The Senate unanimously confirmed William Steele Sessions, chief U.S. District Court judge for the western district of Texas, yesterday for a 10-year term as director of the Federal Bureau of Investigation.

The 90-to-0 vote came after several minutes of debate in which Sen. Phil Gramm (R-Tex.) announced that the choice of Sessions will cause "no celebrations in the halls of organized crime." He said

Sessions' career has been "marked

with knowledge, integrity and effectiveness."

After a search of several months, President Reagan nominated Sessions July 24 to succeed William H. Webster, another former federal judge who now heads the Central Intelligence Agency.

Sessions, 57, a former U.S. attorney, has a reputation as a tough but fair judge who often handed out stiff sentences, particularly to drug traffickers.

He is best known for handling the trials of the killers of U.S. District Court Judge John H. Wood Jr., who was shot in the back outside his San Antonio, Tex., home in 1979, the only federal judge murdered in this century.

Charles Harrelson, the convicted triggerman, received two consecutive life sentences. Others received prison terms of five to 30 years.

After he replaced Wood, Sessions and his family spent 20 months under round-the-clock protection by the U.S. Marshals Service.

After the confirmation vote, Reagan said, "All Americans can be proud to have a man of Judge Sessions' character and integrity leading the FBI in the fight against crime, all the while bearing witness to the nation's unswerving commitment to due process of law.

"Judge Sessions embodies the ideal that the enforcement of our laws must be very tough, but very fair. Under the direction of Judge Sessions, the FBI will carry on its crucial responsibility to safeguard our persons, our property and our constitutional rights," he said.

When Attorney General Edwin Meese III introduced Sessions to reporters, he said the administration "wanted a clone of Judge Webster. We came as close as we could. He answers to 'Judge,' he answers to 'Bill' . . . . The retraining should be minimal."

Webster is credited with improving the FBI's image, tarnished by abuses by longtime director J. Edgar Hoover and by illegal surveillance of antiwar protests in the late 1960s and early 1970s.