IEEE Transactions on Instrumentation and Measurement, 2021
This article presents the measurement of residual stress distribution in ITER (“The Way” in Latin... more This article presents the measurement of residual stress distribution in ITER (“The Way” in Latin) diagnostics windows using a circular polariscope. The method being used is based on the measurement of the change in the state of polarization of a circularly polarized light after transmission/reflection from the stressed window under test. The theory based on Mueller calculus for the experimental setup has been presented. The measurement technique is validated for transmission mode by comparing the stress values measured for borosilicate glass (BK7) sample disks under diametrical compression with the theoretical values obtained using linear isotropic theory of elasticity. The method is, then, applied to an undamaged and a damaged ITER trial window, both in transmission and reflection modes, to observe the stress patterns inside the glass material and on the glass to metal seal. The major observations are that the undamaged window shows higher stress in majority of the cross section with lower stress values at localized regions. The glass near the seal shows high values of stress all along the circumference in case of the undamaged window. The damaged window that has got detached from the metal seal shows much lower stress values in majority of the cross section of the window with higher stress values in some regions. The region where the seal seems to have got detached from the glass shows lower values of stress at the seal location, and also the stress values in the glass near those locations are low. In conclusion, by observing the stress patterns inside the window, this technique helps determine the health of vacuum seal, and hence can be used in taking preventive measures.
The United Kingdom Atomic Energy Authority is involved in the design and manufacture of the diagn... more The United Kingdom Atomic Energy Authority is involved in the design and manufacture of the diagnostic windows for ITER. ITER is an international project, with 35 nations collaborating to design, construct, and operate a prototype controlled nuclear fusion reactor in southern France. As well as providing line of sight for diagnostics, the windows also form part of the reactor primary containment boundary and are consequently classified as nuclear Safety Important Class 1 (SIC-1) components. The windows will be the first SIC-1 components in the world which are non-metallic. The current manufacturing process involves diffusion bonding a glass window to an Inconel 625 ferrule via an aluminium interlayer. This report discusses this diffusion bonding process and details the specific challenges related to component qualification for the intended nuclear SIC-1 application.
The upper port #18 (UP18) in ITER hosts three diagnostic systems: the neutron activation system, ... more The upper port #18 (UP18) in ITER hosts three diagnostic systems: the neutron activation system, the Vacuum Ultra-Violet spectrometer system, and the vertical neutron camera. These diagnostics are integrated into three infrastructures in the port: the upper port plug, interspace support structure and port cell support structure. The port integration in UP18 is at the preliminary design stage and the current design of the infrastructure as well as the diagnostic integration is described here. The engineering issues related to neutron shielding and maintenance are addressed and the design approach is suggested.
Abstract Design and development of the ITER divertor VUV spectrometer have been performed from th... more Abstract Design and development of the ITER divertor VUV spectrometer have been performed from the year 1998, and it is planned to be installed in the year 2027. Currently, the design of the ITER divertor VUV spectrometer is in the phase of detail design. It is optimized for monitoring of chord-integrated VUV signals from divertor plasmas, chosen to contain representative lines emission from the tungsten as the divertor material, and other impurities. Impurity emission from overall divertor plasmas is collimated through the relay optics onto the entrance slit of a VUV spectrometer with working wavelength range of 14.6–32 nm. To validate the design of the ITER divertor VUV spectrometer, two sets of VUV spectrometers have been developed and tested at KSTAR tokamak. One set of spectrometer without the field mirror employs a survey spectrometer with the wavelength ranging from 14.6 nm to 32 nm, and it provides the same optical specification as the spectrometer part of the ITER divertor VUV spectrometer system. The other spectrometer with the wavelength range of 5–25 nm consists of a commercial spectrometer with a concave grating, and the relay mirrors with the same geometry as the relay mirrors of the ITER divertor VUV spectrometer. From test of these prototypes, alignment method using backward laser illumination could be verified. To validate the feasibility of tungsten emission measurement, furthermore, the tungsten powder was injected in KSTAR plasmas, and the preliminary result could be obtained successfully with regard to the evaluation of photon throughput. Graphical abstract
Abstract The generic upper port plug (GUPP) structure in ITER is a 6 m long metal box which deplo... more Abstract The generic upper port plug (GUPP) structure in ITER is a 6 m long metal box which deploys diagnostic components into the vacuum vessel. This structure is commonly used for all the diagnostic upper ports. The final design of the GUPP structure, which has successfully passed the final design review in 2013, is described here. The diagnostic port plug is cantilevered to the vacuum vessel with a heavy payload at the front, so called the diagnostic first wall (DFW) and the diagnostic shield module (DSM). Most of electromagnetic (EM) load (∼80%) occurs in DFW/DSM. Therefore, the mounting design to transfer the EM load from DFW/DSM to the GUPP structure is challenging, which should also comply with thermal expansion and tolerance for assembly and manufacturing. Another key design parameter to be considered is the gap between the port plug and the vacuum vessel port. The gap should be large enough to accommodate the remote handling of the heavy port plug (max. 25 t), the structural deflection due to external loads and machine assembly tolerance. At the same time, the gap should be minimized to stop the neutron streaming according to the ALARA (as low as reasonably achievable) principle. With these design constraints, the GUPP structure should also provide space for diagnostic integration as much as possible. This requirement has led to the single wall structure having the gun-drilled water channels inside the structure. Furthermore, intensive efforts have been made on the manufacturing study including material selection, manufacturing codes and French regulation related to nuclear equipment and safety. All these main design and manufacturing aspects are discussed in this paper, including requirements, interfaces, loads and structural assessment and maintenance.
