The US public deserves to have a clear understanding of the safety and security of the nation’s 54 nuclear plant sites (with a total of 94 operating nuclear reactors): and in particular, the plants that are the poorest performers.
Unfortunately, the Nuclear Regulatory Commission (NRC) doesn’t make it particularly easy for the public to figure that out. And it may get even more difficult if Trump administration executive orders to fully deregulate nuclear power are carried out. But not to worry. Your friendly neighborhood nuclear safety advocate has been diligently compiling this information—so you don’t have to! Without further ado, here are the “Terrible Thirteen:” the baker’s dozen of nuclear plant sites (about 25 percent of the fleet) with the highest (weighted) number of safety and security “findings” discovered by NRC inspectors in calendar years 2022-2024. (A “finding” is a problem that is not exactly the same as a “violation,” but it is close enough. And see text below for an explanation of the weighting process.)
The Terrible Thirteen, 2022-2024
Single-Unit Plants
| Plant | Type | Owner/ Operator | Nearest Population Center | NRC Region | Weighted number of violations (Green + 5x White/ GTG*) |
| River Bend-1 | Mark III BWR | Entergy Nuclear | Baton Rouge, LA (24 mi) | IV | 70 (60 G, 2 W) |
| Grand Gulf-1 | Mark III BWR | Entergy Nuclear | Vicksburg, MS (20 mi) | IV | 58 (58 G, 0 W) |
| Waterford-3 | CE-PWR | Entergy Nuclear | New Orleans, LA (25 mi) | IV | 52 (32 G, 4 W) |
| Fermi-2 | Mark I BWR | DTE | Toledo, OH (25 mi) | III | 41 (41 G, 0 W) |
| Wolf Creek-1 | W-PWR | Wolf Creek Nuclear | Burlington, KS (3.5 mi) | IV | 39 (39 G, 0 W) |
| Davis-Besse-1 | B&W PWR | Energy Harbor | Toledo, OH (21 mi) | III | 36 (11 G, 5 W/GTG) |
| V.C. Summer-1 | W-PWR | Dominion Generation | Columbia, SC (26 mi) | II | 36 (11 G, 5 W/GTG) |
Dual-Unit Plants
| Plant | Type | Owner/Operator | Nearest Population Center | NRC Region | Green + 5 x White/GTG |
| Watts Bar-1,2 | W-PWR | Tennessee Valley Authority | Knoxville, TN (60 mi) | II | 53 (38 G, 3 W/GTG) |
| Millstone-2,3 | CE/W-PWR | Dominion Generation | New London, CT (3.2 mi) | I | 48 (38 G, 2 GTG) |
| Quad Cities-1,2 | Mark I BWR | Constellation | Moline, IL (20 mi) | III | 48 (38 G, 2 W) |
| Farley-1,2 | W-PWR | Southern Nuclear | Dothan, AL (18 mi) | II | 42 (22 G, 4 W/GTG) |
| South Texas Project-1,2 | W-PWR | STP Nuclear/ Constellation | Houston, TX (90 mi) | IV | 42 (42 G, 0 W) |
| Calvert Cliffs-1,2 | CE-PWR | Constellation | Annapolis, MD (40 mi) | I | 41 (21 G, 4 W) |
Key
| W: Westinghouse | B&W: Babcock and Wilcox | CE: Combustion Engineering | PWR: pressurized-water reactor | BWR: General Electric boiling-water reactor | Mark I, III: Denote containment designs |
Source: U.S. Nuclear Regulatory Commission (data accessed May 20, 2025).
*GTG: “Greater than Green.” For security-related findings, the NRC does not publicly disclose the specific severity level if it is greater than Green. Thus, the weighted count may be an underestimate for plants that have received a “Greater than Green” security finding if the underlying color is greater than White (that is, Yellow or Red).
What’s new about this list?
I found it necessary to compile this information because NRC doesn’t provide it to the public in a readily accessible form (although a new feature on the NRC website introduced last year makes it a lot easier). The NRC ranks the significance of safety and security violations discovered during inspections according to a four-color classification system. “Green” violations are considered of “very low” safety or security significance. “White and “Yellow” violations are of “low to moderate” and “substantial” significance, respectively. “Red” is reserved for those of “high” significance (and is very rarely issued). However, the NRC’s process for identifying problematic plants, as reflected in its own table, called the “Action Matrix,” is not based on a tally of the total number of safety and security violations that they rack up each year—but only takes into account the violations that the agency considers more significant.
