In a new setback for the U.S. nuclear power industry, Edison International said Friday it will permanently close the two reactors of its San Onofre plant in California, ending a contentious battle over whether they can be repaired and operated safely after cracks were found last year in the steam generator system.

The two reactors, built at a total cost of around $2.1 billion, once provided 17 percent of the power generated by the utility. The loss of the units has forced Edison International and its Southern California Edison subsidiary to rely more heavily on renewable energy sources and new supplies of natural gas.

The company said it will be able to maintain electricity supplies for Southern California, barring damage to transmission lines from an unusually hot summer or fires. Edison Chief Executive Theodore Craver Jr. said he spoke to California Gov. Jerry Brown on Friday morning about plans to ensure stability of the electrical grid.