UPDATE: Keeping U.S. Reactors Safe from Power Pulses

Scott Burnell
Public Affairs Officer

The NRC requires U.S. nuclear power plants to be able to shut down safely in the face of many extreme events – tornados, hurricanes and earthquakes. But the NRC also takes into account far more unusual events, like solar flares and man-made electromagnetic pulse (EMP). Both can affect generators, transformers and other parts of the electric grid – which in turn could affect nuclear power plants.

The NRC has been examining these issues for more than 30 years, starting in the late 1970s when the agency studied how EMP could affect nuclear power plant safe-shutdown systems. In February 1983 the NRC issued the study’s conclusion: nuclear power plants’ safety systems can do their jobs after an EMP event. The agency revisited the issue in 2007 to account for the increasing use of digital computer systems in nuclear plants, which potentially could be more susceptible to EMP. The agency continued to conclude as recently as two years ago that nuclear power plants can safely shut down following an EMP event.

solarflareThe NRC has also examined “solar storms” and their potential to damage the electric grid. A strong geomagnetic storm on March 13, 1989, for example, severely disrupted electrical power equipment in Canada, Scandinavia, and the United States. After studying the event the NRC issued an Information Notice in June 1990, to ensure nuclear power plants understood how severe solar activity could affect transmission systems and other components of the power grid.

Additional research in 2010 analyzed and compared solar or geomagnetically-induced current events to those of the EMP events previously analyzed. This work led to the same conclusion as the EMP studies – U.S. nuclear power plants can safely shut down if a solar storm disrupts the grid.

The edge of the NRC’s authority lies in a nuclear power plant’s electric switchyard, where our rules mesh with those of the Federal Energy Regulatory Commission, which oversees the nation’s electric grids. Another body, the North American Electric Reliability Corporation develops and enforces grid reliability standards. The NRC works closely with FERC and NERC on grid reliability issues, including the effects of solar or geomagnetic storms and EMP. In 2015 FERC began the process of creating reliability standards to protect the grid against these events.

In 2011 a citizen petitioned the NRC to revisit the issue of grid disruption. The petition discussed ensuring U.S. nuclear power plants have emergency systems to keep spent fuel pools cool for two years after an electric grid failure. The NRC’s draft rule on maintaining key plant safety functions after a severe event, issued last year, includes measures to keep spent fuel pools cool.

The NRC is also participating in a White House-led task force on better understanding and dealing with space weather such as solar flares. Much of this work aims to improve society’s ability to forecast and warn against these events. Both the Department of Energy and electric grid companies have started efforts to stockpile specialized electrical equipment (such as large transformers) needed to restore the grid after these events.

The original blog post ran in October 2011.

Author: Moderator

Public Affairs Officer for the U.S. Nuclear Regulatory Commission

21 thoughts on “UPDATE: Keeping U.S. Reactors Safe from Power Pulses”

  1. “Of course with the core sub-critical reactor heat is not sufficient to keep the plant at high temperature & pressure without the operation of reactor coolant pumps which require off-site power.”

    This is not necessarily true. It depends on the decay heat. If temperature was going down in the core on its own, that means the core would be passively safe without electrical power.

    Decay heat is capable of maintaining a nuke in hot standby for days. Off site power is one way to help heat up to hot standby conditions, but on loss of decay heat removal the decay heat will raise core temp/press up.

  2. Passive Safety Features
    Anon, although the article at this link dates back to the time of the Fukushima disaster in Japan, it has an incredible amount of easily understood nuclear power plant history including discussions about advanced reactors with so-called passive safety features. I highly recommend it.
    Sidebar: You can be sure…if it’s Westinghouse.
    Those of us old enough to remember Westinghouse Electric as the great industrial powerhouse it once was will recognize that slogan and the iconic Circle W logo with some affection.
    Like arch-rival GE, Westinghouse once bestrode the industrial landscape of the world producing amazing technical inventions in defense electronics, power generation, refrigerated transport, nuclear engineering and so on.
    The logo is still visible today. It appears on an odd assortment of products, from solar panels, light bulbs, flat panel TVs and air conditioners. But it’s not your father’s Westinghouse. It’s not even Westinghouse.
    Unlike GE, the company no longer exists. Westinghouse Electric officially died on December 1st 1997.
    On that date a great industrial icon of the 20th Century completed one of the most sweeping corporate transformations in history by morphing itself into CBS Corporation, the broadcasting and media Company it acquired in 1995. What was left of the firm’s industrial business was sold in pieces.
    And so the 111-year-old industrial icon founded on the genius of George Westinghouse vanished from the face of the earth.
    Although the AP1000 has the Westinghouse label, it’s Toshiba of Japan that runs the company & the show.
    When I worked in the utility industry we had both GE & Westinghouse turbine generators in service at our power plants. We had our own version of the Westinghouse slogan, it was…
    “If it is GE it is sometimes messed up, with Westinghouse, you can be sure.”

