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• An analysis strategy was developed in order to assess the DCPSP mechanical integrity against the loads occurring during the VV Baking + SL-2 load combination. • The modal analysis of the DCPSP shows that only the first two natural frequencies are below the f ZPA , which are far from the FRS peaks. • The thermo-mechanical analysis of the DCPSP produces categorized stresses lower than the allowable limits defined in the ASME code. • Additional analyses covering all the rest of applicable load combinations shall be carried out in order to fully validate the DCPSP design. The Double Closure Plate Sub-Plate (DCPSP) was introduced in the Electron Cyclotron Upper Launcher (EC UL) design in order to minimize the openings exposing the interior of the Port Plug (PP) to the port cell; avoiding thus the near environment activation in case of maintenance or intervention on the In-Vessel (IV) components. The load combination Vacuum Vessel (VV) baking + Seismic level 2 is considered as one of the most relevant accidental events in terms of structural conformity affecting the DCPSP. The modal analysis of the DCPSP shows that the natural frequencies are far from the peaks of the ITER reference spectra at the PP flange. Therefore, the feasibility of analyzing the seismic event by using a static method, as a replacement of the Response Spectrum approach, is also investigated. Next, the results due to the seismic event are combined with those produced by loads on the DCPSP that occur during the VV baking scenario. The comparison of the categorized stresses and the allowable design limits showed that the mechanical integrity of the DCPSP is preserved during this load combination. [ABSTRACT FROM AUTHOR]

Abstract The safety classification of Structures, Systems and Components (SSCs) used in nuclear power plants provided in various IAEA guides and other international standards is mostly aimed at the fission applications. For fusion the main safety functions are related to the confinement of radioactive materials and the limitation of personnel radiation exposure and not with heat removal or reactivity control. Similarly, various plant states and events with their severity levels specific to a fusion plant are different. Ranking SSCs according to their significance to safety helps to determine the design, quality and manufacturing requirements to be applied to individual SSCs. Classification is a top down process that begins with a basic understanding of the plant design, its safety analysis and how the main safety functions will be achieved. On the basis of the classification, a complete set of engineering rules must be specified which then dictate the codes and standards that are used by the designers. Guidelines for identification and classification of SSCs that are important to safety for Fusion applications have been provided considering the current practice and highlight the differences in the approaches used to identify and classify SSCs that are important to safety. [ABSTRACT FROM AUTHOR]

Abstract The Mirror one Lower (LM1) is part of the in-vessel quasi-optical beam propagation system for the ITER Electro Cyclotron (EC) Upper Launcher (UL), where eight beams are reflected through four mirrors during its passage to the plasma. The mirrors are grouped into two rows of four beams each and the mirror LM1 refers to a four mirror set. High power millimeter (mm) waves are generated by the gyrotrons and delivered to the in-vessel components via corrugated wave-guides. The design of the LM1 shall guarantee the optimal propagation of the beams during their transmission through the optical system taking into consideration 1) the shape of the reflecting surfaces, 2) loads coming from the beams themselves, the plasma and nuclear reactions as well as off-normal events and 3) the port plug space restrictions. This paper reports the Ohmic loss assessment at LM1 as function of frequency, surface roughness and resistivity using the most suitable material and the power input (1.31 MW at 170 GHz). It describes the design investigation of the cooling solutions for the normal scenario via computational fluid dynamic analyses, based on the ITER Primary Heat Transfer System (PHTS) cooling boundary conditions, needed to remove ∼20 kW of power deposition on the mirror surface. Finite element analyses are performed to guide the design choices in an effort to minimize the maximum mirror surface temperature and thus diminishing the deformation of the reflecting surfaces. The conclusion of this study will provide a feasible design solution for the LM1 and Upper Mirror 1 (UM1). [ABSTRACT FROM AUTHOR]

