Primary First Wall Research Articles

Fast brazing development for the joining of the beryllium armour layer for the ITER first wall panels

This paper describes the development of a flat pancake inductor for brazing beryllium tiles on a primary first wall (PFW) panel heat sink as well as the development of the brazing parameters. Two main variables were tested: brazing filler metal on one hand and PVD coating material on beryllium tiles on the other hand. The nickel coating and silver base brazing filler metal was the best couple and obtained shear values higher than 100 MPa. The inductor design and the choice of materials were applied to the brazing of a mock-up for high heat flux testing. Some tiles sustained 1000 cycles at 1.5 MW.

Activity of the European high heat flux test facility: FE200

FE200 is an electron beam (EB) 200 kW test facility resulting since 1991 from partnership between Framatome Technical Centre in Le Creusot (France) and Tore Supra team in CEA Cadarache (France). It is dedicated to high heat flux testing of small and medium-sized plasma facing components. The performed tests are thermal fatigue tests (100,000 since 1992), critical heat fluxes, disruptions, glancing incidence tests on materials such as Cu–Al25 and CuCrZr alloys, carbon fibre composite (CFC) or tungsten (W). The thermal fatigue behaviour of some primary first wall (PFW), hypervapotron and divertor components is described.

Development of a copper alloy to beryllium HIP bonding technology for the ITER first wall

The primary first wall (PFW) panels of the ITER blanket concept comprise a bi-metallic copper alloy/stainless steel water-cooled heatsink faced with a plasma facing material. Precipitation strengthened CuCrZr is one option for the copper alloy of the heatsink; beryllium, in the form of tiles is an option for the plasma facing material. Over recent years, the technology needed to HIP bond the beryllium tiles to CuCrZr alloy has been developed. This paper describes small samples and larger mock-ups produced during the development of this HIP bonding technology and outlines how structural analyses were used to gain an understanding of the bonding process and refine the design.

Application of a diffusion bonding methodology to develop a Be/Cu HIP bond suitable for the ITER blanket

Due to its low atomic mass and high thermal conductivity beryllium is a candidate plasma facing material for the ITER primary first wall (PFW). HIP bonding and brazing have been used previously to bond beryllium tiles to the copper alloy heatsink. However, both methods employ temperature conditions that are incompatible with the otherwise attractive copper alloy, copper chrome zirconium (CuCrZr). This paper outlines the methodology used to develop a HIP bond compatible with CuCrZr and demonstrates its application towards the production of a PFW mock-up.

ITER primary first wall mock-up fabrication and testing for Be/Cu alloy joining development

This paper presents the main results obtained so far from the development work performed in Europe to define the joining conditions between beryllium (Be) tiles and the dispersion strengthened copper alloy (DS-Cu) heat sink material for the ITER primary first wall (PFW). Two Be/DS-Cu joining techniques were investigated: hot isostatic pressing and furnace brazing. Six PFW mock-ups have been thermal fatigue tested so far. One PFW mock-up with HIPped Be tile was tested at 2.5 MW/m 2 for 1000 cycles without any indication of failure. On two other mock-ups, Be tiles detached at or above 2.7 MW/m 2. Two others were tested at 0.7 MW/m 2 for 13 000 cycles also without any indication of failures. A first PFW mock-up with a furnace brazed Be tile was tested at 1.6 MW/m 2 for 1000 cycles. These results should be compared with the operation conditions of the ITER PFW, namely 0.5 MW/m 2 peak heat flux and off-normal events up to 1.4 MW/m 2. Thermal fatigue testing of other mock-ups is still in progress and the development programme is continuing to further increase the engineering margins while decreasing the fabrication cost of the PFW panels.