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Strategy for the development of EU Test Blanket Systems instrumentation
Fusion Engineering and Design 88 (2013) 2440–2443
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Strategy for the development of EU Test Blanket Systems instrumentation P. Calderoni ∗ , I. Ricapito, Y. Poitevin Fusion for Energy (F4E), C/ Josep Pla 2, Torres Diagonal Litoral B3, 08019 Barcelona, Spain
h i g h l i g h t s • We developed a strategy for the development of instrumentation for EU ITER TBSs. • TBSs instrumentation functions: safety, operation and scientific mission. • Described activities are in support of ITER design review process.
a r t i c l e
i n f o
Article history: Received 18 September 2012 Received in revised form 15 March 2013 Accepted 6 May 2013 Available online 30 May 2013 Keywords: Fusion blanket ITER Test Blanket Module Instrumentation Sensor
a b s t r a c t The instrumentation of the HCLL and HCPB Test Blanket System is fundamental in ensuring that ITER safety and operational requirements are satisfied as well as in enabling the scientific mission of the TBM program. It carries out three essential functions: (i) safety, intended as compliance with ITER requirements toward public and workers protection; (ii) system control, intended as compliance with ITER operational requirements and investment protection; and (iii) scientific mission, intended as validating technology and predictive tools for blanket concepts relevant to fusion energy systems. This paper describes the strategy for instrumentation development by providing details of the following five steps to be implemented in procured activities in the short to mid-term (3–4 years): (i) provide mapping of sensors requirements based on critical review of preliminary design data; (ii) develop functional specifications for TBS sensors based on the analysis of operative conditions in the various ITER buildings in which they are located; (iii) assess availability of commercial sensors against developed specifications; (iv) develop prototypes when no available solution is identified; and (v) perform single effect tests for the most critical solicitations and post-test examination of commercial products and prototypes. Examples of technology assessment in two technical areas are included to reinforce and complement the strategy description. © 2013 Elsevier B.V. All rights reserved.
1. Introduction For several years, Europe and other ITER parties have been developing tritium breeder blankets concepts that will be tested under the form of Test Blanket Modules (TBMs) located in equatorial ports of ITER. Europe is currently developing two reference breeder blankets concepts, the Helium-Cooled Lithium-Lead (HCLL) concept which uses liquid lead-lithium alloy as both tritium breeder and neutron multiplier, and the Helium-Cooled Pebble-Bed (HCPB) concept with lithium-containing ceramic pebbles as tritium breeder and beryllium pebbles as neutron multiplier [1]. HCLL and HCPB-TBMs are connected to two entirely separated ancillary systems that along with the TBMs form the Test Blanket Module
∗ Corresponding author. Tel.: +34 93 320 1185. E-mail addresses: [email protected], [email protected] (P. Calderoni). 0920-3796/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2013.05.012
Systems (TBS) [2]. In view of finalization of the TBS conceptual design and preparation of the preliminary design Fusion for Energy (F4E) has recently included instrumentation development as part of the ongoing design activities for TBSs. The TBS instrumentation is a key feature in enabling the project mission for two fundamental reasons. The first reason is that during the test campaign it allows the safe operation of the TBS by: ensuring the system condition (temperature, tritium concentration, etc.) is within the envelope identified in safety documents (safety function); controlling ancillary equipment (pumps, valves, etc.) to optimize the system performance toward the fulfillment of the experimental test plan (control function); providing required inputs to safety equipment (shut-off valves, auxiliary heaters, etc.) in case of unpredicted events (safety and control function). Instruments related to safety are installed in Safety Important Components (SIC) and they must comply with the stringent requirements applied to such components. Their specific function is the compliance with ITER requirements toward public and
P. Calderoni et al. / Fusion Engineering and Design 88 (2013) 2440–2443
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workers protection. In TBS those are all part of the Ancillary Systems. Instruments related to control may or may not be installed on SIC component, but they are characterized by being always required for system operation as they feed the system control functions, for example coolant pump regulation, heating power regulation, etc. Their specific function is the compliance with ITER operational requirements and TBM Project investment protection. Such instruments will be installed from day 1 and must be active for all types of TBM module (and related ITER operational phase). ITER requirements to the TBS instrumentation and control are imposed by the ITER TBM System Requirements Description. They are recalled hereafter: • Monitoring shall be provided to indicate whether the safety requirements are being met. • The presence of hydrogen isotopes, in particular tritium, in breeder and cooling circuits shall be continuously monitored. • The need for double containment of tritium carrying plumbing has to be checked in compliance