In particular, the agency does not escalate its level of regulatory oversight over a nuclear plant based on the number of inspection findings that it determines to be Green (“very low safety significance”), no matter how many of them the plant accumulates over a given period. Thus Grand Gulf, a nuclear plant that received 27 Green violations in 2024, is currently in the highest performance category (Column 1)—the same as Clinton, which only received two violations.
I have serious concerns with this approach. Although the total number of violations at a nuclear plant—including the Green findings—doesn’t tell the whole story on its own, it is an important indicator of the plant’s overall safety and security performance.
On their face, many Green violations certainly sound more problematic than the “very low safety significance” label implies. Some of them involve serious operator errors or safety issues that plant owners were aware of or neglected for many years or decades. For example, Green findings were recently issued when the following problems were identified:
- The Waterford plant in Louisiana failed to implement a program to address more than 2,500 corrosion issues, some identified as far back as 2011, with around 200 classified as severe and affecting critical safety-related systems.
- Workers at the Quad Cities plant in Illinois incorrectly wired two portable diesel generators after a surveillance test in 2023, rendering them inoperable for eight months before the problem was discovered. This occurred even though the plant had experienced such issues in the past and managers thought they had successfully corrected them. These generators are part of the set of emergency equipment that the NRC required nuclear plants to acquire after the 2011 Fukushima triple meltdown in Japan to help prevent such a disaster from happening here.
- Workers at the Calvert Cliffs plant in Maryland failed to follow procedures in 2017 and installed instrument wiring on a transformer too close to a live bus bar. In 2023, this caused a short circuit that triggered an automatic scram of the Unit 2 reactor and a shutdown of feedwater pumps. Scrams, or unplanned shutdowns, disrupt plant operations and have the potential to cause complications and even trigger serious accidents.
In my approximate determination of the weighted number of findings in the above table, I considered one White violation as equivalent to five Green violations. (There were no publicly documented Yellow or Red findings during the evaluation period.) A three-year period was chosen because some NRC inspections, such as fire protection and force-on-force security testing, occur on three-year cycles. Single-unit and multiple-unit plants are accounted for separately because for multiple unit plants, some findings apply only to one unit and others apply across the entire plant, making it hard to compare with single-unit sites.
How the NRC understates potential dangers
The process by which the NRC assesses U.S. nuclear plant safety and security and responds to violations has a long and fraught history. Once upon a time, the NRC maintained a “Watch List” of the plants which warranted increased regulatory scrutiny due to poor safety performance, which it updated every six months. For example, in January 1997, 14 nuclear reactors out of roughly 110 nationwide were on the list—the highest number since 1988—including all three units then operational at the Millstone plant in Connecticut. (Of those 14 reactors, six are now permanently shut down). Understandably, nuclear reactor owners loathed being placed on the Watch List.
In 1999, partly in response to a threat to drastically cut the NRC’s funding by Republican Senator Pete Domenici of New Mexico, the NRC adopted a new Reactor Oversight Process (ROP) that significantly overhauled its safety assessment process and eliminated the Watch List. A fundamental aspect of the new process was the introduction of the color-coded system—Green, White, Yellow, and Red—to rate the safety and security significance of inspection violations and determine the NRC’s regulatory response. Numerical thresholds for the increases in risk associated with inspection findings were established to delineate the boundaries between these categories. For instance, a Green finding corresponds to an increase in the annual likelihood of a core melt accident (such as the 1979 Three Mile Island accident) of one in one million or less. This is known as the “significance determination process.”
The color assignments of inspection findings partly determine where the NRC places each nuclear reactor on its Action Matrix. (The position is also based on the values of an additional set of metrics, called “performance indicators,” which are based on specific operational parameters, such as the unplanned shutdown rate, rather than inspection findings.) Reactors that only have Green inspection findings and performance indicators are placed in Column 1 of the matrix and subject to a normal level of oversight. However, even a single White finding or indicator will move the reactor to Column 2. One Yellow finding or three White findings in the same “cornerstone” (a specific area of facility operation) will move the reactor to Column 3. The higher the column, the more intensive the NRC’s regulatory response.
In addition, the NRC determined that multiple White findings in a related safety category (or “cornerstone”) should be aggregated to establish a reactor’s position in the Action Matrix. In contrast, however, the agency decided at the outset that Green findings would not be aggregated. This means that NRC’s level of inspection would be the same for any plant in Column 1 no matter how many Green violations were uncovered. The NRC argued that this was appropriate because the numerical risk corresponding to Green findings had no lower bound, so it couldn’t generally estimate the cumulative risk significance of multiple Green findings. And associating higher-risk violations with increased oversight does seem like a reasonable thing to do. However, it violates common sense to argue that the total number of violations, and their cumulative impact on risk, should not be also considered.
