- Email: [email protected]
Conceptual design of the IFMIF Start-Up monitoring module
Fusion Engineering and Design 88 (2013) 729–732
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Conceptual design of the IFMIF Start-Up monitoring module Philippe Gouat a,∗ , Willem Leysen a , Andrei Goussarov a , Papa Sally Galledou a , David Rapisarda b , Fernando Mota b , Angela Garcia b a b
SCK•CEN – The Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol, Belgium CIEMAT – Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Avda. Complutense 40, 28040 Madrid, Spain
h i g h l i g h t s IFMIF test module conceptual design. IFMIF test module foreseen instrumentation. Cerenkov photon flux monitor.
a r t i c l e
i n f o
Article history: Received 14 September 2012 Received in revised form 16 January 2013 Accepted 12 February 2013 Available online 9 March 2013 Keywords: IFMIF STUMM EVEDA Conceptual design C FOS
a b s t r a c t The preliminary engineering design of the test facilities, including the various test modules to be used in the IFMIF plant is a part of the IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project from the Broader Approach to fusion. One presents the current status of the conceptual development of the IFMIF Start-Up Monitoring Module, a dedicated device used in the IFMIF test cell during the commissioning phase of the installation, in order to completely characterise the irradiation conditions behind the target on which the beam of deuterons will be focused. This STUMM embarks a lot of instrumentation to precisely characterise the neutron field, the nuclear heating and the temperatures in the test cell. One briefly describes the measuring instruments (including a specific radiation flux monitor under development), the possible layouts and the possible positioning. One also defines which types of measurements are expected by this especially dedicated commissioning module. © 2013 Elsevier B.V. All rights reserved.
1. Introduction In the frame of the EVEDA phase of the IFMIF development, the conceptual study of a Start-Up module was launched in 2009 [1]. The EVEDA phase terminates at the middle of 2013. One presents here the achievements on the Start-Up monitoring module (STUMM). This module is especially dedicated to the commissioning phase of the IFMIF plant and will be loaded in the test cell prior to any production activity to verify a certain number of operational parameters. As the scenario is not well defined yet, one had to make
Abbreviations: C FOS, Cerenkov fibre-optics sensor; EVEDA, Engineering Validation/Engineering Design Activities; HFTM-V, high flux test module-vertical layout; IFMIF, International Fusion Materials Irradiation Facility; KIT, Karlsruhe Institute of Technology; LFTM, low flux test module; PCP, piping and cabling plug; RH, remote handling; STUMM, Start-Up monitoring module; TMIH, test module interface head; TTC, target and test cell. ∗ Corresponding author. Tel.: +32 14 33 34 08. E-mail address: [email protected] (P. Gouat). 0920-3796/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2013.02.057
some assumptions and propose different options for the module design. 2. Objectives of STUMM One briefly recalls here the objectives of this distinct module. The main goals have been identified as follows: • The characterisation of the whole radiation field in the Test Cell area. The STUMM could be placed in different positions if considered necessary. • The measurement of the spatial distribution of neutrons and photons in the vertical and horizontal planes, perpendicular to the beam. This 3D map will be not only limited to the footprint region (main irradiated area, 5 cm × 20 cm), but also to regions where the ratio between neutrons and photons could change substantially from the centre of the plane. ◦ Measurements of the spatial distribution of neutrons ◦ Measurements of the spatial distribution of photons • The characterisation of the temporal evolution of the radiation field. During the commissioning phase, different levels of neutron
730
P. Gouat et al. / Fusion Engineering and Design 88 (2013) 729–732
and gamma fluxes will exist due to the qualification of the beams (from low to high duty cycles). The monitoring of those changes will be suited to follow variations in the radiation field during the IFMIF normal operation. • The demonstration of the correct functioning of the foreseen instrumentation, including signal levels, noise in the measurements. . . Realistic operation conditions are needed (TTC atmosphere, pressure, directional field. . .). • The validation of the neutronic calculations used to design the test modules. Other objectives that are related to the operation of the STUMM, and that must be taken into account are: • The validation of the STUMM mechanical design, since it could be considered as a Test Module prototype. Therefore, its characterisation (in terms of robustness, dimensional stability, structural integrity. . .) could qualify the fabrication/design of the future test modules. Of course, the operation of this module will be also useful to anticipate the operation of the experimental modules during IFMIF normal operation. • The control of the flow properties under irradiation as well as the behaviour of the connections–interfaces with the Test Cell. • The installation of the STUMM in the TTC and its removal, as a validation of the RH operations and procedures for the future irradiation modules, and the delivery of information concerning the time required to perform them. 3. Description of the instrumentation The STUMM instrumentation can be divided in 2 categories: the passive ones (like activation based monitors) that can be only evaluated after unloading from the test cell, and the on-line chains that can be used continuously. The problem of the last ones is that they only give relative values. Activation methods run in parallel to permit the establishment of reference absolute values. 