with the general ITER Safety Requirements (PR and Tritium Manual). • The TBMs are not SIC components but all ancillary equipments are classified as SIC components. Instrumentation and control items linked with the CSS shall be used for the TBM ancillary systems and they shall be redundant. • Signals such as pressure, temperatures, flow rates, etc. shall be provided to trigger safety actions, such as isolation of part of TBSs or fast plasma shutdown, in case of failure of a confinement barrier or loss of coolant flow rate. In such a case the full chain of detection is SIC. • Monitoring shall be provided as part of tritium accounting requirements, to ensure that the tritium inventory limits are not exceeded. Because of the nature of the TBM program implementation in ITER these general requirements are the only guideline for design implementation. The effectiveness of the design solutions proposed will be evaluated through the ITER Design Review process, which in the case of TBS has not yet started. To provide an example of the status of the pre-conceptual design activities Table 1 reports the instrumentation considered in the reference accidental scenarios defined for the safety analysis of HCLL TBS. The main objective of the analysis is to ensure all safety functions are identified and logically connected, in particularly in relation with ITER interfaces. The control logic preliminary proposed is two out of three (2003) with sensors placed in different location of the sub-systems with the same nominal operating conditions. Further details on instrumentations, such as precise location within sub-components, type of sensor, accuracy and other specifications are not yet defined. The second reason is that the data collected from TBS instrumentation enable the project scientific and technical mission by: allowing the understanding of physical phenomenon and the discrimination among proposed models; creating a database of physical properties of materials and responses of systems in fusion blankets; evaluating the performance of the chosen design; validating simulation tools for fusion blankets that are fundamental to evolve concepts design toward their ultimate energy production mission. Scientific instrumentation is characterized by not being required for TBS operation; hence it could be deployed on specific TBM types or even only for a specific sub-set of experimental runs. Because it is not relevant to safety and operation, there are no requirements imposed by ITER on scientific instrumentation. The range of physical parameters of interest to TBS instrumentation is very wide, given the complex operational environment. The list presented in Table 1 is comprehensive; however others may be added during continuing design activities.
Fig. 1. Summary of F4E planned activities on TBS instrumentation with emphasis on Phase 1.
2. Development strategy The comprehensive strategy for the development and qualification of TBS instrumentation is based on three phases which are characterized by separate F4E contractual tools and summarized schematically in Fig. 1: • Phase 1: specifications mapping and single-effect testing (commercial and prototypes). • Phase 2: prototypes development. • Phase 3: integrated testing and qualification (commercial and prototypes). The three phases are logically consequential, since results from an earlier phase will be used for the next. However, the activities planned for each phase may be scheduled in parallel for specific instrumentation, in particular for the first two phases. Activities are integrated with other F4E contractual tools in related areas, specifically: • TBS design, for instruments integration in TBS. • ITER nuclear data experiments and measurement techniques. • ITER components irradiation tests. Integration with activities external to F4E for ITER diagnostic development is also being implemented, but details are currently under discussion and will not be included in this paper. Phase 1 activities are currently ongoing, organized in the following objectives, discussed below: 1. Provide mapping of operative conditions of TBS instruments and sensors. 2. Develop functional specifications. 3. Assess availability of commercial instruments and sensors for the identified functions. 4. Perform single effect tests for the most critical solicitations on commercial products and prototypes. 5. Perform feasibility studies for prototypes development. The development of the Pre-conceptual Design of the European TBM Systems carried-out through the F4E Grant Action F4E-2008GRT-09 included a preliminary description of the instrumentation requirements for each sub-system, in particularly related to the first two functions discussed in Section 1 (safety and control).
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Table 1 Instrumentation considered in HCLL TBS safety scenarios. Scenario
Measured parameter
Location
Ex-vessel LOCA
Helium pressure < 7 MPa Eurofer temperature > 580 ◦ C Cover gas pressure > 1.5 MPa Eurofer temperature > 580 ◦ C Helium flow rate < 90% nominal Circulator current input < 90% nominal Eurofer temperature > 580 ◦ C Helium temperature variation across heat exchanger < 90% nominal Helium temperature > 320 ◦ C Eurofer temperature > 580 ◦ C Helium pressure < 7 MPa Helium flow rate difference in/out of TBM > 2% nominal
HCS loop TBM box PbLi loop TBM box HCS loop HCS circulator TBM box HCS heat exchanger HCS TBM inlet TBM box HCS loop HCS loop TBM inlet/outlet
In-TBM LOCA HCLL LOFA
LHSA
In-vessel LOCA
LOCA: loss of coolant accident; LOFA: loss of flow accident; and LHSA: loss of heat sink accident.
