NRC Commission Approves More Post-Fukushima Upgrades to Nuclear Plants

Scott Burnell
Public Affairs Officer

JLL gauge iconThe NRC has already ordered numerous upgrades to nuclear power plant safety based on what we’ve learned about the Fukushima nuclear incident in 2011. Now, the NRC’s Commission is doing more. They have just approved a two-track approach for additional improvements to systems at 31 U.S. reactors that would vent pressure during accidents.

The Commission’s decision is outlined in a Staff Requirements Memorandum. It provides details about the decision, but this is the bottom line: the NRC will issue an Order requiring stronger venting systems and will use the agency’s rulemaking process to consider the best approach by which these 31 reactors can keep radioactive material from the environment during a severe accident.

Some background: Some of the U.S. reactors that are similar to the Fukushima Dai-ichi plant have vents that reduce pressure during an accident and keep water flowing to the reactor to cool the fuel. The venting systems at Fukushima played a role in their nuclear crisis, and the NRC, last March, issued an Order to the 31 plants with similar designs to take action. The plants either had to install vents or improve their existing venting system. The goal was to make sure the vents can operate during the early phases of an accident, even if the plant lost all power for an extended time.

In their latest decision, the NRC Commission votes to further strengthen these vents. The NRC staff has 60 days to finalize an Order for these enhancements. Generally speaking, these additional requirements mean the vents could handle the pressures, temperatures and radiation levels from a damaged reactor, and that plant personnel could operate the vents under these conditions.

As part of the same decision, the Commissioners directed the staff to begin a formal rulemaking on filtering methods that would prevent radioactive material from escaping containment in an accident, either through new filter systems or a combination of existing systems. The staff will develop the technical analysis, a proposed rule and then a final rule. Throughout this process, the public and various stakeholders will have opportunities to submit comments and attend meetings to ask questions. And there will be many future posts about the progress!

Author: Moderator

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

20 thoughts on “NRC Commission Approves More Post-Fukushima Upgrades to Nuclear Plants”

  1. My prior experience with the NRC regarding the issue of the zirc-water firestorm – I raised as a safety concern back in 1987 from Westinghouse – was less than positive. But OK, I take the challange and will try to file it as a pensioner retired in Hungary. Post Fukushima I hope that the knowledge will not be denied that indeed the driving process was the firestorm of zirc-water reaction in the core of reactors 1-3 of the Daiichi plant.
    What do You think, Mr. Scott Burnell? Will You sweep it under the rug, again?

  2. Mr. Stolmar:

    You are always welcome to file a petition for rulemaking to request a new or modified NRC requirement for power reactors. The agency will always consider whether the evidence and proper analysis supporting such a petition warrant any rulemaking activities.

    Scott Burnell

  3. Let’s try it again!
    I’m concerned that the NRC is not accepting the real processes of rapid heat-up and ignition of firestorm of zirconium-steam reaction once a stagnant steam volume descends down into the core . I want to change the NRC thinking and prevent the core damage with a rapid depressurization vent directly from the upper volume of the reactor – in order to prevent the stagnant steam volume to ever extend down into the reactor core -, and provide passive staged water injection reserves all the way down to the gravity injection – in order to provide continuous cooling all the way until a secure cold shutdown is achieved. This injection should flow from below the reactor core toward the top volume opened to environment.

  4. The staff issued its revised hardened, reliable vent Order ( ) on June 6, 2013, on to all 31 U.S. reactors similar to Fukushima. The staff continues following Commission direction to consider filtration strategy alternatives through the rulemaking process. The staff expects to complete the regulatory basis for a possible filtration rule by the end of this year. If there is a sound regulatory basis a proposed filtration rule is expected by the end of 2015 and a final rule by early 2017.

    Scott Burnell

  5. Hi Scott,

    Can you please tell us if the hard vent rule is going through a formal rulemaking or if a final rule will just be produced within the 60-day timeframe? Also, regarding filtration, can you ballpark when the technical analysis might be produced?

    Thank you,


  6. In society every thing cannot be weighed against cost risk benefits. All risks to human life in persuit of profit cannot be undermind. I have worked in nuclear power plants for many years. I have corrected drawings and incorporated changes done after a period of more than 10 years in many nuclear plants. We were told do not assume any drawing correct. Go and do 100% walkdown before you make construction drawings. As per rule all drawings has to be updated when design and construction are completed. Why? It is not done?

