A broad-based religious coalition from northeastern Ohio has begun a campaign for millions of dollars in federal aid to help reopen a Youngstown steel mill closed last year at a cost of 7,700 jobs.

The Ecumenical Coalition of the Mahoning Valley is basing its appeal in part on a $350,000 study by the National Center for Economic Alternatives, a private research firm here, which concluded it is "technically feasible" to reopen the plant as a worker-and-community-owned company.

The center, as its name implies, is interested in testing economic alternatives, and particularly the idea of worker and consumer cooperatives.

Thus far, however, its suggestions for a reborn steel plant - including a $15 million federal grant to be followed by much larger federal loan guarantees - have met with a cool response from the government.

Patricia Roberts Harris, Secretary of the Department of Housing and Urban Development, said she would have to see the community's application for the $15 million grant, but noted it would require "a lot of private money up front" and would have to compete with other applications.

Deputy Assistant Commerce Secretary Harold W. Williams noted that Commerce Department policy bars loan guarantees of more than $100 million for any one project. "We would love to have someone come to us with a project we could back," he said, "but at the moment we don't have a viable project."

The Ohio coalition has planned rallies for today, and last week it took out a full-page ad in this newspaper in the form of a letter to President Carter. "Youngstown's Job Crisis Is a Moral Issue," the ad was headlined.

The Center for Economic Alternative's report said the issue in Youngstwwn is "not simply a steel industry problem" - the steel industry has shut down many plants in the last few years in the face of foreign competition and for other reasons - "but ... also an issue of urban decay facing many parts of the country in an era of slower economic growth."

"The justification is not the commercial and economic advantage of one community alone, but the need throughout the nation to develop new strategies to preserve jobs, increase productivity, test new technologies and help urban communities facing economic decay."

Specifically, the report called for creation of a federal task force to work with the ecumentical coalition. The task force and the local leaders would work out detailed plans for making a national showcase of the reopened plant.

The report also asked the administration to authorize - when and if the fledging steel firm gets started - federal guarantees of $300 million in bank loans for the plant.

The study called for an "immediate" federal grant of $15 million to the ecumenical coalition, which would use the money to buy the closed-down sections of Youngstown's Campbell Works form the Lykes Corp,'s Youngstown Sheet & Tube Co. and the LTV Corp.'s Jones & Laughlin Steel Corp., which are in the process of being merged.

Most of the grant would revert to the federal government "if significant progress is not made toward achieving the national demonstration project over the next 18 months," the report said.

It recommended that the government "seriously consider" the plant as the site of a national research program in new steel technology.

Gar Alperovitz, co-director of the national center, said the reopened steel company could be profitable if it sold 1.4 million tons of steel a year commercially and 100,000 tons to the federal government.

The center's report offers four options on how to finance the project, which it said would cost $525 million over eight years. Most of the money would come from loans. A major assumption of the study's favorite option is that $50 million would be raised as equity - $10 million of which would come from Mahoning Valley residents.

The Rev. Edward Stanton, staff director of the ecumenical coalition, said that local residents, businesses, churches and labor unions have opened 4.065 "Save Our Valley" accounts totaling $4 million in local banks. The accounts indicate strong community support for the new steel company, Stanton said.