Energy Secretary Bill Richardson, under pressure from scientists and members of Congress, has sharply reduced the number of federal employees who will be required to take polygraph examinations about their handling of nuclear secrets.

Instead of imposing the "lie detector" tests on more than 5,000 scientists and other employees at the nation's three nuclear weapons laboratories, the Department of Energy will limit the testing to several hundred people per lab, or a total of about 1,000 employees, DOE officials said.

Richardson announced the polygraph testing early this year as one in a series of steps to tighten security at the Los Alamos, Lawrence Livermore and Sandia national laboratories in the wake of allegations that China stole U.S. nuclear secrets from the labs.

Congress subsequently mandated the tests, and the Energy Department held public hearings recently to develop regulations on who will have to take the exams, what questions will be asked and other procedural issues. The hearings revealed widespread anxiety at the labs about the unreliability of the tests, and key members of Congress wrote to Richardson to object to wholesale screening of thousands of employees.

Last month, John C. Browne, the director of the Los Alamos lab, told his employees that he had "considerable reservations" about testing large numbers of people as a deterrent to espionage. However, he said he would support polygraphs for those handling top-secret materials and working in the most sensitive, "special access" nuclear programs, where voluntary polygraphs already are administered.

The new regulations, scheduled to be released Nov. 1, will require testing of nuclear weapons designers, security and counterintelligence officials, some employees at nuclear weapons production plants and a few political appointees at DOE headquarters in Washington.

They will be asked four questions during the tests: whether they have committed espionage, engaged in sabotage, made unauthorized disclosures of classified information or failed to report contact with people from sensitive countries.

As an argument in favor of testing, DOE officials have pointed to the Pentagon's experience. When polygraphs were administered last year to nearly 7,500 employees of the Defense Department and its contractors, they produced "significant security or criminal information" on more than a dozen individuals, according to a report submitted this year to the House and Senate Armed Services Committees.

One civilian employee of the National Security Agency who showed deception in the testing subsequently admitted that he had given classified information to his foreign-born wife, who was in contact with a foreign intelligence agency, according to the report. A Pentagon official said the NSA employee has resigned, but the official would not comment on the status of an FBI investigation triggered by the employee's admission.

According to the Pentagon report, investigations also were opened on several other individuals as a result of polygraphing. One person involved in intelligence operations between 1985 and 1997, for example, showed deception on a question about "having a secret relationship with" a foreign intelligence service.

Another person admitted that during an assignment in Bosnia, he gave Russian military personnel "large quantities" of classified material "that technically should not have been released to non-NATO members," although he said he was acting on orders from superiors.

One U.S. serviceman admitted that he kept classified documents in his home through five military assignments, including two overseas. And another married serviceman assigned to the NSA was barred from that agency after he confessed to having a romantic relationship with a Vietnamese woman while temporarily working abroad.

Two other employees of an NSA contractor disclosed suspicious contacts with foreigners. In one case, a woman admitted that she had a sexual relationship with an Israeli intelligence officer who told her not to mention it "since NSA would not hire her if the relationship were known," according to the report.

Of the 7,461 people tested by Pentagon examiners during fiscal 1998, 127 showed significant deception, but 106 of them were determined to be innocent after further review, according to the report. That put the portion of "false positives"--test results that indicate someone is lying when they are not--at 1.4 percent.