It appears that Byron may have solved the problem but the other plants have not—see Union of Concerned Scientist article shown below.
UPDATE: The Cape Cod TImes (also shown below) picked up the news release and their research reveals that the other nuclear plants have until 2018 to correct the problem.
The News Courier of Athens, Alabama also picked up the Conecerned Scientist letter.
Dangerous Flaw Threatens to Close Nation's Nuclear Fleet
3/04/2016 03:21 pm ET | Updated 1 day ago
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Roger WitherspoonJournalist
After four years of increasingly tense internal discussion, seven Nuclear Regulatory Commission engineers have formally petitioned the governing Commissioners to either order the nation's nuclear power plant to immediately correct a design flaw governing their reactor cooling systems or order them all to shut down.
The flaw is in the original design of the electrical system, and has escaped notice for decades. According to the engineers' petition, as well as a series of staff analyses on file at the NRC, the design flaw occurs in what is called an "single phase" condition in which little or no electricity is entering the plant to operate its backup cooling systems in the event of a blackout or other event cutting off power from the grid. The result is that the motors of backup generators are underpowered and this can cause their motors to burn out. When that happens, there is no way to keep the reactor core cool.
The seven members of the Electrical Engineering Branch in the Office of Nuclear Reactor Regulation, led by Acting Chief Roy K. Mathew, stated in the petition that "the staff determined that all nuclear facilities are susceptible to this design vulnerability except one plant, and recommended that the NRC take prompt regulatory action."
As a result, the petition states, if the plants are not ordered to immediately redesign their electrical systems then the Commissioners should "issue Orders to immediately shutdown the operating nuclear power plants since the licensees are operating their facilities without addressing the significant design deficiency...and with inoperable electric power systems...."
The situation evolved from an unplanned shutdown in January 30, 2012 in Unit 2 of the Byron Station Nuclear Power Plant in Illinois. At the time, it was thought that the shutdowns resulted from a string of unfortunate coincidences. But further examination by the NRC's electrical engineering branch found something more alarming.
Alternating current comes out in three currents, or phases, which are positive, negative, and neutral. At the high voltage levels coming directly from the power plant, the currents are on separate lines, labeled A, B, and C. David Lochbaum, nuclear safety expert with the Union of Concerned Scientists, explained that "the output from A and B are constantly monitored to make sure they are together, or in phase.
"There are circuit breakers and sensors within the system noting if there is a fault and the two are not in phase. When that happens, a circuit breaker opens to block that line and reroute the electricity. The grid operates on the same principal, with circuit breakers isolating lines when there are interruptions so the entire northeast doesn't have a blackout.
"Within the plant there are electrical breakers signaled to open to isolate the problem and others will close for the systems around it. At Byron that didn't happen. And they didn't monitor the phase that failed."
At Byron, however, the single phase, Line C, was not monitored and, in fact, had broken and fallen to the ground between the plant's main transformer and the nearby power substation. Unfortunately, the staff analysis stated, the line on the ground "did not result in a detectable ground fault" since single phases were not monitored. Because of this power shortage, none of the plant's four reactor coolant pumps were operable.
Officials from Exelon, which owns and operates Byron and 10 other nuclear power plants, as well as inspectors from the NRC initially thought that the shutdown was the result of a series of unfortunate coincidences. But On Feb. 28, 2012, there was a similar interrupted and undetected phase which caused a shutdown at Byron's Unit 1. And, as in the earlier event, it disabled the plant's cooling systems. That caused Mathews and the electric unit he led to investigate further and see if there had been any other shutdowns in which an undetected phase disruption disabled the cooling pumps. Their initial look found identical shutdowns at the Beaver Valley Power Station Unit 1 in Pennsylvania in November, 2007; and in New York, the James Fitzpatrick and the neighboring Nine Mile plants, which share a power substation, shut down in December, 2005.
The staff analysis concluded that the design of the electrical systems was "inadequate because it did not consider the possibility of the loss of a single phase... This situation resulted in neither the onsite nor the offsite electric power system being able to perform its intended safety functions" to provide electric power to the plant's safety systems. Plants are required to have two separate sets of electrical power lines and monitors for their core cooling systems so that operators can still control the reactor even if one line is damaged by fire or another event.
The loss of a single phase of alternating current, the NRC staff found, "can potentially damage both trains of the emergency core cooling system." In that case, there is nothing to prevent a meltdown.
