A divorced Fairfax mother of five children says she has been fired from her job as a secretary-receptionist for the Arlington Catholic School system because she planned to marry again without a church annulment of her first marriage.

Pat Sejd Bradburn, 44, said that Msgr. Richard J. Burke, chancellor of the Arlington diocese, fired her on Feb. 22 with only a three-day notice. She quoted him as saying that she was fired because her plans to marry again were "against the teaching of the church."

She was married Feb. 26, with two of her teen-age sons acting as attendants, to Gordon Bradburn, a retired Air Force colonel, at the Ft. Myer chapel.

The Catholic church holds that marriage is indissoluble and that divorced persons cannot remarry without first securing a church annulment of the first marriage.

Mrs. Bradburn, obtained a civil divorce from her first husband of 19 years in December after a 3 1/2-year separation. At the encouragement of her parish priest, she said, she began the "paper work" for a church annulment the following month but more propers need to be filed before it is heard by the diocesan tribunal.

Mrs. Bradburn said her immediate boss, Bernier Mayo, superintendent of schools for the Arlington diocese, told her on Feb. 7 that Msgr. Burke had requested her resignation.

"He (Mayo) said he liked my work, that I was valuable on the job and that he didn't want to ask me to resign, but that Msgr. Burke had told him twice to do it," Mrs. Bradburn said.

Msgr. Burke refused repeated requests to either confirm or deny Mrs. Bradburn's charges and left word with a secretary that he had "no comment."

Mayo at first agreed to talk to a reporter about the case, but when reached later said he had been told by "my boss" (Msgr. Burke) that "it is the policy of the diocese not to comment."

Mrs. Bradburn refused to resign, explaining, "I have bills to pay; I needed the job." She said she told Msgr. Burke that if he was "uncomfortable with my forthcoming marriage, he would have to take the first step."

On Feb. 22, Msgr Burke told her she was fired as of the following Friday, she said.

"I couldn't make him understand that it (her remarriage) wouldn't affect my typing or the way I answered the phone," she said.

She said she asked Msgr. Burke to reconsider, saying she needed the job because she had debts to pay.

"It's not a lot - things like half of the oil bill that I wasn't able to pay last month," she explained in a telephone interview. "But I have enough pride that I don't want begin my marriage with bills not paid."

Mrs. Bradburn said she also asked the priest for a letter stating why she was terminated so that she could file for unemployment compensation and also seek new employment. But she said Msgr. Burke refused to give it to her.

Instead, she said he offered to pay her for two weeks and that she could consider it severance pay.

She said she refused it. "I couldn't take money that I hadn't earned," Mrs. Bradburn explained.

Mrs. Bradburn asserted that she is "not a troublemaker," adding that one of her prize possessions is a letter from Arlington Bishop Thomas Welsh praising her for her volunteer work mobilizing diocesan teen-agers to work for last summer's Eucharistic Congress in Philadelphia.

Mrs. Bradburn said she was distressed about the effect the episode would have on her five children, who range in age from 10 to 18 as well as on her new husband, who is not Catholic.

"I'm embarrassed for the church because of this," she said.

Mrs. Bradburn reflected on the church ruling that brands her - and hundreds of thousands of Catholics in similar circumstances - as an adulterer and excommunicates her when she marries again without an annulment of the earlier marriage.

"Probably the most holy thing that has ever happened to me is to love and be loved by a good Christian man who is willing to accept these five children and love them and give them a home," she said.

Her new marriage, she said, "is an opportunity to create for the first time a loving Christian home for my family and the church says to me 'you can't do that'".

In considering her dilemma over remarrying, knowing that it would automatically excommunicate her, she said she rejected the advice of one priest whome she quoted as saying, "Don't remarry; just live together, then you can still received the sacraments."