Pentagon Seeks to Resume Underground Nuclear Tests : Defense: Experiments are necessary, officials say. But others contend they could set back arms control efforts.

In a proposal that has startled arms control experts, senior Pentagon officials are seeking to resume underground testing of small-scale nuclear bombs with maximum yields of 500 tons of high explosives, Clinton Administration officials said Friday.

The proposal for the tests, which Pentagon officials said can ensure that the nation’s nuclear arsenal remains safe and reliable, has led to a fierce debate within the Administration over whether the controlled blasts would violate the intent of a permanent test ban treaty now being negotiated.

Indeed, the dispute erupted as the Administration works to establish its negotiating position for scheduled talks in Geneva on the Comprehensive Test Ban Treaty, which would permanently end testing of full-scale nuclear weapons. A high-level White House meeting to set U.S. policy on the issue is expected as early as next week.

Senior defense officials contended that the experiments, known as hydronuclear tests, are necessary to guarantee that the vital components in nuclear weapons do not deteriorate over time.

But experts at the Energy and State departments are strongly resisting. They contend that the testing would represent a major setback to nuclear disarmament and to efforts to control nuclear proliferation.

The issue is to be discussed during a secret meeting of senior Administration officials, including the secretaries of defense, state, energy and top military leaders. Recommendations from the meeting will be presented to President Clinton for a final decision before the end of the month, according to an Administration official who spoke on condition of anonymity.

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The United States agreed to a moratorium on underground tests during the George Bush Administration and since then has been negotiating a comprehensive test ban treaty in Geneva through the Conference on Disarmament. Administration officials hope to sign a treaty by next year.

At the heart of the debate is the difficulty of defining what constitutes an explosion. Originally, a hydronuclear test was defined as a nuclear reaction equal to about four pounds of TNT.

The new proposals by Defense Department officials call for a 500-ton test ceiling. A 500-ton test would dwarf any non-nuclear explosion in history, hundreds of times stronger than the Oklahoma City bomb that destroyed the Alfred P. Murrah Federal Building. Still, it would be relatively small by nuclear standards. It would be hundreds of times smaller than bombs tested underground in past decades or even the bombs dropped on Japan during World War II.

Defense Secretary William J. Perry has yet to declare his position on the issue but recommendations that he push for a 500-ton limit have been forwarded to his office by senior defense officials, according to an Administration source.

Energy Secretary Hazel O’Leary, whose agency conducts such nuclear tests through its laboratory system, is firmly opposed to any increase over the currently accepted limit of four pounds of yield for hydronuclear experiments, an Energy Department official said.

O’Leary’s opposition is echoed throughout the arms control community.

“These are bombs,” said John Pike, a defense expert at the Federation of American Scientists. “The whole idea of a treaty is that we are not going to set off nuclear bombs.”

Spurgeon Keeny, director of the Arms Control Assn., added: “It is a terrible idea. It is going to be criticized around the world as representative of the hypocrisy of our policies.”

At the same time experts disagree over how to define a nuclear explosion, they also have sharply conflicting notions of the very purpose of a test ban. Arms control experts say that the purpose is to disengage the world’s military powers from nuclear weapons.

But under formal U.S. policy, nuclear weapons will continue to play an important role in national security. The test ban treaty is envisioned as a way to prevent other nations from developing nuclear capability.

Pentagon nuclear experts are confronting what they consider to be an unprecedented challenge with the test ban treaty: how to keep the nuclear stockpile, containing some of the most complex devices ever made, ready for battle without ever using them.

In a little-noticed decision last January, the Administration adopted a negotiating position that called for the test ban treaty to become permanent, rather than limited to 10 years as originally expected.

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Since then, defense officials have argued that their confidence in the effectiveness and safety of the thousands of nuclear weapons in the U.S. arsenal will erode over time unless there is nuclear testing.

Plutonium cores inside the bombs are subject to corrosion and sensitive electronic components can degrade in the harsh radioactive environment inside the bombs, some experts contend.

“Perry takes this very seriously, though he has not yet made the decision,” a second Administration official said.

Defense experts would like to conduct tests in the range of 300 tons of yield to verify that as the weapons age, they will continue to operate as originally designed. Experts are seeking a 500-ton limit because predicting nuclear yield is an uncertain science. The higher limit would provide a margin of 200 tons in the event that the yield was greater than expected, the Administration official said.

France, Britain, Russia and China have adopted similar proposals for such hydronuclear tests, the Administration official said. France and China have indicated that they will conduct underground nuclear tests until a treaty is signed.

“We are the good guys in this issue,” he said. Nonetheless, the United States, as the sole superpower, will come under far greater international scrutiny and will be seen as a leader in determining how the issue is resolved, all the experts agreed.

Not all nuclear experts agree on the need to conduct such tests. The Jasons, a group of nuclear experts in academia and the federal laboratories who are influential in weapons policy, said in a report last year that hydronuclear tests in general are probably not necessary.

The group is conducting a new study of the issue, attempting to better assess how much confidence in the stockpile will erode if all testing ceases, said Sidney Drell of the Stanford Linear Accelerator. Drell said he could not discuss the Jasons’ current work.

Times staff writer Paul Richter contributed to this story.