this case the volumetric steel/ water ratio shall be 80:20 (as used for the MCNP calculation for cooled components) which is achieved by proper choice and layout of the cooling channels. This applies to the BSM shields, the internal shields and the DWMF shield extension. Beside volumetric nuclear loads also stray radiation from the mirrors has to be taken into account. This stray radiation can be in the order of 2% of the beam power which means that in total around 200 kW heat are affecting the inner surfaces of the Port Plug with a maximum heat flux that can reach 9.7 kW/m² [4]. This is why also the auxiliary shield, despite being placed in a low power area is equipped with cooling channels at its face side since it will be exposed to stray radiation from the mirrors M1 and M2. The internal shield and the auxiliary shield are designed as integral components being part of the Port Plug structure. They are formed from massive forged blocks and welded into the Port Plug assembly. This concept avoids the complex installation of such massive components and also eliminates the remaining gaps between the shield blocks and the port plug structure compared to a design with individual shield elements. The DWMF and the SWMF shield extensions and also the socket shielding are formed as integral part of the regarding Port Plug components as well. An overview of the nuclear heat loads on the most affected shielding components is given in Table 2 [5]. Apart from the heat loads also the mechanical loads have to be taken into account to design the shielding elements properly. Beside the dead weight of the components and the internal cooling water pressure of up to 4.4 MPa during baking, the Electro-Magnetic (EM) loads from plasma disruptions must be considered especially for the individual shielding elements being close to the plasma. Some typical loads are given in Table 3 [6]. The loads given in Table 3 refer to Cartesian coordinate systems with their origins in the Centre of Gravity of the regarding components. The orientation of the x-axis is towards the launcher axis. The cooling integration of the shield blocks takes into account the concept of a mainly “once-through”-cooling scheme of the Primary Heat Transfer System (PHTS) circuit for cooling the Port Plug structure. Additionally the need for minimum complex Remote Handling (RH) maintenance was considered. Hence both the BSM shield blocks are integrated into the BSM cooling circuit with the advantage of removal of the BSM by cutting two main cooling lines only. The DWMF shield
shielding. Depending on the expected efficiency and also considering the technical complexity of their integration into the launcher the particular areas were graded into groups whose shielding contributions subsequently then were studied by dedicated MCNP analyses. The grouping of the shielding is outlined in Fig. 1. Based on the sketched shielding zones, corresponding 3D-CAD models were created for transfer into MCNP geometry. These then were consecutively activated in the particular runs of the MCNP analyses, starting with a basic “run 0”, representing the original layout of the launcher and ending with a fully shielded “run 3”. The calculation was performed with MCNP version 6 and nuclear data from FENDL-2.1 library and mcplib 63/84. The shielding efficiency was then indicated by the maximum neutron streaming in the interspace behind the port plug, where worker access is required. The relevant results are summarized in Table 1 [3]. The shielding optimization task has demonstrated the potential for reducing the neutron streaming up to 49%, considering a fully shielded launcher, corresponding to run 3. The PFC heating inside the coil structure for the same configuration can be reduced about 55.6%. But even the less complex configuration representing run 2 achieves good shielding properties with a reduction of approx. 46% for the neutron streaming and 53.5% for the PFC heating. Since the ALARA principle shall be applied for the EC launcher shielding design, this paper deals with a shielding design approach referring to run 2 of the optimization task with the potential for slight improvement, however. 4. Shielding design The basic shielding equipment of the EC UL included a shield block in the upper area of the BSM, filling the area between the First Wall Panel (FWP) and the mirror M3 (BSM shield); a larger shield block sitting behind the mirrors M4 inside the trapezoidal part of the Launcher Main Frame (internal shield) and a third one located behind the mirrors M1 (auxiliary shield). With the shielding optimization task this basic shield block layout was revised and supplemented by the following components: A bottom shield block in the lower area of the BSM, an additional shield block on top of the internal shield (Backpack); an actively cooled wall extension of the top plate of the Double Wall Main Frame (DWMF); an un-cooled extension of the top plate of the Single Wall Main Frame (SWMF) and additional shield plates inside the socket in the rear part of the Port Plug. Fig. 2 shows the EC Upper Launcher with its main Table 1 Results for shielding optimization. Category
Run 0
Run 1
Run 2
Run 3
Max. n stream. [n/cm² ∙ s] PFC heat [W]
7.41 E08 76.6
7.25 E08 76.5
3.93 E08 34.7
3.78 E08 34.0
2
Fusion Engineering and Design xxx (xxxx) xxx–xxx
P. Spaeh et al.
Fig. 2. EC Upper Launcher Shielding components.