Abstract Each of the 4 ITER Electron Cyclotron Heating Upper Launcher (ECHUL) features 8 transmission lines used to inject microwave power of up to 1.31 MW (at the source) per line, into the plasma at 170 GHz. The microwaves are guided from the gyrotrons via (ø50 mm) waveguide transmission lines, into the plasma via the First Confinement System (FCS), consisting of a 'Z'-shaped set of straight corrugated aluminum waveguides, totaling ∼13 m per line, connected by miter bends (MB). The orientation of the transmission line is achieved by reflecting the microwaves with mirrors. The MBs perform these reflections at angles of ∼90°; they also form part of the primary vacuum boundary and serve as a Tritium barrier, for which SIC-1 safety classification requirements apply. By reason of ohmic dissipation, mm-wave power is converted into heat, reaching a peak thermal flux of approximately 5.3 MW/m2 at the MB mirror center. Due to this intense peaked power density in the middle of the MB mirror, a dedicated cooling system needs to be designed and tested. In addition to handling the ohmic losses, the MB of the FCS shall be capable of resisting the applied external loads and imposed displacements and also comply with material and space restrictions. This study describes the evolution of several cooling concepts (evaluated via computational fluid dynamic analysis), leading to the optimization of the final chosen cooling system, which integrates the innovative use of vapor chamber technology. In addition, consideration is given to the final design parameters (material choice and structural dimensioning), concluding with the presentation of the MB assembly concept deemed most suitable for the final FCS design. [ABSTRACT FROM AUTHOR]

Highlights • A design concept of double CPSP for the ITER EC UL has been developed by SPC in the framework of the F4E grant F4E-GRT-615. • The fluid-dynamic analyses show that the power dissipated during normal operation can be properly removed with an acceptable mass flow. • The simulation for the baking event indicates that the Thermal Isolation CPSP properly isolates the Aluminum Alloy 6061-T6 ex-vessel waveguides. • The comparison between the classified stress and the allowable limits shows that the double CPSP withstands the loads due to normal operation. Abstract The Closure Plate Sub-Plate (CPSP), which defines the border between ex-vessel and in-vessel components of the Electron Cyclotron Upper Launcher (EC UL), bundles the waveguides into a sub-assembly which can be manipulated separately from the UL Port Plug (PP). The primary CPSP functions are to provide transmission line feedthroughs, support and alignment of the attached waveguides, neutron and gamma shielding, and Tritium/vacuum containment. The double CPSP concept, which is divided into In-vessel Waveguides CPSP and Thermal Isolation CPSP, was recently introduced in order to minimize the openings that expose the interior of the plug, to avoid the near environment activation in case of maintenance or intervention on the in-vessel components. This paper reports the most recent status of the CPSP as well as the analyses carried out to validate the design for normal operation. The fluid-dynamic analyses show that the power dissipated due to mm-wave transmission can be properly removed with an acceptable mass flow producing admissible values of pressure drop and temperature rise in the cooling systems. The results obtained in the thermo-mechanical simulation, validated using the ASME code, shows that the CPSP design is capable of withstanding the expected loads taking place during normal operation. [ABSTRACT FROM AUTHOR]

The ITER electron cyclotron (EC) upper launcher has passed the CDR (conceptual design review) in 2005 and the PDR (preliminary design review) in 2009 and is in its final design phase now. The final design will be elaborated by the European consortium ECHUL-CA with contributions from several research institutes in Germany, Italy, the Netherlands and Switzerland. Within this consortium KIT is responsible for the design of the structural components (the upper port plug, UPP) and also the design integration of the launcher. As the selection of applicable codes and standards was under discussion for the past decade, the conceptual and the preliminary design of the launcher structure were not elaborated in straight accordance with a particular code but with a variety of well-acknowledged engineering practices. For the final design it is compulsory to validate the design with respect to a typical engineering code in order to be compliant with the ITER quality and nuclear requirements and to get acceptance from the French regulator. This paper presents typical design validation of the closure plate, which is the vacuum and Tritium barrier and thus a safety relevant component of the upper port plug (UPP), performed with the ASME boiler and pressure vessel code. Rationales for choosing this code are given as well as a comparison between different design methods, like the “design by rule” and the “design by analysis” approach. Also the selections of proper load specifications and the identification of potential failure modes are covered. In addition to that stress categorizations, analyses results, and prove of the soundness of the design are presented. [ABSTRACT FROM AUTHOR]