In a practical sense, said Lochbaum, who assisted the NRC in updating their operator training manuals, the situation facing Byron resembled a brownout, in which only a small amount of electricity is getting through to the equipment. "The problem at Byron was that all the electrical equipment could not get enough electricity to operate effectively.
"The larger motors on the cooling pumps need a lot of current. If they aren't getting the flow they need they can sit there and try to run, and basically their motors will burn up."
Continue reading at Energy Matters http://bit.ly/1Y9UkjC
Above is from: http://www.huffingtonpost.com/roger-witherspoon/dangerous-flaw-threatens-_b_9382364.html
Here is what the Union of Concerned Scientists says about the issue.
The NRC Seven: Petitioning the NRC over Safety
Dave Lochbaum, director, Nuclear Safety Project | March 4, 2016, 3:37 pm EST
….The NRC Seven filed a petition with their employee seeking to resolve a safety problem affecting every operating nuclear plant in the United States, and the handful of new reactors currently under construction.
The Mercury Seven wore special gear to protect them from the harsh environment they could encounter during their journeys.
Hopefully, the NRC Seven will not encounter a harsh environment in response to their efforts to protect millions of Americans from a longstanding nuclear safety problem.
The key milestones leading to the NRC Seven submitting their petition are summarized below.
Revealing the problem: Byron event on January 30, 2012
As described in Fission Stories #111, the Phase C connection for a three-phase power source to Byron Unit 2 from the plant’s switchyard broke loose and fell to the ground (Fig. 2). The open phase condition was detected, causing the automatic shut down of the reactor.
Fig. 2 (Source: NRC)
But the open phase was not detected by the protection system for the two electrical circuits that supply electricity to vital equipment needed to cool the reactor core and perform other safety functions. Those electrical circuits continued to receive electricity from the degraded power source for about eight minutes until workers manually opened breakers to isolate the equipment and trigger automatic switchovers to a reliable power source.
A design vulnerability prevented the protection system from detecting the open phase condition affecting these two vital electrical circuits. The system compared Phase A to Phase B and Phase B to Phase C and required detections from both comparisons to trigger automatic protective actions. The Phase C failure was detected by the Phase B to Phase C comparison, but not by the other comparison. So, no automatic protection measures happened.
The open phase condition did not directly affect the emergency diesel generators. The emergency diesel generators stepped in at Byron to enable workers to sustain cooling of the reactor core.
The NRC calculated that the event at Byron posed a risk of core damage of approximately 1×10-4 per reactor year, or having one reactor meltdown due to an open phase condition every 10,000 years. That sounds like, and is, a low risk. But in nuclear safety, it’s a relatively high number. Risks are typically in the 1×10-6 per reactor year range.
Thus, the open phase condition was about 100 times riskier than risks routinely experienced at nuclear power plants.
Open phase conditions
The main generators at nuclear power plants produce three phase alternating current. Each phase is conducted separately to the main transformer where the voltage and current is adjusted to the needs of the offsite power grid (Fig. 3).
Fig. 3 (Source: NRC, edited and annotated by UCS)
In an open phase condition, one of the three phases fails. That failure could be where the phase is connected at either end, as in the Byron event. Or that failure could occur between the endpoints such as when broken insulation allows a metal wire to contact a nearby piece of metal to short out.
An open phase can occur when the circuit is energized or it can happen when no electricity is flowing through the phases.
Open phase condition consequences
Open phase conditions have different consequences depending on whether the circuit is energized or not.
My parents experienced an open phase condition years ago while they were away on vacation. The line connecting the house’s main power panel to the power line in the neighborhood developed a fault causing an open phase condition. Because they were away on vacation, only small electrical appliances like clock radios were running, with one notable exception—the refrigerator. The open phase condition did not affect the 120 volt electrical circuits that supplied clock radios and other small appliances. But it impaired the 240 volt power supply for larger appliances like the electric stove, clothes dryer, air conditioner, and refrigerator. Of those, only the refrigerator was running during my parent’s absence. The open phase condition meant that the refrigerator was getting 120 volts. The electric motor on the refrigerator’s compressor tried to run, but burned itself out in the effort. The additional electrical current the motor used trying to run tripped the breaker in the house’s main power panel.
Thus, the problem when an open phase condition occurs on an energized circuit is that electrical equipment can be damaged by the degraded power supply unless breakers/fuses operate to isolate the equipment from the problem.
