The chairman of the House Ways and Means Committee yesterday flatly rejected President Carter's new proposals to trim back several popular Social Security benefits, virtually killing chances for their passage this session.

Rep Al Ullman (D-Ore.), whose panel has jurisdiction over those programs, said the committee would no even consider the proposals this year because it would "open up Pandora's box" and revive the fight over a payroll tax cut.

Ullman's rejection all but wipes out any possibility for enactment of the measures. The cutbacks, which Carter proposed in his budget Monday, affect turial payments, subsidies for teenagers, minimum benefits and federal pensions.

Carter had been banking on congressional approval of the provisions to "save" $600 million toward his $29 billion budget deficit goal. If the measures are not passed, the deficit will rise at least to $29.6 billion.

Although the cutbacks are relatively modest, the plans have sparked controversy. One group that includes former health, education and welfare secretary Wilbur Cohen has already protested the moves.

Ullman also reiterated his assessment that Carter's proposal for a "real wage insurance" tax credit to protect workers who follow the new wage guideline is facing serious opposition in the committee -- and a possible quick demise.

While declining to "bury" the new plan before hearings start next Monday, Ullman made clear he will shelve the measure promptly if it does not muster sufficient support. "We'll just have to reconnoiter," he said.

The Oregon Democrat made his remarks during an interview in which he outlined mixed prospects for several key proposals in Carter's new budget, from enactment of major trade legislation to minor tax-revision plans.

Ullman said his panel probably will move this year to limit federal disability benefits to discourage abuse -- a step he said could produce some savings over the next few years.

At the same time, he said Congress would move to grant "most-favorednation" trade concessions to both China and the Soviet Union -- despite 1974 legislation denying benefits to the Soviets unless Jewish emigration restrictions are eased.

Ullman also listed these prospects:

Carter's new scaled-back hospital cost-containment proposal has "a better chance" for committee approval this year, in part because of a change in subdommittee chairmanships -- but it still faces a tough floor fight.

The lawmakers probably will approve the new international trade pact agreed on in the recent Tokyo Round trade talks, but the battle "won't be easy" and may involve some tough bargaining.

The Ways and Means Committee definitely "will deal with" Carter proposals to resolve three controversial tax-revision issues that panel members blocked last year -- taxation of fringe benefits, carryover basis and independent contractors.

The carryover basis proposal involves increasing taxes on the sale of inherited property. The "independent contractors" measure would limit the ability of workers to avoid payment of some taxes by classifying themselves as self-employed.

Ullman said the committee may begin hearings later this year on how to overhaul the present method of financing the Social Security system, but asserted it definitely would not report out legislation on the issue.

And he ruled out any move this year to push through a value-added tax, a form of European-style national sales tax that he and Sen. Russell B. Long (D-La.), chairman of the Senate Finance Committee have been advocating.

The Social Security cutbacks Carter has proposed are relatively minor, comprising changes that budget reformers have been recommending for years. They would not alter basic Social Security retirement benefits.

The measures include:

Eliminating the special Social Security payment for dependent children who are in college. Carter contends the benefit merely duplicates those now available from the newly expanded federal college scholarship program.

Ending the $225 lump-sum "death benefit" the Social Security system now provides to help widows with funeral expenses. The White House says this aid now is available under other programs.

Cutting off the monthly benefit now paid to a surviving spouse with a teen-age child when the youngster reaches 16, instead of the present 18-year maximum. Carter says enough widows are now working that the benefit is unneeded.

Repealing the present requirement that all Social Security recipients be guaranteed at least $122 a month in benefits. The administration complains this provides a windfall for persons who already get large federal pensions.

Cracking down on federal retirees whose Social Security benefits amount to a second pension -- by reducing their monthly Social Security checks $1 for each $3 they receive in federal pension income.