Share Button

Diablo and the deep blue sea: A shelved NRC tsunami study is generating new interest 11 years later

New Times (2014-08-07) Colin Rigley

This Page:
Media Link:
More Info: Shutdown Diablo

Diablo and the deep blue sea: A shelved NRC tsunami study is generating new interest 11 years later


Despite its 85-foot elevation above sea level, an NRC report more than a decade old could reach different conclusions about the potential tsunami threat at Diablo Canyon—but that report remains outside the public view.

On March 16, 2011, the full picture was beginning to come into focus of just how bad things were in Fukushima, Japan.

A massive earthquake and corresponding tsunami knocked out power and backup systems at the Fukushima Daiichi Nuclear Power Plant, and at the time Japanese officials were asking residents within 12 miles of the plant to evacuate as dangerous levels of radiation were threatening to reach surrounding areas, according the LA Times. Officials with the U.S. Nuclear Regulatory Commission (NRC) were telling Americans to evacuate at least 50 miles from the plant, while British officials warned foreign nationals as far away as Tokyo to flee even farther.

On that same day, at 9:44 a.m., a man named Dr. Robert Sewell sent an email to Dr. Nilesh Chokshi, deputy director of the NRC’s Division of Site and Environmental Reviews in the Office of New Reactors. In the email, Sewell attached several reports that dated as far back as 2003 and “that pertained to the tsunami licensing bases for Diablo Canyon Power Plant and, more generally, to other coastal U.S. plants.”

“Unfortunately, the recommendations went unheeded at that time, and the NRC was not then willing to open up the prospect of re-evaluating the tsunami design basis for [Diablo Canyon Power Plant],” Sewell wrote in that email.

“… A major problem that I believe remains is the limited scope of tsunami generators that are often included in tsunami studies, the lack of a complete treatment of epistemic uncertainty, and the lack of resolve to truly re-evaluate facilities.”

Sewell said that he’d visited Diablo Canyon the previous year, during which PG&E presented its latest tsunami hazard assessment.

“Following that (admittedly) brief assessment, my concerns with the plant remained and do even more so today (in general, for all coastal [nuclear power plants]),” he wrote.

That email was released as a small fraction of a massive FOIA dump MSNBC published in March of this year on the third anniversary of the Fukushima disaster. Within the thousands of pages of emails, internal documents, and redacted papers, MSNBC uncovered that within the first days of the mounting disaster, NRC officials were strategizing a public message to assure that what happened in Fukushima could not happen here. In some cases, this was the message whether they knew for certain it was true.

In one email sent March 20, 2011—which New Times has left unedited—Communications Director for the Office of the NRC Chairman Susan Loyd wrote: “Chu got in a bit of trouble whrn asked directly if US plants could withstand a 9,0 earhquake. He talked aboit acceleration and shaking. Was directly asked about what diablo canyon could handle. He got tied up in saying aboit 6.2.”

A few minutes later, Public Affairs Officer David Mc Intyre wrote, “He should just say ‘Yes, it can.’ Worry about being wrong when it doesn’t. Sorry if I sound cynical.”

Three days after those emails were sent, and exactly one week after Sewell sent his message, Chokshi forwarded Sewell’s correspondence. According to various NRC public documents, it was the first time since 2006 that anyone had discussed Sewell’s report related to tsunamis and potential flooding at Diablo Canyon. Though Sewell’s report was later discussed again in the aftermath of Fukushima, the NRC maintains—as of its most recent analysis—that the findings aren’t subject to further outside review, nor suitable for regulatory decision making, and the report is exempt from public disclosure.

Sewell himself hasn’t been provided an opportunity to discuss the report with NRC staffers. Pacific Gas & Electric (PG&E), which operates Diablo Canyon, was never issued a copy, even as the utility continues its work toward applying for a new license to extend operations of both reactors for another 20 years beyond the license expiration dates in 2024 and 2025, respectively.

What is known about the report is due, in large part, to David Weisman.

‘Regulatory bugaboo’

At the heart of Diablo Canyon sits its control center, where technicians monitor identical sets of instrumentation for each of the plant’s two reactors.

