Fairfax County officials called yesterday for stricter federal inspection of vehicles carrying hazardous materials following Monday's chemical spill on the Capital Beltway, which paralyzed evening rush hour traffic and forced temporary evacuation of as many as 630 people from their homes.

The spill stranded an estimated 7,000 cars on the Beltway and forced the closing of a 2 1/4-mile segment of the interstate for eight hours and the evacuation of the Mount Hebron Park subdivision.

A tank truck was carrying corrosive chemicals known to burn lungs and skin; 500 gallons leaked onto the eastbound, outer loop of the Beltway between Van Dorn Street and Shirley Highway (I-95).

Fairfax officials estimated that the massive cleanup job involved more than 100 firefighters and cost more than $50,000, but the expense estimate could double as personnel and other costs are tallied.

"We have no idea what's going through our localities on the highways," said county Supervisor Joseph Alexander, whose Lee District includes the spill site.

Fairfax County Board of Supervisors Chairman John F. Herrity criticized federal hazardous waste inspection procedures, calling them inadequate. He called for an increase in both the number of inspectors and the frequency of inspections of the vehicles transporting dangerous materials.

The leaking tanker, carrying 5,000 gallons of chemicals that had been used to cleanse ships and submarines at the Norfolk Naval Shipyard in Portsmouth, Va., was 17 years old, according to Dennis J. Miele, who owns the vehicle.

Miele, president of Applied Technology Transportation, a national transporter of hazardous wastes in Toms River, N.J., said yesterday he purchased the Heil tanker in February for $15,000. He said it was inspected then by the U.S. Department of Transportation and certified for use.

Federal transportation workers are required to inspect tankers only when they are purchased, said James E. Becker, acting chief of the hazardous materials division of the National Transportation Safety Board. But Becker said federal and state inspectors can periodically and without notification inspect any hazardous waste container.

A team of NTSB investigators will be dispatched to Exton, Pa., where the tanker was moved after the cleanup yesterday, to determine the leak's cause. "We have several other major operations right now; it's not our top priority," Becker said, referring to several recent disasters, including a toxic spill in Arizona and an airplane crash in Manassas.

Herrity said the county was considering requesting money from the federal "Superfund," which is used for cleaning hazardous waste sites.

Overtime pay for the personnel from 10 county agencies and use of the county helicopter to transport engineers over the traffic could push Fairfax's cost above $100,000, he said.

Miehe said the cost of removing 45.5 cubic yards of contaminated materials around the tanker, about $13,000, will be paid by his company. He said an emergency response team dug 18 inches into the asphalt and soil and shoveled it into thirteen 55-gallon drums. The contaminated soil is to be dumped at a yet-unspecified hazardous waste landfill.

Nationwide, the number of transportation accidents involving hazardous materials has dropped in recent years, according to Kevin Coburn of Wilson Hill Associates, consultants for the federal transportation department's national hazardous data base. But Coburn said the enormous drop since 1981 was caused almost entirely by a change in the reporting requirements. There were 8,686 reported incidents in 1981, 5,683 in 1982, 4,888 in 1983 and 4,486 in 1984.

In Virginia, the number of hazardous materials spills has been rising in recent years, according to Mike LaCivita, an official with the emergency services office of the Virginia transportation department.

LaCivita said the increase has been caused, in part, by stricter state reporting requirements. In 1981, there were 23 reported hazardous waste incidents involving trucks, cars, rails or barges. In 1982 there were 48, in 1983 there were 43, and in 1984 there were 54.

Last year, the Northern Virginia Planning District Commission warned that more hazardous waste accidents could occur in the suburban area because the state was relaxing some restrictions on the transportation of hazardous waste and more such materials would be moved on Virginia highways. Virginia officials said they were making the changes because the General Assembly passed a law to prevent state standards from exceeding federal ones.