3.1. Activation based monitors Samples made of judiciously chosen isotopes can be positioned in the beam to react with the neutron field and to provide dosimetry data. Simakov et al. [2,3] performed a thorough study of the best promising solutions in an expected spectrum like in the IFMIF plant. For an accurate determination of the neutron flux, one has to produce activities between 102 and 105 Bq without reaching saturation. Therefore, one has to estimate the amount of nuclides and the irradiation time prior to the manufacturing. Generally, even if the capture cross sections are small, the admissible irradiation time is quite short and this solution requires an early opening of the test cell. It is possible to correct for saturation, burn-up and decay effects [4] but then the method loses in precision. The addition of a pneumatic transfer system (also called rabbit system and further referred) to the module is another possibility, as the short term opening of the test cell is difficult to achieve, but it brings complexity and requires additional penetrations. 3.1.1. Activation foils Thin square plates of a comparable size to the one of the neutronic calculation mesh are mounted on a frame and positioned in line with the theoretical footprint. They are intended to be easily dismountable to be brought in front of a multichannel analyser. 3.1.2. Activation wires Similar to the foils, wires can be loaded in tiny tubes and positioned along the steepest neutron flux gradient. The tubes are easily dismountable and can be cut in several pieces. Measured
separately, the wires can give valuable information on a quickly varying spatial flux evolution. 3.1.3. Activation balls This geometry introduces additional uncertainties as compared to the two prior ones, as in this case, the sensitive isotope is cladded in an aluminium sphere and its inside geometry is not well defined. But those balls can be loaded in pneumatic conveyor tubes and extracted from the test cell during the beam operation. 3.2. On-line sensors The on-line sensors do not need to be changed during the commissioning phase if they are reliable enough. 3.2.1. Fission chambers The fission chamber is the preferred solution for studying the neutron field. Qualified [6,7] sub-miniature (∅3 mm) chambers are used in the high flux region. They are sensitive enough to discriminate any variation in the field even if collated against one another. Chambers with a diameter of 7 mm are also foreseen in regions where the flux is low, but they do not undergo the qualification process for the IFMIF environment. 3.2.2. Ionisation chambers As the fission chambers are sensitive to the photon field also, ionisation chambers of the same size are required to subtract this “parasitic” information from the sole neutron response. Fission and ionisation chambers are actually very expensive. Therefore, cost awareness requires to carefully choose their amount and preferred positions. 3.2.3. thermometers In conjunction with the ionisation chambers, one can also use ␥ thermometers to obtain information about the photon distribution. SCK•CEN is currently developing [1] a new type of this sensor that is expected to be more suited to a gas cooled environment as compared to the existing design optimised for use in liquid flow. 3.2.4. Thermocouples Information about temperature under radiation is obtained by means of K type thermocouples. They are very reliable in the expected temperature range (60–200 ◦ C) and less influenced by transmutation as compared to other thermocouples types. 3.2.5. Optical fibres SCK•CEN also launched the development [5] of a new radiation measuring method based on the Cerenkov radiation generated in optical fibres detector. In this case the optical fibre serves both as light-generating and light-guiding medium. The intensity of Cerenkov photons is proportional to the gamma flux along the fibre. It was experimentally demonstrated that the method can be applied to monitor radiation levels in fission reactors [5]. In the core of a fission reactor the radiation field is rather uniform, while in the IFMIF environment strong directional effects are expected and theoretical studies are led by CIEMAT to determine the best fibre orientation and properties. It is important to use a radiationhard fibre because an excessive radiation-induced absorption may degrade the signal below the detection level. To mitigate the induced absorption, a design with two fibre arrangements is foreseen. U-shaped fibre arrangement passing through the beam zone is used to measure the temporal evolution of the signal attenuation due to the beam. Additional fibres with an aluminium mirror at their end are used for measuring the Cerenkov
P. Gouat et al. / Fusion Engineering and Design 88 (2013) 729–732
Fig. 1. HFTM-V like (yellow, in front) and LFTM like (violet, behind) modules, loaded together in the test cell. The HFTM design is best suited to come close to the target backplate. Connectivity with PCPs must still be optimised. (For interpretation of the references to color in figure legend, the reader is referred to the web version of the article.)
