Grand Gulf nuclear plant has struggled with reliability issues in last three years
In 2015, former Mississippi Gov. Haley Barbour told the Mississippi Business Journal that the Kemper Project clean coal power plant would rival that of Mississippi's lone nuclear reactor, the Grand Gulf Nuclear Power Station, in the long run.
While that prediction never panned out for Kemper, which is now powered by natural gas, Entergy's nuclear plant has problems of its own.
The Grand Gulf plant in Port Gibson has struggled with reliability issues in the last three years, according to an examination of records from the U.S. Nuclear Regulatory Commission. In the last three years, the reactor has been the lowest rated among reactors of similar design when the daily reactor status reports issued by the NRC are averaged over a year's time.
Since 2005, the reactor's performance, which is reported by Entergy and other nuclear plants to the NRC daily, has been either the lowest rated among similar reactors or the next lowest. The performance average allows one to see how much the plant has been shut down or derated (not run at its full generation capacity) for maintenance, repairs or upgrades over a year's time.
Grand Gulf has a single General Electric Type 6 boiling water reactor with a generation capability of 1,440 megawatts that became operational in 1985 and it supplies power to four states. It's one of four of this design of reactors operational nationally. The other are: Unit 1 of the Clinton Power Station in Illinois, Unit 1 of the Perry Nuclear Power Plant in Ohio and Entergy's River Bend Station in Louisiana.
In 2018 so far, the plant has only generated, on average, 52.01 percent of its capability and the reactor has been shut down 106 days so far this year. In comparison, Clinton's reactor was running at 86.12 percent, Perry's ran at 99.26 percent and River Bend averaged 82.28 percent.
As a rule, the higher the average capacity number, the less time the reactor spends shut down.
In 2017, the reactor generated at 60.85 percent of its capacity and the reactor was shut down for 91 days. That same year, Clinton's reactor averaged 87.31 percent of its capacity, while Perry was at 89.3 percent and River Bend averaged 82.7 percent.
Grand Gulf's woes were one of the reasons why Entergy's 445,000 customers in western and central Mississippi were on the verge of rolling blackouts during record cold on January 17, 2017.
Grand Gulf began a forced outage on January 8 that didn't end until January 17, when the plant was generating at 17 percent of its capacity. Grand Gulf's reactor was scrammed on January 30, which means an emergency shutdown using the control rods was initiated. The report filed with the NRC says that an oscillation in the electricity-generating turbine of 30 megawatts precipitated the scram.
It was an improvement over 2016, which was the worst performance of the reactor in 14 years with an average of 48.06 percent of its capacity. The reactor was shut down for 176 days in 2016. That same year, Clinton's reactor averaged 93.34 percent of its capacity, Perry was at 94.07 percent and River Bend averaged 83.24 percent.
This state of affairs wasn't always the case.
In 2005, the Grand Gulf reactor generated 89 percent of its nameplate power rating on average. From 2005 to 2011 the reactor had its lowest two average ratings in 2008 and 2007 at 84.58 percent and 84.22 percent respectively.
Shutting down Grand Gulf and replacing with less manpower intensive natural gas plants would likely be expensive. It cost Entergy $1.24 billion to close down its Vermont Yankee plant in 2014.
Perry will likely shut down in 2021 as its owner, FirstEnergy, is riddled with debt. Clinton needed a subsidy from Illinois taxpayers to stay open until at least 2026.