VEPCO'S CUSTOMERS are likely to feel more relief than exasperation at the latest turn in the company's nuclear program. Vepco says that it is going to have to consider converting to coal the two nuclear reactors under construction at its North Anna site. It already has built four reactors, two at North Anna and two at Surry. It is still convinced, Vepco says, that nuclear energy is the best course for the country to pursue. But in regard to the two additional plants on which it is working at North Anna, it gloomily sites regulartory uncertainties and economic realities. The heart of the matter is that Vepco has completed four nuclear reactors over the past decade, the last two at costs approaching $1 billion each, and at the moment none of them is in operation.

Vepco's troubles with its reactors have been something out of the ordinary. Its dispute with the federal regulators over the geology of the North Anna site has a long and intricate history. This year's cycle of misfortunes began in March when the federal Nuclear Regulatory Commission ordered the shutdown of the Surry I reactor. The NRC cited a design error that resulted in piping that was less well protected against earthquake shock than it should have been. The Surry II reactor was already shut down for replacement for leaking tubing.

In April, a valve misfunctioned at the North Anna I reactor and the plant automatically shut itself down. The valve, it should be noted, was not part of the nuclear system but controlled steam to the turbine. Meanwhile, the company had completed the North Anna II reactor but was not able to put it into operation because the NRC has put a moratorium on new operating licences.

Also in April, a supervisor at Surry was exposed to readiation over the allowed limit. Seeing a water leak, he had gone into a radioactive area to investigate. The NRC fined Vepco $15,000 for the violation, bringing the company's total of fines for nuclear violations up to $127,400.

It was also in April that a store of fuel rods at Surry was sabotaged. Two former Vepco employees, convicted of it Tuesday, described the destruction as a protest against unsafe conditions at the plant.

In May, North Anna I went back on line. In late September, a chain of malfunctions released a small amount of radioactive gas into the atmosphere. The reactor will remain down several months for a previously scheduled refueling. With that, all four Vepco reactors were off line again.

Vepco's record does not recommend a larger nuclear operation at North Anna. Its alternative, coal, is by no means a safe technology. Mining coal is hazardous, and the toxic gases in coal smoke present a substantial danger to public health. Operating a coal-fired generator's pollution-control equipment is not simple. But it is a technology that seems better suited to Vepco. For other utilities, in other circumstances, nuclear power will remain a viable and valuable source of energy. But Vepco's reconsideration of coal deserves the encouragement of its friends, neighbors and customers.