JACKSON, Miss. (AP) - Another unplanned outage at Mississippi's Grand Gulf nuclear power plant is adding to regulators' concerns that reliability problems at the largest single-unit nuclear power plant in the United States may be affecting power markets.

  

Operators at the Entergy Corp. plant in southwest Mississippi took it offline Wednesday, citing problems with a turbine bypass valve. The outage came to light Tuesday when the federal Nuclear Regulatory Commission announced a special inspection citing equipment issues "the agency wants to better understand."

  

The plant has been running at reduced or zero power output for much of the time since 2016. That can stress power supplies and cause higher prices across Mississippi, Arkansas, Louisiana and eastern Texas. Tuesday, the commission said Grand Gulf was running at 18 percent power.