  3. I know little about the AP1000 nukes, Anon, but the little I know indicates that they are indeed a much safer nuke that the ancient dinosaurs we currently have. They still have some of Achilles heels that their predecessors had including the economics as you point out. As long as they continue to have substantial government subsidies they probably will be viable. Time will tell.

  4. Bro- I think you effectively brought the “curtains down ” on nukes – they are undependable in a power grid down in a blackout mode. These days, nuclear power is economically loosing out to other competing sources suc as, solar, fracking, natural gas etc. It is universally accepted that, single nuke units are not viable and as if, rubbing salt to the wound, operators like Entergy are throwing in their towels shutting down nuclear units (Pilgrim), unable to comply with NRC, while utilities like Exelon are shutting down multiple site units (Quad cities and Clinton) showing revenue losses close to a billion dollars (or close enough). So you think prospects for nukes are bleak !!!

    Do you think the new generations of AP1000 will be harbingers and usher a dawn for nuclear power in this country?

  5. Nukes are not only worthless without offsite power they are in a degraded safety state. The NRC, who does not effectively regulate the nuclear industry but rather helps ensure its viability, brags about nuke plants being designed to shut down safely, even if all offsite power is lost. Of course what the NRC fails to tell you is that as soon as offsite power is lost a nuclear plant owner has to declare a state of emergency at that site. If onsite diesel generators at that plant fail to start after that offsite power loss, standby for your worst nuclear nightmare. Even if things go as planned & onsite emergency diesel generators start, declaring a state of emergency at a nuclear site is a serious matter. State, county, & local emergency groups are alerted just at a time when they are undoubtedly trying to contend with what that loss of offsite power has wrought throughout an entire community. Mother Nature or, God forbid, Father Terrorist may have precipitated such a loss of power. Then compound this situation by the loss of other power plants in the area, even including other nuke plants.
    Just another reason nuclear plants are much more of a liability than an asset.

  6. Black Start
    Nuke plants, wind generators & solar power do not have the capability for a so-called black start. A black start is the process of restoring an electric power station to operation without relying on the external transmission network.
    A hydroelectric station on the other hand needs very little initial power to start (just enough to open the intake gates and provide excitation current to the generator field coils), and can put a large block of power on line very quickly to allow start-up of fossil-fueled or nuclear stations. Also certain types of combustion turbines can be configured for black start, providing another option in places without suitable hydroelectric plants.
    Not all generating plants are suitable for black-start capability. Wind turbines are not suitable for black start because wind may not be available when needed. And, of course, solar power at night is problematic.
    Let’s face it, hydro, coal & gas-fired power plants are the backbone of our nation’s electrical grid. Nukes, solar & wind generation cannot be counted on to be there when the going gets tough.

  7. I think we are here on to something like the Achilles Heel – the weakness to re-power electric grid with a bunch of base load dependent grid on nukes, who are without offsite power (which was the situation in 1989) and on “hot standby” (reportedly, correct me if wrong) – Is in fact a Trojan Horse? We know the grid came back after four days, how did they achieve it?

  8. Got a confirmation from a friend in the nuke business about hot standby…
    “As you surmised, reactors in Hot Standby cannot be used to re-power the offsite power grid. They need electricity from the offsite power grid in other to roll the turbine and place the generator online.
    The balance of plant equipment (turbine lubricating oil system, generator main exciter, etc.) are not powered from the onsite emergency diesel generators. Thus, they cannot function without offsite power being available. And the reactor cannot roll the turbine and get the generator online without offsite power.”

  9. Nukes without Offsite Power are Worthless
    I truly wish you were right about nuke plants being ready on “Hot Standby” to “re-synchronize” to the grid when & if the grid was ready to receive the power. To even heat up or maintain a nuke in Hot Standby requires off-site power. I found this definition of “Hot Standby” in the standard Tech Specs…
    “Hot stand-by: The Condition in which plant is maintained in high temperature and pressure, and the core is maintained sub-critical.”
    Of course with the core sub-critical reactor heat is not sufficient to keep the plant at high temperature & pressure without the operation of reactor coolant pumps which require off-site power.
    In fact those plants could not have been even maintained in a Hot Shutdown condition for long.
    I wish it were different, but nukes without offsite power are worthless.

