Abstract:
In the design of the Test Blanket Module (TBM) for ITER, it is required to provide a design concept
that is demonstration power reactor (DEMO) relevant. It should be noted that in the U.S., DEMO is defined to be
a good representation of the first generation fusion power reactor. In order to find a relevant DEMO design, a
system evaluation was performed with the GA system code, and the physics results were benchmarked to ITER.
With the selection of ferritic steel as the structural material, the maximum neutron wall loading is limited to
3 MW/m2. When designed to a ~2 GW fusion, device an aspect ratio of 2.6 was selected based on this
assessment. For the ITER-TBM design, the design guidance is to apply a 2 mm Be layer onto the plasma facing
surface. When extrapolated to the DEMO design, the Be layer will not be suitable due to radiation damage.
Similarly, a carbon surface will not be suitable due to high physical and chemical erosion rates, radiation damage
of the material and potential large retention of tritium. Unfortunately, the remaining commonly proposed
material, tungsten (W), could suffer radiation damage from alpha charged particle implantation and experience
blistering and the formation of submicron fine structure, which could result in W transport to the plasma core
and severely limit the core performance. To resolve this potential impasse, different out-of-the-box options were
evaluated. A clear indication was noted that boron or silicon has been used to condition all high performance
tokamak experiments. Correspondingly, it is found that in order to maintain a boronized layer on the chamber
wall, in-situ boronization will be required. This boronized layer could also protect the W substrate, while
retaining low-Z wall characteristics. To support this idea, an invention on the use of boron-infiltrated W-mesh surface is proposed to withstand ELMs and disruptions while retaining the capability of transmitting high grade
heat for power conversion. Initial development and identified requirements for this BW-mesh concept will be
reported.
