In a heavily shielded, aquamarine pool across the James River from historic Jamestown, a monumental array of burned-out nuclear fuel is slowly building up, a waste heap that is very hot, extraordinarily costly and highly radioactive.

Virginia Electric and Power Co., the troubled owner of this uranium refuse at its Surry generating plant, says it faces a crisis: Unless it finds a quick way to get rid of some of the used-up fuel, it may have to shut down the $409 million plant as early as March 1985. Such a drastic step, the utility warns, would cost its customers more than $300 million a year, adding $5 to $10 to a typical homeowner's monthly electric bill.

"This problem is not one caused by Vepco," says Ronald H. Leasburg, the company's vice president for nuclear operations. Instead, he argues, Vepco and other utilities are victims of frequently changing federal policies for storing nuclear waste. "We were working under the assumption that there would be a place to ship this to."

With no such federal dump in the offing, Vepco has weighed its options and embarked on a controversial scheme. It wants to truck 30 to 90 loads of nuclear waste annually over Virginia highways to another storage pool at its North Anna plant in rural Louisa County about 75 miles southwest of Washington. The Louisa government has banned such shipments and Vepco officials concede they may be stymied. Building costly new storage quarters at Surry, they contend, would take too long.

The Louisa Board of Supervisors is scheduled to hear Vepco's proposal today.

In its last-ditch efforts to unload its nuclear garbage, Vepco is far from unique. Spent fuel is accumulating at 75 nuclear plants run by 40 utilities across the nation. The Department of Energy says new storage space will be needed by 1986 for about 120 metric tons, nearly 265,000 pounds, of burned-out utility fuel. By 1990, the department estimates, this will grow to 1,800 metric tons, about 4 million pounds. Surry is expected to be among the first six U.S. plants to exhaust their nuclear storage space.

"There is an absolutely urgent need for nuclear waste management legislation," Sherwood H. Smith Jr., chairman of the American Nuclear Energy Council, an industry group, told Congress last October. The utilities' nuclear junk heap, big as it may be, is far outstripped by the radioactive waste left from U.S. weapons production, which already occupies more than 10 million cubic feet in storage tanks at several government sites, according to DOE.

Some critics blame the nuclear power industry, rather than the federal government, for the utilities' present waste predicament. "The utilities would rather it be somebody else's headache," says David Berick, an Environmental Policy Center official, who accuses the industry of "playing chicken with the federal government." Many environmentalists oppose shipment of nuclear waste because of possible accidents or sabotage and contend the utilities should be required to store it at the companies' own sites.

While spent nuclear fuel contains some of the most hazardous substances on earth, its continued storage in the utilities' holding pools, such as the one at Surry, poses no special safety threat, according to most nuclear officials. For the utilities, the chief risk is economic. Uranium fuel gradually burns out and must be replaced with new fuel. Once a storage pool is full, a utility may have no place to put its used-up fuel. So a generating plant would have to shut down.

The storage pool at the 10-year-old Surry plant is already more than half filled, packed with nearly 1 million pounds of radioactive waste in 40 feet of cooling water. By March 1985, officials say, space will remain in the pool to hold only part of the fuel in the plant's two reactors. This is risky, they say, because all the fuel must sometimes be unloaded for repairs to reactor systems. Otherwise, the plant would face a permanent shutdown. By March 1987, officials say, the pool will be entirely filled and no more burned-up fuel can then be unloaded.

Unless the spent fuel is shipped to Louisa or stored in some other way, Surry would close sometime between 1985 and 1988, Vepco executives say. Customers' electric bills would rise, they say, because Vepco would have to switch to using more costly oil- and coal-fueled generating plants and to buying electricity from other companies. Instead of producing electricity, Surry would become an elaborate storage bin for radioactive waste.

Nuclear fuel consists chiefly of uranium dioxide, a radioactive compound, housed in long, slender metal tubes. Groups of fuel rods are aligned in metal frames shaped like rectangular prisms. These are known as assemblies. Each Vepco reactor holds 157 assemblies. The 1,575-pound assemblies are moved about by special cranes and other mechanical equipment.

The nuclear fuel is used to produce heat, just as oil and coal are burned to provide heat at other electric plants. The heat is needed to create steam that powers a turbine to produce electricity. Uranium fuel gives off heat through nuclear fission, the splitting of a uranium or other atom when struck by a neutron, a subatomic particle.

