WASHINGTON (AP) _ An advocacy group asked the Nuclear Regulatory Commission today to order the shutdown of eight nuclear reactors made by the Babcock & Wilcox Corp. on the grounds that the plants are too sensitive to minor disturbances to be safe.

The eight plants have had at least 30 accidents since they came into use in the late 1970s, said the Union of Concerned Scientists, an anti-nuclear group. The total does not include the accident at the Babcock & Wilcox reactor at Three Mile Island in 1979 near Harrisburg, Pa.

Robert Pollard, a former NRC official who works for the anti-nuclear group, told a news conference he considered the B&W reactors the most dangerous of all the pressurized water reactors that make up about two-thirds of the nation's 105 licensed civilian nuclear power plants.

The petition asked that the commission hold public hearings on what changes should be made in the plants. Ellen Weiss, general counsel to the group, said the results of previous studies indicate ''the shelves are full of what could be done.''

The commission ordered a special safety study of B&W reactors a year ago. The study was scheduled to be completed last December, but Pollard said the study, in effect, has been turned over to the utilites operating the reactors. He said the results are not expected until July.

Jim Taylor, manager of licensing for Babcock & Wilcox Corp., said the information presented by the Union of Concerned Scientists was ''generally out of date'' and there was ''no reason at all'' to close the plants or order hearings.

He and commission spokesman Joe Fouchard said many improvements had been made in the reactors and their control systems. Fouchard said it was ''appropriate'' that the utilities conduct the special study under commission supervision.

Dennis Crutchfield, head of the commission's Babcock & Wilcox study, said the control system was being changed so that a power failure would bring the plant to a known, safe shutdown condition regardless of operation before the failure. Previously, such a failure had varying effects depending on operating conditions, some of which overstressed some reactors.

The eight plants are Arkansas 1, near Russellville, Ark.; Crystal River, near Crystal River, Fla.; Davis-Besse, near Toledo, Ohio; Oconee 1, 2, and 3; near Greenville, S.C.; Rancho Seco, near Sacramento, Calif.; and the second Three Mile Island reactor, near Harrisburg.

The group also asked that the commission suspend construction permits for the Bellefonte 1 and 2 reactors near Huntsville, Ala.

A spokesman for Duke Power Co., Joe Maher, said that the reactors ''are safe units.'' Duke operates the three Oconee units.

Maher charged that ''the petition by the Union of Concerned Scientists is technically unsupportable. It is quite simply irresponsible of them to recommend shutdown of the Babcock & Wilcox reactors based on unsupportable and outdated information. ...

''Unit 2 at Oconee has the world record of its type of reactor for continuous days of operation. The Oconee units have an excellent record.''