Ursula Niebuhr doesn't suffer fools gladly, to say the least. And thank heavens for that. The world does not need another saccharine grandmother in front of a warm television set. In fact, she thinks television is wretched, and won't even keep sugar in the house, let alone saccharine.

"My grandchildren come to visit and ask if I have any sugar. Nope! Try honey. Sugar rots your teeth. I told my grandson I couldn't possibly let him drink a Coca Cola, and he said that if I wasn't in the room I'd never know!"

Mrs. Niebuhr was in Washington yesterday to present some tapes of her late husband Reinhold's lectures to one of his most famous admirers, a man named Jimmy Carter.

Carter has often spoken of the influence theologian Niebuhr's writings had on him in developing his attitudes about the relationship of religion and politics in a just society. Carter has quoted Niebuhr in saying that it is "the sad duty of politics to establish justice in a sinful world," reaching toward a philosophy that aims at practicality without sacrificing idealism. Niebuhr died in 1971 at the age of 78, hailed as one of the "intellectual giants of the 20th century."

Mrs. Niebuhr received a letter from $&(WORD ILLEGIBLE Carter after his nomination in which, she said, he wrote of Niebuhr's influence and particularly "the idea of love and justice." She wrote back. "I said it wasn't just my husband who said that; Pope John said "Let love be the motive and justice the instrument.""

Evidently, she said, Carter has read and "apprently found useful, my husband's - what I call - stuff."

Now 72, Mrs. Niebuhr retains the no-nonsense accent of her native England, the slightly hurried cadence of what has been called the socially acceptable "U" accent (as opposed to "non-U"). She lives in Stockbridge, Mass., on a "retired academic's pension" and spends a great deal of her time answering mail about her husband, which irritates her because it cuts into time for her own writing. She taught history of religion for 25 years at Barnard College and Columbia University, and is extremely interested in biblical archeology.

"I get these letters that say, "Dear Mrs. Neibuhr, I am a friend of so-and-so, and because I am contemplating writing a book on liberal politics, or your husband's interests, or politics in the '30s, could I come and interview you." I have a form letter to send them, but often I feel I must answer myself...I am overcome with guilt when I've written a nasty letter. I tell the lovely woman who types them for me to %Iedit them if I've been too nasty."

How could she possibly be nasty?

"I tell them to go to hell!" she laughed.

She also gets several letters a week inquiring about her friend W. H. Auden, about whom three biographies are being prepared, and letters from "retired choir directors who want to set the Serenity prayer to music."

Niebuhr has been immortalized unwittingly in the commercial and amateur reproduction of a prayer he wrote that goes "O God, give us serenity to accept what cannot be changed, courage to change what should be changed, and wisdom to distinguish one from another."

"It was used by some wretched company as the quintessential prayer of Middle Maerica in the days of Spiro Agnew," she said, "and some of our former students got together and wanted to start court action.... All these things take time! A lot of you're think that if you're as old as I am you-re sitting by the fire or out in the garden digging up dead flowers. Poor old thing, she's lonely, she's a widow...So they send me these tomes to read. I have a feeling I should be in a two-room apartment somewhere and throw all this stuff out.00

Before coming to the United States on a fellowship to study philosophy at Union Theological Seminary, where she met her husband, she was a scholar in history and theology at Oxford University. To become a scholar she had to take a test in which she had to read documents in "medieval French and late medieval Latin," and it was one of these that got her interested in studying religion.

In those days women were a rarity at Oxford, and "the higher degrees (in theology) were limited to clerks in holy orders" (ordained priests)...even after the Enabling Act in 18-whatever, when they let in non-conformists, and Catholics and lunatics and dogs, women weren't even members of the University. When I went, women were only titular members at Cambridge - my family was really more Cambridge than Oxford - at Oxford at least they were members. They wore caps and gowns like men and had the same rights and privileges. As a scholar, she was allowed to choose her own room and read verses from the Bible in chapel. It was a dubious privilege, but rather fun."

She met Niebuhr after arriving at Union Theological Seminary and finding many of the professors similar to the ones she'd had at Oxford. "I thought I should be broadminded and talk to the natives."

Her adviser suggested she attend Niebuhr's lectures because "he was nice and I'd like him. And I did." They married in 1931.

She became a teacher during World War II, meanwhile having had two children. Her daughter is now a senior editor at Viking and married to a federal judge, and her son is with the New York state government.

"I was paid $800 a semester, which was less than I paid for the nursemaid," she said. "My husband transcended his specialized audience at Union; I was a very minor person in a women's college. I liked my little pigeon hole."

She did get a little peeved when she and her husband would attend scholarly gatherings and one of her husband's colleagues would say to her, ""I didn't know wives were invited." I'd say, "Oh, I'm not a wife, we live in sin!" I'm sure they thought I was a disaster."

But her husband, the eminent theologian, was "very sporting about it." And as she said in a BBC radio program, he was very "nice" and "helped with the babies and the washing up." When people ask her if he ever got "cross," she says, "No, I was the one who got cross."

And when in 1960 some eminent gentlemen planned a retirement dinner honoring her husband and "didn't even bother to find out if I could go," and scheduled the event for a day when she was supposed to give a speech elsewhere, she did not change her plans. "Nope, I said, "Can't make it.""

Her boss, a woman who had five children and later became the first woman board member of CBS, once joined her in a panel discussion on "Wives, Women and Work" in the 1950s."She said she could summarize everything she had to say into three words: "Choose Your Man!""

She retired in the late '60s when her husband's health worsened. He had suffered a stroke in 1952 on his way back from a trip to speak in "some ghastly place in Texas." He had been asked to talk to Adlai Stevenson on his way back, who was then contemplating his run for the presidency.

"He wasn't exactly a father confessor to Adlai Stevenson, but they knew each other. And they thought it would be a useful thing for Adlai Stevenson to talk to my husband about his doubts and problems." Stevenson called to tell her about her husband's stroke.

One of the "intriguing" memories she has is of listening, with her husband and Felix Frankfurter (Uncle Felix to her kids), to the 1952 Democratic convention on her "cheap Sears-Roebuck radio" while her husband recuperated in Stockbridge.

She's sad that most of the tapes of her husband speaking in the set that she gave Carter yesterday (the originals are in a collection at Union Theological Seminary in Richmond) were recorded after his stroke and thus his voice is less strong than it once was.

Actually, she said, she listened to some of the tapes the other day and decided that what her husband had to say was actually "not bad."

"You can criticize him for his scholarship, or his generalizations, but really what he had to say has stood the test of time. He really was rather good." CAPTION: Picture, Ursula Niebuhr, by Linda Wheeler