Rancho Seco nuclear power plant near Sacramento, closed by voters, apparently will not be reopened soon--if ever. Directors of the Sacramento Municipal Utility District rejected a $250-million proposal by Golden State Energy Inc., a consortium headed by Quadrex Corp. of Campbell, Calif., to buy the plant and operate the power plant. Rancho Seco had suffered numerous breakdowns during its 15-year life, and voters approved a ballot measure last June 6 closing down the citizen-owned utility. Rancho Seco generated about half of SMUD’s electrical capacity. SMUD now buys power from Pacific Gas & Electric Co. and Southern California Edison.