The problem when an open phase condition occurs on a de-energized circuit is different. Federal regulations require nuclear plants have at least two connections to offsite electrical power supplies. When nuclear plants are operating, it is not unusual for one or more of the connections to these offsite power sources to be de-energized in a standby role. Electricity produced by the plant itself is used to power its electrical equipment. If the plant were to suddenly shut down and stop producing electricity, systems are installed to automatically swap in-plant electrical circuits to the offsite power sources.
An open phase condition on a de-energized circuit could result in the in-plant electrical circuits swapping to a “dead” backup.
The bottom line is that an open phase condition could prevent electrical equipment from performing the safety roles needed to prevent or mitigate nuclear plant accidents.
Seeking the extent of condition: July 27, 2012
The NRC sent a Special Inspection Team to investigation the event at Byron. Because the design vulnerability that factored in the Byron event likely affected other nuclear plants, the NRC sent Bulletin 2012-01 to all plant owners in July 2012. The NRC required owners to evaluate their electrical power systems to determine if they had the design vulnerability like the one revealed at Byron. The NRC gave the owners up to 90 days to report the results from their evaluations.
Defining the extent of condition: February 26, 2013
The owners responded to Bulletin 2012-01 during the third week of October 2012. The responses for each nuclear plant are available in the NRC’s online digital library using the following links:
Arkansas Nuclear One (AR)
Beaver Valley (PA)
Braidwood (IL)
Browns Ferry (AL)
Brunswick (NC)
Byron (IL)
Callaway (MO)
Calvert Cliffs (MD)
Catawba (SC)
Clinton (IL)
Columbia Generating Station (WA) – not found in the digital library
Comanche Peak (TX)
Cooper (NE)
Crystal River 3 (FL)
Dresden (IL)
Davis-Besse (OH)
Diablo Canyon (CA)
Farley (AL) – not found in the digital library
Fermi 2 (MI)
FitzPatrick (NY)
Fort Calhoun (NE)
Ginna (NY)
Grand Gulf (MS) – not found in the digital library
Harris (NC) – not found in the digital library
Hatch (GA) – not found in the digital library
HB Robinson (SC)
Hope Creek (NJ)
Indian Point (NY)
Kewaunee (WI)
LaSalle (IL)
Limerick (PA)
McGuire (NC)
Millstone (CT)
Monticello (MN)
Nine Mile Point (NY)
North Anna (VA)
Oconee (SC)
Oyster Creek (NJ)
Palisades (MI) – not found in the digital library
Palo Verde (AZ)
Peach Bottom (PA)
Perry (OH)
Pilgrim (MA)
Point Beach (WI)
Prairie Island (MN)
Quad Cities (IL)
River Bend (LA)
Salem (NJ)
San Onofre (CA)
Seabrook (NH)
Sequoyah (TN)
South Texas Project (TX)
St. Lucie (FL)
Summer (SC)
Surry (VA)
Susquehanna (PA)
Three Mile Island (PA)
Turkey Point (FL)
Vermont Yankee (VY)
Vogtle (GA) – not found in the digital library
Waterford (LA)
Watts Bar (TN)
Wolf Creek (KS)
The NRC staff reviewed the responses and prepared a memo summarizing the results and recommending next steps. The NRC staff wrote that all plant owners “stated that the relay systems were not specifically designed to detect a single-phase open circuit in a three-phase system.” In other words, all nuclear plants in the U.S. shared the kind of design vulnerability that caused problems at Byron.
As a result, the NRC staff concluded that the plants “may not be in compliance with the existing regulations.” The NRC staff recommended that the NRC take action to require all owners fix the design vulnerabilities at their plants (Fig. 4).
Fig. 4 (Source: NRC)
Seeking the solution: 2012-2013
As described in Fission Stories #168, Byron’s owner developed a hardware fix to monitor all three phases for an open phase condition. What impressed me was that the owner offered to provide details of its fix to any other nuclear plant owner—for free.
Spreading the solution: 2013-2015
The NRC staff initiated a number of steps intended to resolve the open phase condition problem at all other nuclear plants. Chief among these steps was developing an “answer key” for plant owners and NRC staff to judge whether the fix at a specific plant is acceptable and drafting the paperwork that would require the owners to implement fixes.
The “answer key” came in the form of an addition to the NRC’s Standard Review Plan for nuclear power plants. The Standard Review Plan articulates applicable regulatory requirements and conveys the NRC’s expectations on what would, and sometimes would not, constitute compliance with the requirements. In this case, the NRC issued Branch Technical Position 8-9 in July 2015.
