F. Escourbiac

Experimental optimisation of a hypervapotron® concept for ITER plasma facing components

Abstract Historically developed for cooling of klystron electronic tubes, metallic hypervapotron® prototypes with different width were manufactured for high heat flux plasma facing components (PFC) applications. They were critical heat flux (CHF) tested on the European 200 kW electron beam facility (FE200), the 54 measured values have shown their good performances—up to 25–30 MW/m2 at low axial velocities (2–6 m/s)—interesting for ITER divertor dome and vertical target design. An important conclusion is that CHF decreases when the width increases.

Non-Destructive Testing of Divertor Components

This task within the EU RD (2) blind non-destructive round robin test of the prototype; (3) HHF test in FE200 electron beam (EB) facility; (4) post-fatigue blind non-destructive round robin test; (5) destructive examination. The general final conclusion was that the NDT techniques can reliably detect and locate defects having dimensions well below those, which could impair the thermal fatigue lifetime.

Manufacturing and testing of a prototypical divertor vertical target for ITER

Abstract After an extensive R&D activity, a medium-scale divertor vertical target prototype has been manufactured by the EU Home Team. This component contains all the main features of the corresponding ITER divertor design and consists of two units with one cooling channel each, assembled together and having an overall length and width of about 600 and 50 mm, respectively. The upper part of the prototype has a tungsten macro-brush armour, whereas the lower part is covered by CFC monoblocks. A number of joining techniques were required to manufacture this component as well as an appreciable effort in the development of suitable non-destructive testing methods. The component was high heat flux tested in FE200 electron beam facility at Le Creusot, France. It endured 100 cycles at 5 MW/m 2 , 1000 cycles at 10 MW/m 2 and more then 1000 cycles at 15–20 MW/m 2 . The final critical heat flux test reached a value in excess of 30 MW/m 2 .

European achievements for ITER high heat flux components

This paper summarises the main activities carried out by the EU Home Team to develop suitable solutions for the ITER high heat flux components, namely the divertor, the baffle and the limiter. The available results demonstrate that the EU have the capability to manufacture high heat flux components with carbon fibre reinforced carbon, tungsten and beryllium armours which all exceed the ITER design requirements.

In-situ monitoring of actively cooled plasma facing components using acoustic and thermal methods

Plasma facing components (PFC) for modern steady state fusion devices have to withstand heat fluxes up to 20 MW m−2. In case of internal defects in the components, a critical heat flux event can occur at an incident heat flux lower than expected in a defect-free component. It is therefore essential to develop in-vessel means for on line safety monitoring to prevent PFC destruction, and health monitoring during shutdown to control PFC damage. Two methods are developed in this paper, covering these topics.

Possible divertor solutions for a fusion reactor. Part 2. Technical aspects of a possible divertor

Safe operation of a fusion reactor divertor requires the exhaust of heat fluxes ranging from 5 to 30 MW m−2. The different technical solutions which are proposed rely on various water cooled copper heat sink designs. The protective armour may be Tungsten, Beryllium or Carbon depending on the plasma interaction. Optimisation is achieved by an overall comparison stressing the compliance to industrial defects. Reliable designs have been proposed and tested on large elements with carbon tiles for several thousand cycles, at power levels up to 10 MW m−2.

Possible divertor solutions for a fusion reactor.

Safe operation of a fusion reactor divertor requires the exhaust of heat fluxes ranging from 5 to 30 MW m−2. The different technical solutions which are proposed rely on various water cooled copper heat sink designs. The protective armour may be Tungsten, Beryllium or Carbon depending on the plasma interaction. Optimisation is achieved by an overall comparison stressing the compliance to industrial defects. Reliable designs have been proposed and tested on large elements with carbon tiles for several thousand cycles, at power levels up to 10 MW m−2.

High heat flux behaviour of damaged plasma facing components

A medium scale prototype of the ITER divertor vertical target, manufactured with calibrated internal bonding defects is tested and studied via infrared characterisation, thermal fatigue testing and finite element analysis. Tools for defect detection and behaviour of these defects along in-service lifetime are presented in this document.

Definition of acceptance criteria for the ITER divertor plasma-facing components through systematic experimental analysis

Experience has shown that a critical part of the high-heat flux (HHF) plasma-facing component (PFC) is the armour to heat sink bond. An experimental study was performed in order to define acceptance criteria with regards to thermal hydraulics and fatigue performance of the International Thermonuclear Experimental Reactor (ITER) divertor PFCs. This study, which includes the manufacturing of samples with calibrated artificial defects relevant to the divertor design, is reported in this paper. In particular, it was concluded that defects detectable with non-destructive examination (NDE) techniques appeared to be acceptable during HHF experiments relevant to heat fluxes expected in the ITER divertor. On the basis of these results, a set of acceptance criteria was proposed and applied to the European vertical target medium-size qualification prototype: 98% of the inspected carbon fibre composite (CFC) monoblocks and 100% of tungsten (W) monoblock and flat tiles elements (i.e. 80% of the full units) were declared acceptable.

Infrared characterization and high heat flux testing of plasma sprayed layers

Abstract Four series of plasma sprayed actively cooled mock-ups have been evaluated by infrared measurements and heat flux testing. Infrared characterization showed heat transfer capability of the plasma sprayed layer bonded to the substrate. Even if the thermal conductivity of the B 4 C plasma sprayed coating is only 5% of the bulk material, the coating can easily survive 1000 cycles at 7.5 MW/m 2 if the thickness is less than 150 μm. Thick tungsten coatings (3–5 mm) were more fragile, depending on the plasma spray technology. The highest heat flux acceptable for 1000 cycles is 4 MW/m 2 with a vacuum plasma spray coating and a Ni–Al–Si–W precoating, accounting for a reduction in the thermal conductivity by a factor of 3.