flux intensity (C FOS). They are oriented at a fixed angle to the neutron flux direction. The spatial radiation intensity distribution is derived from data on fibres with different lengths. 3.2.6. Strain gauges In one of the possible STUMM concepts (see next section), one uses an HFTM-V like design. The structural external envelope has the same shape and one can expect obtaining valuable information on the actual stress levels by placing strain gauges at specially interesting positions on the box. 4. Description of the whole module 4.1. HFTM-V like concept Except the strain gauges, the above described sensors are mounted on irradiation frames. Like the HFTM-V [8], this concept of the STUMM offers 8 channels where instrumentation rigs can be inserted. The IFMIF final user is free to choose which type of rig he wants to load in a dedicated position. The 4 central ones are in front of the theoretical footprint while the 4 remaining are expected to be in lower flux zones but with a larger gradient. This concept achieves thus a complete modular loading of the module in response to the desired measurement specialisation. Nevertheless the modular design has a consequence. If it is found to be necessary to exchange the measurement rigs, it requires more sophisticated and wider connection heads at the TMIH level. The RH tools within the cell must have more dexterity for opening the connection caps, disconnecting the connection heads and displacing them, load and remove the rigs. It also requires more intervention time at the test cell. One module should be sufficient during the commissioning campaign, but to achieve a full mapping of the cell, one needs to displace it several times. But this also permits to study the effect of other modules loaded at the same time. As the measuring rigs are very expensive (around 400 kEUR each), this concept could limit their quantity. Taking into account the costs of irradiation time (200 kEUR/day), a reduced duration of the commissioning could compensate the investment costs. A good
731
Fig. 2. Test cell filled by three identical HFTM-V like STUMMs. Rabbit systems are mounted at their rear.
compromise could be to load several modules of this type at the same time (see Fig. 2). The optimal solution is strongly dependent on the user commissioning schedule which is not clearly established at the moment. The cooling of the module is ensured by the pressurised helium circuit foreseen for the HFTM-V. The thickness of the external envelope is very small at the beam level (5 mm). It is already difficult to position extractible rigs within. As a consequence, the rabbit system is placed at the rear of the module (see Fig. 3) and is dismountable. Restrictions are foreseen on two-way pneumatic tubes, at the theoretical footprint midplane. The weight of an activation ball is small enough to be lifted by the 6 bar pressure available from the cooling system. 4.2. Other possibilities In contrast to the scenario with dedicated measuring devices and campaigns, one can conceive a huge module filling the whole cavity and loaded once and for the whole commissioning period. In this configuration, one cannot replace defective sensors, cannot extract foils in a relatively short time (balls in the rabbits are
Fig. 3. Restrictions in the tubes of the rabbit system permit a correct positioning of the activation balls in-line with the theoretical footprint.
732
P. Gouat et al. / Fusion Engineering and Design 88 (2013) 729–732
then the best solution), cannot study the effect of other things loaded at the same time and one needs RH equipment foreseen for that scenario. One should also take care that there is enough space in all auxiliaries to handle it. In Fig. 1, one can see a draft scheme of such a module, based on the LFTM design [9]. The instrumented rigs are hung in cylindrical receptacles with the downcomer at the external side. The coolant repartition is ensured by manifolds. At the moment, the instrumentation is limited to the region in-line with the theoretical footprint but taller cylinders can be foreseen. In this design, larger sensors can be used if needed. In the current version, the peripheral rigs are in preference loaded with ∅7 mm chambers.