Weisman, outreach coordinator for the ratepayer advocacy group the Alliance for Nuclear Responsibility, said he first came across Sewell’s report “a few years ago when [he] was investigating the problems of transparency and opaqueness, generically, as a nuclear industry or regulatory bugaboo.”

When an associate first showed him the report, it was more of a curiosity because the report had been redacted in its entirety. Weisman said he didn’t think much of it. That was before Fukushima, before public perception of the U.S. nuclear industry became tied with earthquakes and tsunamis, and before most eyes were looking at coastal power plants like Diablo Canyon.

A few years later, when Weisman saw Sewell’s name pop up again in the email obtained by MSNBC, he remembers thinking, “Wait a minute, here’s that guy’s name again.”

“It was one thing when it was an abstract study; it’s another thing when the author, Dr. Sewell, raises the ante,” Weisman told New Times. “When the author does that, I’m like, ‘Now I’m concerned.’”

Weisman is small in stature, and he regularly speaks publicly about Diablo Canyon with the cadence and mannerisms of a confident Woody Allen. As he’s wont to do, he recently rehashed what he’d learned at a nuclear oversight group, specifically the Diablo Canyon Independent Safety Committee in June.

“I thought that would be a really interesting report to see then from Dr. Sewell, but I can’t, because the entire thing is redacted,” Weisman told committee members, including Dr. Robert Budnitz, who later noted that Sewell is a long-time friend and colleague.

“Because?” Budnitz asked.

“We don’t know,” Weisman said, then read a response he received from an NRC representative.

In that response, a copy of which was provided to New Times, the NRC rep said, “Diablo Canyon has been deemed safe to operate based on our current understanding of potential external hazards for the site and the design and construction of the facility.”

In regard to Sewell’s report, the representative said the NRC had reviewed it several times, most recently when the Japan FOIA Task Force “determined that this document falls under relevant FOIA exemptions for draft documents. … However, this report, even in its draft form, was appropriately considered during NRC licensing reviews for Diablo Canyon.”

“Wait up; wait up,” Budnitz said after Weisman finished reading. “So it was submitted to the NRC and they’ve somehow determined that it’s exempt from Freedom of Information Act release? … That sounds outrageous.”

When New Times contacted Budnitz after that meeting, he provided little comment, but said, “We asked the NRC for a copy of the report,” and, “They’re working on it.”

He added, “And when we get it, we’re going to review it.”

More than a decade after the report was created, others are now making the same request. According to NRC Public Affairs Officer Scott Burnell, there have been “congressional requests related to the report,” though he declined to specify when asked which member or members of Congress were seeking it out.

A representative for Sen. Diane Feinstein said her office hadn’t made such a request. Calls and emails to the offices of Sen. Barbara Boxer and Rep. Lois Capps—both of whom have spoken publicly about issues related to Diablo Canyon and the NRC—weren’t returned as of press time.

To date, ostensibly no one outside the NRC umbrella has been able to read, analyze, or discuss Sewell’s report in detail. Diane Curran, a Washington, D.C., attorney who’s represented such groups as the San Luis Obispo Mothers for Peace, said she, too, plans to ask for a copy of the report.

“There’s a pattern when documents are critical of the safety situation at Diablo, that it’s hard to get them,” she said. “The process moves awfully slowly.”

What we do know

On a tour of Diablo Canyon, New Times was taken below one of the two massive steam turbines to see the guts of the only active nuclear power plant in California.

About all that is known about Sewell’s report has been inferred from what the NRC has said is wrong with it.

On April 28, 2005, three offices within the NRC—the Office of Nuclear Material Safety and Safeguards (NMSS), the Office of Nuclear Reactor Regulation (NRR), and the Office of Research (RES)—held a meeting to discuss Sewell’s report, just months after the late-2004 Indian Ocean earthquake and tsunami. In a May 5, 2005, NMSS memo outlining that meeting, staffers decided to revisit Sewell’s report.