  7. The NRC’s actions regarding vents are currently limited to the 31 U.S. reactors with designs most similar to those at Fukushima. These designs have smaller structures for containing the effects of an accident, and the agency’s actions will enhance the ability of these structures to safely release pressure and maintain their ability to keep radioactive material out of the environment. Other U.S. reactor designs have larger containment structures that allow more time for nuclear plant operators to prevent radioactive material from getting out into the environment if an accident occurs. Even so, the NRC plans to review these other containment designs when our technical experts have completed their work on the plants that are similar to the Fukushima units.

    Scott Burnell

  8. If these new vents are so helpful then why aren’t all the plants going to be upgraded to using them?

  9. I did submit my concern, again.

    I’m concerned that the NRC is not accepting the real processes of rapid heat-up and ignition of firestorm of zirconium-steam reaction once a stagnant steam volume descends down into the core and pushes instead for Hydrogen re-combiners and filtered vents which could be useful only after the damage of the fuel. I want to change the NRC thinking and prevent the core damage with a rapid depressurization vent directly from the upper volume of the reactor – in order to prevent the stagnant steam volume to ever extend down into the reactor core -, and provide passive staged water injection reserves all the way down to the gravity injection – in order to provide continuous cooling all the way until a secure cold shutdown is achieved. This injection should flow from below the reactor core toward the top volume opened to environment. (Through filtration, indeed…)

  10. Our actions regarding Fukushima’s lessons learned have further reduced the already very small possibility of accident conditions leading to a steam/zircaloy reaction. All of our new venting-related requirements for Mark I/II BWRs help ensure that water can get to the reactor core during an accident from a variety of engineered safety systems. In addition, the NRC’s “mitigating strategies” requirements will ensure that portable pumps and other equipment necessary to provide cooling water to a reactor, even after a major quake or flooding event, are available to support every U.S. reactor’s installed safety equipment. The NRC staff will follow the Commission’s latest direction in further exploring ways of limiting the release of radioactive materials during venting, even after core damage has occurred.

    If you have further concerns, please submit your letter to for consideration.

    Scott Burnell

  11. As the NRC considers all the systems and procedures in place both to prevent accidents and mitigate them if they do occur, we continue to conclude U.S. reactors can operate safely. The Commission’s decision involves enhancing what’s already acceptable at Mark I and II designs, not only through filtration but also by enhancing the plants’ capabilities to deal with other aspects of a nuclear accident. We’re taking the necessary time to seek input on that comprehensive approach from the public, nuclear industry, and other key stakeholders through our comprehensive rulemaking process.

    The staff continues its examination of the issues involved in a potential accelerated transfer of spent fuel to dry casks. The staff updated the Commission on that topic and the remainder of the Fukushima lessons-learned activity on Feb. 14 ( — spent fuel transfer is discussed in Enclosure 1, page 14 of the PDF).

    Scott Burnell

  12. As go the banks, so goes the nuclear Industry. Regulating in the service of public protection and public safety is trumped by the industries’ economic health and survival. The NRC is just another regulatory agency influenced, captured and controlled by the industry it’s supposed to regulate. Not filtering the vents rationalized by a “cost benefit analysis” weighing public safety against the black ink on a corporate balance sheet says is all. Accidents on the order of Fukushima are acceptable risks. Easy to say when the profits are privatized and the risks are socialized.

  13. Another whitewashing attempt by NRC, circumventing the real key process of stagnant steam bubble extending down to the core and igniting a firestorm of zirc-water reaction.
    Zircaloy Mass in Fuel Cladding [kg / lb] 16,465/ 36,300 in the PWR and 40,580 /89,500 in BWR from NRC-2012-0022-0002 and NRC-2012-0022-0003.

    Zr (91) + 2 H2O (36) = ZrO2 (123) + 2 H2 (4) + 5 MJ/kgZr
    Water required for complete reaction for the PWR 16,465 * 36/91 = 6513,6 kg or about 6.5 m3 (available), it produces 16,465 * 123/91 ZrO2 = 22,255 kg zirconium dioxide and 16,465 * 4/91 = 723.7 kg Hydrogen and 82,325 MJ heat. For a 10 second firestorm duration it gives 8GW power… or twice the full power of the reactor…
    Water required for complete reaction for the BWR 40,580 * 36/91 = 16053,6 kg or about 16 m3 (available), it produces 40,580 * 123/91 ZrO2 = 54,850 kg zirconium dioxide and 40,580 * 4/91 = 1784 kg Hydrogen and 204,250 MJ heat. For a 10 second firestorm duration it gives 20GW power… or five-six times the full power of the reactor…
    Considering that NRC does not require a top of the reactor depressurization vent to prevent the zirconium firestorm in the reactor, the above back of the envelope calculated worst case scenario should be considered for designing the filtered vents.