Developing the implementation paperwork proved more challenging and as yet unachievable. I have been told that the NRC staff drafted the paperwork and distributed it for internal review by appropriate sections of the agency. I was informed that the Office of General Counsel concluded that the paperwork did not satisfy the provisions of the backfit rule. The backfit rule prevents the NRC from imposing regulatory requirements on plant owners unless they are needed for adequate protection of public safety or achieve sufficient safety improvements to justify their cost. The NRC staff revised the draft and re-distributed it for internal review. Once again, the Office of General Counsel concluded that it did not satisfy the backfit rule.
I was told that the NRC staff working on the paperwork was not getting adequate feedback from the Office on General Counsel on how the drafts violated the backfit rule. Thus, they felt it impossible to solve the “secret” concerns no matter how many times they revised the draft.
Side-stepping the stall: February 29, 2016
Seven members of the NRC staff submitted a petition to the NRC seeking to have the NRC order the known design vulnerability at all U.S. nuclear power plants to be remedied. The NRC Seven did not submit the petition as NRC staff members. Instead, they acted as private citizens desperately seeking overdue protection for other private citizens.
Why must seven members of a federal safety regulator take such drastic steps?
Why indeed.
Suppose that seven members of the staff at the Springfield Nuclear Plant near Anytown, USA petitioned the Board of Directors of their company to resolve a nuclear safety problem at the plant. The NRC would quite properly recognize their action as prima facie evidence of a safety culture problem at Springfield needing investigation.
The NRC Seven’s action constitutes prima facie evidence that the NRC has a safety culture problem.
Concerned Scientists artilce is at: http://allthingsnuclear.org/dlochbaum/the-nrc-seven-petitioning-the-nrc-over-safety
CAPE COD TIMES
Posted Mar. 7, 2016 at 2:00 AM
Updated at 10:37 AM
Seven engineers who work for the Nuclear Regulatory Commission have called on their employer to force nuclear power plant owners to fix a design flaw that could affect emergency core cooling systems. If the flaw is not fixed, they say, the plants should be shut down.
The engineers, filing as private citizens, have submitted a formal petition, the process used by the public when asking the federal agency to take action.
The design flaw in the system used to detect electrical supply problems has been known since an incident at Exelon’s Byron 2 Nuclear Station in Illinois in 2012. The plant went into automatic shutdown and remained so for a week after an undetected open-phase condition in its electrical system.
An open phase involves a damaged circuit that has failed or is providing imbalanced voltage to equipment.
“An open phase at a nuclear plant, if not detected and isolated by tripping breakers, could damage the motors of lots of emergency equipment,” explained David Lochbaum, director of the Nuclear Safety Program for the Union of Concerned Scientists. “If so, even when the bad power is turned off and good power from a source like the emergency diesel generators is provided, the broken motors could prevent the emergency equipment from running."
If the motors burn out, the plant loses its backup ability to cool the reactor.The design flaw in Byron’s detection system, which has since been fixed, exists in nearly all U.S. nuclear reactors, including Pilgrim Nuclear Power Station in Plymouth, although Pilgrim has never experienced an open-phase condition in its system.In a letter send by Entergy Corp. to the NRC in 2013, Entergy experts stated that Pilgrim’s relay systems weren’t designed to detect an open single phase of the three-phase system, but the existing protective circuitry would separate the plant’s power lines from an off-site connection failure or sustained imbalance in voltage.According to the petition, 13 open-phase events have occurred in the last 14 years in the United States and internationally.The Nuclear Regulatory Commission required all plants in 2012 to provide information regarding their detection systems for open-phase conditions.Plants have not yet been required to put in new systems to resolve the design flaw permanently. They have been given until the end of 2018 to permanently address the problem.The NRC is satisfied with actions taken to date, according to Neil Sheehan, the agency’s spokesman.“Based on plant owners’ responses to the bulletin and our requests for additional information, the NRC staff determined that appropriate interim corrective actions (fixes) have been implemented at all affected plants,” Sheehan wrote in an email. “As such, the risk associated with an (open-phase condition) is significantly reduced.”
At Pilgrim, its existing system was supplemented by interim safeguards that include twice daily checks by employees of the switchyard, where the plant’s lines connect to offsite power.
Entergy spokesman Patrick Thomas O'Brien said via email that "because of the way Pilgrim receives power, the station is unlikely to be affected by these potential concerns. In addition, Pilgrim has an existing automatic detection system that mitigates this concern, and given that the station will permanently shut down not later than mid-2019, additional upgrades are not planned."
The NRC will follow its usual procedure for reviewing formal petitions when considering the petition from the engineers, Sheehan said.