Even though the NRC does not escalate oversight based on the total number of Green findings, it does have a “cross-cutting issues” program that is designed to look for common themes among violations—including Green ones—that may signify broader organizational problems and a lack of safety culture. However, the program has undergone multiple changes over the years that have weakened its effectiveness. According to the “vast majority” of NRC staff surveyed for a 2020 review, the current program is ineffective because the threshold number of cross-cutting issues that a nuclear plant would have to have to trigger a more intensive examination is “too high to add any value,” resulting in a “failure to identify adverse trends in some cases.”
And the losers are …
It is apparent from the Terrible Thirteen list that Entergy Nuclear is over-represented, with three of its four nuclear plants making an appearance at the top of the single-unit category. River Bend and Grand Gulf are by far the worst violators. This does not come as a surprise, as accusations of financial problems and mismanagement of its nuclear fleet have swirled around Entergy for decades.
In 2021, the Louisiana Public Service Commission and other officials filed a complaint against Entergy at the Federal Electric Regulatory Commission (FERC), alleging that safety and reliability problems caused “sub-par” performance of the Grand Gulf nuclear plant and excessive costs for ratepayers. Entergy’s poor performance should be kept in mind as the company plans to increase the power output of its nuclear fleet—which works the reactors harder—and is even considering building a new reactor at the Grand Gulf site.
After Entergy, the company with the second-highest number in the Terrible Thirteen is Constellation, with three plants on the list (it is a co-owner of the South Texas Project). These include Quad Cities, where the NRC recently issued six violations for a potentially serious accident and coverup in 2023. (These are not included in the Terrible Thirteen tally because the NRC has not yet assessed their significance.) As Constellation is the nation’s largest owner of nuclear plants, with operating reactors at 14 sites, these poor performers represent about 20 percent of the sites that it owns or co-owns, which is not as bad as the 75 percent rate for Entergy. Dominion, which owns four nuclear plants, has two on the list, including Millstone, a plant with the doubly dubious distinction of also having been on the NRC’s last Watch List in 1999, although it had a different owner at the time.
A caveat: regional inconsistencies
There is one caveat to note when interpreting the data. It has long been observed that there are disparities among the four NRC regional offices in the issuance of violations: especially Green ones. In 2013 the Government Accountability Office (GAO) found that NRC’s Region IV, covering the western and south-central US (which includes Entergy’s plants) had the most Green findings averaged per reactor over the previous 12 years—nearly three times the rate as Region II, covering the southeast. The GAO pointed out at the time that the NRC had not conducted a comprehensive assessment of the reasons for this disparity, although it may have had to do with differences in the way personnel in the different regions identify and resolve findings (that is, Region IV inspectors are tougher than those in Region II).
A disparity apparently still persists today, as the rate of Green findings per plant in Region IV from 2022-2024 was more than twice the rate in Region II. Thus, the over-representation of Region IV in the Terrible Thirteen (38 percent, even though Region IV only has 22 percent of the plants) may be due in part to these regional differences. Even so, the numbers of violations racked up by all the plants on the list remain impressive.
The ongoing attack on NRC oversight
There is a strong case for the NRC to consider the total number of Green findings as an additional input into its Reactor Oversight Process—at least to see if it helps predict which plants may experience more serious problems in the future. Unfortunately, the NRC is headed in the opposite direction. Invoking the “spirit” of the ADVANCE Act—a 2024 law that is intended to make the NRC more “efficient” (that is, by getting out of industry’s way)—the agency is considering significant changes that would greatly weaken oversight and enforcement.
Instead of treating Green findings more seriously, the NRC is proposing to further downplay their significance by creating a new category of “good” performers that would get a reduced level of oversight based on sustained Column 1 performance (where “sustained” is not yet defined). That is, even a plant as violation-ridden as Grand Gulf (58 Green violations in 2022-2024 but none that were White or higher) could get rewarded for “good” performance as long as it did not get any greater-than-Green findings. Oversight programs that are being considered for reduction or elimination for these “good” performers include those that look for patterns that could signify an organizational lack of safety culture.
The sum total of these changes could create a blind spot for NRC inspectors that would make it even harder for the agency to identify and correct safety culture problems before they became significant enough to result in a serious nuclear accident—as almost happened at the Davis-Besse plant in Ohio in the early 2000s. Strong and independent regulatory oversight doesn’t only protect the public —it deters plant owners from cutting corners that could improve their bottom line but also jeopardize safety. Instead of weakening its inspection programs, the NRC should strengthen its mechanisms for detecting adverse safety trends and nipping them in the bud—and the total number of inspection findings is likely to be one critical input.