[2]
[3]
[4]
[5]
Acknowledgments [6]
This work is supported by the Belgian Federal and Spanish Governments and has been performed within the framework of the Broader Approach Agreement. The views and opinions expressed herein do not necessarily reflect those neither of the Governments nor of the IFMIF project team.
[7] [8]
References [9] [1] P. Gouat, P. Jacquet, B. Van Houdt, B. Brichard, W. Leysen, V. Massaut, Present status of the Belgian contribution to the validation and design activities for the
development of the IFMIF radiation-testing modules, Fusion Engineering and Design 86 (2011) 627–631. S.P. Simakov, P. Bém, V. Burjan, U. Fischer, M. Götz, M. Honusek, V. Kroha, ˇ cková, Development of activation foils method for the J. Novák, E. Simeˇ IFMIF neutron flux characterization, Fusion Engineering and Design 82 (2007) 2510–2517. S.P. Simakov, U. Fischer, P. Bém, V. Burjan, M. Götz, M. Honusek, V. Kroha, J. ˇ Novák, E. Simeˇ cková, Final report on the EFDA task TW6-TTMI-003, Deliverable 3: development of activation foils dosimeters for the determination of IFMIFrelevant flux spectra: analytical tools, 26 February 2007. Stefaan G. Pommé, Frank E.M.C. Hardeman, Piotr B. Robouch, Nestor Etxebarria, Frans A. De Corte, Antoine H.M.J. De Wispelaere, Robbert van Sluijs, Andras P. Simonits, General activation and decay formulas and their application in neutron activation analysis with k0 standardization, Analytical Chemistry 68 (24) (1996) 4326–4334. B. Brichard, A.F. Fernandez, H. Ooms, F. Berghmans, Fibre-optic gamma-flux monitoring in a fission reactor by means of Cerenkov radiation, Measurement Science and Technology 18 (2007) 3257–3262. D. Rapisarda, L. Vermeeren, A. Garcia, O. Cabellos, J. Garcia, A. Ibarra, et al., Study on the response of IFMIF fission chambers to mixed neutron–gamma fields: PH2 experimental tests, in: 26th Symposium on Fusion Technology (SOFT), Porto, Portugal, 27 September–1 October 2010, Fusion Engineering and Design 86 (6–8) (2011) 1232–1235, ISSN 0920-3796. D. Rapisarda, A. García, O. Cabellos, F. Mota, et al., Fusion Engineering and Design 84 (2009) 1570–1574. Frederik Arbeiter, Ali Abou-Sena, Yuming Chen, Bernhard Dolensky, Tobias Heupel, et al., Development and validation status of the IFMIF high flux test module, Fusion Engineering and Design 86 (6–8) (2011) 607–610. Willem Leysen, Philippe Gouat, Joël Janssens, Bart Van Houdt, Natalia Casal, Kuo Tian, Conceptual design of the IFMIF low flux test module, submitted for publication.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Conceptual design of the IFMIF Start-Up monitoring module Philippe Gouat a,∗ , Willem Leysen a , Andrei Goussarov a , Papa Sally Galledou a , David Rapisarda b , Fernando Mota b , Angela Garcia b a b
SCK•CEN – The Belgian Nuclear Research Centre, Boeretang 200, B-2400 Mol, Belgium CIEMAT – Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Avda. Complutense 40, 28040 Madrid, Spain
h i g h l i g h t s IFMIF test module conceptual design. IFMIF test module foreseen instrumentation. Cerenkov photon flux monitor.
