President Bush said Tuesday he will nominate James S. Halpern, a partner in a Washington law firm, as a judge on the U.S. Tax Court. If confirmed by the Senate, Halpern would succeed Meade Whitaker. In other personnel decisions, Bush: _Said he will nominate Ming Hsu to be a federal maritime commissioner for the remainder of a term expiring June 30, 1991, succeeding Elaine L. Chao. She is director of the New Jersey Commerce Department's division of international trade, and is the governor's special trade representative. _Reappointed Andrew Camp Barrett to the Federal Communications Commission. _Accorded the rank of ambassador to Robert L. Barry of the State Department during his service as special advisor for East European assistance. _Said he will nominate Steven E. Steiner, onetime director of defense and arms control for the National Security Council, as ambassador during his service as the U.S. representative on a commission dealing with arms verification.