SAN DIEGO - For the first time, a source from inside the San Onofre nuclear power plant has come forward to warn that restarting the power plant is too dangerous.
"There is something grossly wrong," said the inside source, a safety engineer who worked at San Onofre and has 25 years in the nuclear field.
The source, who requested anonymity, is not alone in concerns over the safety San Onofre Nuclear Generating Station (SONGS).
*Click here for a timeline of San Onofre incidents
The concerns stem from inside the concrete containment walls, which house steam generators unique to the plant.
Japanese manufacturer Mitsubishi Heavy Industries (MHI) built replacement generators for the aging nuclear plant in 2010 and 2011.
"There were many, many changes," said Dr. Joe Hopenfeld, a former employee of the Nuclear Regulatory Commission (NRC). He described himself as pro-nuclear.
Hopenfeld spent his entire professional life working with steam generators and nuclear power. Though he lives in Maryland, he is familiar with San Onofre, which is run by Southern California Edison (SCE).
The new generators were designed to provide low cost power for decades. Instead, they shut it down in just eleven months because of a radiation leak.
"The manufacturer didn't have experience in this size unit," said Hopenfeld. "I have reviewed thousands of pages of assessment and reports that Edison has submitted."
He says the 2011 radiation leak that shuttered the plant revealed a potentially catastrophic problem with the tubes that carry scalding water.
"As far as I'm concerned, it's a very serious risk," Hopenfeld said.
Tubes carry water to and from the reactor core. This creates steam, which turns the turbines and produces energy.
"The tubes operate under very high pressure," Hopenfeld said, adding there is no protection provided between the tubes, which are placed in rows, to keep them from hitting each other.
Our sources said the redesign of the generators had unintended consequences. Tubes began hitting each other, creating cracks.
"These tubes were hitting each other -- that's dangerous," said Team 10's anonymous source.
He wants to remain anonymous because he told Team 10 he fears for his safety.
"When they made these changes, they did not look at the academic research nor use critical question and an investigative attitude," said the source.
Hopenfeld said the worst case scenario is a main steam line break, which he says could be caused by tubes cracking, the tube walls thinning or metal fatigue.
The anonymous insider and Hopenfeld said if there is a main steam line break, there is potential for the reactor core to overheat - which could mean a full or partial meltdown.
"Many tubes, and I don't know how many, have exhausted their fatigue life - they have no fatigue life left," Hopefeld said.
Just like the airline industry, the effect of fatigue on metal is something of concern in the nuclear industry.
While metal may not show the effects of fatigue to the naked eye, it is weakened after use.
According to Hopenfeld, that is what has happened inside SONGS.
SCE proposed a solution for the restart. The company said out of an abundance of caution, it would operate only Unit Two at 70 percent power if the NRC approves a restart.
Both Team 10 sources said that may reduce risk, but it is no guarantee of safety.
"Maybe the vibrations wouldn't be as severe, but it doesn't mean they are going away," Hopenfeld said.
"If an accident like this happens, (an) emergency plan is not geared to handle such a public safety devastation," the inside source said. "Those things have never been practiced or demonstrated in a drill scenario."
SCE did not agree with the insider's assessment of its disaster drills. A spokeswoman called late Thursday afternoon and said SCE runs drills four times a year and includes community partners.
The spokeswoman said the company plans for any issue that can happen at the plant.
Team 10 obtained an internal safety report that states in part:
With both units in shutdown due to leaks in the Steam Generator tubes, SONGS Senior Management attention is focused on resolving this problem and seeking NRC’s permission to restart the units. With SONGS under NRC, INPO, NOB, Public and Media scrutiny, Station cannot afford the luxury of dealing with adverse performance and publicity in Emergency Preparedness caused by declining SONGS Drill/Exercise Performance (DEP) indicator metric.
The inside source said the report refers to the plant's drill success rate. The NRC's website states the Exercise Performance Indicator monitors the "timeliness and accuracy of licensees performance in drills and exercises with opportunities for classification of emergencies..."
Hopenfeld and the inside source said no one can predict what will happen if the plant restarts.
"I am not trying to scare anybody -- you can live there, but you should know what the risk is," Hopenfeld said.
The NRC is expected to make a decision about the possible restart of San Onofre within the coming weeks.
SCE maintains the plant is safe to restart and declined an on-camera interview. SCE did send this statement:
While Dr. Hopenfeld has an extensive resume, his SONGS analysis is significantly flawed, reflecting his lack of specific expertise in tube vibration analysis provided by the three experts that performed SCE's analysis, which included more than 170,000 inspections.
The NRC is the appropriate authority to evaluate steam generator tube integrity and continues in that oversight and regulatory role for SONGS.
-- A fatigue analysis submitted by Dr. Hopenfeld to the CPUC contains many allegations that have been presented before and been refuted; the most obvious example is his criticism of the original initial 50.59 analysis for the Replacement Steam Generator. This issue has been addressed by the NRC in several public venues, and the NRC noted that SCE followed all required regulations in completing the 50.59 analysis.
