August 24, 1986

SOMETIME next month, at worst the month after that, barring some unforeseeable mishap, the House and Senate will pass, and President Reagan will sign, the Internal Revenue Code of 1986 - the product of a crisis-fraught, two-year, more-or-less bipartisan exercise in tax revision. In a tax-driven economy, the engine is about to be changed, with some consequences evident to everyone and many more that no one can foretell with confidence. As it finally emerged a week ago from protracted bargaining between House and Senate leaders, the bill represents, on one level, an ideological trade. The liberals closed dozens of loopholes for corporations and wealthy individuals and removed millions of poor people from the tax rolls altogether, while the conservatives got lower tax rates for almost everyone. In announcing his Program for Economic Revolution in February, 1981, Mr. Reagan boldy asserted that ''the taxing power of the Government must not be used to regulate the economy or bring about social changes.'' With the President's blessing, the new code, like all tax codes, will do both of those things, and the White House is positioning itself to seek amendments if the new engine starts to miss or knock a few months after it starts.

Just the other day, the directorship of the National Gallery in London was offered to a 43-year-old American, Edmund Pillsbury, who since 1980 has been director of the Kimbell Art Museum in Fort Worth. He is a very good director, and one of the pleasantest people around. As an acquisitor, he is in a high class. His temporary exhibitions compare well with anyone else's. He is young, ambitious, energetic, outgoing and not poor. Against that, it could be said that he has been spared the rough work of museum life. Where some other American museum directors have to deal with decrepit or inapposite buildings, difficult trustees, volatile donors, intriguing politicians and very small budgets, he had been fortunate on all five counts. Be that as it may, he was the unanimous choice of the selection committee, which included some of the most exacting and experienced people in the British museum world. Yet the offer caused a sensation. An American head of the National Gallery?

For years, John H. Lese, a real-estate developer based in Rye, N.Y., walked past a large rock on a small plot of vacant land directly across the street from the Mamaroneck railroad station. Finally, his curiosity got to him.

AT 33, Bill O'Donnell Jr. had succeeded. He was vice president of Bally Manufacturing, had an annual salary of $150,000, owned two Mercedes Benz's and an expensive house in Winnetka, Ill. He also cheated on his wife, missed meetings he had called and used 4 grams of cocaine a day. ''I was pursuing the American Dream, and I thought cocaine would get me there faster,'' he said. ''I was running through life so fast I didn't see that my role as a husband and father to my three sons was disintegrating, that my business abilities were crumbling.''

THE Chernobyl disaster produced much more radioactive contamination and spread it over a much larger area than had been previously acknowledged, according to a Soviet report disclosed last week. The report, to be discussed tomorrow at a conference of the International Atomic Energy Agency in Vienna, also said residents of the area near the plant, in the Ukraine, may not be able to return for as long as four years.