The report was originally prepared to identify potential tsunami hazards to Diablo Canyon’s above-ground spent fuel storage, which has since been installed but at the time was still a PG&E proposal to add dry-storage infrastructure perched on a hill above Diablo’s two reactors. While the NRC allowed construction of those dry-storage casks per various satisfactory hazard studies, Sewell’s report outlined 13 tsunami scenarios that, based on his conclusions, indicated that earlier tsunami predictions didn’t go far enough.

“Although NMSS did not rely on the information in the report in reaching a licensing decision on Diablo Canyon [spent fuel storage], NMSS recognized that the issues identified in the report could have broader applicability and should be provided to the other program offices for consideration,” staff said in the May 5, 2005, memo.

Located on a small portion of a larger sequestered expanse of rugged coastal land, a few miles northwest of the first PG&E security checkpoint near Avila Beach, Diablo Canyon’s two reactors rest comfortably at 85 feet above sea level, well beyond the reach of most large waves. At such an elevation, regulators say the plant is safe from any tsunami up to 32 feet above mean sea level. According to the existing hazard assessment, a wave larger than 32 feet has an annual probability of about two in 1 million. The Fukushima plant, by comparison, is located at only about 20 feet above sea level, a fact that nuclear industry experts regularly use to illustrate the vast differences between the two facilities.

“At Diablo Canyon, PG&E has taken many steps to further safety at the plant site and to prepare for the unexpected, including extreme events that could challenge the plant’s design,” PG&E spokesman Blair Jones said in a written response. “We began this work immediately following the Fukushima accident, which includes adding additional backup systems to provide an uninterrupted supply of electricity and cooling water to protect critical plant safety systems at all times.”

On a recent New Times visit, plant operators highlighted the backup generators and battery system that could keep vital components running in the event of a disaster.

In addition to a number of other studies about potential hazards, PG&E is continuing to draft a re-evaluated flood hazard report, which is due to the NRC in March 2015. The standing hazard analysis concludes that the plant is safe to operate. And in its post-Fukushima studies, the NRC Near-Term Task Force concluded that an accident on par with Fukushima “is unlikely to occur in the United States.”

“While we haven’t received a copy of the [Sewell] report, we have performed work on analyzing methodologies to determine how to update the tsunami hazard and the effects of underwater landslides,” Jones said. “… Using the latest models, techniques, and methodologies, experts are quantifying and re-evaluating various tsunami scenarios, including those generated by underwater landslides, and comparing them against the plant’s design to ensure it is safe.”

He added that the plant’s seawater intake structure and pumping equipment are designed for a wave height of 45.5 feet, and is well above the largest anticipated wave height of 32 feet.

However, Sewell reportedly reached a different conclusion. One leaked page of his report obtained by New Times gives a small glimpse of Sewell’s conclusions that seem to contradict Diablo Canyon’s previous flood-hazard design, and it calls for further studies. Though the specific scenarios aren’t detailed, the “Site Challenge Impact Matrix” raises questions of how Diablo Canyon’s various systems would fare when put up against 13 “landslide scenarios” that might occur as frequently as every 1,500 years, to as infrequently as every 500,000 years. According to the matrix, the main plant site, perched 85 feet above sea level, would be susceptible in all but two of the hypothesized scenarios.

Furthermore, the study found that the plant’s auxiliary saltwater system could be impacted in all 13 scenarios.

In early 2006, the NRC’s Seismic Issues Technical Advisory Group (SITAG) determined that Sewell’s study was, essentially, wrong, and to be kept as an internal document. According to an analysis released on Jan. 17 of that year, SITAG staff determined that Sewell’s conclusions relied on incorrect assumptions and low-resolution data. Additionally, they said Sewell failed to account for the relatively low slope of the ocean floor as it leads to the Diablo Canyon site, which would make it unlikely for the same large waves as those that occur in other parts of the world.

In a subsequent memo to the NMSS director, staff determined that the report “was not suitable for regulatory applications.” The memo further shows that staff considered releasing the report to PG&E, along with their analysis of the findings, but “received direction form the Commission that the report was not to be released.”