The group has asked federal regulators for a response by March 21.
It was a brave move for a group of employees to file a petition, Lochbaum said, and also signals the seriousness of the problem.
“If employees of the NRC do not trust the NRC to have acted to protect members of the public and have to petition their employer to protect the public, why should any member of the public trust the NRC to have its back (other than to have its back covered with a target)?” Lochbaum wrote.
— Follow Christine Legere on Twitter: @ChrisLegereCCT
Above is from: http://www.capecodtimes.com/news/20160307/engineers-fix-design-flaw-or-shut-down-nuclear-plants?rssfeed=true
Petition claims vulnerability at nuclear power plants
- Adam Smith
Adam Smith
- Petition claims vulnerability at nuclear power plantshttp://www.enewscourier.com/news/local_news/petition-claims-vulnerability-at-nuclear-power-plants/article_1df7cc7e-e58c-11e5-89d4-5fa5b729067e.html
A petition filed last month by seven engineers with the U.S. Nuclear Regulatory Commission is urging swift action to correct a power distribution issue at nuclear power plants. If the issue is not resolved, the engineers have asked the NRC to shut those plants down.
The engineers' concern stems an open-phase condition that occurred at Exelon’s Byron 2 Nuclear Station in Illinois in 2012. Power to large industrial facilities, like nuclear power plants, is delivered in three phases. In this case, one of the phases dropped out in the plant's switchyard, which impacted how electrical current was being distributed throughout the plant.
NRC Spokesman Scott Burnell explained in this situation, the plant's automatic systems did not recognize a phase had dropped out, and it took operators in the control room “some time” to realize it. During that time, he said, the plant's reactor safety systems did not operate as effectively as they could have. Once the problem was discovered, the power was rerouted accordingly and the plant was shut down safely.
“The Byron event identified a vulnerability in the design of U.S. and international, operating plants. The current design requires an accident signal to automatically connect the emergency core cooling systems to the preferred power source to mitigate the consequences of a design-basis event,” says the petition. “... If the preferred power source, has an undetected open phase-condition, redundant trains of electrical equipment (electric motors that drive the pumps and valves) could burn out in few minutes and therefore will not be available for safe shutdown, even after restoration of an operable power source.”
A design-basis event, or accident, is defined by the NRC as a “postulated accident that a nuclear facility must be designed and built to withstand without loss to the systems, structures, and components necessary to ensure public health and safety.”
Burnell said the incident led the NRC to examine the issue more closely, and a bulletin was issued to all nuclear power plants, including Browns Ferry Nuclear Plant, explaining the open-phase incident. The bulletin also requested information from the operators explaining how they would handle the issue if it occurred at their plants.
Those operators analyzed the condition and responded with answers, Burnell said, and some modified control room procedures so operators could check to see if all three electrical phases are available. Based on information received by plant operators, the NRC made the decision to allow plants to continue operation “while the industry looked for a more comprehensive resolution to the issue,” Burnell said.
The petition says 13 open-phase events have been identified over the last 14 years at domestic and international nuclear power plants, with the most recent occurring in December at the Oconee Nuclear Station in Seneca, South Carolina. In that case, the petition says, two separate transformers required for safe shutdown of three operating nuclear units had open-phase conditions.
“Since the transformers are common to one onsite and one offsite power source, both power sources were rendered inoperable, indicating that the lessons learned and manual compensatory actions implemented after the Byron Event were ineffective,” the petition says.
The petition filed by the engineers asks the NRC to resolve the issue more promptly, however. Burnell said the petition requires the NRC to look at all available information and make a decision on whether anything needs to be done. He added the NRC “has a firm goal” to respond to the petition within 30 days of its filing, which would be March 21.
The response would tell the petitioners they have met the requirements for a full review or the matter would not be subject to a full review.
“The NRC considers the plants safe for continued operation, but we do expect to have an answer in a couple of weeks,” he said. “If the agency determines anything needs to be done, the decision to prompt further action would be months down the road.”
Jim Hopson, spokesman for the Tennessee Valley Authority, said the utility would not make any changes at Browns Ferry Nuclear Plant unless directed to do so by the NRC.
“We'll continue to monitor this and if changes are necessary, we'll do what we can to implement those,” he said. “(The NRC and TVA) share the concept that safety is the overriding priority.”
Adam Smith article is from: http://www.enewscourier.com/news/local_news/petition-claims-vulnerability-at-nuclear-power-plants/article_1df7cc7e-e58c-11e5-89d4-5fa5b729067e.html