    What I am proposing is a direct rapid depressurization vent allowing the operators to vent the steam directly out of the upper part of the reactor before a stagnant steam bubble would extend down into the core.

    In the PWR the accumulator injection (ECCS) ports connected to the hot leg side could be utilized for such vent, in the BWR the existing safety relief lines could be rerouted to the vent stack.

    The use of this rapid depressurization vent is proposed in three cases:(1) the state of the reactor is unknown, (2) the forced circulation through the core is lost or (3) the heat transfer to the ultimate heat sink is severed

    And please, add these to the existing plants too with sufficient gravity water reserves.

    And here is my December 15, 2011 letter, a serious answer I’m still waiting for…

    Dear Director Skeen,

    Considering the TMI-2, Fukushima Daiichi 1, 2 and 3 reactor severe accidents and the Paks-2 fuel washing vessel incident, also the SFD and other related nuclear reactor fuel severe damage experiments it is evident that the ignition and firestorm of the Zirconium-steam reaction occurs several hours after the severe reduction in cooling capability arises. The attached solution utilizes this time gap and proposes the equipment and response modifications aiming the elimination of ignition of Zirconium-steam reaction in PWR and BWR reactors. Also the same solution deals with the results of such ignition and Zirconium-steam reaction in the maximum extent, in case the ignition despite the efforts occurs.
    Aiming the public safety in presence of nuclear power plant two questions have to be answered: Do You prevent the ignition of Zirconium in the steam? And Do You protect the surrounding of the plant from radioactive releases in case the entire Zirconium inventory burned in a firestorm? The presented here solution gives positive answers to both questions.
    The key element of this solution is the rapid reactor depressurization using a top vent from the reactor head. The same will provide a controlled routing for the Hydrogen generated in case the ignition of Zirconium-steam reaction still occurs.

    Aladar Stolmar

  14. One would think that the Industry itself would be trying to “fact track” these safety improvements rather than waiting to see how they can getaway with spending less of their ratepayers money when the cost of a Fukushima is about a Trillion Dollar Eco-Disaster, which the Country and the Industry cannot afford!

    For all those in Nuclear Denial* that think a Trillion Dollar Eco-Disaster is too high, check out what the latest French report says:
    French Nuclear Disaster Scenario Was So Bad The Government Kept It Secret
    Catastrophic nuclear accidents, like Chernobyl in 1986 or Fukushima No. 1 in 2011, are, we’re incessantly told, very rare, and their probability of occurring infinitesimal.

    But when they do occur, they get costly. So costly that the French government, when it came up with cost estimates for an accident in France, kept them secret.

    But now the report was leaked to the French magazine, Le Journal de Dimanche. Turns out, the upper end of the cost spectrum of an accident at the nuclear power plant at Dampierre, in the Department of Loiret in north-central France, amounted to over three times the country’s GDP.

    Hence, the need to keep it secret. The study was done in 2007 by the Institute for Radiological Protection and Nuclear Safety (IRSN), a government agency under joint authority of the Ministry of Defense and the Ministry of Environment, Industry, Research, and Health.With over 1,700 employees, it’s France’s “public service expert in nuclear and radiation risks.” This isn’t some overambitious, publicity-hungry think tank.
    It evaluated a range of disaster scenarios that might occur at the Dampierre plant. In the best-case scenario, costs came to €760 billion—more than a third of France’s GDP. At the other end of the spectrum: €5.8 trillion! Over three times France’s GDP. A devastating amount. So large that France could not possibly deal with it.

    Remember as of today: 1 Euro equals 1.29 US Dollars


    The illogical belief that Nature cannot destroy any land based nuclear reactor, any place anytime 24/7/365!

  15. This is a step in the right direction but it also leaves a bigger question. If the NRC’s first priority is safety, then why would you allow any plant to continue operating when you know that it is not adequately protected? Does the NRC have an obligation to keep plants running or do you operate specifically on the basis of safety?

    In a similar line of thinking, why are things taking so long to move spent fuel from pools to Hardened On Site Storage? One would hope that preventing a Fukushima-like disaster would be your only consideration. Isn’t this something that staff recommended to take place ASAP? I understand it will not even be considered for another 6 years. At San Onofre in particular, 8.5 million people live within harms way if we get the long overdue mega-quake that everyone is expecting.

    I’m sure that there are tremendous financial pressures for the status quot, but they must be weighed against the unimaginable impact for generations to come on public health and economy of California and the rest of the country for that matter. I know that if it was my responsibility to act in ways to protect the public and the environment for generations to come, I would not allow for any such risk regardless of what the utilities say or do.

    This is a race against time. Let’s not waste the opportunity to do something about this before it is too late.

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