State-of-the-Art 3-D Assessment of Elements Degrading the TBR of the ARIES DCLL Blanket

Diagnostic systems in DEMO: Engineering design issues

“…Although a continuous volume of lithium-bearing breeding material completely surrounding the plasma and several metres thick could achieve a tritium breeding ratio (TBR) of around two, the design of a breeding blanket in a practical tokamak reactor necessarily incorporates many features that reduce this figure considerably. The successive effects of introducing a sequence of very plausible practicalities were thoroughly assessed in [16], figure 5 therein showing that even with a neutron multiplier and considerable enrichment of the natural lithium with 6 Li (to make better use of the thermalised neutrons), it is quite difficult to achieve a TBR of 1.05, while 1.15 is often a design target to allow for uncertainties in the nuclear data and the eventual engineering implementation. It should be noted that in this study, the first wall area given over to diagnostics was confined to the outboard wall and only ~0.7% of the area of that, to be compared to nearly 20% of the outboard vessel area in ITER, while the thickness of tungsten cladding in the first wall was taken to be 10mm in the important outboard mid-plane region and 50mm in narrow strips (to enhance vertical plasma position control) well away from the mid-plane.…”

Overview of ARIES nuclear assessments: neutronics, shielding, and activation

“…To address these concerns, we recently developed a novel stepwise approach to identify the exact cause of the degradation in TBR and examine almost all questions collectively in an integral fashion. This new approach was first applied to an interim ARIES-ACT design [4] to address the questions and concerns mentioned above. Here, we reapplied the stepwise approach to the near-final ARIES-ACT design to confirm that the most recent modifications made to the top/bottom ends of the outboard dual-cooled lithium-lead (DCLL) blanket comply with the ARIES breeding requirements (overall TBR of 1.05 with 6 Li enrichment < 90%).…”

TBR and shielding analyses in support of ST-FNSF study

“…Achieving a TBR of 1 (or more) is a strong requirement for ST-FNSF. Several design elements could easily degrade the TBR [5]. Efforts should be made from the outset to maximize the TBR via increasing the blanket coverage, reducing the structural content within the first wall (FW) and blanket, and minimizing the OB penetrations.…”

“…At this early stage of the design, homogenization was considered for the internal LiPb flow channels and He/FS cooling channels. However, several design elements that degrade the breeding significantly [5] were included in this model. For instance, for the inner blanket only, the 3.8 cm thick He-cooled FW and 3 cm thick back wall are modeled separately.…”

“…We expect modeling the details of the blanket internals, adding the five NBI ports, and inclusion of a few blanket test modules on the OB midplane to degrade the 1.08 TBR by 7-8%. The uncertainty in LiPb nuclear data [5] could further reduce the TBR by 3%. However, a few design changes could enhance the TBR and bring it closer to the threshold for T self-sufficiency.…”