A scenario ito obtain initial tritium to reach steady state DT operation by DD commissioning phase of the fusion plant is presented. By the DD reaction, resulted T and neutron that produces T in the breeding blanket will be accumulated. ANeutronics of LiPb liquid blanket with 90% enriched lithium-6 was evaluated with neutron transport code MCNP-5.14 using FENDL-2.1 data libraries. System dynamics code STELLA-10.0.2 was used for the analysis of tritium system and the scenario of the breeding. As the result, calculated local tritium breeding ratio in the blanket is 1.20 by DT neutron and 0.84 by DD neutron. The required extension period of DD commissioning operation without initial tritium is estimated closely 90 days, depending on the coverage and inventory. These results reveal that launching DT fusion projects without initial tritium is possible with additional DD operation period to obtain extra tritium to start up DT operation.