The memo concludes: “staff is terminating further consideration of the draft report.”

With those words, the NRC intended to shelve Sewell’s report indefinitely—and likely would have, had it not been for the Japanese earthquake five years later, and had it not been for Sewell’s email urging the NRC to reconsider the matter.

In an email response, Sewell told New Times that he “has an interest in discussing the study, but only if the study sponsors make the study publicly available … and in that case, I believe it would be appropriate for the sponsors to also first seek my explanation and discussion concerning the study.”

It’s that point—that no one outside the NRC has had the chance to dissect the report with NRC staff, including Sewell himself—that concerns people like Dave Lochbaum.

“It seemed like he sincerely felt it was relevant to the current problem,” Lochbaum said. “So I’d like to see the report to see if I can agree or disagree with the decision.”

Lochbaum is director of the Nuclear Safety Project for the Union of Concerned Scientists and one of the authors ofFukushima: The Story of a Nuclear Disaster. In his discussions with NRC staffers, Lochbaum said he was assured that previous and ongoing tsunami studies at Diablo Canyon and other nuclear power plants will fully address the issues Sewell raised, even if his report isn’t referenced directly. But without an opportunity to pore over Sewell’s existing work, Lochbaum said it’s difficult for outsiders to know whether the eventual tsunami analysis takes into consideration all of the potential bizarre scenarios nature has up its sleeve.

“You just don’t know, if it’s not relevant or if it’s been superseded,” Lochbaum said of the report’s conclusions and whether they’ll be incorporated into new studies. “Just show us the report and prove it to us.”

And historically, he said, the NRC hasn’t always been adept at analyzing unforeseen scenarios. Lochbaum said this particular report was disregarded, in part, because Sewell used methods that were “beyond state of the art,” which was the language used in the 2006 staff assessment. In other words, Sewell’s methods “departed from the traditional analytic process,” Lochbaum said.

“What the NRC traditionally doesn’t do is start combining things: an earthquake that causes a fire,” Lochbaum said as an example. “Sewell did look at that.”

Sewell isn’t known as some renegade engineer with whacked-out theories or a reputation for fear-mongering through shoddy work. Today, he’s still working as a consultant in probabilistic hazard and risk analysis. As Budnitz said during the June Independent Safety Committee meeting, “Sewell is a colleague of two decades’ standing with me. … He’s absolutely a terrific engineer, thoughtful and careful.”

But when it comes to a report that appears to question the historic conclusions about Diablo’s safety from tsunamis and flooding, Weisman said “they just brush it off the table.”

“All we’re saying is, ‘What’s in this report?’ And if it’s debatable, let Dr. Sewell unzip his lips,” Weisman said. “Let him have the opportunity to defend his work in public.”

In the time since Sewell released his report, PG&E has amassed a glut of new data about the seismicity of the area surrounding Diablo Canyon. Various seismic experts have convened in myriad research groups, most notably the Senior Seismic Hazard Analysis Committee, to analyze new data obtained through two-dimensional and three-dimensional studies. In fact, in the time since Sewell’s report made its way through the NRC, geologists discovered a new fault line, the Shoreline Fault, located about 600 yards offshore, according to the 2011 Near-Term Task Force Review for the NRC.

But what little is known about Sewell’s report came about almost by accident. Asked what might have happened if Sewell hadn’t sent that email back in March 2011, Weisman said the report “would still remain buried.”

“Or we’d just be looking at it as an amusing, yet frightening, pile of blank pages.”

Contact Senior Staff Writer Colin Rigley at

Additional documents:


Media Form edit

Title Diablo and the deep blue sea: A shelved NRC tsunami study is generating new interest 11 years later
Publisher New Times
Author Colin Rigley
Pub Date 2014-08-07
Media Link
Embed HTML
Forum Link
Keywords Shutdown Diablo
Media Type Linked Article
Media Group News
Curator Rating Plain
Author Name Sortable
Thumbnail Link
Topic revision: r2 - 10 Aug 2014, RaymondLutz
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding Cops? Send feedback