Global Security Newswire
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Fears Mount Over Reactor’s Vulnerability to Sabotage
WASHINGTON – The Nuclear Regulatory Commission is facing increasing pressure from key lawmakers and watchdog groups to stop an ailing California reactor from being put back into use – a move activists fear could prove catastrophic in the event of a terrorist attack.
Unit 3 of the San Onofre Nuclear Generating Station was shut down in January 2012 after a tube in its steam generator – a key part of a reactor’s cooling system that is meant to prevent a meltdown -- burst. It was revealed shortly afterward that Unit 2 of the plant also had hundreds of damaged tubes, and neither reactor has operated since. Unit 1 closed two decades ago.
Plant operator Southern California Edison is exploring the possibility of restarting Unit 2, which it argues is not as in poor condition as Unit 3 or other reactors throughout the United States generally. Watchdog groups, including the Natural Resources Defense Council and Friends of the Earth, are pursuing legal action aimed at having the Nuclear Regulatory Commission block such a move. Key members of Congress are also raising red flags, saying they have evidence that industry officials knew about design problems with the steam generators before they were installed.
Among activists’ concerns is that faulty steam generator tubes could allow massive amounts of radioactivity to be released into the surrounding environment, particularly in a situation where other reactor components have been sabotaged. Steam generators play a crucial role in cooling a reactor and preventing meltdown, and a rupture would also provide a direct pathway to the outside environment, Daniel Hirsch, president of the nongovernmental Committee to Bridge the Gap, told Global Security Newswire.
“So let’s assume a terrorist can cause some damage at a nuclear plant and you have defective steam generators – you might not be able to ride out that event,” said Hirsch, a nuclear policy lecturer at the University of California-Santa Cruz.
Steam generator tubes are meant to carry a reactor’s primary coolant and, by their relatively thin nature, transfer heat to secondary coolant. The systems are located inside the reactor containment structure meant to prevent radiation from escaping, but are connected to a steam line that travels outside the containment structure, providing a potential clear route for the escape of radiation.
In the event that a terrorist broke a reactor’s main steam line, secondary steam outside the steam generator tubes could become depressurized and cause high pressure, primary coolant inside the tubes to potentially rupture the already weakened tubes at at the plant near San Diego, Hirsch said.
Reactors have backup cooling systems, and reserve generators to power them in the event a terrorist or natural disaster cut access to off-site power, but these systems also have limitations and vulnerabilities, Hirsch contended. For example, in November, Edison notified NRC officials that it was investigating the possible sabotage by an employee of a backup diesel generator at San Onofre.
“It’s not OK to have your primary system deficient because you have a backup,” said Hirsch, noting that numerous reserve systems failed during the 2011 Fukushima Daiichi nuclear plant disaster in Japan.
Nuclear Regulatory Commission staff acknowledged the possibility that steam generator tube ruptures could lead to a reactor fuel meltdown and the release of radiation directly into the outside environment during a Thursday briefing at commission headquarters in Rockville, Md.
“The worst that could happen [in the event of tube ruptures] is that you wouldn’t have safety systems, you would drain the reactor coolant system and fail the fuel and have a direct release path to the environment,” said Chris Jackson, head of the commission’s nuclear reactor regulation branch. “You could have another event, a steam line break, that could result in a fuel failure as well.”
Jackson played down the likelihood of such an event occurring, suggesting that power plant operators would be able to detect problems early enough to prevent a catastrophe.
“Multiple tube ruptures would challenge the operators in a different way but we have studied that from a risk perspective and we chose not to take regulatory action,” Jackson said.
Industry officials argued that tube degradation at San Onofre Unit 2 is not as significant as that in Unit 3 and is comparable to other reactors throughout the country. In addition, computer modeling shows that the steam generator tubes in Unit 2 are less likely to rub up against each other and become damaged, argued Pete Dietrich, senior vice president and chief nuclear officer for Edison.
Hirsch, the only nonindustry official permitted to testify during Thursday’s briefing, noted that NRC data obtained by Senator Barbara Boxer (D-Calif.) showed that approximately 1,600 tubes were showing wear in Unit 2, only about 200 less than the approximately 1,800 damaged tubes in Unit 3.
At the time the problems were reported, the steam generators in Units 3 and 2 were approximately one and two years old, respectively, as they had been installed as replacements for the reactors’ original systems. Edison in a July press release said the detected wear is not unusual during the first years of operation of a new steam generator and “is part of the equipment settling in.”
Inspection report data Hirsch and UC Santa Cruz students compiled for other replacement steam generators in the United States showed, though, that the median number of steam generator tubes showing wear in their initial years of operation was four – about 400 times less than identified at San Onofre Unit 2.
Edison has also argued that the rate of tube degradation typically declines after the first years of operation, but Hirsch said data pertaining to the similar Palo Verde Nuclear Generating Station in Arizona shows otherwise.
In a Wednesday letter to NRC Chairwoman Allison Macfarlane, Boxer and Representative Edward Markey (D-Mass.) said they had evidence that Edison and Mitsubishi Heavy Industries, which built the replacement steam generators at San Onofre, were aware of “serious problems” with the devices’ design before they were installed. The companies elected not to make changes for fear that doing so would force Edison to apply for an NRC license amendment and complete a rigorous safety review process, according to the letter. The lawmakers said the evidence could be found in a 2012 Mitsubishi document and called on the commission to investigate.
“All people in our nation, including the 8.7 million people who live within 50 miles of the San Onofre plant, must have confidence in the NRC’s commitment to put safety before any other concern,” the lawmakers said.
Mitsubishi and Edison officials participated in the Thursday briefing, but the commissioners did not ask them any questions about the lawmakers’ allegations. In a Friday letter to Boxer, Macfarlane said the commission was looking at the Mitsubishi document as part of its ongoing investigation into the issue.
In June, the Natural Resources Defense Council and Friends of the Earth filed a legal petition arguing Edison illegally replaced the steam generators without obtaining an NRC license amendment. The petition asks the commission to conduct a formal hearing on the matter and to delay any decision on whether to allow a restart of the reactor until after that meeting takes place.
In a November ruling, the commission called on its staff to investigate whether installation of the replacement steam generators required a license amendment. It deferred the groups’ request for a formal hearing to its Atomic Safety and Licensing Board, which has yet to rule on the matter.
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