Las Vegas • A nuclear reactor vessel from Southern California’s decommissioned San Onofre Nuclear Generating Station made its way through Las Vegas by rail this week, headed to a transfer site and placement on a truck to become the heaviest object ever moved on a Nevada highway.

“By far, the biggest object ever moved on a road in the state,” Nevada Department of Transportation spokesman Tony Illia told the Las Vegas Review-Journal . “Our people have been scratching their heads for months to figure out a route that could work.”

The vessel is bound for burial at Clive, Utah, a remote site about 75 miles (121 kilometers) west of Salt Lake City. Movers and Nevada transportation crews were working to ensure it won’t damage state roads on the way.

The 770-ton nuclear reactor vessel was at the Apex Industrial Park in North Las Vegas, a transportation department heavy transport site adjacent to Interstate 15, where Illia said it will take a couple of weeks for cranes to lift it from the train car and deposit it on a 45-axle, 180-tire trailer for the trip toward Wendover, Utah.

The 300-foot-long (91.4-meter) shipment will also consist of two tractors to pull and another two tractors to push the more than 1.5-million pound load some 400 miles (643.7 kilometers) at no more than 10 mph (16.1 kph) .

It won't move until the transportation department issues a permit 24 hours before hitting the highway, Illia said.

Until then, workers plan to reinforce roads to handle the load along the undisclosed route north.

“The drainage structures along the transport route through southern Nevada need reinforcing,” Illia said. “The structures would get crushed like a soda can because the load is so heavy.”

Heavy equipment movement specialists with the company Emmert International plan to use heavy-duty hydraulic jacks to support culverts when the vehicle hauling the reactor passes over, Illia said.

Security will be making the trip as well, the Review-Journal said. The newspaper said the train with the railroad car hauling the reactor departed the California coast south of San Clemente around midnight Sunday.

The Review-Journal reported a trainorders.com message board indicated the Schnabel car was to be taken on Burlington Northern Sante Fe tracks to Barstow and Yermo, California, to be switched to Union Pacific tracks for the slow mostly uphill trip to Las Vegas.

Holding the slightly radioactive reactor is the world’s largest train car, a 36-axle Schnabel machine that weighs 2.2 million pounds by itself.

The reactor began generating electricity when the San Onofre plant opened on Jan. 1, 1968. It was withdrawn from service in 1992 and has been stored on the plant site enclosed in a carbon steel jacket since 2002.

Southern California Edison, which operated the plant for decades, says the vessel gives off one-10th of the radiation of a regular chest X-ray.

EnergySolutions, a company that dismantles nuclear power plants, owns the reactor and will dispose of it at its Utah facility, where low-grade nuclear waste is buried. Company spokesman Mark Walker said EnergySolutions has dismantled at least four decommissioned reactors in recent years.

Other infrastructure from the San Onofre plant will be transported through Nevada to Utah in coming years, although not necessarily along the same route as the reactor, officials said.

Rock outcroppings and two tunnels along the Union Pacific tracks further north prevent the reactor from being shipped by rail to Salt Lake City and then west to Clive.

Any asphalt or road surface could buckle under the 1.5 million-plus pounds of the reactor, plus a shipping skid that adds 7 tons to the total. Making such a shipment during warmer months is a bigger issue than it would be in colder weather.

When the San Onofre plant is eventually dismantled over eight years, all of the low-level waste from the plant will be buried in Utah, leaving only canisters of spent nuclear fuel. There is still no central repository authorized for such highly radioactive waste, so it will remain at the original site and be guarded 24/7.