The Salem 2 plant - one of three nuclear reactors on Salem County's Artificial Island - automatically went off line at 6:20 p.m. Thursday. The two other plants there - Salem 1 and Hope Creek - were not affected and continue to operate at full power.
PSEG Nuclear, which operates all three plants, said the low water level was caused by the failure of a feedwater pump that supplies water to the steam generator. The firm says the generator and pump are on the non-nuclear side of the plant.
It's not yet clear what caused the pump to fail, and it's not known when the Salem 2 plant will resume normal operations.