ATLANTA — The world's largest builder of nuclear reactors apologized to regulators Wednesday over a shipment of equipment that contained a radiation "hot spot" that exceeded federal guidelines and traveled more than 400 miles from Virginia to Tennessee.

A team of inspectors said the quarter-sized spot, which was located on cleaning equipment in an Areva NP Inc. shipment, measured 10 times higher than the level of radiation allowed by federal regulators for transport. Areva said its own tests showed that the "hot spot," or concentrated area of radiation, was four times higher than the federal limits.

Areva NP is a subsidiary of France's Areva Group. Another Areva subsidiary, Areva NC Inc., announced earlier this month that it will build a $2 billion uranium enrichment plant near Idaho Falls, Idaho.

The Nuclear Regulatory Commission and Areva both concluded the radiation didn't pose a threat to the truck's driver, employees or the public. But company leaders conceded the incident exposed "weaknesses" in Areva's shipping procedures.

"It was a deep disappointment to us. We regret that it ever took place," Dominique Grandemange, an Areva nuclear fuel plant site manager, told an NRC panel.

"My commitment to you today is we'll continue to monitor the progress to make sure we don't have a recurrence," he said.

The radiation was found on the bottom of a box of fuel-cleaning equipment located on an open flatbed truck that made a seven-hour trip from Areva's Mount Athos Road facility near Lynchburg, Va., to the Watts Bar Nuclear Plant north of Chattanooga, Tenn.

The equipment arrived on Feb. 3. The next morning Watts Bar plant employees found a spot at the bottom of the truck they measured at 2,000 millirem per hour — 10 times higher than the commission's guidelines of 200 millirem per hour. A millirem is a unit of measurement of radiation. A chest X-ray usually is about 10 millirem, according to the U.S. Department of Energy.

Areva sent its own technician, who measured the spot at around 800 millirem an hour. Geoffrey Wertz, an Areva inspector, said the incident was likely caused by faulty pre-shipment procedures.

Wertz said the company's pre-shipment review showed that the equipment on the truck was below the allowed level of radiation. He said Areva has since added another layer of reviews if radiation passes certain levels as well as more training for employees.

He also said inspectors will no longer ship fuel-cleaning equipment on open flatbeds.