4.1. BSM top shield
Table 2 Nuclear heat loads on EC UL shield components. Component
Nuclear heat (total) [W]
Nuclear heat (av.) [W/cm³]
BSM top shield BSM bottom shield Int. shield (integral) Int. shield (backpack) DWMF Top
27,500 49,500 10,300 2,940 13,900
1.34 2.28 0.027 0.03 0.3
The BSM top shield block is one of the basic shield blocks and was part of the preliminary design already. It fills the top area of the BSM between the back side of the focusing mirror M3 and the backside of the FWP. The BSM top shield block is designed as an individual component with an internal cooling circuit. It has a typical dimension of 460 × 370 x 300 mm³. The total mass is approx. 163 kg and the water content is around 6.5 liters. The volumetric steel/water ratio is ca. 76:24 and is still subject to optimization by slight variation of the thickness of the embedded plates. However in this case water flow and pressure loss must be taken into consideration again. The shield block is formed by a welded shell with embedded plates. It is fastened inside the BSM by three bolts M14 of which two sit on the back side and one is located at the front side. The load case given in Table 3 causes tension forces of up to 70 kN in the bolts at the back side and also shear forces of up to 45 kN in the bolt, sitting at the front. This is why the fastening of the shield block must be supported by additional mechanical stops in y-direction. The heat load of 27.5 kW causes a temperature rise of 1.7 K, which is in accordance with the design limits. A cutaway of the BSM Top shield including the flow scheme of the cooling water is shown in Fig. 4. The cooling water circuit of the BSM top shield block causes a pressure drop of Δp = 0.016 MPa for the nominal mass flow of dm/ dt = 4 kg/s. This value was calculated along with standard book equations and must be confirmed with CFD analysis since the rather complex geometry does not fully comply with the standard formulas for loss coefficients. The coolant velocity ranges from 3.8 m/s for the
Table 3 EM loads on selected shielding components. Shield
Fx [kN]
Fy [kN]
Fz [kN]
Mx [kNm]
My [kNm]
Mz [kNm]
BSM top BSM bottom Intern. Back
−1.7 −20.0 1.3
−2.7 6.3 1.5
0.8 7.7 0.3
10.0 36.9 15.0
1.5 −5.2 −0.1
13.5 23.6 5.5
and the integral part of the internal shield are integrated into the wall cooling circuit of the Port Plug. The individual internal backpack shield is connected via two pipes with the same circuit. Fig. 3 shows the PHTS cooling layout for the entire UL structure. The following sub-chapters deal with particular design features of the most relevant shield blocks only.
Fig. 3. PHTS cooling circuit for the EC UL structure. 3
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P. Spaeh et al.
Fig. 7. Backpack internal shield.
profiles allow inspection of the circumferential welds of the Main Frame as well as the installation of supply lines for the In-vessel mirrors. The front part features precisely machined fasteners for fixation of the mirrors M4 which steer the beams into the plasma. To dissipate the heat generated from neutrons, the integral part of the internal shield is equipped with cooling channels and integrated into the PHTS main cooling loop. The integral shield block is displayed in Fig. 5 and a typical layer of the gun-drilled cooling channels is shown in Fig. 6.
Fig. 4. BSM top shield cutaway with coolant flow.
4.4. Internal shield backpack The backpack shield is machined from a forged SS 316 L(N) block and will be fastened on top of the integral shield. It has a total length of 1100 mm and a mass of ca. 780 kg. It is equipped with gun-drilled cooling channels and provides lateral space for supply lines integration for the In-Vessel mirrors M3 and M4. The fastening concept with four bolts M20 causes shear stresses in the bolts of up to 25 MPa mainly from Mz and the dead weight, which is why shear keys shall be considered for the manufacturing design. Fig. 7 shows an semi-transparent view of the backpack shield.
Fig. 5. Integral internal shield.
5. Conclusion The layout of the EC Upper Launcher shielding has undergone an optimization task in 2017. As a consequence the shielding performance was improved up to ca. 50%. Regarding shielding elements were added and existing shielding elements design was improved, taking into account space requirements, installation, mechanical integrity and cooling needs. Fig. 6. Typical cooling layer in the internal shield.