-- Hopenfeld's fatigue analysis concerning in-plane tube vibration is significantly flawed in that it applies an unreasonably high stress concentration factor based on solid body geometry rather than the more realistic stress concentration factors for a cylindrical geometry applicable to the SONGS steam generator tubes.
SCE also responded to Team 10 questions by sending past news releases sent to regional media. Read those statements here.
Mitsubishi Heavy Industries is based in Japan. Team 10 emailed MHI specific questions. Here are those questions and answers:
Q: Edison says that a letter from MHI to the NRC proves that SCE believed the San Onofre nuclear plant's steam generators were safe when installed and that safety measures were not sacrificed for licensing reasons. Is that true?
A: MHI's top priority is, and always has been, the safe and reliable operation of all the plants and components that it designs, engineers, supplies and supports. In designing steam generators, minimizing tube wear due to tube vibration is always given a high priority, and this was a priority for MHI during the design of the SONGS replacement steam generators (RSGs). The SONGS RSGs were designed according to industry standards and our customer's specifications. The design went through an extensive review process which included the participation of third-party experts and MHI believed they would operate as expected: safely and successfully. No safety measures were sacrificed in the design.
Q: Why is the NRC's Augmented Inspection Team (AIT) putting all the blame on MHI and not SCE?
A: It is important to understand that the AIT Report reflected the NRC's understanding of the issues as of July 2012, and is just one part of an on-going inspection that the NRC has been conducting since the tube leak in one of the SONGS Unit 3 RSGs was detected in January 2012. MHI is committed to cooperating fully with the NRC in its inspection activities and has made and is making available internal MHI documents as they are requested.
Q: MHI knows how to build steam generators. Were Edison's design specifications faulty (Demanding 11% Additional Heat transfer area) or MHI did not how to build these San Onofre Replacement Steam Generators?
A: MHI has built more than 100 steam generators according to customer specifications, industry standards, practices and operating data and experience. MHI worked closely with SCE on the RSG design and fabrication, using the best available technology to meet the customer's specified requirements and the industry's high standards.
The SONGS RSGs experienced an unprecedented condition: in-plane tube vibration resulting in tube-to-tube wear. The NRC and other industry experts have confirmed that the occurrence of in-plane tube vibration causing tube-to-tube wear at SONGS was unexpected and without precedent and that MHI had followed industry practice in its design.
Q: Did SCE exceed the power limits in Unit 3 the generators could safely produce? Is it possible to anticipate these sort of problems? Does MHI know that Unit 2 steam generators were running at much higher pressures than Unit 3?
A: The SGs were designed to operate at the licensed power for SONGs, and to our knowledge that licensed power level was not exceeded. The thermo-hydraulic conditions in the RSGs for both SONGS units have been shown to be the same. The in-plane vibration and related tube-to-tube wear discovered at SONGS had never been previously observed in an operating nuclear power plant of this design. The in-plane tube vibration, observed at the steam generators of Unit 3, was caused by the use of smaller, more uniform tube-to-support gaps than Unit 2, which reduced the contact force available to restrain tube movement in the in-plane direction.
Q: Is there a way to measure fatigue in the tubing you created?
MHI did analyze the potential for fatigue failure of the RSG tubes under operating conditions and determined that fatigue was not a credible tube failure mechanism because the stresses sustained by the tubes due to in-plane vibration are well below the stresses that would cause fatigue failure. The analysis that supports this conclusion is contained in Appendix 16 to the "Tube wear of Unit-3 RSG - Technical Evaluation Report." It should be noted that the technical reviews and analysis, both by the NRC and industry experts, have not mentioned fatigue failure of the tubing.
A: What is the possibility that the “tubes” at issue could be removed from UNITS 2 & 3? What are the problems you might face in pulling this off? Is this a cost effective solution? Has your firm ever done tube removal at other nuclear facilities? Where and when?
Tubes exhibiting significant wear or which are potentially vulnerable to such wear have already been removed from service at SONGS by plugging. Plugging tubes within the limits set by the plant licensing documents is a standard practice in the industry and poses no safety concern. It has been implemented to some extent or another by all nuclear utilities whose facilities include steam generators.
|Examples of steam generators made by Mitsubishi to be sold outside of Japan|
|Image credit: Mitsubishi Heavy Industries, Ltd.|
The Team 10 source who worked at SONGS says Mitsubishi "did not have the experience to design these replacement steam generators."
Units 2 and 3 were much larger steam generators then the company had ever built. The Mitsubishi literature shows that the SONGS plant is considerably bigger than other generators the company had built across the world.
In a response to the NRC, Mitsubishi Heavy Industries, Ltd said, "The design went through an extensive design review process which included the participation of third-party experts ..."