a r t i c l e
i n f o
Article history: Received 14 September 2012 Received in revised form 16 January 2013 Accepted 12 February 2013 Available online 9 March 2013 Keywords: IFMIF STUMM EVEDA Conceptual design C FOS
a b s t r a c t The preliminary engineering design of the test facilities, including the various test modules to be used in the IFMIF plant is a part of the IFMIF/EVEDA (Engineering Validation and Engineering Design Activities) project from the Broader Approach to fusion. One presents the current status of the conceptual development of the IFMIF Start-Up Monitoring Module, a dedicated device used in the IFMIF test cell during the commissioning phase of the installation, in order to completely characterise the irradiation conditions behind the target on which the beam of deuterons will be focused. This STUMM embarks a lot of instrumentation to precisely characterise the neutron field, the nuclear heating and the temperatures in the test cell. One briefly describes the measuring instruments (including a specific radiation flux monitor under development), the possible layouts and the possible positioning. One also defines which types of measurements are expected by this especially dedicated commissioning module. © 2013 Elsevier B.V. All rights reserved.
1. Introduction In the frame of the EVEDA phase of the IFMIF development, the conceptual study of a Start-Up module was launched in 2009 [1]. The EVEDA phase terminates at the middle of 2013. One presents here the achievements on the Start-Up monitoring module (STUMM). This module is especially dedicated to the commissioning phase of the IFMIF plant and will be loaded in the test cell prior to any production activity to verify a certain number of operational parameters. As the scenario is not well defined yet, one had to make
Abbreviations: C FOS, Cerenkov fibre-optics sensor; EVEDA, Engineering Validation/Engineering Design Activities; HFTM-V, high flux test module-vertical layout; IFMIF, International Fusion Materials Irradiation Facility; KIT, Karlsruhe Institute of Technology; LFTM, low flux test module; PCP, piping and cabling plug; RH, remote handling; STUMM, Start-Up monitoring module; TMIH, test module interface head; TTC, target and test cell. ∗ Corresponding author. Tel.: +32 14 33 34 08. E-mail address: [email protected] (P. Gouat). 0920-3796/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2013.02.057
some assumptions and propose different options for the module design. 2. Objectives of STUMM One briefly recalls here the objectives of this distinct module. The main goals have been identified as follows: • The characterisation of the whole radiation field in the Test Cell area. The STUMM could be placed in different positions if considered necessary. • The measurement of the spatial distribution of neutrons and photons in the vertical and horizontal planes, perpendicular to the beam. This 3D map will be not only limited to the footprint region (main irradiated area, 5 cm × 20 cm), but also to regions where the ratio between neutrons and photons could change substantially from the centre of the plane. ◦ Measurements of the spatial distribution of neutrons ◦ Measurements of the spatial distribution of photons • The characterisation of the temporal evolution of the radiation field. During the commissioning phase, different levels of neutron
730
P. Gouat et al. / Fusion Engineering and Design 88 (2013) 729–732
and gamma fluxes will exist due to the qualification of the beams (from low to high duty cycles). The monitoring of those changes will be suited to follow variations in the radiation field during the IFMIF normal operation. • The demonstration of the correct functioning of the foreseen instrumentation, including signal levels, noise in the measurements. . . Realistic operation conditions are needed (TTC atmosphere, pressure, directional field. . .). • The validation of the neutronic calculations used to design the test modules. Other objectives that are related to the operation of the STUMM, and that must be taken into account are: • The validation of the STUMM mechanical design, since it could be considered as a Test Module prototype. Therefore, its characterisation (in terms of robustness, dimensional stability, structural integrity. . .) could qualify the fabrication/design of the future test modules. Of course, the operation of this module will be also useful to anticipate the operation of the experimental modules during IFMIF normal operation. • The control of the flow properties under irradiation as well as the behaviour of the connections–interfaces with the Test Cell. • The installation of the STUMM in the TTC and its removal, as a validation of the RH operations and procedures for the future irradiation modules, and the delivery of information concerning the time required to perform them. 3. Description of the instrumentation The STUMM instrumentation can be divided in 2 categories: the passive ones (like activation based monitors) that can be only evaluated after unloading from the test cell, and the on-line chains that can be used continuously. The problem of the last ones is that they only give relative values. Activation methods run in parallel to permit the establishment of reference absolute values. 