The first objective of TBS instrumentation development is to critically review and compile the information contained in the various sub-systems design documents and create an overall map of instrumentation for TBS reflecting the most update development status (Table 2). The second objective is the development of the functional specifications for the TBS instruments and sensors identified, including but not limited to: detection range; accuracy; sensitivity; time response; geometrical requirements; lifetime and reliability; maintenance requirements. Issues of integration between components and within the ITER hosting systems will be considered, as well as an evaluation of the level of the intrusiveness that can be tolerated based on the component operation. The specifications should consider relevant operational conditions including: magnetic field, temperature, pressure, neutron flux, gamma flux, compatibility with materials. Those will be assessed through results of TBS design activities, from thermo-mechanical analysis of the TBM box for the evaluation of strain levels to activation analysis in the port cell for the evaluation of doses to ancillary systems instrumentation. Some of the solicitations expected for TBS instruments and sensors are common to other industrial applications, such as temperature in excess of 550 ◦ C for structural materials (power systems, petrochemical, etc.), high heat fluxes (rocket nozzles) and neutron fluxes (fission reactors). Others are unique to the ITER environment, for example 5 T variable magnetic field, 14 MeV neutron flux and contact with lead-lithium eutectic. However, preliminary information can still be extrapolated from relevant industrial applications, such as magnetic resonance imaging facilities for the assessment of the effect of high magnetic fields. Consequently the third objective of TBS instrumentation development activities is the evaluation of commercially available options that fulfill the functional requirements developed for the parameters of interest to TBS. Examples of commercial products potentially viable as TBS instruments have been identified in the design documents previously mentioned and
Table 2 Physical parameters of interest. Structural analysis pebble-bed mechanics
Thermal-hydraulics MHD
Electro-magnetics
Neutronics Corrosion
Position/displacement Force Strain Vibration Temperature Pressure Flow rate Velocity Magnetic field Electric field Current Neutron flux Radioactivity Chemical composition
summarized in [3] based on the operation of experimental facilities involved in components R&D and design validation activities. The goal is to generalize this search to all TBS components and to widen the sectors of industrial applications considered to areas that may have no connection to fusion R&D but nevertheless share relevant instrumentation. This evaluation should attempt to categorize the instruments needs of TBS in three classes: a. Parameters for which there is one or more commercially available product that satisfies all functional specifications. b. Parameters for which there is one or more commercially available product that satisfies most functional specifications except for one (or few) feasibility issues unique to TBS. c. Parameters for which there are no commercially available products that satisfy most functional specifications or with feasibility issue that require integrated testing in order to be resolved. When several commercial products are identified for the same function a rating analysis will be performed based on the best performance against the technical specifications, and eventually extended to include other considerations such as: cost, reliability, waste generation, level of technological maturity and others specific to the area under consideration. For category ‘a’, the product with the highest potential will be considered directly for procurement for integrated testing to be performed in Phase 3. For category ‘b’ the product with the highest potential will be considered for characterization tests. For category ‘c’ the best available options should be considered as the starting point for the feasibility study aimed at the development of a prototype that can overcome the existing limitations. The fourth objective is to perform laboratory tests of commercial products identified as category ‘b’ above. In general, tests will be performed in facilities that are normally used to qualify the performance of the products that are being procured, likely extending the range of operation or accommodating for specific requirements related to TBS design (geometrical, materials, etc.). Furthermore, the tests will be performed for a single solicitation (for example, temperature) or controlling a single parameter in case of naturally coupled phenomena (for example, temperature and thermal expansion). When applicable, the product will be tested to failure in order to understand the operating window and analysis of failure modes will be performed. Examples of laboratory tests include: reliability assessment (for example, repetitive temperature cycling for thermal fatigue); test to failure (for example, temperature ramping for thermal expansion); performance degradation assessment (for example, effect of neutrons or variable B field on thermocouples response); material compatibility assessment (for example, effect of PbLi on pressure sensors); performance optimization (for example, tuning gas chromatograph sensitivity for hydrogen traces in helium gas); post-test examination (for example, metallographic
P. Calderoni et al. / Fusion Engineering and Design 88 (2013) 2440–2443
analysis). The same type of tests will be performed also for prototype instruments developed under Phase 2. When no available instruments or sensors have been identified or characterization tests in fusion relevant conditions are not successful detailed feasibility studies for the development of prototypes in Phase 2 will be carried out (objective 5). 