  10. Nukes Not There When You Need Them
    Not only are nuke plants not there when you really could use the electricity they produce, but you cannot get them back on line without lots of offsite power. The NRC boasts about nukes being able to shut down safely but who needs a power plant that stays shut down when our nation’s power grid really needs the power?! And just where does all that offsite power come from to even begin to restart a nuke plant? It comes from coal & gas-fired power plants. If an EMP pulse knocks power plants offline (nukes & even fossil-fired power plants) which plants can immediately restart? Just those much-maligned fossil plants. Nukes would be down for the count & totally out of the picture. The security & integrity of our nation’s electrical grid depends on the 24/7 power available from fossil plants.

  11. William R. Harris, Secretary and Member of the Board, Foundation for Resilient Societies says:

    Diablo Canyon Power Plant (DCPP) is projected to operate through year 2025 per present plans of Pacific Gas & Electric Co. How can this plant be more prudently protected from solar geomagnetic storms with forecasts of about a 10% to 12% chance per decade of a Carrington-magnitude storm, or about 5% to 6% chance per decade of a geomagnetic storm within the “kill zone” impacting the U.S. electric grid?

    Mid-level latitude is no guarantee of solar storm immunity, because the larger magnitude solar storms may peak at lower latitudes than most lower intensity storms. The so-called Hydro-Quebec solar storm of March 1989 peaked over New York State (according to Los Alamos scientists), but melted the windings of the high voltage transformer at the more southerly Salem-1 nuclear plant at latitude of 39°27′. Diablo Canyon is not much further south than is Salem-1 in southern New Jersey.

    Other nuclear power plants that incurred transformer damage in solar storms included Maine Yankee (1989, 1991) at latitude of 39°27, and Seabrook Unit 1 (n 1998) in New Hampshire at latitude of 42°89′.

    If Diablo Canyon’s operators installed geomagnetic induced current (GIC) monitors at the neutral of each of the two generator step up transformers — at a cost of about $15,000 plus installation costs per GIC monitor — the record of GICs during moderate solar storms would help the operators determine if neutral ground blockers would be a prudent means to protect these transformers from solar storm damage. Another advantage of GIC monitor installation and remote read-out is that most solar storms are of low intensity. This could enable the NRC to avoid a mandatory shutdown of nuclear power plants where GIC monitors indicated that transformers were not significantly harmed during an ongoing solar storm. Averting needless shutdowns promotes safety and reduces operating costs.

    Because there is a “coastal effect” where electrojets from solar storms pass from highly-conductive saline waters to highly resistive land masses near nuclear power plants, GIC monitoring is a prudent means to know whether transformers need current blockers, to know that a power plant can operate through a moderate solar storm, and to safely shut down nuclear power plants if conditions so require.

    With an ongoing deficit of underground gas storage capabilities at California’s Aliso Canyon in years 2016-2017, the availability of power from Diablo Canyon could make the difference between experiencing blackouts or avoiding blackouts with voluntary electric conservation this summer. So small investments to protect Diablo Canyon from needless tripping in moderate solar storms makes sense.

  12. Shutting down a nuclear reactor is no problem- even a moron can do it, in a jiffy – Just hit the scram button, rest of the complex action are automatic and computer control takes over. But what is tricky and painstakingly difficult, is how to restore the regional grid, as seen in the March 1989 spurious trip that triggered “Blackout over Us-Canada North-East region” back to business, with a number of Nuclear units ready on Hot-Standby to re-synchronize the power grid, but could not, for few days! The NRC and consortium partners report released later did not sarisfactorily explain how to get the grid back to action, nor explain the cause.

  13. Since Scott is his usual helpful self I will try to be cordial & try to answer as I have worked in both nukes & fossil plants. You are right of course, an EMP could adversely affect fossil plants as well. But nukes have many more automatic trips/runback features than fossil units so they are more susceptible.

    Sent via DroidX2 on Verizon Wireless™

  14. The NRC focuses on ensuring U.S. nuclear power plants shut down safely and remain safe if an EMP or solar storm affects the nation’s electric grid. Fossil-fuel plants lie outside the NRC’s responsibilities.
    Scott Burnell

  15. What is so different in coal and gas fired power stations that they would not be affected by an EMP in a similar way? Do they work without computer controls, pumps, motors and wound transformers?

