RIVERSIDE - Southern California Edison crews are hauling a gigantic piece of slightly-radioactive spent nuclear equipment down Southern California freeways this week.

The piece of metal served as part of a lower assembly inside the boilers of the San Onofre Nuclear Generating Station for years, until the containment domes were cut open and the boilers replaced over the past few years.

"The steam generator contains extremely low levels of radiation," the Edison company said in a statement. "The exposure that a person could receive standing five-to-ten feet away from the transport for an hour would be equivalent to a dental x-ray."

A 400-foot-long vehicle hauled the 700,000-pound piece of steel onto Interstate 5 at San Onofre Sunday night. SCE said it would pass through San Diego, Riverside and San Bernardino counties before passing through Las Vegas and Salt Lake City.

The transport is on freeways only at night, and will take three weeks to reach a disposal site at Clive, Utah, about 35 miles west of Salt Lake City.

Two new gigantic steam generators were manufactured in Japan and barged to Advertisement

[ Murrieta Volkswagen ] Oceanside when the project started. They were hauled up the beaches of Camp Pendleton to San Onofre.

Edison engineers cut holes in the containment domes at San Onofre, brought the old boilers and heat exchangers out, and placed the massive new generators inside. The old generators are in four pieces, and this would be the third shipment of huge components to Utah, SCE said.

Last week, state regulators began an investigation into why the massive project essentially failed. The replacement steam generators had been redesigned by SCE and the manufacturer, Mitsubishi Heavy Industries, to generate additional power in a controversial move that was not approved in advance by federal regulators.

The explosive force of steam inside the exchangers' tubes began to tear them apart, and the station was shut off on Jan. 8. The nuclear station had generated about 20 percent of the electricity delivered to 14 million residents in the SCE service area for two decades.

The California Public Utilities Commission estimates that ratepayers have spent $1.1 billion so far on fixing the problem, and buying expensive replacement power.