3. Assessment of technological maturity of sensors for selected applications There are general challenges to the application of commercial instruments to ITER that are common to many of its components, including the Test Blanket Systems. Those include: • Magnetic field noise (i.e., induced eddy currents). • Insulation performance (i.e., high temperature operation, dielectric properties degradation, radiation induced conductivity). • Fiber optic sensors applicability (i.e., high temperature operation, radiation effects on transmissivity, luminescence and refractive index). • Low activation brazing techniques (i.e., without silver). • Design integration (i.e., space limitation, limited access). • Transient mechanical loads and vibrations (i.e., loss of alignment and induced strain). • Fabrication procedures (i.e., welds and heat treatments). TBS helium components instrumentation is an example of an area in which commercial sensors already meet identified functional specifications [2,3]. The operating conditions are challenging, in particular in relation with the high nominal pressure (up to 10 MPa depending on component), but not uncommon in industrial applications. The design also allows for flexibility in terms of sensors location, so instrumentation is not exposed to the most challenging conditions encountered in the TBM modules. Furthermore, operating experience in TBM relevant conditions has been accumulated in R&D activities related to fusion blanket development [4,5]. During design development activities commercial products have been identified for all safety and control functions (including thermocouples, pressure sensors, flow meters and sensors monitoring compressor performance) and most scientific functions as well (for example, sampling mass spectrometer to detect gaseous impurities). Tritium detection is an example of an area of instrumentation that spans across all functions and technical maturity described before. As room monitors, tritium sensors will carry a safety function. Within tritium measuring stations (for example, in the HCPB Tritium Extraction System) the sensors will determine performance of physical processes and therefore provide feedback for system operation. Finally, tritium sensors will collect essential data for the validation of transport models to assess the Tritium Breeding Ratio of fusion blanket design. Some types of tritium monitors are widely used in industrial systems, in particular for routine process control of nuclear installations while others are in early R&D phases. As for most other radionuclides, tritium monitors can be separated in two main families based on the physical process used for detection: radiometric or spectrometric measurements [6]. Radiometric (or activity) measurements include the two most widely used types of sensors for radiological safety and process control: Liquid Scintillation Counting (LSC) and ionization counting (ion chambers) [7]. Other techniques in the same family include: calorimetry [8], which is mainly used for calibration purposes; Beta Induced X-ray Spectroscopy (BIXS) [9] and photo-stimulated luminescence (PSL)
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measured by Imaging Plate (IP) technique [10], which could have specialized applications to determine inventories in plasma facing components and TBS process streams, in particularly water. The second family of sensors does not rely on detecting tritium by its natural decay bur rather on its conventional chemical properties, first and foremost its mass. Conventional techniques, such as gas chromatography [11] and mass spectrometry [12], are optimized to separate the contribution of the 3 hydrogen isotopes, as well as those of other elements of similar properties (such as helium in the case of mass). Advanced spectroscopic techniques, such as Laser Raman (LARA) and IR adsorption, are also being investigated because of specific advantages they offer, in particular for accountancy systems [13]. Other specialized instruments are related to the measurement of tritium in the two types of breeder materials foreseen in the HCPB and HCLL TBM. Development of sensors to measure in situ tritium production is part of ongoing neutronics R&D activities coordinated by F4E, a description of which is beyond the scope of this paper [14]. The measurement of tritium concentration in the liquid metal breeder material of HCLL (PbLi alloy) is under investigation. The most promising system, referred to as permeation sensor [15] relies in the end on ionization counting for tritium detection, but its main feature is the tritium-permeable membrane that relates the measurement of tritium in the vacuum side of the instrument to the local concentration in the liquid metal flow. An alternative option is the use of electro-chemical sensors based on proton conductor ceramic materials [16], but such technology is in very early stage of development for fusion relevant materials. 4. Conclusions Fusion for Energy (F4E) has developed a strategy for the development of instrumentation for the two EU Test Blanket Systems to be deployed in ITER, HCLL and HCPB. This strategy constitutes the technical basis for contracted R&D and design activities to be carried out in support of the ITER Design Review process, and its details are presented in this paper. References [1] Y. Poitevin, L.V. Boccaccini, M. Zmitko, I. Ricapito, J.-F. Salavy, E. Diegele, et al., Fusion Engineering and Design 85 (2010) 2340–2347. [2] I. Ricapito, O. Bede, L.V. Boccaccini, A. Ciampichetti, B. Ghidersa, L. Guerrini, et al., Fusion Engineering and Design 85 (2010) 1154–1161. [3] A. Li Puma, G. Aiello, F. Gabriel, G. Laffont, G. Rampal, J.-F. Salavy, Fusion Engineering and Design 85 (2010) 1642–1652. [4] A. Aiello, L. Bühler, A. Ciampichetti, D. Demange, L. Dörr, J.F. Freibergs, et al., Fusion Engineering and Design 85 (2010) 2012–2021. [5] B.E. Ghidersa, M. Ionescu-Bujor, G. Janeschitz, Fusion Engineering and Design 81 (2006) 1471–1476. [6] X. Hou, P. Roos, Analytica Chimica Acta 608 (2008) 105–139. [7] N.P. Kherani, W.T. Shmayda, Fusion Technology 21 (1992) 340–345. [8] M. Matsuyama, K. Takatsuka, M. Hara, Fusion Engineering and Design 85 (2010) 2045–2048. [9] W.M. Shu, M. Matsuyama, T. Suzuki, M.F. Nishi, Nuclear Instruments and Methods A 521 (2004) 423–429. [10] Y. Hatano, M. Hara, H. Ohuchi, H. Nakamura, T. Yamanishi, Fusion Engineering and Design 87 (2012) 965–968. [11] Z. Köllö, D. Demange, B. Bornschein, L. Dörr, K. Günther, B. Kloppe, Fusion Engineering and Design 84 (2009) 1073–1075. [12] H. Miyake, K. Ichimura, M. Matsuyama, K. Ashida, K. Watanabe, S. Nakamura, et al., Fusion Engineering and Design 10 (1989) 417–421. [13] R. Lässer, C. Caldwell-Nichols, L. Dörr, M. Glugla, S. Grünhagen, K. Günther, et al., Fusion Engineering and Design 58–59 (2001) 411–415. [14] P. Batistoni, Fusion Engineering and Design 85 (2010) 1675–1680. [15] A. Ciampichetti, M. Zucchetti, I. Ricapito, M. Utili, A. Aiello, G. Benamati, Journal of Nuclear Materials 367–370 (2007) 1090–1095. [16] C.O. Park, S.A. Akbar, W. Weppner, Journal of Materials Science 38 (2003) 4639–4646.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Strategy for the development of EU Test Blanket Systems instrumentation P. Calderoni ∗ , I. Ricapito, Y. Poitevin Fusion for Energy (F4E), C/ Josep Pla 2, Torres Diagonal Litoral B3, 08019 Barcelona, Spain
h i g h l i g h t s • We developed a strategy for the development of instrumentation for EU ITER TBSs. • TBSs instrumentation functions: safety, operation and scientific mission. • Described activities are in support of ITER design review process.
