Qualification & Testing of Joining Development for DEMO Limiter Component

Qualification & Testing of Joining Development for DEMO Limiter Component

Qualification & Testing of Joining Development for DEMO Limiter Component 150 150 Mathew
UKAEA-CCFE-PR(21)51

Qualification & Testing of Joining Development for DEMO Limiter Component

A development plan for validation of functional principles is defined to support the challenges of mock-up manufacturing and testing. It is aimed to develop the process and infrastructure for qualifying fusion components for the limiters in the European DEMO. The limiters are components that define the plasma boundary by direct contact during normal and off normal transient events and thus they protect the First Wall of the Breeding Blanket System from extreme heat fluxes during these events. Within this framework, the joints play an important role for making feasible the combination of dissimilar materials required for the plasma facing components (PFCs) by providing a compliant interlayer. The main limiter PFC functionality is to act as thermal barrier, therefore the materials combination shall be able to support the thermal gradient between the high heat flux (HHF) from the plasma and the heat sink. The primary aim of the PFC is to ensure the structural integrity of the heat sink of the PFC (to prevent in-vessel loss of coolant accident), as it is foreseen that the during the off-normal transients the PFC surface may melt or evaporate. Minimizing the large deformation and guaranteeing the strength and fatigue behaviour of the joints is required to achieve this. Therefore, a testing programme for joining development and qualification based on brazing technology is performed. It is focused on joint assessment between representative filler metals (OB1025TM, OB950TM, PB950TM, NBLMTM & H-BronzeTM) from the different families in the market and the chemical compatibility, capillarity flow and spreadability on the typical base materials used for PFC (laser powder bed fusion additive manufactured W-6%Ta, W, P91, OFHC Copper, CuCrZr). The main results show good wetting of the gold-copper alloy (OB1025TM) with all the base materials. It allows to progress with the integration of a PFC to create the process and infrastructure for optimizing the design of critical joints. NBLMTM seems to be an interesting filler for materials with high melting temperature as tungsten and P91 and OB950TM presents acceptable wetting condition with the base materials. It would need to optimize the joint design. PB950TM is rejected because the excess of wetting on all the base materials.

Collection:
Journals
Journal:
Fusion Engineering and Design
Publisher:
Elsevier