April 28, 1984

The 11-day siege of the Libyan Embassy ended peacefully today as 30 diplomats and other occupants of the building in central London filed silently out, hands at their sides, eyes fixed straight ahead, and clambered into police vans. Scotland Yard took the Libyans to a ''safe house'' in the London suburbs, where they were closely questioned, before putting them aboard a Libyan Arab Airlines flight to Tripoli. The group was believed almost certainly to have included the gunman who, according to witnesses, killed a policewoman, Yvonne Fletcher, and wounded 10 opponents of Col. Muammar el-Qaddafi, the Libyan leader, who were demonstrating outside the embassy on April 17. Tonight, the Libyans were reported to have received a vociferous welcome in Tripoli, the Libyan capital. In a carefully synchronized move, the remaining British officials in Libya hauled down the Union Jack over their embassy, and all but two of them then left for home. (Page 3.)

Walter F. Mondale, bowing to criticism from his rivals for the Democratic Presidential nomination, announced today that he would return about $300,000 contributed to committees supporting delegates who back his candidacy. Mr. Mondale acted two days after announcing that he would terminate all such committees but would not return the money they had raised. On Thursday he had told reporters that it was all right for the groups to keep the money, which came largely from organized labor. Mr. Mondale said that, because of questions raised about the finances of the delegate committees, the money the groups had spent in behalf of the Mondale candidacy would be counted toward his $20.2 million Federal limit on spending in the nomination battle.

In the 26 years J. E. Adkinson has spent as a pipe welder at Ingalls Shipbuilding here, he has helped build anything from submarines and frigates to freighters and destroyers. But he says he has never worked on anything quite like the U.S.S. Iowa. ''This country has a ship it can be real proud of,'' says Mr. Adkinson, who is 44 years old and has spent the last several months helping refit the World War II battleship for sea duty. ''Working on her was like working with American history.''

More than two years after the long and dramatic trial in which Claus von B"ulow was convicted of twice trying to murder his wealthy wife, the Rhode Island Supreme Court overturned the jury's verdict today and ordered a new trial. A majority of the justices said the evidence justified conviction if considered in the light most favorable to the prosecution. But the court ruled some of the evidence had been tainted by lack of a search warrant and should not have been admitted. Furthermore, the court said evidence that might have been helpful to the defense had been improperly supressed by the trial judge. Reacting calmly to the decision, Mr. von B"ulow said in an interview in New York City that he would not necessarily object if prosecutors sought a new trial, although he said he was reluctant to subject himself to another such ordeal. ''I obviously want to be vindicated, and I feel that our new evidence would vindicate me completely at a new trial,'' he said. (Page 7.)

Victor M. Thompson Jr. resigned today from the board of the Synthetic Fuels Corporation, amid widening charges of improprieties. His departure leaves the embattled Government-sponsored company without a quorum to conduct business. At least two critics of the corporation on the Senate Energy Committee, Bill Bradley of New Jersey and Howard M. Metzenbaum of Ohio, both Democrats, quickly seized on the existence of a crippled board to try to force a review of the company's mission to spur development of synthetic fuels, or even to shut it down. The corporation, created under a law signed by President Carter with great fanfare in mid-1980, was designed to be the catalyst for private-sector development of a major new American industry. It was envisioned that the Government would provide up to $88 billion in aid but, largely because of the decline in world oil prices, interest in the development of synthetic fuels has waned.