a r t i c l e
i n f o
Article history: Received 18 September 2012 Received in revised form 15 March 2013 Accepted 6 May 2013 Available online 30 May 2013 Keywords: Fusion blanket ITER Test Blanket Module Instrumentation Sensor
a b s t r a c t The instrumentation of the HCLL and HCPB Test Blanket System is fundamental in ensuring that ITER safety and operational requirements are satisfied as well as in enabling the scientific mission of the TBM program. It carries out three essential functions: (i) safety, intended as compliance with ITER requirements toward public and workers protection; (ii) system control, intended as compliance with ITER operational requirements and investment protection; and (iii) scientific mission, intended as validating technology and predictive tools for blanket concepts relevant to fusion energy systems. This paper describes the strategy for instrumentation development by providing details of the following five steps to be implemented in procured activities in the short to mid-term (3–4 years): (i) provide mapping of sensors requirements based on critical review of preliminary design data; (ii) develop functional specifications for TBS sensors based on the analysis of operative conditions in the various ITER buildings in which they are located; (iii) assess availability of commercial sensors against developed specifications; (iv) develop prototypes when no available solution is identified; and (v) perform single effect tests for the most critical solicitations and post-test examination of commercial products and prototypes. Examples of technology assessment in two technical areas are included to reinforce and complement the strategy description. © 2013 Elsevier B.V. All rights reserved.
1. Introduction For several years, Europe and other ITER parties have been developing tritium breeder blankets concepts that will be tested under the form of Test Blanket Modules (TBMs) located in equatorial ports of ITER. Europe is currently developing two reference breeder blankets concepts, the Helium-Cooled Lithium-Lead (HCLL) concept which uses liquid lead-lithium alloy as both tritium breeder and neutron multiplier, and the Helium-Cooled Pebble-Bed (HCPB) concept with lithium-containing ceramic pebbles as tritium breeder and beryllium pebbles as neutron multiplier [1]. HCLL and HCPB-TBMs are connected to two entirely separated ancillary systems that along with the TBMs form the Test Blanket Module
∗ Corresponding author. Tel.: +34 93 320 1185. E-mail addresses: [email protected], [email protected] (P. Calderoni). 0920-3796/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2013.05.012
Systems (TBS) [2]. In view of finalization of the TBS conceptual design and preparation of the preliminary design Fusion for Energy (F4E) has recently included instrumentation development as part of the ongoing design activities for TBSs. The TBS instrumentation is a key feature in enabling the project mission for two fundamental reasons. The first reason is that during the test campaign it allows the safe operation of the TBS by: ensuring the system condition (temperature, tritium concentration, etc.) is within the envelope identified in safety documents (safety function); controlling ancillary equipment (pumps, valves, etc.) to optimize the system performance toward the fulfillment of the experimental test plan (control function); providing required inputs to safety equipment (shut-off valves, auxiliary heaters, etc.) in case of unpredicted events (safety and control function). Instruments related to safety are installed in Safety Important Components (SIC) and they must comply with the stringent requirements applied to such components. Their specific function is the compliance with ITER requirements toward public and
P. Calderoni et al. / Fusion Engineering and Design 88 (2013) 2440–2443
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workers protection. In TBS those are all part of the Ancillary Systems. Instruments related to control may or may not be installed on SIC component, but they are characterized by being always required for system operation as they feed the system control functions, for example coolant pump regulation, heating power regulation, etc. Their specific function is the compliance with ITER operational requirements and TBM Project investment protection. Such instruments will be installed from day 1 and must be active for all types of TBM module (and related ITER operational phase). ITER requirements to the TBS instrumentation and control are imposed by the ITER TBM System Requirements Description. They are recalled hereafter: • Monitoring shall be provided to indicate whether the safety requirements are being met. • The presence of hydrogen isotopes, in particular tritium, in breeder and cooling circuits shall be continuously monitored. • The need for double containment of tritium carrying plumbing has to be checked in compliance with the general ITER Safety Requirements (PR and Tritium Manual). • The TBMs are not SIC components but all ancillary equipments are classified as SIC components. Instrumentation and control items linked with the CSS shall be used for the TBM ancillary systems and they shall be redundant. • Signals such as pressure, temperatures, flow