Israel, at the time it was considering bombing in Iraq, requested and received U.S. government asistance in assessing how much damage would be inflicted on a nuclear plant by 2,000-pound bombs, according to documents obtained yesterday by The Washington Post.

Israeli scientists met with structure specialists at the Nuclear Regulatory Commission here last October, the month in which Israeli Prime Minister Menachem Begin's Cabinet approved in principle bombing the Iraqi nuclear plant outside Baghdad.

The U.S. experts on nuclear buildings had no idea they might be helping Israel plan its raid against Iraq, NRC spokesman Frank L. Ingram said. "We had no inkling in advance of any offensive proposition," he said.

The Israeli Air Force demolished Iraq's nuclear plant June 7 by dropping 2,000-pound bombs at low levels.

Israeli scientists at the October meeting focused so hard on what the explosives would do, rather than how to protect against them, that one NRC branch chief was moved to state afterward in an internal memo:

"Because of any lack of real interest in underground siting on a protective measure against sabotage, it was unclear whether the Israelis were interested in defending their own plants or destroying someone else's. . . ."

The same memo, dated Oct. 15, 1980, states that Israeli scientists "clearly defined" the threat they wanted the U.S. experts to assess: "a 1,000-kilogram (2,200-pound) charge which penetrates concrete barries and detonates after penetration."

Apparently, that is exactly what the Israelis did with the 16 2,000-pound bombs dropped on Iraq. Cement walls protecting the reactor complex were penetrated and the plant was demolished.

Ingram confirmed the authenticity of documents summarizing the meeting, which were obtained outside the agency by The Post, and said they are not classified. But commission executives were disturbed that they have become public.

Throughout yesterday afternoon, Ingram was authorized to release officially a copy of the summary, then directed to retrieve it for possible after-the-fact classification and finally allowed to release it again.

A spokeman for the State Department's Near Eastern Bureau, which ordinarily would arrange for the department the kind of briefing the Israel scientists recieved, said it neither arranged the meeting nor knew until recently that it had taken place.

Administration officials and U.S. intelligence executives have insisted that they had no advance knowledge of the Israeli raid, raising the question of whether the NRC scientist's suspicions about Israel's intentions disappeared in the federal bureaucracy.

Israeli Embassy spokeman Avi Pazner said an assistant to the embassy's science counselor arranged the meeting directly with the NRC and did not go through the State Department.

The meeting "had nothing to do with what happened in Iraq," Pazner said. "The embassy was asked to arrange the meeting by the Israel electric company who . . . was making inquiries about the safety of a civilian power reactor" Israel is considering buying from the United States.

The electric company, Pazner continued, "wanted to know about the safety problems in case of bombardment. It was completely routine. We have been interested in this question since 1976."

On Oct. 9, 1980, according to a published NRC summary of foreign visits, "Drs. Joseph Kivity and Joseph Saltovitz, engineers at Technion University in Haifa met with L. Shao and J. O'Brien of RES [the NRC's Office of Nuclear Regulatory Research] to discuss the dynamic response of reactor subsystems to explosions within the reactor containment building."

Larry C. Shao, is deputy director of the engineering and technology division, and John A. O'Brien is a structures specialist. Shao said last night that he did not attend the meeting with Israeli scientists but that two other nuclear plant structures specialists not mentioned in the NRC summary did. He identified them as James Costello and Shou Hou.

An internal meno, entitled "Bi-Weekly Highlights" and issued by the NRC's mechanical engineering research branch, said the meeting with agency experts was arranged "at the request of the Israeli ambassador . . . . The discussion focused on identifying vulnerable safety systems, whose failure might have significant consequences, and optimal targets for sabotage. . . ."

The NRC was establshed in 1974 as an independent agency to license and regulate "the uses of nuclear energy to protect the public health and safety and the environment."