Abstract Four EC H&CD (Electron Cyclotron Heating and Current Drive) launchers will be installed into the upper ports #12, #13, #15 and #16 in ITER. Beside plasma heating their main purpose is to counteract plasma instabilities by injecting up to 20 MW of microwave power at a frequency of 170 GHz at dedicated positions into the plasma. The microwave power is generated in 24 Gyrotrons outside the Tokamak and transmitted into the dedicated ports by 8 waveguide lines per launcher. After passing a CVD (Chemical Vapor Deposition) diamond window and another section of circular waveguides, the microwaves are quasi-optically guided into the plasma by an adjusted set of mirrors. These mirrors and also the foremost segments of the waveguides are mounted into the Upper Port Plug, which is a massive steel structure capable to dissipate up to 800 kW heat and to withstand heavy mechanical loads induced mainly from plasma disruptions. This paper presents the most recent status of the design of the EC H&CD Upper Port Plug (UPP), featuring the construction of the supporting structure and the BSM (Blanket Shield Module) with its plasma facing First Wall, the PHTS (Primary Heat Transfer System) water cooling layout, the shielding components engineering, the microwave system integration and comprehensive manufacturing strategies. Also correlated computational analyses to prove the final design of the launcheŕs structural system are given. [ABSTRACT FROM AUTHOR]

Abstract The diamond window is part of the ex-vessel waveguide system of the ITER ECRH Upper Launcher and consists of an ultra-low loss CVD diamond disk mounted in a system of metallic parts. On the one hand the window has to fulfil adequate transmission capability for high power mm-waves and on the other hand it serves, together with an isolation valve, as primary vacuum boundary of the ITER vacuum vessel, and has the function of tritium confinement. Therefore it is classified as Protection Important Component and high requirements for quality and safety apply. The window assembly cannot be entirely covered by codes and standards and thus an ad-hoc qualification program is required, including prototyping activities. The mm-wave transmission capability of the window, which is mainly defined by the dielectric loss of the diamond disk, has to be demonstrated as well as its structural integrity. For previous and current window prototypes, diamond disks with low dielectric losses have been chosen with a diameter of 80 mm and a thickness of 1.11 mm. This thickness satisfies the resonance condition (d = n*λ eff /2) for the 170 GHz beam, ensuring a high transmission, but it also needs to be validated with respect to the mechanical loads, especially the expected pressure loads. Investigations on the flexural strength of diamond disks (D = 30 mm, d = 1.11 mm) have been performed using a ring-on-ring set-up and the results lead to an estimation of the failure behavior. In addition, pressure tests of a mock-up consisting of a diamond disk (D = 80 mm, d = 1.11 mm) brazed to a copper cuff are under examination. The dedicated test program includes cyclic tests at lower pressures and high pressure tests (up to 2 bar) allowing a simulation of the expected events. This paper will give an overview on the qualification activities for the ITER torus window with a focus on the qualification of the diamond disk and with respect to its mechanical properties. Respective parts of the test program, which need F4E and IO review and approval, will be described and first results will be presented. [ABSTRACT FROM AUTHOR]

The Electron Cyclotron Upper Launcher is an eight beamline ITER antenna whose main goal is to drive current locally, inside magnetic islands that may form on the q = 3/2 or 2 rational magnetic flux surfaces, in order to stabilize neoclassical tearing modes (NTMs). The primary vacuum boundary at the port plug extends into the port cell region through the ex-vessel mm-wave waveguide components, defining the so-called First Confinement System (FCS). Thermal expansion, seismic events and plasma disruption events result in displacements of the vacuum vessel, relative to the tokamak building, that are transferred to the FCS at its interfaces with the port plug. In absence of suitable inline waveguide bellows, the adaptation to such imposed displacements is provided by bending compliance of the straight waveguide sections. An analysis methodology for the ex-vessel components was developed which covers a preliminary set of applicable load combinations throughout the system life-cycle. This methodology describes the FCS numerical model developed to assess the system against independent events as well as the load combination strategy followed to combine the results. Some simplifications like the simulation of the Vertical Displacement Events (VDEs) by a static approach are considered in order to develop this methodology. The analysis of the results shows that the miter bends and the pieces of waveguides rigidly attached to the port cell ceiling are the most demanded components for most of the considered load combinations. [ABSTRACT FROM AUTHOR]