rates, etc. shall be provided to trigger safety actions, such as isolation of part of TBSs or fast plasma shutdown, in case of failure of a confinement barrier or loss of coolant flow rate. In such a case the full chain of detection is SIC. • Monitoring shall be provided as part of tritium accounting requirements, to ensure that the tritium inventory limits are not exceeded. Because of the nature of the TBM program implementation in ITER these general requirements are the only guideline for design implementation. The effectiveness of the design solutions proposed will be evaluated through the ITER Design Review process, which in the case of TBS has not yet started. To provide an example of the status of the pre-conceptual design activities Table 1 reports the instrumentation considered in the reference accidental scenarios defined for the safety analysis of HCLL TBS. The main objective of the analysis is to ensure all safety functions are identified and logically connected, in particularly in relation with ITER interfaces. The control logic preliminary proposed is two out of three (2003) with sensors placed in different location of the sub-systems with the same nominal operating conditions. Further details on instrumentations, such as precise location within sub-components, type of sensor, accuracy and other specifications are not yet defined. The second reason is that the data collected from TBS instrumentation enable the project scientific and technical mission by: allowing the understanding of physical phenomenon and the discrimination among proposed models; creating a database of physical properties of materials and responses of systems in fusion blankets; evaluating the performance of the chosen design; validating simulation tools for fusion blankets that are fundamental to evolve concepts design toward their ultimate energy production mission. Scientific instrumentation is characterized by not being required for TBS operation; hence it could be deployed on specific TBM types or even only for a specific sub-set of experimental runs. Because it is not relevant to safety and operation, there are no requirements imposed by ITER on scientific instrumentation. The range of physical parameters of interest to TBS instrumentation is very wide, given the complex operational environment. The list presented in Table 1 is comprehensive; however others may be added during continuing design activities.
Fig. 1. Summary of F4E planned activities on TBS instrumentation with emphasis on Phase 1.
2. Development strategy The comprehensive strategy for the development and qualification of TBS instrumentation is based on three phases which are characterized by separate F4E contractual tools and summarized schematically in Fig. 1: • Phase 1: specifications mapping and single-effect testing (commercial and prototypes). • Phase 2: prototypes development. • Phase 3: integrated testing and qualification (commercial and prototypes). The three phases are logically consequential, since results from an earlier phase will be used for the next. However, the activities planned for each phase may be scheduled in parallel for specific instrumentation, in particular for the first two phases. Activities are integrated with other F4E contractual tools in related areas, specifically: • TBS design, for instruments integration in TBS. • ITER nuclear data experiments and measurement techniques. • ITER components irradiation tests. Integration with activities external to F4E for ITER diagnostic development is also being implemented, but details are currently under discussion and will not be included in this paper. Phase 1 activities are currently ongoing, organized in the following objectives, discussed below: 1. Provide mapping of operative conditions of TBS instruments and sensors. 2. Develop functional specifications. 3. Assess availability of commercial instruments and sensors for the identified functions. 4. Perform single effect tests for the most critical solicitations on commercial products and prototypes. 5. Perform feasibility studies for prototypes development. The development of the Pre-conceptual Design of the European TBM Systems carried-out through the F4E Grant Action F4E-2008GRT-09 included a preliminary description of the instrumentation requirements for each sub-system, in particularly related to the first two functions discussed in Section 1 (safety and control).
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Table 1 Instrumentation considered in HCLL TBS safety scenarios. Scenario
Measured parameter
Location
Ex-vessel LOCA
Helium pressure < 7 MPa Eurofer temperature > 580 ◦ C Cover gas pressure > 1.5 MPa Eurofer temperature > 580 ◦ C Helium flow rate < 90% nominal Circulator current input < 90% nominal Eurofer temperature > 580 ◦ C Helium temperature variation across heat exchanger < 90% nominal Helium temperature > 320 ◦ C Eurofer temperature > 580 ◦ C Helium pressure < 7 MPa Helium flow rate difference in/out of TBM > 2% nominal
HCS loop TBM box PbLi loop TBM box HCS loop HCS circulator TBM box HCS heat exchanger HCS TBM inlet TBM box HCS loop HCS loop TBM inlet/outlet
In-TBM LOCA HCLL LOFA
LHSA
In-vessel LOCA
LOCA: loss of coolant accident; LOFA: loss of flow accident; and LHSA: loss of heat sink accident.
