[en] Japan Atomic Energy Agency (JAEA) has been performing the research, development and design of blankets with water-cooled solid breeder for fusion power plant as a leading institute in Japan, according to the long-term R and D program established by the Fusion Council in 1999. For our design, pebbles of a ceramic tritium breeder (Li₂TiO₃) and a beryllium neutron multiplier (Be) are packed in the constitutive layer structures of a test blanket module (TBM) for ITER. These reports are results of one-dimensional nuclear and thermal analyses on the TBM emphasizing on optimized configuration of the breeder and multiplier layers. Taking into account increment of TBR, the radial widths of the breeder and multiplier layers are optimized. The main results of our study are as follows: (1) In multilayered structures of pebble beds, existence of the peak of the TBR was revealed within the range of the volume ratio R=V(Be)/V(Li₂TiO₃)=4-5. (2) In the case of optimized layer structure for the single packing, a layer of Be was set to be the two layers behind a layer of Li₂TiO₃. The R became available for staying in the range of R=4-5. Consequently, the TBR respectively increased by 2.0%, 3.2% and 4.0% with 7.5%(nature), 40% and 90% of enrichment of ⁶Li compared to TBR of TBM in which the layers of Be and Li₂TiO₃ were interlaminated. This database of TBR for optimized layer structure contributes to the estimation of TBR at the design stage of the TBM and demonstration blanket aimed to strengthen the commercial competitiveness and technical feasibility. (author)