The only commercial nuclear power plant in Massachusetts returned to full service on Tuesday after a $70 million, monthlong, refueling and maintenance project that owners say makes the plant safer.
Entergy Corp., owner of the Pilgrim Nuclear Power Station in Plymouth, said control room operators reconnected the plant to the grid after a 35-day planned shutdown.
The plant's 600 employees, as well as nearly 1,200 temporary workers brought in specifically to work on the project, spent that time upgrading, replacing, overhauling and inspecting hundreds of pieces of equipment and also replacing the reactor's fuel.
John Dent, Entergy's site vice president, said in a statement that the project "resulted in a safer and more reliable plant." The project takes place every two years.
The workers performed hundreds of activities that can be done only while the unit is shut down, including replacement of a water heater, post-Fukushima upgrades and condenser boot seal replacements.
The project did nothing to convince anti-nuclear activists in Massachusetts that the plant is safe.
Pilgrim, which began commercial operation in 1972 and generates 680 megawatts of electricity, was relicensed by the Nuclear Regulatory Commission in 2012 for an additional 20 years. Entergy has owned the plant since 1999.
"Pilgrim is a failed reactor, run by a failed corporation with failed oversight by the NRC," said Diane Turco, of Cape Downwinders, a grass-roots citizens group still fighting to close down the plant.
"We need to close Pilgrim because public safety cannot be ensured," she said. "It is a catastrophe in the making."
Critics have pointed out that Pilgrim has a similar design to the Fukushima plant in Japan, which failed after an earthquake and tsunami.
But Entergy officials say Pilgrim has backup systems that the Japanese plant lacked, including extra diesel generators and better venting systems.