What was going on when I was born?

The lead participant in the Seabrook nuclear power project in New Hampshire bowed to intense pressure from the other owners yesterday and said it would agree, under certain conditions, to cancel the second Seabrook reactor. This move by the Public Service Company of New Hampshire appeared to clear the way to scrap Unit 2, a 1,150-megawatt facility that is 23 percent complete and has already cost a consortium of 16 New England utilities about $2.5 billion. Public Service owns 35.6 percent of the project, and until yesterday it had consistently vetoed efforts by the other owners - particularly utilities in Massachusetts, Maine and Connecticut - to cancel the project. No Change in Basic Stand Dallas Hamerlinck, vice president for public affairs of Public Service, said the company's position favoring completion ''hasn't changed.'' But he added, ''You sometimes get to a point when you can't go on.''

POTATOES, every day. Black sour bread, every day. Mushrooms, always. Mushrooms, because we have had many wars, and they replaced meat then. Mushrooms have been the nation's food in hard times.'' Helene Celmina was describing the staples of her native Latvia, one of the republics of the Soviet Union, bordering the Baltic Sea in northeastern Europe. ''There are always mushrooms, because we have many forests,'' she continued as she stirred a skillet bubbling with her version of Latvian-style mushrooms, the earthy aroma of a rain-washed forest rising in the kitchen. A Recipes are on page C8. tall woman with straight auburn hair and a clear gaze, Mrs. Celmina is fluent in four languages, including English.

Senator Gary Hart scored a decisive victory last night over Walter F. Mondale and the Rev. Jesse Jackson in Connecticut's Democratic Presidential primary, completing a sweep of primaries and caucuses in the six New England states. According to complete but unofficial returns, Mr. Hart had 115,915 votes, or 54.9 percent; Mr. Mondale had 63,963 votes, or 30.3 percent, and Mr. Jackson had 25,833 votes, or 12.2 percent. That translated into a preliminary estimate of 33 delegates for Mr. Hart, 18 delegates for Mr. Mondale and one for Mr. Jackson. Mondale Holds Delegate Lead Overall, however, Mr. Mondale still retained his big lead in convention delegates. The latest tabulation by United Press International, Connecticut included, showed Mr. Mondale with 698 delegates, compared with 429 for Mr. Hart and 87 for Mr. Jackson, with 1,967 delegates needed for the nomination.

A headline last Friday on a dispatch from Stanford, Calif., about plagiarism allegations gave an incorrect title for Kenneth Melmon, who is under investigation by a university ethics committee and two publishing concerns. As correctly identified in the article, Professor Melmon is chairman of Stanford Medical School's department of medicine, not the school's dean.

An article on the Washington Talk page yesterday about young activists incorrectly identified the editor of People & Taxes, a monthly publication of Public Citizen, which is affiliated with Ralph Nader. The editor is Tyler Bridges.

One day earlier this month, Government security officers closed the Atlantic port of El Bluff, preventing fishing boats from entering the harbor and barring civilian workers from the docks. Soon a freighter arrived and large unmarked cases were placed aboard military trucks. Within hours news had spread through Managua, the capital, that another shipment of Soviet arms had arrived in Nicaragua. Western diplomats say that such shipments arrive about once every three months, and that they are the most important element in Moscow's aid to Managua.

The Suffolk County Legislature today passed an antismoking bill that supporters said was one of the most restrictive in the country. The measure would require companies with more than 75 employees to segregate smokers from nonsmokers. It would also require restaurants with 35 or more seats to reserve one-third of their places for nonsmokers. The bill, which was opposed by many businessmen, would also prohibit smoking in most public places where it is now permitted, such as waiting rooms and public restrooms. The county already bans smoking in most large stores, hospitals and nursing homes.

General Motors' latest and perhaps most important gamble, analysts and company executives say, is that buyers will accept the smaller size and wedge shape of its top-of-the-line luxury cars being introduced this week. Within the company they are called the ''C'' bodies. In dealers' showrooms they will be the new Cadillac DeVille and Fleetwood, Oldsmobile 98 and Buick Electra. The gamble is especially important for G.M. since this is the second generation and most radical downsizing of its largest and most profitable cars.

A work program for homeless men and women is being expanded to provide a dozen crews from municipal shelters to clean subway stations nightly near their lodgings, Mayor Koch announced yesterday. The expanded program started Monday with a crew of 10 men from a homeless shelter in Harlem helping to clean the 145th Street IND subway station. City officials hope that 3,000 of the people who live in municipal shelters will eventually be in the program, which will also provide for cleaning small neighborhood parks and the homeless lodgings themselves.

Treasury Secretary Donald T. Regan suggested today that the Administration might relax regulations requiring that American banks reduce their reported earnings to reflect overdue interest payments from Argentina. But Federal bank regulators questioned the move. Argentina faces a deadline Saturday to pay $650 million in overdue interest on loans of $10 billion from American banks. Argentine officials indicated today that they needed at least several days past the deadline to make these payments. Major American banks are resigned to the likelihood that some of them will have to report sharp drops in earnings as a result of the loans. But they add that the effects of such declines - in lower stock prices, for example - have already been felt and thus the companies' condition will not deteriorate sharply. (Page D6.)

If the Westway, the covered highway along the Hudson River in lower Manhattan, is ever built - still, after a dozen years, an unanswered question - it will have on top of it a 93- acre park that will go a long way toward removing the curse of the urban highway. To open up the waterfront by covering the roadway with usable land was the basis of the Westway plan from the beginning, but until the actual designs were made public recently it was impossible even to begin to judge how worthwhile all the complexities and expense of the Westway might be. Now, the tentative beginnings of a design concept for the park have emerged, and the prospect is encouraging. Actually, not one but three designs were made public, in accordance with the request of state authorities that three alternatives for the park be designed and offered for public comment. Public officials will select a preferred alternative sometime this spring.

Ahmed Sekou Toure, the President of Guinea for 26 years and a symbol of African independence and defiance, died Monday in a Cleveland heart clinic. He was 62 years old. A peasant's son who became a union leader before entering politics, Mr. Toure led his western African country to independence from France in 1958 and then served as its only President so far. (He ruled with an iron hand, taking power as a radical who pursued Marxist revolutionary policies but seeking Western ties in recent years. Obituary, page A6.)