•The manufacturing of the divertor structure and coils has been performed according to the technical specifications.•The scale one dummy coils have been tested, the last test (curing process ...validation) being scheduled to be done in September 2016.•The divertor in situ assembly has been carried out successfully.•The brazing process was carried out with an excellent repeatability.•The impregnation and curing phase of the divertor coils are scheduled to be done in November 2016.
In order to fully validate “ITER-like” actively water cooled tungsten plasma facing units, addressing the issues of long plasma discharges, an axisymmetric divertor structure has been studied and manufactured for the implementation in the WEST (W-Tungsten Environment in Steady state Tokamak) tokamak platform.
This assembly, called divertor structure and coils (4m diameter, 20t), is composed of two stainless steel casings containing an actively water cooled (up to 180°C, 4MPa) copper winding pack designed for a conductor current in the range of 12.5kA (up to 1000s). It must sustain harsh environmental conditions in terms of ultra-high vacuum, high temperatures and electrodynamic loads. One major difficulty is the assembly by induction brazing of individual bended conductor sectors inside the vacuum vessel and the consecutive sealing of the casings by TIG welding.
Therefor development activities have been carried out on a scale one dummy coil, such as brazing, assembly, thermal cycling and electrical insulation tests (5kV ground voltage). Whereas the brazing assembly technics and the conductor installation were validated without major difficulties, different technical solutions for the electrical insulation had to be tested. The chosen solution is a resin epoxy impregnated fiber glass fabric layered around the conductors followed by a polymerization procedure.
In parallel the manufacturing of divertor structure components started in the second half of 2013 with a total delivery at the end of 2015.
The paper will illustrate the technical developments which have been performed in order to fully validate the design. It concerns mainly the dummy coil and the complex conductor installation procedure assisted by virtual reality tools. The manufacturing methods proposed by industry in order to fulfil the technical requirements will be also addressed. Finally the processes and associated tools used in order to implement this large component inside the WEST vacuum vessel will be detailed.
We have performed real-time soft error rate (RT-SER) measurements on bulk 65-nm static random access memories (SRAMs) during deuterium–deuterium (D-D) plasma operation at W–tungsten–Environment in ...Steady-state Tokamak (WEST). The present measurement campaign was characterized by the production of several tens of long pulse discharges (∼60 s) and by a total neutron fluence (at the level of the circuits under test) up to ∼10 9 n·cm−2, improving the error statistics by a factor of more than 6 with respect to the first measurements obtained in 2020. The experimental results demonstrate the occurrence of bursts of single-event upsets (SEUs) during the most efficient shots and 12% of multiple cell upset (MCU) events. Time-resolved data also show that MCUs are preferentially detected in the last part of these long pulses, providing further evidence that higher energy neutrons, initiated by deuterium–tritium (D-T) reactions due to triton burn-up in the D-D plasma, may play a role in the production of MCUs that cannot be attributed in such large proportions to “low-energy” neutrons produced in D-D reactions.
We conducted a real-time soft-error rate characterization of CMOS bulk 65-nm static random access memories (SRAMs) subjected to fusion neutrons during deuterium-deuterium (D-D) plasma operation at ...W-tungsten-Environment in Steady-state Tokamak (WEST). The test equipment, installed in the experimental hall at several locations of the tokamak, was irradiated during machine shots by a flux of particles dominated by primary 2.45-MeV neutrons. Real-time neutron metrology, neutron spectrometry, complementary characterization with monoenergetic neutrons, and Monte Carlo numerical simulations at both material and circuit levels have also been performed to analyze the experimental data. Our results suggest that higher energy neutrons, simultaneously produced by deuterium-tritium (D-T) reactions due to triton burn-up in the D-D plasma, play a significant role in the radiation response of SRAMs for which multiple cell upsets are detected and cannot be attributed to D-D neutrons.
► The WEST programme is a unique opportunity to experience the industrial scale manufacture of tungsten plasma-facing components similar to the ITER divertor ones. ► In Tore Supra, it will bring ...important know how for actively cooled W divertor operation. ► This can be done by a reasonable modification of the Tore Supra tokamak. ► A fast implementation of the project would make this information available in due time. ► This allows a significant contribution to the W ITER divertor risk minimization in its manufacturing and operation phase.
The WEST programme consists in transforming the Tore Supra tokamak into an X point divertor device, while taking advantage of its long discharge capability. This is obtained by inserting in vessel coils to create the X point while adapting the in-vessel elements to this new geometry. This will allow the full tungsten divertor technology to be used on ITER to be tested in anticipation of its use on ITER under relevant heat loading conditions and pulse duration. The early manufacturing of a significant industrial series of ITER-similar W plasma-facing units will contribute to the ITER divertor manufacturing risk mitigation and to that associated with early W divertor plasma operation on ITER.