Acknowledgments entrance and the exit pipe down to 0.6–1.8 m/s inside the shield block. The total length of the cooling path is ca. 1.6 m. For baking with water mass flow of dm/dt = 0.4 kg/s the pressure loss is negligible.
This work was supported by Fusion for Energy under the grant contract No. F4E-2010-GRT-161. The views and opinions expressed herein reflect only the author’s views and do not necessarily reflect those of F4E and the ITER Organization.
4.2. BSM bottom shield
References
The design of the bottom shield is challenging due to substantial heat loads [7] and mechanical EM loads as well. This is why only a concept was developed so far. An U-shaped shield block in an upsidedown position is fastened to the bottom wall of the BSM. A small-meshed cooling-circuit is integrated into the shape by gun-drilled channels, enclosed by weld caps.
[1] D. Strauss, et al., Approaching final design of the ITER EC H&CD Upper launcher, Proceedings of This Conference, (2019). [2] M. Loughlin, et al., Radiation Maps, Presentation at CCB-233 Meeting, Cadarache, Private Communication, (2016). [3] M. Gagliardi, et al., EC Upper Launcher: Optimization of Nuclear Shielding v3.1, Private Communication, (2017). [4] T. Goodman, RF Stray Radiation Management in the ITER UL, Design Report, 2018, Private Communication, (2019). [5] B. Weinhorst, Report on Nuclear Heating for the Upper Launcher, Design Report, 2018, Private Communication, (2019). [6] G. Aiello, et al., Dup3 report on analysis macros, guidelines and results, Design report 2018, Private communication, (2018). [7] J. Pacheco, et al., Cooling optimization of the electron cyclotron upper launcher blanket shield module, Proceedings of This Conference, (2019).
4.3. Integral internal shield The integral internal shield basically is part of the front segment of the SWMF. It has a total length of 1470 mm of which the center part with a length of 730 mm is circumferently welded into the SWMF. On both face sides of this center part are structural extensions whose
4
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Design of the ITER EC upper launcher nuclear shielding ⁎
P. Spaeha,b, , G. Aielloa,b, N. Casald, M. Gagliardie, J. Pachecoe, T. Scherera,b, S. Schrecka,b, D. Straussa,b, B. Weinhorsta,c a
Karlsruhe Institute of Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany Institute for Applied Materials, Germany Institute for Neutron Physics and Reactor Technology, Germany d ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067St., Paul Lez Durance Cedex, France e F4E, Fusion for Energy, Joint Undertaking, Barcelona, Spain b c
A R T I C LE I N FO
A B S T R A C T
Keywords: ITER ECRH Upper port plug Neutronics Shielding
ITER will be equipped with four EC (Electron Cyclotron) Upper Launchers (UL) of 8 MW microwave power each with the aim to counteract plasma instabilities during operation. These launcher antennas will be installed into four upper ports of the ITER vacuum vessel. Beside their functional purpose the port plugs which are the structural system of the launchers, have to provide as much shielding as possible in order to protect adjacent components from neutrons and photons and to minimize the shutdown dose rate in the port interspace and the port cell, being located further back in the ITER Tokamak building. Thus appropriate shielding blocks shall be installed at proper positions inside the plug. In addition several structural components will be dressed up geometrically in order to provide maximum shielding capability. This paper presents the general design of the shielding elements and their technical integration into the EC Upper Launcher.