  16. Diablo Canyon Power Plant (DCPP) is at a low latitude: 35°16′27″N 120°39′47″W, per Wikipedia. The pair of connections between the DCPP switchyard and the “backbone” of the California power grid are relatively short, about 50 miles. The connection points are the switchyards at Gates and Midway. These are some of the reasons why the issues raised by Lloyds of London in their 2013 article, “Solar Storm Risk to the North American Power Grid” https://www.lloyds.com/~/media/lloyds/reports/emerging%20risk%20reports/solar%20storm%20risk%20to%20the%20north%20american%20electric%20grid.pdf are unlikely to impact DCPP. Appropriate use of lightning arrestor technology on electric power transmission lines is beneficial. I asked the Diablo Canyon Independent Safety Committee (DCISC dot org) to confirm that DCPP was robustly designed regarding solar storms. DCISC agreed.

  17. William R. Harris, Secretary and Member of the Board, Foundation for Resilient Societies says:

    Potential electromagnetic pulse (EMP) effects on commercial nuclear power plants include: the fast pulses (E-1 pulses) and the slower pulses (E-3) from either High Altitude EMP (HEMP) detonations or from solar geomagnetic disturbances, or from ground-based radiofrequency weapons. Past assessments indicate that Commission-licensed commercial power plants can safely shut down after experiencing these events. But this does not eliminate all relevant risks.

    One month before the tsunami and loss of outside power at Fukushima Dai’ichi, Japan, in February 2011 Thomas Popik submitted to the Commission a Draft Petition to augment the type and duration of backup on-site power at nuclear power plants, to reduce risks of spent fuel fires at nuclear power plants. The Nuclear Regulatory Commission accepted Petition PRM 50-96 in December 2012, nine months after incorporation in New Hampshire of the Foundation for Resilient Societies, sponsor of that initiative. The nuclear power industry has made substantial progress in extending the duration of on-site backup power, so extended loss of outside power will not result in fires within spent fuel pools lacking water or water-boron replenishment. And to protect facility security and control systems.

    Federal initiatives to reduce both the likelihood and duration of widespread grid blackouts have been sporadic, but are intensifying. In May 2013 the Federal Energy Regulatory Commission (in Order 779) commenced development of a reliability standard to cope with solar storms but not man-made EMP hazards. The proposed FERC standard for assessment of protective hardware is pending, but the underlying industry model would require assessments to protect only a limited number of transformers, mainly in the northern states. This would be nearly useless to protect against HEMP attack. At present, only one (1) of about 2500 high voltage transformers in the United States has a neutral ground blocking device to protect against E-3 pulses from solar storms.

    A Space Weather Action Plan, released in October 2015, receives widespread federal and international support, and may lead to better standards to protect the electric grid. More recently, a revived Congressional EMP Commission is mandated to assess impacts of GMD and EMP upon the resilience of the U.S. electric grid. Concurrently, the U.S. Department of Energy and the Electric Power Research Institute are developing assessment and mitigation options for man-made EMP hazards.

  18. This report on storing electrical equipment is similar to the intent of owners of nuclear plants who store equipment (motors, valves, piping, etc. at an offsite location. Public Service of New Mexico and TVA all have such storage sites. This has been part of the lessons learned fro Fukushima regarding the efforts of the Japanese owners to contain the damage and environmental hazards. If my recollection is correct, isn’t this part of the issues that were codified by the NRC personnel who visited Fukushima, following the accident

  19. So let me get this straight: The transformers are going to go out, the transmission wires are going to fry, the electronics are going to fail, the pump motor windings are going to burn up, the control cables are going to short out, and the nukes are going to safely shut down and the spent fuel pool isn’t going to overheat and all will be well? Amazing! What’s more amazing is that the NRC keeps revisiting the topic even as the risk gets greater (due to the increased use of microelectronics), and concludes the same thing over and over. I wish we could all live in your dream world. And don’t forget that many components are undoubtedly bogus/counterfeit, so how you can know how those are going to operate is beyond me.

  20. No doubt nukes can normally shut down safely. They have been designed from day one to do just that. They even shut down when they don’t need too; even when you don’t need them too; even when you really need the electrical power from them. Natural gas-fired plants & even those unpopular coal-fired plants are there when the nukes have long ago “safely” shutdown. Yes, when Mother Nature or Islamic terrorist strikes you cannot depend on the nukes. The backbone of our nation’s electrical grid will always be the 24/7 power available from natural gas & coal-fired plants.

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