3.1. Activation based monitors Samples made of judiciously chosen isotopes can be positioned in the beam to react with the neutron field and to provide dosimetry data. Simakov et al. [2,3] performed a thorough study of the best promising solutions in an expected spectrum like in the IFMIF plant. For an accurate determination of the neutron flux, one has to produce activities between 102 and 105 Bq without reaching saturation. Therefore, one has to estimate the amount of nuclides and the irradiation time prior to the manufacturing. Generally, even if the capture cross sections are small, the admissible irradiation time is quite short and this solution requires an early opening of the test cell. It is possible to correct for saturation, burn-up and decay effects [4] but then the method loses in precision. The addition of a pneumatic transfer system (also called rabbit system and further referred) to the module is another possibility, as the short term opening of the test cell is difficult to achieve, but it brings complexity and requires additional penetrations. 3.1.1. Activation foils Thin square plates of a comparable size to the one of the neutronic calculation mesh are mounted on a frame and positioned in line with the theoretical footprint. They are intended to be easily dismountable to be brought in front of a multichannel analyser. 3.1.2. Activation wires Similar to the foils, wires can be loaded in tiny tubes and positioned along the steepest neutron flux gradient. The tubes are easily dismountable and can be cut in several pieces. Measured
separately, the wires can give valuable information on a quickly varying spatial flux evolution. 3.1.3. Activation balls This geometry introduces additional uncertainties as compared to the two prior ones, as in this case, the sensitive isotope is cladded in an aluminium sphere and its inside geometry is not well defined. But those balls can be loaded in pneumatic conveyor tubes and extracted from the test cell during the beam operation. 3.2. On-line sensors The on-line sensors do not need to be changed during the commissioning phase if they are reliable enough. 3.2.1. Fission chambers The fission chamber is the preferred solution for studying the neutron field. Qualified [6,7] sub-miniature (∅3 mm) chambers are used in the high flux region. They are sensitive enough to discriminate any variation in the field even if collated against one another. Chambers with a diameter of 7 mm are also foreseen in regions where the flux is low, but they do not undergo the qualification process for the IFMIF environment. 3.2.2. Ionisation chambers As the fission chambers are sensitive to the photon field also, ionisation chambers of the same size are required to subtract this “parasitic” information from the sole neutron response. Fission and ionisation chambers are actually very expensive. Therefore, cost awareness requires to carefully choose their amount and preferred positions. 3.2.3. thermometers In conjunction with the ionisation chambers, one can also use ␥ thermometers to obtain information about the photon distribution. SCK•CEN is currently developing [1] a new type of this sensor that is expected to be more suited to a gas cooled environment as compared to the existing design optimised for use in liquid flow. 3.2.4. Thermocouples Information about temperature under radiation is obtained by means of K type thermocouples. They are very reliable in the expected temperature range (60–200 ◦ C) and less influenced by transmutation as compared to other thermocouples types. 3.2.5. Optical fibres SCK•CEN also launched the development [5] of a new radiation measuring method based on the Cerenkov radiation generated in optical fibres detector. In this case the optical fibre serves both as light-generating and light-guiding medium. The intensity of Cerenkov photons is proportional to the gamma flux along the fibre. It was experimentally demonstrated that the method can be applied to monitor radiation levels in fission reactors [5]. In the core of a fission reactor the radiation field is rather uniform, while in the IFMIF environment strong directional effects are expected and theoretical studies are led by CIEMAT to determine the best fibre orientation and properties. It is important to use a radiationhard fibre because an excessive radiation-induced absorption may degrade the signal below the detection level. To mitigate the induced absorption, a design with two fibre arrangements is foreseen. U-shaped fibre arrangement passing through the beam zone is used to measure the temporal evolution of the signal attenuation due to the beam. Additional fibres with an aluminium mirror at their end are used for measuring the Cerenkov
P. Gouat et al. / Fusion Engineering and Design 88 (2013) 729–732
Fig. 1. HFTM-V like (yellow, in front) and LFTM like (violet, behind) modules, loaded together in the test cell. The HFTM design is best suited to come close to the target backplate. Connectivity with PCPs must still be optimised. (For interpretation of the references to color in figure legend, the reader is referred to the web version of the article.)