Abstract
WEST database analysis shows a correlation of the recycled neutral source around the separatrix with core performances. This observation questions the causality chain between particle source ...and turbulent transport up to the core in L-mode, high recycling plasmas, an unavoidable phase of all scenarios. The best core performances correlate with the lowest values of the density at the separatrix,
n
sep
, similarly to ASDEX Upgrade (AUG) tokamak and Joint European Torus (JET) tokamak in H-mode (Verdoolaege
et al
2021
Nucl. Fusion
61
076006). Reflectometry in the midplane provides
n
sep
, while the temperature at the separatrix,
T
sep
is inferred by the ‘two-point model’ using Langmuir probe data on divertor targets. Lower separatrix resistivity does not correlate with better core performances, unlike H-mode observations (Eich
et al
2020
Nucl. Fusion
60
056016). As expected in the presence of an efficient neutral source due to recycling fluxes,
n
sep
correlates with the D recycled particle flux at the divertor measured by visible spectroscopy. Coherently, at a given controlled central line integrated density
n
ˉ
, lower
n
sep
correlates with a larger density gradient around the separatrix as well as a larger global density peaking,
n
ˉ
/
⟨
n
⟩
, measured by interferometry. The latter correlates as well with lower collisionality in the core, similarly to JET and AUG H-modes (Angioni
et al
2007
Nucl. Fusion
47
1326). The correlations reported allow phrasing the subsequent causality question: what is the interplay chain between low neutral recycling at the divertor plates, low density at the separatrix, high density peaking at the separatrix, high global density peaking, higher central temperature and better core energy confinement quality? Understanding the causality chain is essential to prepare ITER operation and design DEMO scenarios where the ratio of the divertor leg to the ionization length will be larger and where the pumped flux with respect to the plasma volume will be lower than presently operating tokamaks.
Design and manufacturing of WEST Baffle Batal, Tristan; Firdaouss, Mehdi; Richou, Marianne ...
Fusion engineering and design,
10/2015, Letnik:
98-99
Journal Article
Recenzirano
•Disruption's torque in the PFC was simulated thanks to ANSYS.•The ANSYS thermal results comply with WEST project requirements.•The cycling analysis complies with WEST project requirements.•316L ...components comply with A level RCC-MRx criteria.
The Tore Supra tokamak is being transformed in an X-point divertor fusion device in the frame of the WEST project, launched in support to the Iter tungsten divertor strategy. The WEST Baffle aims to evacuate particles by creating a toroidal pumping throat. It also protects the lower divertor cooling pipes and the passive stabilization plate from heat fluxes. The Baffle is made of actively cooled plasma facing components (PFCs), with underneath a passive stabilization plate and a support beam. The Baffle design is presented in a first part. In a second time the different ANSYS simulations are described: electromagnetic, thermal and mechanical results are presented. The design choices are justified for the different results obtained thanks to the simulation. In a final part, some aspects of the PFC manufacturing are presented.
•The divertor PFU integration has been studied regarding existing environment.•Magnetic, electric, thermal, hydraulic, mechanical loads and assembly are considered.
In the context of the Tokamak ...Tore-Supra evolution, the CEA aims at transforming it into a test bench for ITER actively cooled tungsten (ACW) plasma facing components (PFC). This project named WEST (Tungsten Environment in Steady state Tokamak) is especially focused on the divertor target. The modification of the machine, by adding two axisymmetric divertors will make feasible an H-mode with an X-point close to the lower divertor. This environment will allow exposing the divertor ACW components up to 20MW/m2 heat flux during long pulse. These specifications are well suited to test the ITER-like ACW target elements, respecting the ITER design.
One challenge in such machine evolution is to integrate components in an existing vacuum vessel in order to obtain the best achievable performance. This paper deals with the design integration of ITER ACW target elements into the WEST environment considering magnetic, electric, thermal and mechanical loads. The feasibility of installation and maintenance has to be strongly considered as these PFC could be replaced several times. The ports size allows entering a 30° sector of pre-installed tungsten targets which will be plugged as quickly and easily as possible. The main feature of steady state operation is the active cooling, which leads to have many embedded cooling channels and bulky pipes on the PFC module including many connections and sealings between vacuum and water channels. The 30° sector design is now finalized regarding the ITER ACW elements specifications. No major modifications are expected.
•The mechanical design and integration of the divertor structure have been performed.•The design of the casing and the winding-pack has been optimized.•The coil assembly process has been ...assessed.•The realization of a coil mock-up scale one is scheduled.
In order to fully validate “ITER-like” actively water cooled tungsten plasma facing units, the implementation of an axisymmetric divertor structure in the Tokamak Tore-Supra has been studied. With this major upgrade, the so-called WEST (Tungsten Environment in Steady state Tokamak), Tore-Supra will be able to address the issues of long plasma discharges using a tungsten divertor based on monoblock targets.
The divertor structure and coils assembly are made up of two stainless steel casings containing a copper winding pack cooled by a pressurized hot water circuit (up to 180°C, 4MPa) in which a total divertor current of up to 16×13kA is circulating in steady state. The conductor is electrically insulated and wedged inside the casing in order to be mechanically protected.
The divertor which is designed to perform steady state plasma operation (up to 1000s), must sustain harsh environmental conditions in terms of ultra light vacuum conditions, electromagnetical loads and electrical insulation (5kV ground voltage) under high temperature (180°C).
Therefore, a feasibility study of such a complex structure has been performed. It implied activities on a scale one dummy coil, such as installation, assembly issues and representative tests (electric, thermal and hydraulic).
The manufacturing of the divertor structure, which is a large assembly of 4-m diameter representing a total weight of around 20tonnes, started in the second half of 2013 and is expected to be delivered by the end of 2014.
The paper will illustrate the technical developments and tests performed during 2013 and beginning of 2014 in order to fully validate the design concept before the industrial phase. The manufacturing methods proposed by the contractor in order to fulfil the technical requirements will be also addressed.
In current fusion devices, the components located in front of plasma, the so-called plasma facing components (PFCs), sustain severe constraints such as high thermal flux (several MW/m super() ...super(2), erosion, flux of particles. The management of this first material interface is critical from a plasma performance point of view. ITER, as nuclear facility, is initiating a new era for fusion, which will be reinforced for a future fusion power plant which will add specific requirements (sufficient lifetime, a cooling system to produce energy, use of low activation material) while increasing nuclear constraints.
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