The ITER Electron Cyclotron Heating Upper Launcher (ECHUL) will be used to drive current locally inside magnetic islands located at the q = 2 (or smaller) rational surfaces in order to stabilize neoclassical tearing modes (NTMs). Each antenna consists of eight beam lines that are designed for the transmission of up to 1.5 MW of mm- wave power at 170 GHz, with at least 90% of the power in the main HE11 mode. Mm-wave power is assumed to be converted into heat by ohmic dissipation in the waveguide, with intensity peaks reaching up to 9000 W/m 2 , consequently to enable continuous working operation at nominal transmitted power, temperature control of the waveguide is required via an active cooling system. Available commercial solutions for the cooled waveguide are incompatible with the FCS, which will be subject to higher heat fluxes and shall comply with ITER SIC-1 requirements. Therefore a dedicated cooling system must be designed. This study presents the results of the thermal mechanical analyses of two different cooling concepts, and concludes the most suitable concept for the final Upper Launcher FCS system design. [ABSTRACT FROM AUTHOR]

The diamond window is part of the electron cyclotron heating upper launcher system for ITER. Together with the isolation valve it constitutes the primary vacuum boundary and it also acts as first tritium barrier. Therefore the window is classified as Safety/Protection Important Component (SIC/PIC) with the nuclear safety function “confinement”. As the diamond window unit is not entirely covered by standard codes, an ad-hoc qualification program needs to be defined, including analysis, prototyping and testing. In the framework of a contract with F4E, the test program for a diamond window prototype is being developed with the aim to prove its operability for normal, accidental and incidental conditions as identified in the ITER load specifications. Tests range from dielectric loss measurements for the bare Chemical Vapour Deposition (CVD) diamond disk up to mechanical and vacuum tests for the complete window assembly. Finally mm-wave properties have to be characterized for the complete window. A clear definition of the testing requirements and of the acceptance criteria is necessary as well as a complete documentation of the process. This paper will present the development of the test plan for a window prototype, which is currently under manufacturing. First tests are directed to the characterization of the bare diamond disk with a focus on its dielectric properties. [ABSTRACT FROM AUTHOR]

The four electron cyclotron (EC) upper port antennas (or “upper launchers” —UL) will be used to drive current locally inside magnetic islands located at the q = 2 (or smaller) rational surfaces in order to stabilize neoclassical tearing modes (NTMs), as well as heat inside of ρ of about 0.4. Each antenna consists of eight beam lines that are designed for the transmission of 1.5 MW of mm-wave power at 170 GHz. The First Confinement System (FCS) is formed by the ex-vessel mm-wave waveguide components, for which SIC-1 classification requirements apply. The beam lines in the FCS comprise a Z shaped set of straight corrugated waveguides with a nominal diameter of 50 mm connected by miter bends. This system is subjected to imposed displacements coming mainly from the thermal expansion of the vacuum vessel, seismic events and/or plasma disruption events. In absence of suitable SIC-1 waveguide bellows, the FCS waveguides must provide the necessary mechanical functional compliance. This has required the development of a dedicated, flange type coupling system with double metallic seals, capable of resisting the generated external loads while maintaining vacuum tightness and alignment. This paper presents the results of the design, analysis and pre-qualification experimental work done on the waveguides and the integrated SIC-1 compliant coupling system. [ABSTRACT FROM AUTHOR]

The magnetic perturbation due to the ferromagnetic test blanket modules (TBMs) may deteriorate fast ion confinement in ITER. This effect must be quantified by numerical studies in 3D. We have implemented a combined finite element method (FEM) – Biot-Savart law integrator method (BSLIM) to calculate the ITER 3D magnetic field and vector potential in detail. Unavoidable geometry simplifications changed the mass of the TBMs and ferritic inserts (FIs) up to 26%. This has been compensated for by modifying the nonlinear ferromagnetic material properties accordingly. Despite the simplifications, the computation geometry and the calculated fields are highly detailed. The combination of careful FEM mesh design and using BSLIM enables the use of the fields unsmoothed for particle orbit-following simulations. The magnetic field was found to agree with earlier calculations and revealed finer details. The vector potential is intended to serve as input for plasma shielding calculations. [ABSTRACT FROM AUTHOR]