flux intensity (C FOS). They are oriented at a fixed angle to the neutron flux direction. The spatial radiation intensity distribution is derived from data on fibres with different lengths. 3.2.6. Strain gauges In one of the possible STUMM concepts (see next section), one uses an HFTM-V like design. The structural external envelope has the same shape and one can expect obtaining valuable information on the actual stress levels by placing strain gauges at specially interesting positions on the box. 4. Description of the whole module 4.1. HFTM-V like concept Except the strain gauges, the above described sensors are mounted on irradiation frames. Like the HFTM-V [8], this concept of the STUMM offers 8 channels where instrumentation rigs can be inserted. The IFMIF final user is free to choose which type of rig he wants to load in a dedicated position. The 4 central ones are in front of the theoretical footprint while the 4 remaining are expected to be in lower flux zones but with a larger gradient. This concept achieves thus a complete modular loading of the module in response to the desired measurement specialisation. Nevertheless the modular design has a consequence. If it is found to be necessary to exchange the measurement rigs, it requires more sophisticated and wider connection heads at the TMIH level. The RH tools within the cell must have more dexterity for opening the connection caps, disconnecting the connection heads and displacing them, load and remove the rigs. It also requires more intervention time at the test cell. One module should be sufficient during the commissioning campaign, but to achieve a full mapping of the cell, one needs to displace it several times. But this also permits to study the effect of other modules loaded at the same time. As the measuring rigs are very expensive (around 400 kEUR each), this concept could limit their quantity. Taking into account the costs of irradiation time (200 kEUR/day), a reduced duration of the commissioning could compensate the investment costs. A good
731
Fig. 2. Test cell filled by three identical HFTM-V like STUMMs. Rabbit systems are mounted at their rear.
compromise could be to load several modules of this type at the same time (see Fig. 2). The optimal solution is strongly dependent on the user commissioning schedule which is not clearly established at the moment. The cooling of the module is ensured by the pressurised helium circuit foreseen for the HFTM-V. The thickness of the external envelope is very small at the beam level (5 mm). It is already difficult to position extractible rigs within. As a consequence, the rabbit system is placed at the rear of the module (see Fig. 3) and is dismountable. Restrictions are foreseen on two-way pneumatic tubes, at the theoretical footprint midplane. The weight of an activation ball is small enough to be lifted by the 6 bar pressure available from the cooling system. 4.2. Other possibilities In contrast to the scenario with dedicated measuring devices and campaigns, one can conceive a huge module filling the whole cavity and loaded once and for the whole commissioning period. In this configuration, one cannot replace defective sensors, cannot extract foils in a relatively short time (balls in the rabbits are
Fig. 3. Restrictions in the tubes of the rabbit system permit a correct positioning of the activation balls in-line with the theoretical footprint.
732
P. Gouat et al. / Fusion Engineering and Design 88 (2013) 729–732
then the best solution), cannot study the effect of other things loaded at the same time and one needs RH equipment foreseen for that scenario. One should also take care that there is enough space in all auxiliaries to handle it. In Fig. 1, one can see a draft scheme of such a module, based on the LFTM design [9]. The instrumented rigs are hung in cylindrical receptacles with the downcomer at the external side. The coolant repartition is ensured by manifolds. At the moment, the instrumentation is limited to the region in-line with the theoretical footprint but taller cylinders can be foreseen. In this design, larger sensors can be used if needed. In the current version, the peripheral rigs are in preference loaded with ∅7 mm chambers.
[2]
[3]
[4]
[5]
Acknowledgments [6]
This work is supported by the Belgian Federal and Spanish Governments and has been performed within the framework of the Broader Approach Agreement. The views and opinions expressed herein do not necessarily reflect those neither of the Governments nor of the IFMIF project team.
[7] [8]
References [9] [1] P. Gouat, P. Jacquet, B. Van Houdt, B. Brichard, W. Leysen, V. Massaut, Present status of the Belgian contribution to the validation and design activities for the
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