Office of Management and Budget Associate Director Arlene Triplett will leave government in September to join the national management and research consulting firm of McManis Associates Inc. as a principal associate. Triplett, a veteran Reagan administration official, directed OMB's management improvement and cost reduction programs and, earlier, was assistant secretary for administration at the Commerce Department.

Touche Ross partner Joseph Freimuth has been appointed national director of the accounting firm's tax policies, operations and practices. Freimuth, currently president of the Touche Ross Foundation, has shared responsibility for the firm's tax functions since 1978, serving most recently as national director of tax operations. Following establishment of national headquarters here in 1983, the firm's tax practice continues to be its fastest-growing area. Freimuth succeeds John T. Connor, who was named a regional partner and remains a director of the firm's Washington Service Center.

Planning Research Corp., the McLean-based engineering and information services firm, has recruited Douglas H. Poretz as director of corporate affairs, a new position that will include responsibility for public and investor relations. Poretz had held a similar post with Flow General Inc., and was the founder and president of a Washington public relations firm.

CACI Inc., the Arlington-based high-tech services firm, has promoted Kenneth Sprinkle to senior vice president and manager of its decision support system division and Robert Neil to vice president and manager of its advanced systems development division. Charles Revoile has joined the firm as a senior vice president, general counsel and corporate secretary.

George L. Gleason, a former executive vice president and general counsel of the American Nuclear Energy Council, a nuclear industry advocacy group, has joined NUS Corp., an international engineering and consulting firm, as senior vice president and general counsel.