ETD

• DEMO
• in-box-LOCA
• ITER
• LIFUS5MOD3
• Lithium-Lead

In the framework of the advanced design of the European DEMO nuclear fusion reactor, the Water-Cooled Lithium Lead (WCLL) concept represents one of the most promising options for the Breeding Blanket (BB) technology. Based on this assessment, the WCLL BB has been confirmed to be part of the ITER Test Blanket Module (TBM) program, which aims to provide the first experimental data on the performance of breeding blankets within the integrated fusion nuclear environment, with the objective of supporting the development of functional fusion reactors such as DEMO. The testing of four mock-up breeding blanket concepts is then foreseen by the program, with the blanket technologies located inside proper test boxes, named Test Blanket Modules (TBMs), which are installed in two dedicated ITER equatorial ports, starting from the beginning of the ITER operation. The Test Blanket Module and its associated ancillary systems, which include the tritium extraction system and the cooling system, form the Test Blanket System, which will be fully integrated in ITER machine and its supporting infrastructure.
The WCLL BB concept relies on the use of liquid Lithium-Lead (PbLi) as breeder, neutron multiplier and tritium carrier, while water operates as coolant under Pressurized Water Reactor conditions. This configuration poses a major safety concern in the potential interaction between lithium, present in the PbLi alloy, and water. The interaction could occur following a tube rupture in the breeding zone, an event named in-box Loss of Coolant Accident (LOCA). The potential progression of this scenario must be carefully evaluated and analysed through experimental investigations, requiring the collection of experimental data. The results of these analyses are fundamental to support the development of a qualified system code for deterministic safety analysis. A reliable code is clearly essential to assess accident consequences, propose mitigation measures and also to suggest design improvements that could prevent severe structural damage.
In order to meet these objectives, ENEA developed the LIFUS5/Mod3 separate effect test facility, in which experimental campaigns were conducted, involving high-pressure water injection into a pool of PbLi under WCLL relevant conditions.
In this context, University of Pisa is developing a coupling tool between SIMMER and RELAP5/Mod3.3 to perform preliminary simulations of the in-box LOCA scenario, with the aim of building a multi-physics coupling scheme able to support the design of the WCLL BB under different postulated initiating events. With the series of experimental campaigns conducted at the ENEA Brasimone Research Center, a consistent database of test results of lithium-lead/water chemical reaction was established, which has been further extended with the new experimental campaign (Series F) performed in 2024. The coupling tool developed by University of Pisa has been validated based on post-test analyses of LIFUS5/Mod3 Separate Effect Test facility, using the Fast Fourier Transform Based Method (FFTBM).