WISCASSET (AP) – With a thunderclap of explosives, Maine Yankee’s containment dome toppled to the ground Friday in one of the final steps toward completion of the nuclear power plant’s decommissioning.

The 150-foot-tall structure served as the most visible symbol of the 900-megawatt plant during 24 years of operation.

Friday’s event marked the first time explosives have been used to knock down a commercial reactor containment building, officials said.

About 1,100 pounds of explosives were placed in holes drilled into the structure to topple the reinforced concrete dome that was designed to withstand earthquakes, tornadoes and hurricane-force winds.

As the countdown concluded, the explosives lit up, the legs supporting the dome buckled and the structure came down in one piece as planned.

The crowd broke into applause as a cloud of dust rose from the rubble.

The nearly 500 people permitted to enter Maine Yankee property to witness the blast were required to stay 1,000 feet from the containment.

Dudley Leavitt Sr., who helped build the dome, watched its destruction with a tinge of sadness. He said he thought the plant had a lot more life left in it.

“It’s a shame that they shut this down. There are plants that are older that are still in operation across the country,” said Leavitt, 66, of Topsham, who oversaw the steel reinforcement of the dome.

Steve Ward, Maine’s public advocate for utility issues, had mixed emotions about what he witnessed.

Maine Yankee provided low-cost energy without producing greenhouse gases, he said, but the problem of long-term storage of the nuclear fuel assemblies has never been resolved.

“The federal government has utterly failed to deal with the spent fuel issue. It’s like building a wonderful, livable mansion that has no septic system. It doesn’t even have an outhouse,” Ward said.

Ray Shadis, a nuclear power opponent who lives in neighboring Edgecomb, noted that the dome could be seen above the trees from homes near the plant.

“This is strictly symbolic and nothing more,” he said of the demolition, calling it just another step in the lengthy decommissioning process. “It’s the last major demolition activity.”

In advance of Friday’s blast, a steel plate lining the structure was removed and holes were cut to weaken the structure, whose walls were 4 feet thick at the base and 2 feet thick at the top.

The explosives were not designed to reduce the dome to rubble. The idea was simply to lower the dome so it could be reached by heavy equipment that would complete the job of picking apart the structure.

About 20 million pounds of rubble from the building will be hauled by rail to a low-level radioactive waste repository in Utah.

The pressurized water reactor began operation in 1972 and survived three statewide referendums aiming to close the plant in the 1980s.

It was shut down following operational problems that escalated after the discovery of cracked steam generator tubes in 1994. The plant was shut down in 1995 while sleeves were installed to reinforce each of the 17,000 tubes.

Problems continued to mount in 1996 and the plant was placed on the Nuclear Regulatory Commission’s list of worst-run plants in 1997.

Maine Yankee’s board voted to close the plant permanently in August, 1997, 11 years before the plant’s license was set to expire.

By the time decommissioning is completed next year, it will have cost $500 million. All that will remain are a security building and storage facility where 60 canisters contain the highly radioactive fuel rods.

The spent fuel assemblies will remain until the federal government follows through with its promise to build a repository for high-level radioactive waste.

Maine Yankee and other utilities have sued the federal government for the costs of storing the fuel rods until 2010, the target for the proposed national nuclear waste site to open at Nevada’s Yucca Mountain.

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