[en] This Yucca Mountain Project Technical Status Report (TSR) on site characterization is the second in a series of reports that will be issued at approximately six-month intervals during site characterization. In addition, progress made toward the initiation and conduct of new site characterization activities is included. For this report, information on the technical progress made by Yucca Mountain Project participating organizations has been compiled covering the period from October 1989, through March 31, 1990. The status report consists of three sections: an introductory section; a section on the status of site characterization, which includes preparatory activities, sites programs, repository design, seals system design, waste package design, and performance assessment; and a reference section, which provides a complete listing of all published documents cited in the text. 59 refs