The first objective of TBS instrumentation development is to critically review and compile the information contained in the various sub-systems design documents and create an overall map of instrumentation for TBS reflecting the most update development status (Table 2). The second objective is the development of the functional specifications for the TBS instruments and sensors identified, including but not limited to: detection range; accuracy; sensitivity; time response; geometrical requirements; lifetime and reliability; maintenance requirements. Issues of integration between components and within the ITER hosting systems will be considered, as well as an evaluation of the level of the intrusiveness that can be tolerated based on the component operation. The specifications should consider relevant operational conditions including: magnetic field, temperature, pressure, neutron flux, gamma flux, compatibility with materials. Those will be assessed through results of TBS design activities, from thermo-mechanical analysis of the TBM box for the evaluation of strain levels to activation analysis in the port cell for the evaluation of doses to ancillary systems instrumentation. Some of the solicitations expected for TBS instruments and sensors are common to other industrial applications, such as temperature in excess of 550 ◦ C for structural materials (power systems, petrochemical, etc.), high heat fluxes (rocket nozzles) and neutron fluxes (fission reactors). Others are unique to the ITER environment, for example 5 T variable magnetic field, 14 MeV neutron flux and contact with lead-lithium eutectic. However, preliminary information can still be extrapolated from relevant industrial applications, such as magnetic resonance imaging facilities for the assessment of the effect of high magnetic fields. Consequently the third objective of TBS instrumentation development activities is the evaluation of commercially available options that fulfill the functional requirements developed for the parameters of interest to TBS. Examples of commercial products potentially viable as TBS instruments have been identified in the design documents previously mentioned and
Table 2 Physical parameters of interest. Structural analysis pebble-bed mechanics
Thermal-hydraulics MHD
Electro-magnetics
Neutronics Corrosion
Position/displacement Force Strain Vibration Temperature Pressure Flow rate Velocity Magnetic field Electric field Current Neutron flux Radioactivity Chemical composition
summarized in [3] based on the operation of experimental facilities involved in components R&D and design validation activities. The goal is to generalize this search to all TBS components and to widen the sectors of industrial applications considered to areas that may have no connection to fusion R&D but nevertheless share relevant instrumentation. This evaluation should attempt to categorize the instruments needs of TBS in three classes: a. Parameters for which there is one or more commercially available product that satisfies all functional specifications. b. Parameters for which there is one or more commercially available product that satisfies most functional specifications except for one (or few) feasibility issues unique to TBS. c. Parameters for which there are no commercially available products that satisfy most functional specifications or with feasibility issue that require integrated testing in order to be resolved. When several commercial products are identified for the same function a rating analysis will be performed based on the best performance against the technical specifications, and eventually extended to include other considerations such as: cost, reliability, waste generation, level of technological maturity and others specific to the area under consideration. For category ‘a’, the product with the highest potential will be considered directly for procurement for integrated testing to be performed in Phase 3. For category ‘b’ the product with the highest potential will be considered for characterization tests. For category ‘c’ the best available options should be considered as the starting point for the feasibility study aimed at the development of a prototype that can overcome the existing limitations. The fourth objective is to perform laboratory tests of commercial products identified as category ‘b’ above. In general, tests will be performed in facilities that are normally used to qualify the performance of the products that are being procured, likely extending the range of operation or accommodating for specific requirements related to TBS design (geometrical, materials, etc.). Furthermore, the tests will be performed for a single solicitation (for example, temperature) or controlling a single parameter in case of naturally coupled phenomena (for example, temperature and thermal expansion). When applicable, the product will be tested to failure in order to understand the operating window and analysis of failure modes will be performed. Examples of laboratory tests include: reliability assessment (for example, repetitive temperature cycling for thermal fatigue); test to failure (for example, temperature ramping for thermal expansion); performance degradation assessment (for example, effect of neutrons or variable B field on thermocouples response); material compatibility assessment (for example, effect of PbLi on pressure sensors); performance optimization (for example, tuning gas chromatograph sensitivity for hydrogen traces in helium gas); post-test examination (for example, metallographic
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analysis). The same type of tests will be performed also for prototype instruments developed under Phase 2. When no available instruments or sensors have been identified or characterization tests in fusion relevant conditions are not successful detailed feasibility studies for the development of prototypes in Phase 2 will be carried out (objective 5). 