The Pilgrim nuclear power plant permanently shut down last Friday after 47 years of generating electricity, bringing an end to nuclear power in Massachusetts.

Preparations for cleaning up and dismantling the plant already have started. The NRC is reviewing Entergy’s proposal to sell Pilgrim to Holtec International that promises a speedier decommissioning.

The closing reduced the region’s nuclear capacity from 25% to 20%, leaving Seabrook in New Hampshire and Millstone in Connecticut as New England’s only still-operating commercial nuclear plants.

ISO-New England, which operates the region’s bulk power system, says three new power plants that can burn either natural gas or oil will be online by this summer and several small solar facilities and a new wind farm will help absorb the impact.

Pilgrim nuclear plant employed about 600 professionals, generated 680 MW of carbon-free electricity, enough to power more than 600,000 homes.