IEEE Transactions on Instrumentation and Measurement, 2021
This article presents the measurement of residual stress distribution in ITER (“The Way” in Latin... more This article presents the measurement of residual stress distribution in ITER (“The Way” in Latin) diagnostics windows using a circular polariscope. The method being used is based on the measurement of the change in the state of polarization of a circularly polarized light after transmission/reflection from the stressed window under test. The theory based on Mueller calculus for the experimental setup has been presented. The measurement technique is validated for transmission mode by comparing the stress values measured for borosilicate glass (BK7) sample disks under diametrical compression with the theoretical values obtained using linear isotropic theory of elasticity. The method is, then, applied to an undamaged and a damaged ITER trial window, both in transmission and reflection modes, to observe the stress patterns inside the glass material and on the glass to metal seal. The major observations are that the undamaged window shows higher stress in majority of the cross section with lower stress values at localized regions. The glass near the seal shows high values of stress all along the circumference in case of the undamaged window. The damaged window that has got detached from the metal seal shows much lower stress values in majority of the cross section of the window with higher stress values in some regions. The region where the seal seems to have got detached from the glass shows lower values of stress at the seal location, and also the stress values in the glass near those locations are low. In conclusion, by observing the stress patterns inside the window, this technique helps determine the health of vacuum seal, and hence can be used in taking preventive measures.
The United Kingdom Atomic Energy Authority is involved in the design and manufacture of the diagn... more The United Kingdom Atomic Energy Authority is involved in the design and manufacture of the diagnostic windows for ITER. ITER is an international project, with 35 nations collaborating to design, construct, and operate a prototype controlled nuclear fusion reactor in southern France. As well as providing line of sight for diagnostics, the windows also form part of the reactor primary containment boundary and are consequently classified as nuclear Safety Important Class 1 (SIC-1) components. The windows will be the first SIC-1 components in the world which are non-metallic. The current manufacturing process involves diffusion bonding a glass window to an Inconel 625 ferrule via an aluminium interlayer. This report discusses this diffusion bonding process and details the specific challenges related to component qualification for the intended nuclear SIC-1 application.
The upper port #18 (UP18) in ITER hosts three diagnostic systems: the neutron activation system, ... more The upper port #18 (UP18) in ITER hosts three diagnostic systems: the neutron activation system, the Vacuum Ultra-Violet spectrometer system, and the vertical neutron camera. These diagnostics are integrated into three infrastructures in the port: the upper port plug, interspace support structure and port cell support structure. The port integration in UP18 is at the preliminary design stage and the current design of the infrastructure as well as the diagnostic integration is described here. The engineering issues related to neutron shielding and maintenance are addressed and the design approach is suggested.
Abstract Design and development of the ITER divertor VUV spectrometer have been performed from th... more Abstract Design and development of the ITER divertor VUV spectrometer have been performed from the year 1998, and it is planned to be installed in the year 2027. Currently, the design of the ITER divertor VUV spectrometer is in the phase of detail design. It is optimized for monitoring of chord-integrated VUV signals from divertor plasmas, chosen to contain representative lines emission from the tungsten as the divertor material, and other impurities. Impurity emission from overall divertor plasmas is collimated through the relay optics onto the entrance slit of a VUV spectrometer with working wavelength range of 14.6–32 nm. To validate the design of the ITER divertor VUV spectrometer, two sets of VUV spectrometers have been developed and tested at KSTAR tokamak. One set of spectrometer without the field mirror employs a survey spectrometer with the wavelength ranging from 14.6 nm to 32 nm, and it provides the same optical specification as the spectrometer part of the ITER divertor VUV spectrometer system. The other spectrometer with the wavelength range of 5–25 nm consists of a commercial spectrometer with a concave grating, and the relay mirrors with the same geometry as the relay mirrors of the ITER divertor VUV spectrometer. From test of these prototypes, alignment method using backward laser illumination could be verified. To validate the feasibility of tungsten emission measurement, furthermore, the tungsten powder was injected in KSTAR plasmas, and the preliminary result could be obtained successfully with regard to the evaluation of photon throughput. Graphical abstract
Abstract The generic upper port plug (GUPP) structure in ITER is a 6 m long metal box which deplo... more Abstract The generic upper port plug (GUPP) structure in ITER is a 6 m long metal box which deploys diagnostic components into the vacuum vessel. This structure is commonly used for all the diagnostic upper ports. The final design of the GUPP structure, which has successfully passed the final design review in 2013, is described here. The diagnostic port plug is cantilevered to the vacuum vessel with a heavy payload at the front, so called the diagnostic first wall (DFW) and the diagnostic shield module (DSM). Most of electromagnetic (EM) load (∼80%) occurs in DFW/DSM. Therefore, the mounting design to transfer the EM load from DFW/DSM to the GUPP structure is challenging, which should also comply with thermal expansion and tolerance for assembly and manufacturing. Another key design parameter to be considered is the gap between the port plug and the vacuum vessel port. The gap should be large enough to accommodate the remote handling of the heavy port plug (max. 25 t), the structural deflection due to external loads and machine assembly tolerance. At the same time, the gap should be minimized to stop the neutron streaming according to the ALARA (as low as reasonably achievable) principle. With these design constraints, the GUPP structure should also provide space for diagnostic integration as much as possible. This requirement has led to the single wall structure having the gun-drilled water channels inside the structure. Furthermore, intensive efforts have been made on the manufacturing study including material selection, manufacturing codes and French regulation related to nuclear equipment and safety. All these main design and manufacturing aspects are discussed in this paper, including requirements, interfaces, loads and structural assessment and maintenance.
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