Case studies

On Hana's last day in regulatory affairs, Elena Marchetti gathers the whole cast of her rotation in the conference room: Teodora Vasquez, Rohan Desai, Malik Osei, Marcel Thibodeau and Lise Fortin. "We each chose one case," Elena says. "Not because they are the most famous, but because each one taught the regulators something they still use. Hana, your job is to tell us at the end what they have in common." This lesson follows their cases, each read through the ideas of the earlier lessons.

Case 1: Ontario Hydro and the 1997 lay-up

Marcel goes first, because he was there. In the mid-1990s the performance of Ontario Hydro's nuclear stations had been declining for years. The Atomic Energy Control Board had raised concerns repeatedly, and in 1997 the utility commissioned an independent integrated performance assessment by a team of experienced managers, many from the United States. Its report, delivered in August 1997, rated the performance of the nuclear division as minimally acceptable and found deep problems in management, safety culture, maintenance and the handling of known issues. In response the utility laid up seven of its oldest reactors, the four units of Pickering A and three units at Bruce A, so that it could concentrate its resources on the newer stations.

The recovery took years. Pickering A Units 4 and 1 returned to service in 2003 and 2005 after costly rehabilitation, while Units 2 and 3 never restarted. Bruce A Units 3 and 4 restarted in 2003 and 2004 under Bruce Power, which leased the Bruce site from 2001, and Units 1 and 2, which had been shut down earlier, were refurbished and restarted in 2012. The episode reshaped Canadian nuclear governance: Ontario Hydro was split up in 1999 and its generating business became OPG, and the regulator, renamed the CNSC in 2000, adopted a more systematic approach to rating licensee performance.

The lesson Marcel draws is that a regulator can see a problem for years without forcing it to be fixed, and that the most important indicators of decline are organizational: backlogs that grow, concerns that go unanswered, and managers who stop hearing bad news. The tools in lesson 7, from performance ratings to the attention paid to the corrective action programme, were shaped by cases like this.

Case 2: The NRU shutdown and regulatory independence

Teodora's case tests the principle of independence from lesson 1. In November 2007 the NRU research reactor at Chalk River, then the source of a large share of the world's supply of molybdenum-99 for medical imaging, was shut down for routine maintenance. The CNSC found that upgrades to the reactor's emergency power supply for its cooling pumps, which were required by its licence, had not been completed, and the operator kept the reactor shut down while the issue was addressed. The resulting shortage of medical isotopes became an international crisis. In December 2007 Parliament passed a law authorizing the reactor to restart for 120 days notwithstanding the licence, and in January 2008 the government removed Linda Keen from her position as President of the CNSC.

The episode is still debated. Supporters of the government's action argued that the health risk to patients from the isotope shortage outweighed the small incremental risk from running the reactor before the upgrade was complete. Critics argued that the government had overridden an independent regulator's decision for political reasons, setting a precedent that could weaken safety everywhere, and noted that the reactor's owner had not met its own licence. Teodora's view is that both safety and independence were at stake, and that the episode showed why a regulator must be able to explain its decisions in terms of risk, and why governments must be very cautious about overriding them. The upgrade was later completed, and the NRU reactor continued to operate until it was permanently shut down in 2018.

Case 3: Fukushima Daiichi and regulatory capture

Lise's case is the 2011 accident at Fukushima Daiichi, which she followed closely because of its effects on the ocean. The earthquake shut the operating reactors down safely, but the tsunami that followed flooded the site, disabled the emergency diesel generators and electrical switchgear and caused a loss of all cooling at three reactors, whose cores melted. Hydrogen explosions damaged the reactor buildings, and radioactive releases led to the evacuation of more than a hundred thousand people. The independent investigation commission set up by the Japanese parliament concluded in 2012 that the accident was preventable and called it a profoundly man-made disaster: the regulator and the operator had known for years that larger tsunamis were possible but had not required or made the necessary improvements, and the regulator had lacked independence from the industry and the ministry that promoted nuclear power.

Japan responded by creating the Nuclear Regulation Authority in 2012, an independent body outside the ministry that promotes nuclear energy, which wrote new requirements and required every reactor to show that it met them before restarting. Regulators around the world reviewed their own plants, as lesson 1 described. Lise draws a lesson about the danger of regulatory capture, where a regulator comes to share the views and interests of the industry it regulates, and about the importance of revisiting the design basis when new evidence about natural hazards emerges.

Case 4: Licensing a new build

Teodora takes a second case, this time from the United States, because it is the most recent completed new build in North America. The Vogtle 3 and 4 project in Georgia received the first combined licences under Part 52 in 2012, for two AP1000 reactors. Construction was beset by problems: the first-of-a-kind modular construction proved harder than planned, the design needed many licence amendments, the reactor vendor filed for bankruptcy in 2017 and the cost rose to more than thirty billion dollars. Unit 3 entered commercial operation in 2023 and Unit 4 in April 2024. The project showed both that the Part 52 process can deliver licensed reactors and that licensing is only one of the risks of a first-of-a-kind project.

The contrast with recent SMR projects is instructive. The BWRX-300 at Darlington received its licence to construct in April 2025 and the Clinch River unit its construction permit in 2026, each after reviews of roughly two years, helped by shared technical work between the two regulators and by the use of existing sites with completed environmental studies. Whether construction goes more smoothly than at Vogtle will be the real test. Teodora's lesson is that licensing success depends on a mature design and good preparation, and that construction success depends on supply chains, workforce and project management that the regulator does not control.