3. Assessment of technological maturity of sensors for selected applications There are general challenges to the application of commercial instruments to ITER that are common to many of its components, including the Test Blanket Systems. Those include: • Magnetic field noise (i.e., induced eddy currents). • Insulation performance (i.e., high temperature operation, dielectric properties degradation, radiation induced conductivity). • Fiber optic sensors applicability (i.e., high temperature operation, radiation effects on transmissivity, luminescence and refractive index). • Low activation brazing techniques (i.e., without silver). • Design integration (i.e., space limitation, limited access). • Transient mechanical loads and vibrations (i.e., loss of alignment and induced strain). • Fabrication procedures (i.e., welds and heat treatments). TBS helium components instrumentation is an example of an area in which commercial sensors already meet identified functional specifications [2,3]. The operating conditions are challenging, in particular in relation with the high nominal pressure (up to 10 MPa depending on component), but not uncommon in industrial applications. The design also allows for flexibility in terms of sensors location, so instrumentation is not exposed to the most challenging conditions encountered in the TBM modules. Furthermore, operating experience in TBM relevant conditions has been accumulated in R&D activities related to fusion blanket development [4,5]. During design development activities commercial products have been identified for all safety and control functions (including thermocouples, pressure sensors, flow meters and sensors monitoring compressor performance) and most scientific functions as well (for example, sampling mass spectrometer to detect gaseous impurities). Tritium detection is an example of an area of instrumentation that spans across all functions and technical maturity described before. As room monitors, tritium sensors will carry a safety function. Within tritium measuring stations (for example, in the HCPB Tritium Extraction System) the sensors will determine performance of physical processes and therefore provide feedback for system operation. Finally, tritium sensors will collect essential data for the validation of transport models to assess the Tritium Breeding Ratio of fusion blanket design. Some types of tritium monitors are widely used in industrial systems, in particular for routine process control of nuclear installations while others are in early R&D phases. As for most other radionuclides, tritium monitors can be separated in two main families based on the physical process used for detection: radiometric or spectrometric measurements [6]. Radiometric (or activity) measurements include the two most widely used types of sensors for radiological safety and process control: Liquid Scintillation Counting (LSC) and ionization counting (ion chambers) [7]. Other techniques in the same family include: calorimetry [8], which is mainly used for calibration purposes; Beta Induced X-ray Spectroscopy (BIXS) [9] and photo-stimulated luminescence (PSL)
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measured by Imaging Plate (IP) technique [10], which could have specialized applications to determine inventories in plasma facing components and TBS process streams, in particularly water. The second family of sensors does not rely on detecting tritium by its natural decay bur rather on its conventional chemical properties, first and foremost its mass. Conventional techniques, such as gas chromatography [11] and mass spectrometry [12], are optimized to separate the contribution of the 3 hydrogen isotopes, as well as those of other elements of similar properties (such as helium in the case of mass). Advanced spectroscopic techniques, such as Laser Raman (LARA) and IR adsorption, are also being investigated because of specific advantages they offer, in particular for accountancy systems [13]. Other specialized instruments are related to the measurement of tritium in the two types of breeder materials foreseen in the HCPB and HCLL TBM. Development of sensors to measure in situ tritium production is part of ongoing neutronics R&D activities coordinated by F4E, a description of which is beyond the scope of this paper [14]. The measurement of tritium concentration in the liquid metal breeder material of HCLL (PbLi alloy) is under investigation. The most promising system, referred to as permeation sensor [15] relies in the end on ionization counting for tritium detection, but its main feature is the tritium-permeable membrane that relates the measurement of tritium in the vacuum side of the instrument to the local concentration in the liquid metal flow. An alternative option is the use of electro-chemical sensors based on proton conductor ceramic materials [16], but such technology is in very early stage of development for fusion relevant materials. 4. Conclusions Fusion for Energy (F4E) has developed a strategy for the development of instrumentation for the two EU Test Blanket Systems to be deployed in ITER, HCLL and HCPB. This strategy constitutes the technical basis for contracted R&D and design activities to be carried out in support of the ITER Design Review process, and its details are presented in this paper. References [1] Y. Poitevin, L.V. Boccaccini, M. Zmitko, I. Ricapito, J.-F. Salavy, E. Diegele, et al., Fusion Engineering and Design 85 (2010) 2340–2347. [2] I. Ricapito, O. Bede, L.V. Boccaccini, A. Ciampichetti, B. Ghidersa, L. Guerrini, et al., Fusion Engineering and Design 85 (2010) 1154–1161. [3] A. Li Puma, G. Aiello, F. Gabriel, G. Laffont, G. Rampal, J.-F. Salavy, Fusion Engineering and Design 85 (2010) 1642–1652. [4] A. Aiello, L. Bühler, A. Ciampichetti, D. Demange, L. Dörr, J.F. Freibergs, et al., Fusion Engineering and Design 85 (2010) 2012–2021. [5] B.E. Ghidersa, M. Ionescu-Bujor, G. Janeschitz, Fusion Engineering and Design 81 (2006) 1471–1476. [6] X. Hou, P. Roos, Analytica Chimica Acta 608 (2008) 105–139. [7] N.P. Kherani, W.T. Shmayda, Fusion Technology 21 (1992) 340–345. [8] M. Matsuyama, K. Takatsuka, M. Hara, Fusion Engineering and Design 85 (2010) 2045–2048. [9] W.M. Shu, M. Matsuyama, T. Suzuki, M.F. Nishi, Nuclear Instruments and Methods A 521 (2004) 423–429. [10] Y. Hatano, M. Hara, H. Ohuchi, H. Nakamura, T. Yamanishi, Fusion Engineering and Design 87 (2012) 965–968. [11] Z. Köllö, D. Demange, B. Bornschein, L. Dörr, K. Günther, B. Kloppe, Fusion Engineering and Design 84 (2009) 1073–1075. [12] H. Miyake, K. Ichimura, M. Matsuyama, K. Ashida, K. Watanabe, S. Nakamura, et al., Fusion Engineering and Design 10 (1989) 417–421. [13] R. Lässer, C. Caldwell-Nichols, L. Dörr, M. Glugla, S. Grünhagen, K. Günther, et al., Fusion Engineering and Design 58–59 (2001) 411–415. [14] P. Batistoni, Fusion Engineering and Design 85 (2010) 1675–1680. [15] A. Ciampichetti, M. Zucchetti, I. Ricapito, M. Utili, A. Aiello, G. Benamati, Journal of Nuclear Materials 367–370 (2007) 1090–1095. [16] C.O. Park, S.A. Akbar, W. Weppner, Journal of Materials Science 38 (2003) 4639–4646.