1. Introduction In four of the upper ports of ITER, Electron Cyclotron launchers will be installed for heating and plasma stabilization [1]. The inner volume of the launchers is characterized by a relatively open structure which is unavoidable since the propagation of the microwave beams shall not interfere with any structural components. Thus it is essential to fill all remaining volumes with shielding components to guarantee the compliance of the launchers with the neutronic design requirements. That is why the EC Upper Launchers will be armed with five major shielding elements, of which two will be installed into the plasma-facing Blanket Shield Module (BSM Shields), two further ones in the front area of the launcher main structure (Internal Shields) and the fifth one in its rear part (Auxiliary Shield). Further shielding capability will be added by extending regular components of the launcher towards its inner volume. Some of these shielding components must be equipped with suitable internal cooling structures in order to dissipate heat loads from neutrons and photons and stray radiation from the microwave beams as well. The cooling passages of the shield blocks shall be integrated into the general PHTS cooling circuit of the structural system of the EC UL. Further design requirements concern stable fastening and structural integrity to sustain substantial mechanical loads from plasma
⁎
disruptions, an acceptable pressure drop inside the cooling systems and proper steel/water ratio for optimum shielding performance. 2. Motivation During the ITER CCB-233 (Configuration Control Board) sessions, radiation maps were presented and the EC Upper Launchers were identified to contribute on high radiation streaming towards the upper cryostat area [2] and thus cause relevant heating of the PFC (Poloidal Field Coils), being located above the upper ports. As a consequence a shielding improvement task was performed. It started with a survey of the composition of the EC launcher and identification of potential areas for additional shielding [3]. Then several runs of MCNP analyses have been made to investigate the effectiveness of adding the contemplated shielding elements. Having assessed the feasibility of integrating shield blocks at the specified locations, the mechanical design of these shielding components has started. 3. Shielding optimization To get the optimization task started a cutaway drawing of the CAD model of the EC UL was used to identify potential zones for additional
Corresponding author. E-mail address: [email protected] (P. Spaeh).
https://doi.org/10.1016/j.fusengdes.2019.01.036 Received 8 October 2018; Received in revised form 19 December 2018; Accepted 8 January 2019 0920-3796/ © 2019 Published by Elsevier B.V.
Please cite this article as: Spaeh, P., Fusion Engineering and Design, https://doi.org/10.1016/j.fusengdes.2019.01.036
Fusion Engineering and Design xxx (xxxx) xxx–xxx
P. Spaeh et al.
Fig. 1. Potential shielding enhancement zones.
components and the shielding elements. All structural components of the launcher are made from stainless steel 316 L(N)-IG. The total length of the Launcher is around 5.60 m and the total weight sums up to ca. 19,000 kg. For integration and manufacturing reasons, the BSM top- and bottom shields are designed as individual components to be fastened into the BSM structure. Also the internal backpack shield block is designed as an individual part for installation reasons. All shield components being situated in the area where nuclear heat loads higher than 0.05 MW/m³ occur, require active water cooling which is why these are equipped with cooling water channels. In this case the volumetric steel/ water ratio shall be 80:20 (as used for the MCNP calculation for cooled components) which is achieved by proper choice and layout of the cooling channels. This applies to the BSM shields, the internal shields and the DWMF shield extension. Beside volumetric nuclear loads also stray radiation from the mirrors has to be taken into account. This stray radiation can be in the order of 2% of the beam power which means that in total around 200 kW heat are affecting the inner surfaces of the Port Plug with a maximum heat flux that can reach 9.7 kW/m² [4]. This is why also the auxiliary shield, despite being placed in a low power area is equipped with cooling channels at its face side since it will be exposed to stray radiation from the mirrors M1 and M2. The internal shield and the auxiliary shield are designed as integral components being part of the Port Plug structure. They are formed from massive forged blocks and welded into the Port Plug assembly. This concept avoids the complex installation of such massive components and also eliminates the remaining gaps between the shield blocks and the port plug structure compared to a design with individual shield elements. The DWMF and the SWMF shield extensions and also the socket shielding are formed as integral part of the regarding Port Plug components as well. An overview of the nuclear heat loads on the most affected shielding components is given in Table 2 [5]. Apart from the heat loads also the mechanical loads have to be taken into account to design the shielding elements properly. Beside the dead weight of the components and the internal cooling water pressure of up to 4.4 MPa during baking, the Electro-Magnetic (EM) loads from plasma disruptions must be considered especially for the individual shielding elements being close to the plasma. Some typical loads are given in Table 3 [6]. The loads given in Table 3 refer to Cartesian coordinate systems with their origins in the Centre of Gravity of the regarding components. The orientation of the x-axis is towards the launcher axis. The cooling integration of the shield blocks takes into account the concept of a mainly “once-through”-cooling scheme of the Primary Heat Transfer System (PHTS) circuit for cooling the Port Plug structure. Additionally the need for minimum complex Remote Handling (RH) maintenance was considered. Hence both the BSM shield blocks are integrated into the BSM cooling circuit with the advantage of removal of the BSM by cutting two main cooling lines only. The DWMF shield