Nuclear waste consists of fuel rod assemblies whose contents have undergone fission. Some of the uranium is converted to other radioactive elements, including plutonium, strontium and cesium. Someday, the remaining uranium and plutonium may be chemically extracted to produce new nuclear fuel, but no such commercial "reprocessing" is currently being carried out. Other highly dangerous elements, such as strontium and cesium, must be securely stored or safely buried for centuries to protect society.

These burned-out fuel assemblies are now filling up the vertical underwater storage slots at Surry and other nuclear plants. Today, 634 of Surry's 1,044 slots are filled. The surrounding water cools the radioactive waste and helps prevent emissions of hazardous radiation.

Although Vepco's plans are embroiled in controversy, its attempts to find enough space for its nuclear waste illustrate the problems faced by utilities throughout the United States. Vepco has considered nearly every strategy now being examined by federal officials, scientific and economic researchers, Congress and environmental activists.

Shipping burned-out fuel from one plant, such as Surry, to another with more storage room, such as North Anna, is a much-debated option. Vepco contends this is the cheapest solution to its problems and probably the only one that could be carried out soon enough to avoid a plant shutdown. "We can't put together a schedule that would do away with transshipment," says Vepco's Leasburg.

Louisa County, worried about becoming a nuclear dumping ground, adopted an ordinance in 1978 to ban storage of radioactive waste from any plant other than North Anna. Vepco is the county's largest taxpayer. But Louisa officials say they want to keep their law unchanged. "I'm worried about the highway safety and the accidents," says Board of Supervisors Chairman Nancy F. Winks, pointing to growing opposition among county residents.

Vepco officials contend fuel shipments are safe and say they may consider going to court if Louisa refuses to amend its ordinance. Such a move would be complicated, however, by a recent federal court ruling upholding a similar New York City ban. Moreover, Vepco executives say a legal challenge might take too long to avoid a plant shutdown. Even if Louisa modifies its ordinance, Vepco would still need federal approval to truck waste from Surry.

Environmentalists, arguing that the safest option is to keep Surry's waste at Surry, want Vepco to buy or build additional facilities, possibly using new techniques for storing spent fuel in air-cooled containers. Such dry storage, they contend, would offer a greater safety margin than water-filled pools in the event of a nuclear catastrophe, such as a reactor meltdown. The Energy Department is studying air-cooled storage, and the Tennessee Valley Authority is considering trying it at one nuclear plant.

"I just wish we had time to do that," responds Vepco's Leasburg. Vepco says experimenting with dry storage or building another water-cooled pool at Surry would take too long. And, officials add, both proposals would cost more money than shipping spent fuel to Louisa. Another pool would cost $190 million, Vepco officials estimate. Air-cooled storage could cost $90 million, they say. In comparison, Vepco argues, shipments to Louisa would cost $37 million.

Vepco considered overhauling its existing pool at Surry to make room for more fuel assemblies--a step the company plans to take at its Louisa plant, at a cost of up to $48 million. But at Surry, officials concluded, the structure is not strong enough to hold a bigger fuel load and assure an adequate safety margin in case of unforeseeable events, like an earthquake.

Vepco has already reduced its immediate storage needs by switching to longer-burning fuel, enriched with slightly more uranium-235, the isotope, or form, essential for fission. Neither Vepco nor federal officials see any immediate prospect of further boosting the enrichment to make the fuel last longer.

These options have been weighed by Vepco and other utilities amid zigzags and uncertainties in national waste policies. Even though President Reagan overturned President Carter's ban on commercial reprocesssing of spent fuel, utilities remain stuck with their waste. Allied Corp., the only prospective reprocessor, abandoned its plan last year, citing economic uncertainties.

In addition, Reagan reversed a Carter plan for a federally run, temporary storage setup. Congress remains stalled by conflict over this and other waste issues, with legislative prospects uncertain. The industry is pushing for short-term federal warehousing, which environmentalists oppose. Long-term deep-rock burial of nuclear waste is not expected before 1999.

In Louisa County, skepticism about Vepco's waste abounds. "It's real questionable whether it's that critical right now," says Maureen Hale, a Louisa activist. "They should have been planning this before now. It's their problem, not our problem."