WASHINGTON (AP) _ Sales of U.S. savings bonds are up, and economists are crediting the bonds' popularity to competitive interest rates.

The government reported Monday that the value of savings bonds held by the public reached an all-time high of $80.83 billion last month, surpassing the old record of $80.55 billion set in December 1978.

The Treasury Department said sales totaled $520 million in February, 32 percent over a year ago, while a total of $430 million in bonds were cashed in, down 7 percent from a year earlier.

Since October, savings bonds sales have increased 40 percent while redemptions have declined by 12 percent compared to the same five-month period a year ago.

The current interest rate for a bond held five years or longer is 8.36 percent.

--- Hungary Honors Astronauts With Stamp

WASHINGTON (AP) - American stamp collectors can buy a Hungarian stamp honoring the seven astronauts who died in the space shuttle explosion, but the U.S. Postal Service says it has no plans to issue a commemorative stamp.

Hugh McGonigle of the U.S. Postal Service's stamp information branch said postal policy requires a 10-year wait after a death before issuing a stamp.

In the one exception, deceased presidents are honored on their birth anniversary following death.

''That rule has not been set aside in the past,'' McGonigle said.

The 20-forint Hungarian stamp, showing the shuttle leaving the launch pad, was issued Feb. 21, less than a month after the Jan. 28 disaster. The seven crew members who died are listed on the border of the sheet.

Linn's, a weekly stamp newspaper, reported that 248,000 sheets were printed, one stamp to a sheet. The sheets are for sale for $2.15.

Stamp collectors, writing in Linn's, have urged the Postal Service to honor the astronauts, and Rep. Raymond J. McGrath, R-N.Y, has called on his colleagues to write to the postmaster general asking for such a stamp.

--- Gramm-Rudman Hits Meat Inspectors

WASHINGTON (AP) - The Agriculture Department will be reducing its force of full-time meat and poultry inspectors by more than 500 this year because of federal spending cuts, and one official says the reductions are coming at a bad time.

''... At the same time our budget is shrinking, the meat and poultry industry is expanding,'' said Dr. Donald L. Houston, head of the department's Food Safety and Inspection Service.

Testifying Monday before a House subcommittee, Houston said a hiring freeze instituted in November should reduce the number of full-time inspectors in meat and poultry plants from 7,541 last fall to 7,020 by the end of September.

In addition, he said, the service is ''drastically curtailing'' its use of some 1,200 temporary and part-time employees, including use of a streamlined poultry inspection program that will cut 400 inspectors.

Processing lines in poultry plants, which handle some 70 birds per minute, will now have only two inspectors, rather than the three that were used in the past, he said.

In addition to those cuts, he said, the entire inspection service faces a three-day furlough. To avoid disrupting business schedules, he said, the furloughs will take the form of unpaid holidays for Memorial Day, the Fourth of July and Labor Day.

The Reagan administration has proposed replacing the $365 million, taxpayer-financed inspection service with one supported entirely by user fees, a proposal rejected by Congress last year.

--- Protesters Vow To Keep Library Of Congress Open

WASHINGTON (AP) - The main reading room of the Library of Congress, usually hushed as scholars and writers concentrate on their work, echoed with the shouts of speakers who were angry that budget cuts forced elimination of the library's traditional evening hours.

At 5:30 p.m. Monday, as the library's doors were scheduled to close under the new austerity plan, about 100 protesters remained at their desks, donned black armbands and applauded the first of a series of speeches demanding that the library remain open, as usual, until 9:30 p.m.

''President Reagan wants to turn the body politic into a mentally retarded body and that's why I'm here,'' shouted one speaker from the top of the high circular desk in the center of the ornate chamber. ''Power to the People 3/8''

Library officials did nothing as the protesters cheered, pounded their desks and clapped their books open and shut as speakers took turns delivering anti-Reagan tirades.

Associate Librarian Donald Curran said, ''It's our practice to avoid unnecessary confrontation.''

The budget for the largest library in the world was reduced from $238.5 million for fiscal 1985 to $220.3 million in recent months as a result of a campaign to reduce federal budget deficits. Librarian of Congress Daniel J. Boorstin responded by ordering a wide array of cuts in services, including closing the library's reading rooms during weekday evenings, except Wednesday, and on Sundays and federal holidays.

--- Growers of Three Varieties of Tobacco Reject Price Supports

WASHINGTON (AP) - Growers of three lesser kinds of tobacco have rejected government price supports and controls, while farmers producing a fourth type have approved the federal program, the Agriculture Department says.

Quotas were rejected for Maryland, cigar filler and cigar binder tobaccos for the 1986, 1987 and 1988 crops. As a result, those producers are ineligible for price supports. The department said 94.9 percent of the 99 growers of Virginia sun-cured tobacco approved the quotas.

The vote was conducted in a mail referendum from Feb. 24-27. A two-thirds majority was needed to approve the quotas.