Scientists told Congress that the nation's stockpile of nuclear weapons should be rebuilt with the latest safety devices and warned the danger of an accidental explosion is greater than once thought.

The sobering look at the nation's stockpile of weapons amassed during the Cold War was accompanied also by the suggestion that the government consider changing the design of the newest submarine-launched missile and rebuild the entire supply of an air-launched nuclear missile that already has been taken off alert bombers parked at airstrips.Although the unclassified portion of the report presented to the House Armed Services Committee this week did not quantify the issue, it said that new super computers have led to advances in models of how an accidental explosion would affect a warhead and its plutonium core.

"A major consequence of these results (computer models) is a realization that unintended nuclear detonations present a greater risk than previously estimated and believed for some of the warheads in the stockpile," said the report. It did not identify which warheads were involved.

The report was made for the panel by Dr. Sidney Drell, deputy director of the Stanford Linear Accelerator Center, Nobel laureate Dr. Charles Townes of the University of California at Berkeley and Dr. John Foster, head of the Defense Science Board.

At the Pentagon, spokesman Pete Williams said the department welcomed the report and added, "We consider the safety of nuclear weapons to be a matter of the utmost importance. We give it the highest priority. The goals of the Drell report are consistent with both departments' established priorities for safety. The specific recommendations will require careful joint evaluation by the Department of Energy and the Department of Defense."

Williams said Defense Secretary Dick Cheney has asked his deputy, Donald Atwood, to study the report and suggest ways to implement its findings.

The report was prompted by a decision earlier in the year by Cheney to pull the Short Range Attack Missile - known as the SRAM-A - from planes kept on alert at air bases. It is equipped with the W-69 warhead.

Some warheads, like the W-69 and the W-88 aboard the Trident II missile, are built with high explosives or HE rather than the more stable insensitive high explosives, or IHE.

Pound for pound, it takes more IHE than HE to trigger a nuclear blast, meaning that missile payload or range suffers if IHE is used in place of HE. In the case of the Trident missile, concerns are raised because the warheads sit adjacent to the third-stage rocket motor, and some fear the accidental ignition of the propellant might be sufficient to trigger the HE to explode, either scattering dangerous plutonium about or even causing a blast with nuclear-level yields.

The Drell panel had high praise for the attention to safety and security exhibited by personnel who handle nuclear weapons.