shielding. Depending on the expected efficiency and also considering the technical complexity of their integration into the launcher the particular areas were graded into groups whose shielding contributions subsequently then were studied by dedicated MCNP analyses. The grouping of the shielding is outlined in Fig. 1. Based on the sketched shielding zones, corresponding 3D-CAD models were created for transfer into MCNP geometry. These then were consecutively activated in the particular runs of the MCNP analyses, starting with a basic “run 0”, representing the original layout of the launcher and ending with a fully shielded “run 3”. The calculation was performed with MCNP version 6 and nuclear data from FENDL-2.1 library and mcplib 63/84. The shielding efficiency was then indicated by the maximum neutron streaming in the interspace behind the port plug, where worker access is required. The relevant results are summarized in Table 1 [3]. The shielding optimization task has demonstrated the potential for reducing the neutron streaming up to 49%, considering a fully shielded launcher, corresponding to run 3. The PFC heating inside the coil structure for the same configuration can be reduced about 55.6%. But even the less complex configuration representing run 2 achieves good shielding properties with a reduction of approx. 46% for the neutron streaming and 53.5% for the PFC heating. Since the ALARA principle shall be applied for the EC launcher shielding design, this paper deals with a shielding design approach referring to run 2 of the optimization task with the potential for slight improvement, however. 4. Shielding design The basic shielding equipment of the EC UL included a shield block in the upper area of the BSM, filling the area between the First Wall Panel (FWP) and the mirror M3 (BSM shield); a larger shield block sitting behind the mirrors M4 inside the trapezoidal part of the Launcher Main Frame (internal shield) and a third one located behind the mirrors M1 (auxiliary shield). With the shielding optimization task this basic shield block layout was revised and supplemented by the following components: A bottom shield block in the lower area of the BSM, an additional shield block on top of the internal shield (Backpack); an actively cooled wall extension of the top plate of the Double Wall Main Frame (DWMF); an un-cooled extension of the top plate of the Single Wall Main Frame (SWMF) and additional shield plates inside the socket in the rear part of the Port Plug. Fig. 2 shows the EC Upper Launcher with its main Table 1 Results for shielding optimization. Category
Run 0
Run 1
Run 2
Run 3
Max. n stream. [n/cm² ∙ s] PFC heat [W]
7.41 E08 76.6
7.25 E08 76.5
3.93 E08 34.7
3.78 E08 34.0
2
Fusion Engineering and Design xxx (xxxx) xxx–xxx
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Fig. 2. EC Upper Launcher Shielding components.
4.1. BSM top shield
Table 2 Nuclear heat loads on EC UL shield components. Component
Nuclear heat (total) [W]
Nuclear heat (av.) [W/cm³]
BSM top shield BSM bottom shield Int. shield (integral) Int. shield (backpack) DWMF Top
27,500 49,500 10,300 2,940 13,900
1.34 2.28 0.027 0.03 0.3
The BSM top shield block is one of the basic shield blocks and was part of the preliminary design already. It fills the top area of the BSM between the back side of the focusing mirror M3 and the backside of the FWP. The BSM top shield block is designed as an individual component with an internal cooling circuit. It has a typical dimension of 460 × 370 x 300 mm³. The total mass is approx. 163 kg and the water content is around 6.5 liters. The volumetric steel/water ratio is ca. 76:24 and is still subject to optimization by slight variation of the thickness of the embedded plates. However in this case water flow and pressure loss must be taken into consideration again. The shield block is formed by a welded shell with embedded plates. It is fastened inside the BSM by three bolts M14 of which two sit on the back side and one is located at the front side. The load case given in Table 3 causes tension forces of up to 70 kN in the bolts at the back side and also shear forces of up to 45 kN in the bolt, sitting at the front. This is why the fastening of the shield block must be supported by additional mechanical stops in y-direction. The heat load of 27.5 kW causes a temperature rise of 1.7 K, which is in accordance with the design limits. A cutaway of the BSM Top shield including the flow scheme of the cooling water is shown in Fig. 4. The cooling water circuit of the BSM top shield block causes a pressure drop of Δp = 0.016 MPa for the nominal mass flow of dm/ dt = 4 kg/s. This value was calculated along with standard book equations and must be confirmed with CFD analysis since the rather complex geometry does not fully comply with the standard formulas for loss coefficients. The coolant velocity ranges from 3.8 m/s for the
Table 3 EM loads on selected shielding components. Shield
Fx [kN]
Fy [kN]
Fz [kN]
Mx [kNm]
My [kNm]
Mz [kNm]
BSM top BSM bottom Intern. Back
−1.7 −20.0 1.3
−2.7 6.3 1.5
0.8 7.7 0.3
10.0 36.9 15.0
1.5 −5.2 −0.1
13.5 23.6 5.5
and the integral part of the internal shield are integrated into the wall cooling circuit of the Port Plug. The individual internal backpack shield is connected via two pipes with the same circuit. Fig. 3 shows the PHTS cooling layout for the entire UL structure. The following sub-chapters deal with particular design features of the most relevant shield blocks only.
