Technical Meeting on Tritium Breeding Blankets and Associated Neutronics

European Test Blanket Modules: An Overview of Fabrication Technologies Development and Their Feasibility Assessment

3 Sept 2025, 14:10

40m

IAEA Headquarters, Vienna, Austria

Invited Track II: Manufacturing, assembly, and licensing Topic II

Speaker

Milan Zmitko (Fusion for Energy (F4E))

Description

Within the framework of European fusion strategy, two reference tritium Breeder Blankets concepts are developed to be tested in ITER as Test Blanket Modules (TBMs): Water-Cooled Lithium-Lead (WCLL) which uses liquid Pb-16Li as a breeder and neutron multiplier, and Helium-Cooled Ceramic Pebble (HCCP) with lithiated ceramic pebbles as breeder and beryllium pebbles as neutron multiplier materials. Both concepts use as a structural material Reduced Activation Ferritic Martensitic steel, EUROFER97 (X10CrWVTa9-1) [1]. Pressurized water (15.5 MPa, 295-328ºC for WCLL) and pressurized helium (8 MPa, 300-500ºC for HCCP) are used for heat extraction.
The TBM structure is constituted of a Box (made of two Side Caps (SC) and First Wall (FW)), stiffened by horizontal and vertical Stiffening Plates (SP) and closed on its back, in the manifold area, with several Back Plates (BP) of different thicknesses with passing through elements. Inside the Box, cooled elements, Double Wall Tubes (DWT) for WCLL concept and Cooling Plates (CP) for HCCP concept, are assembled into breeder units delimited by Stiffening Plates. All HCCP structural subcomponents are internally cooled with He circulating in meandering square section channels. Similar concept is used for the water-cooled First Wall of the WCLL.
This paper briefly describes the strategy adopted for the development of the TBM-related fabrication technologies, and an approach used for manufacturing and delivery of the TBMs on ITER, considering particularities of EUROFER97 structural material and relevant regulatory aspects (TBM is classified as a Nuclear Pressure Equipment) [2]. The main characteristics of the EUROFER97 structural material are given in this context [3].
Fabrication technologies developed to (i) manufacture TBM subcomponents (FW, SC, SPs, CPs), (ii) assemble TBM Box, (iii) assemble TBM Box structure, and (iv) assemble TBM back manifold, are overviewed and discussed [4-6]. The applied welding technologies are based on fusion welding (laser beam, GTAW) and diffusion bonding (HIP) considering specificities of EUROFER97 steel. Preliminary Welding Procedure Specifications (pWPS) are developed following requirements of professional standards and RCC-MRx construction code [7].
Moreover, the paper presents the main outcomes related to the phase of consolidation of welding processes and related technologies for manufacturing of EUROFER97 structures and components. It discusses (i) EUROFER97 weldability demonstration for various welding techniques used for the TBM manufacturing (like GTAW/TIG, EBW, LBW and HIP), (ii) filler material acceptance studies, (iii) assessment of the effect of multiple Post-Weld Heat Treatment (PWHT) on mechanical properties of weld joints, (iv) dissimilar welding between EUROFER97 and 316L(N)-IG stainless steel, and (v) Double-Wall Tubes (DWT) manufacturing and DWT/BP weld joint development and characterization.
The conclusions of the paper discuss the main encountered issues and challenges related to the TBM manufacturing feasibility and relevant Return-of-eXperience (RoX).