Yellow bulldozers are stopped in their tracks. Under empty skeletons of buildings, mammoth pipe sections lie abandoned in the snow. All around is an eerie moonscape of dirt mounds and craters.

A month ago, the construction site of the $2 billion Seabrook nuclear plant was teeming with 800 hardhatted workers. Today many of them have been laid off, about $1 million of equipment stands idle and the company building the plant fears it may have to abandon the project.

To put it simply, Seabrook is strangled in red tape. How it got that way is a case study - though an admittedly extreme one - of the uncertainties confronting nuclear power today.

Once widely thought to be the salvation of America's energy problems, atomic power faces stronger and more skilled environmental opposition than ever before, plus increasing safety and pollution regulations and escalating costs.

Moreover, President Carter's expressed skepticism about the economics and safety of nuclear energy, and Congress' recent abolition of the pro-nuclear Joint Energy Committee, have thrown the industry's planned expansion into daubt.

Seabrook, the most heated nuclear controversy in the country, may be one of the new administration's first important decisions in the swirling conflicts over how to meet the nations energy needs as cheaply and safely as possible.

The plant was first proposed in 1972 for this small coastal town on the Massachusetts border. The beaches here, 45 mile north of Boston, attract thousands of New Englanders each summer. After four years of legal skirmishing, the Nuclear Regulatory Commission gave Seabrook a construction permit last July, but debate over the plant continued.

Backed by the state's major newspaper, the outspoken Manchester Union Leader, Gov. Meldrim Thomson has collected 100,000 signatures in recent months on a pro-Seabrook petition to the White House. Opposing the plant are national and local environment groups, the New Hampshire and Massachusetts attorneys general, and the town of Seabrook.

The battles - some bizarre, some boring - have raged in the Washington offices of two federal agencies, in the federal courts, on the pages of The Wall Street Journal, which is supporting Seabrook as a cause celebre , on the site itself, where 180 protesters were arrested last summer, and now in Congress, which has launched Investigations by the General Accounting Office and a House Public Works subcommittee.

If it is built, the 2,300-megawait plant would provide 80 per cent of New Hampshire's electricity by the mid-1980s, while selling half its power to other New England states.

Public Service Co. of New Hampshire, which, with eight other New England utilities, would own the plant, sees it as the only alternative to dependence on Arab oil or reliance on coal, which is increasingly expensive and pollutes the air.

Environmentalists say nuclear power is not needed and would cost too much; that the plant is located on an earthquake fault; that it would polute coastal waters; thatlow-level radiation, the risk of nuclear accidents and the problem of radioactive waste disposal present unacceptable hazards.

The NRC's construction permit was given on the condition that the Environmental Protection Agency approved the plant's cooling system.

EPA, a year earlier, had given the cooling system preliminary approval, but environmentalists appealed the ruling. In November, four months after construction began, EPA's regional administrator in Boston, John McGlennon, reversed his original decision, putting the plant's status in limbo.

"It's a disaster for the company," said Public Service Co. vice president Donald E. Sinville. "We've had a sick feeling ever since."

McGlennon, who says he personally read 5,000 pages of testimony before an EPA administrative judge, told the company it must modify its cooling system to protect the delicate eco-system of the Seabrook estuary.

Nuclear plants make steam to drive a turbine and then condense the steam in a cooling system for re-use. The Federal Water Pollution Control circulate cooling water in towers or ponds, unless EPA grants an exception for what is called a "once-through" system."

Seabrook's once-through system would suck water through a 19-foot-wide tunnel, cut like a subway through three miles of solid rock under a salt marsh and out to the ocean. McGlennon says large numbers of fish and equatic organisms would be drawn in with the ocean water and "fried" to death.

After circulating through the reactors, 1.2 billion gallons of water a day - equal to the flow of a large river - would be discharged through another offshore pipe. Its temperature - 39 degrees warmer than the surrounding ocean and higher than any existing power plant discharge - might harm marine life, McGlennon said.

While the company contends that the environmental effect would be minimal, McGlennon wants the pipes extended farther into the ocean or replaced with a closed system.

However, the NRC expressly forbade cooling towers could be seen for miles and would fog the air of a nearby landing strip.

The company says it can't afford to change its cooling system.

This regulatory snafu has thrown the project into financial chaos. Two utilities are trying to sell 12 per cent of their interests. Another, which had planned to buy 15 per cent, has withdrawn its offer.

Public Service can't get short-term construction loans, and has cut spending from $62 million to $8 million for the first six months of this year. While NRC is allowing limited expavation to continue, about 506 workers have been laid off and delays are costing $15 million a month.

"The company took a corporate risk to start construction without a final permit," McGlennon said. "They should be held accountable."

Public Service has appealed McGlennon's decision to the EPA administrator, who has yet to be appointed by Carter. The decision will set a precedent for all power plant cooling systems.

EPA has granted cooling system exceptions with "impunity," McGlennon said. "The line got drawn at Seabrook . . . virtually all life begins in coastal areas. Thousands of organisms live in an interdependent ecosystem. If you eliminate the plankton you affect lobsters, social and moral responsibility to protect the earth's ecosystem for future generations."

Such concerns led The Wall Street Journel to lable McGlennon an "EPA apparatchik" and the Union Leader to insinuate he is a Communist "sleeper." One local editorialist accused him of "playing Lord Neptune to mentally retarded fish."

The company emphasizes the 7,000 construction jobs and the energy the plant would provide. "Even with a lot of consercatism, we expect 7.5 per cent annual increase in demand for electricity," Sinville said. "The price of electricity from a nuclear plant is much cheaper than from oil or coal." Other experts, however, say coal is now competitive with nuclear energy.

The water discharged by the plant would be no warmer than water flowing through the marsh on a hot summer day, Sinville said.

The company says the plant's location in a seismic area presents little danger because it has been designed to withstand earthquakes.

Whatever the EPA's decision, it is bound to be challenged in court by the company or by the Seacoast AntiPollution League, the New Hampshire Audubon Society and the New England Coalition on Nuclear Pollution, groups that have fought the plant since the project's inception. An NRC attorney, Richard C. Browne, said it could be six months or as long as three years before the "regulatory maze" is negotiated. CAPTION: Picture 1, Limited work continues on digging the foundation of the $2 billion Seabrook, N.H., nuclear power plant. Most other construction at the site has stopped. By Larry Morris - The Washington Post; Picture 2, Engineer John Herrin and Public Service Co. officer Donald Sinville stand in section of water pipe that company wats touse in plant's cooling system. By Larry Morris - The Washington Post