Comparing the timelines

Elena asks Hana to put the cases on a common time axis, measuring how long each took from the first warning signs to the regulatory response, and from the response to the outcome.

# Durations between milestones in the case studies (years rounded; early warning dates approximate).
cases = {
    "Ontario Hydro lay-up": {"warnings": 1993, "response": 1997, "outcome": 2003},
    "Millstone": {"warnings": 1992, "response": 1996, "outcome": 1998},
    "Davis-Besse": {"warnings": 1998, "response": 2002, "outcome": 2004},
    "Fukushima Daiichi": {"warnings": 2008, "response": 2011, "outcome": 2012},
    "Vogtle 3 and 4": {"warnings": 2008, "response": 2012, "outcome": 2024},
}
labels = {"Vogtle 3 and 4": ("application", "licence", "Unit 4 operation"),
          "Fukushima Daiichi": ("tsunami estimate", "accident", "new regulator")}
for name, m in cases.items():
    a, b, c = labels.get(name, ("warning signs", "regulatory response", "first recovery"))
    print(f"{name:22s} {a} -> {b}: {m['response'] - m['warnings']:2d} y   {b} -> {c}: {m['outcome'] - m['response']:2d} y")
decline = [m for n, m in cases.items() if n != "Vogtle 3 and 4"]
avg = sum(m["response"] - m["warnings"] for m in decline) / len(decline)
print(f"mean time from first warning to response in the decline cases: {avg:.1f} years")

Ontario Hydro lay-up   warning signs -> regulatory response:  4 y   regulatory response -> first recovery:  6 y
Millstone              warning signs -> regulatory response:  4 y   regulatory response -> first recovery:  2 y
Davis-Besse            warning signs -> regulatory response:  4 y   regulatory response -> first recovery:  2 y
Fukushima Daiichi      tsunami estimate -> accident:  3 y   accident -> new regulator:  1 y
Vogtle 3 and 4         application -> licence:  4 y   licence -> Unit 4 operation: 12 y
mean time from first warning to response in the decline cases: 3.8 years

The output makes a pattern visible. In every case of decline, warning signs preceded the regulatory response by years, and recovery took years more. The time from warning to response is the window in which a regulator, or the licensee itself, could have acted at much lower cost. The new build cases show a different pattern: long licensing and construction periods for the first unit, which the industry hopes to shorten for the units that follow.

What the cases have in common

At the end of the session Hana gives her answer. In each case of decline, the hardware problem was real but the root cause was organizational: management that did not want to hear bad news, a regulator that was too slow, too close to the industry or overruled, and warning signs that were noticed but not acted on. In each case recovery required changes in people, culture and oversight, not just repairs. And in each case the lesson was built into the regulatory system that exists today, from performance ratings and the reactor oversight process to independence, safety culture oversight and periodic re-examination of the design basis. The new build cases add a different lesson: that clear, predictable licensing is necessary but not sufficient for a project to succeed.

Elena nods. "That is the job," she says. "Not just to know the rules, but to remember why they were written. Every page in that binder I gave you on your first day has a story like these behind it."

Two cases from across the border

Rohan adds two cases from the United States that Canadian regulators studied closely. At Millstone in Connecticut, engineers raised concerns in the early 1990s that the plant was operating outside its licensing basis and that management was ignoring them. Their persistence exposed a culture in which workers who raised concerns were harassed, and in 1996 the NRC kept all three units shut down until the licensee had replaced its management and reviewed its design basis. At Davis-Besse in Ohio in 2002, workers found that boric acid leaking from a cracked nozzle had eaten a cavity through the carbon steel of the reactor vessel head, leaving only the thin stainless steel cladding to hold the pressure. The NRC had agreed to let the plant run a few more months before inspecting, and the licensee had cleaned acid deposits for years without finding their source. The plant stayed down for two years, and the NRC imposed what was then its largest civil penalty.

Placed side by side, the four North American cases show the same pattern in two different regulatory systems. Each began with technical symptoms that were noticed but not acted on, each involved an organization that had stopped listening to its own people or to its regulator, and each changed how regulators in both countries think about oversight.

Safety culture as a regulatory topic

One outcome of these cases is that regulators now treat safety culture as something they can and should assess. Safety culture is commonly described as the assembly of characteristics and attitudes in an organization and its people that establishes that, as an overriding priority, safety issues receive the attention warranted by their significance. It shows in whether workers raise concerns and managers act on them, in whether procedures are followed and questioned when they seem wrong, in whether decisions favour safety when it conflicts with schedule or cost, and in whether the organization learns from its own experience and that of others.

The CNSC published REGDOC-2.1.2, Safety Culture, in 2018, which requires licensees of Class I facilities and uranium mines and mills to foster a healthy safety culture, to assess it periodically and to act on the results. CNSC staff review the assessments and observe safety culture during inspections, though they do not rate it as a separate area.

Rohan adds a caution about measurement. "You cannot audit culture the way you audit a test record. Surveys and interviews help, but the real evidence is in how people behave when something goes wrong and nobody is watching. That is why the best indicator is still the corrective action programme: how many problems people report, how quickly they are fixed, and whether the same problem comes back."

Lise adds that the cases are not only about failure. In each, people inside the organizations saw the problems and spoke up, and in each the eventual response, though late, made the system stronger. "The test of a regulatory system is not whether it ever fails," she says, "but whether it learns when it does, and whether it listens to the people who see trouble coming."