An electron cyclotron system is one of the four auxiliary plasma heating systems to be installed on the ITER tokamak. The ITER EC system consists of 24 gyrotrons with associated 12 high voltage power supplies, a set of evacuated transmission lines and two types of launchers. The whole system is designed to inject 20 MW of microwave power at 170 GHz into the plasma. The primary functions of the system include plasma start-up, central heating and current drive, and magneto-hydrodynamic instabilities control. The design takes present day technology and extends towards high power CW operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond. The EC system is faced with significant challenges, which not only includes an advanced microwave system for plasma heating and current drive applications but also has to comply with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012. Since conceptual design of the EC system established in 2007, the EC system has progressed to a preliminary design stage in 2012, and is now moving forward towards a final design. The majority of the subsystems have completed the detailed design and now advancing towards the final design completion. [ABSTRACT FROM AUTHOR]

• A new design concept of both upper and lower MBMBs, compliance with ITER EC UL requirements, is described in this paper. • The fluid-dynamic analyses show that the highest temperature values occur in the MB mirror centers, reaching up to 203°C. • The thermo-mechanical analyses demonstrate that the stress peak takes place at the MB mirrors, reaching up to 324 MPa. • The categorized stresses obtained in the MBMBs are lower than the allowable limits defined in the ASME code. The ITER Electron Cyclotron Heating (ECH) system will be used to counteract magneto-hydrodynamic plasma instabilities by aiming up to 20 MW of mm-wave power at 170 GHz. The primary vacuum boundary at the Electron Cyclotron Upper Launcher (EC UL) extends into the port cell region through eight beamlines, defining the so-called First Confinement System (FCS). Each beamline, designed for the transmission of 1.31 MW, is delimited by the closure plate at the port plug back-end and by a diamond window in the port cell. The FCS essentially consists of a Z-shaped set of straight corrugated waveguides (WG) connected by Mitre Bends (MB) with a nominal inner diameter of 50 mm. Due to the space restrictions, the eight MBs at the last FCS section are grouped into two monoblocks. Each Monoblock Mitre Bend (MBMB) consists of a body with corrugated feedthroughs defining a specific angle for each beamline and four mirrors attached by bolted connection to reflect the mm-wave power. The thermal expansion arising from the ohmic losses, the cooling pressure, the bolt pre-tension and the imposed displacements coming from the connection with the transmission lines are the primary design loads for the MBMBs. The fluid-dynamic analyses performed for both upper and lower MBMBs show that highest temperature takes place in the MB mirrors, reaching a maximum value of 203 °C at the beam center. The thermo-mechanical analyses demonstrate that the peak stress also occurs at this location with a maximum value of 324 MPa. These stresses are categorized and compared with the allowable limits defined in the ASME code, what probes that the current design of both upper and lower MBMBs are able to withstand the loads taking place during the mm-wave normal operation. [ABSTRACT FROM AUTHOR]

• Nuclear analyses in support of ECUL port plug design: computation of nuclear heating to the BSM during plasma operation, and mitigation of dose rate during maintenance. • Significant mitigation of dose rate achieved by shielding options located within the port plug itself; further reductions only possible by optimization of the surrounding environment. • Pioneering application of the MCNP conformal unstructured mesh capability for both geometry description and result tallying for computation of the nuclear heating in the BSM. • The UM succeeds in accelerating geometry preparation and result post-processing, and in removing unphysical results inherent to MCNP's conventional approach. The ITER Electron Cyclotron Upper Launcher (ECUL) port plug is undergoing final design evolutions towards manufacturing, which include engineering efforts to ascertain and manage the radiation conditions during operation and maintenance. Two important aspects of these efforts are discussed here. First, design and analysis activities undertaken to ameliorate the residual radiation field (shut-down dose rate, SDDR), present during maintenance due to activation of components by plasma neutrons, are presented. Several shielding options were proposed and analysed. It was concluded that very significant improvement is achieved by those located within the port plug itself, and that further necessary reductions are only possible by considering changes in the surrounding environment. Second, the nuclear heating profile in the critical blanket shield module (BSM) component was computed. For this part of the work, a pioneering application of the novel MCNP conformal unstructured mesh capability (UM) for both geometry description and results tallying was made, in addition to the conventional approach of MCNP native geometry plus superimposed structured mesh. Different aspects of the results and functionality of both approaches were compared in a variety of conditions. It is concluded that, whilst the UM succeeds in accelerating geometry preparation and post-processing and in removing unphysical results inherent to the conventional approach, the latter still provides a more computationally efficient representation leading to uniform precision. These may be limiting factors for large analysis models such as those needed for ITER systems. [ABSTRACT FROM AUTHOR]