Fig. 3. PHTS cooling circuit for the EC UL structure. 3
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Fig. 7. Backpack internal shield.
profiles allow inspection of the circumferential welds of the Main Frame as well as the installation of supply lines for the In-vessel mirrors. The front part features precisely machined fasteners for fixation of the mirrors M4 which steer the beams into the plasma. To dissipate the heat generated from neutrons, the integral part of the internal shield is equipped with cooling channels and integrated into the PHTS main cooling loop. The integral shield block is displayed in Fig. 5 and a typical layer of the gun-drilled cooling channels is shown in Fig. 6.
Fig. 4. BSM top shield cutaway with coolant flow.
4.4. Internal shield backpack The backpack shield is machined from a forged SS 316 L(N) block and will be fastened on top of the integral shield. It has a total length of 1100 mm and a mass of ca. 780 kg. It is equipped with gun-drilled cooling channels and provides lateral space for supply lines integration for the In-Vessel mirrors M3 and M4. The fastening concept with four bolts M20 causes shear stresses in the bolts of up to 25 MPa mainly from Mz and the dead weight, which is why shear keys shall be considered for the manufacturing design. Fig. 7 shows an semi-transparent view of the backpack shield.
Fig. 5. Integral internal shield.
5. Conclusion The layout of the EC Upper Launcher shielding has undergone an optimization task in 2017. As a consequence the shielding performance was improved up to ca. 50%. Regarding shielding elements were added and existing shielding elements design was improved, taking into account space requirements, installation, mechanical integrity and cooling needs. Fig. 6. Typical cooling layer in the internal shield.
Acknowledgments entrance and the exit pipe down to 0.6–1.8 m/s inside the shield block. The total length of the cooling path is ca. 1.6 m. For baking with water mass flow of dm/dt = 0.4 kg/s the pressure loss is negligible.
This work was supported by Fusion for Energy under the grant contract No. F4E-2010-GRT-161. The views and opinions expressed herein reflect only the author’s views and do not necessarily reflect those of F4E and the ITER Organization.
4.2. BSM bottom shield
References
The design of the bottom shield is challenging due to substantial heat loads [7] and mechanical EM loads as well. This is why only a concept was developed so far. An U-shaped shield block in an upsidedown position is fastened to the bottom wall of the BSM. A small-meshed cooling-circuit is integrated into the shape by gun-drilled channels, enclosed by weld caps.
[1] D. Strauss, et al., Approaching final design of the ITER EC H&CD Upper launcher, Proceedings of This Conference, (2019). [2] M. Loughlin, et al., Radiation Maps, Presentation at CCB-233 Meeting, Cadarache, Private Communication, (2016). [3] M. Gagliardi, et al., EC Upper Launcher: Optimization of Nuclear Shielding v3.1, Private Communication, (2017). [4] T. Goodman, RF Stray Radiation Management in the ITER UL, Design Report, 2018, Private Communication, (2019). [5] B. Weinhorst, Report on Nuclear Heating for the Upper Launcher, Design Report, 2018, Private Communication, (2019). [6] G. Aiello, et al., Dup3 report on analysis macros, guidelines and results, Design report 2018, Private communication, (2018). [7] J. Pacheco, et al., Cooling optimization of the electron cyclotron upper launcher blanket shield module, Proceedings of This Conference, (2019).
4.3. Integral internal shield The integral internal shield basically is part of the front segment of the SWMF. It has a total length of 1470 mm of which the center part with a length of 730 mm is circumferently welded into the SWMF. On both face sides of this center part are structural extensions whose
4