Aging Nuclear Plants have Problems

 

Aging Nuclear Plant's Emergency Shutdown Highlights Safety Concerns at Mississippi Facility

Federal regulators cite Grand Gulf station for violations following reactor SCRAM, raising questions about reliability of 40-year-old facility

PORT GIBSON, Miss. — A malfunctioning control valve forced the emergency shutdown of Mississippi's only nuclear power plant in December 2018, triggering a federal investigation that revealed operator training deficiencies and persistent equipment problems at the aging facility.

The Grand Gulf Nuclear Station experienced an unplanned reactor shutdown—known in industry parlance as a SCRAM—when operators lost control of a turbine bypass valve that was supposed to remain closed. As technicians attempted to close the valve, it instead opened wider, forcing plant personnel to manually shut down the reactor as a precautionary measure on December 12, 2018.

The incident marked the seventh unplanned power reduction at the facility in an 18-month period, according to Nuclear Regulatory Commission documents, underscoring ongoing reliability challenges at the 1,443-megawatt plant that began commercial operations in 1985.

Post-Shutdown Complications

Following the emergency shutdown, operators encountered additional complications while attempting to maintain proper cooling of the reactor core. The reactor core isolation control system, a critical safety mechanism designed to pump water into the reactor during emergencies, initially failed to operate because internal reactor pressure remained too high.

"After the scram, operators struggled to keep the pressure right inside the reactor as they tried to add water to keep the still-hot reactor core from overheating," according to a detailed timeline compiled by federal regulators.

Operators eventually resolved the pressure issue by releasing steam and briefly activating a high-pressure water spray system, which reduced internal pressure sufficiently to allow the isolation control system to function properly.

Federal Citations and Training Concerns

The NRC's subsequent investigation, detailed in a March 29, 2019 report, identified training and simulation deficiencies that contributed to the operators' initial inability to activate critical safety systems. The agency issued two low-level violations to plant owner Entergy Corporation, citing both the operational problems during the December incident and the company's failure to address recurring issues with a different pump system.

"Clearly they have kind of persistent problems with controlling this reactor," said Edwin Lyman, a senior scientist with the Union of Concerned Scientists. "The unplanned scram rate is high."

The facility experienced another unplanned shutdown just two months later, in February 2019, due to problems with a turbine valve—further evidence of the plant's operational challenges.

Reactor Age and Safety Implications

Grand Gulf's operational difficulties come as the facility approaches its fifth decade of service. Construction began in May 1974, and the plant was commissioned in 1985, making it 40 years old as of 2025. The facility houses a General Electric boiling water reactor with Mark III containment, representing technology from the 1970s and 1980s.

At the time of the 2018 incident, Grand Gulf was one of only three nuclear plants nationwide not rated at the highest safety level by federal regulators. Since 2016, the plant has frequently operated below full capacity, which can stress regional power supplies and contribute to higher electricity prices across the Southeast.

The facility's reliability issues have broader implications for Mississippi's energy security. Grand Gulf generates approximately 16% of the state's electricity while emitting no greenhouse gases, making it a critical component of the regional power grid.

Backup Systems and Safety Protocols

Nuclear plants like Grand Gulf rely on multiple layers of safety systems designed to prevent core damage even during equipment failures. The reactor core isolation control system that initially malfunctioned during the December 2018 incident represents one of several emergency core cooling systems required by federal regulations.

These backup systems are tested periodically to ensure they can deliver specified water flow rates under varying pressure conditions. Equipment failures during such testing have previously forced extended shutdowns at Grand Gulf, including a month-long outage in 2017 when a residual heat removal pump required replacement.

The reactor's emergency cooling systems are housed in a structure adjacent to the main containment building and are designed to operate independently of normal plant systems. During the December 2018 incident, operators successfully utilized alternative cooling methods when the primary system initially failed to function.

Economic and Regulatory Context

Grand Gulf is owned 90% by Entergy Corporation through its subsidiary System Energy Resources Inc., with the remaining 10% owned by Cooperative Energy. The facility employs more than 800 people with an annual payroll exceeding $113 million and contributes approximately $30 million in state and local taxes.

The NRC has granted Grand Gulf an operating license extension through 2044, allowing the facility to continue providing power for another two decades. However, the plant's recent performance record has raised questions about its long-term reliability as it ages.

Entergy officials have emphasized their commitment to continuous improvement following the federal citations. "We respect and value the NRC's feedback," company spokesman Mike Bowling stated in response to the regulatory findings. "We are currently reviewing the report for full understanding and incorporation into our plans for continuous improvement and achieving excellence."

The December 2018 incident and subsequent regulatory response highlight the ongoing challenges of operating aging nuclear infrastructure while maintaining the highest safety standards. As the U.S. nuclear fleet continues to age, with most reactors now operating beyond their original 40-year design life, incidents like those at Grand Gulf underscore the importance of robust maintenance programs and operator training to ensure public safety.

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Sources

1. Associated Press. "Nuclear regulator cites plant for 2 low-level violations." April 12, 2019. https://apnews.com/a299553e00974b7098d1f664c429faf1

2. Insurance Journal. "Mississippi Nuclear Plant Cited for 2 Low-Level Violations." April 17, 2019. https://www.insurancejournal.com/news/southeast/2019/04/17/524042.htm

3. Wikipedia. "Grand Gulf Nuclear Station." Accessed April 26, 2025. https://en.wikipedia.org/wiki/Grand_Gulf_Nuclear_Station

4. Mississippi State Senate. "SC 525 (As Adopted by Senate) - 2025 Regular Session." 2025. https://billstatus.ls.state.ms.us/documents/2025/html/SC/SC0525PS.htm

5. Entergy Nuclear. "Grand Gulf Nuclear Station." https://www.entergy-nuclear.com/sites/grand-gulf/

6. U.S. Nuclear Regulatory Commission. "Grand Gulf Nuclear Station, Unit 1." https://www.nrc.gov/info-finder/reactors/gg1.html

7. Union of Concerned Scientists. "Grand Gulf: Emergency Pump's Broken Record and Missing Record." October 31, 2017. https://blog.ucs.org/dlochbaum/grand-gulf-emergency-pumps-broken-record/