U.S. NRC Blog

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Monthly Archives: April 2012

The Attack of the Jellyfish

An influx of tiny, jellyfish-like creatures last week forced the shutdown of one of the reactors at the Diablo Canyon nuclear power plant in California. The creatures are called “Salp” and they can be held in the palm of a hand, although they can grow up to four inches in length. They maneuver in the water just like squid by pumping water through their gelatinous bodies and ejecting it in a stream.

Because of an influx of the photoplankton they feed off, millions of the little critters were swarming in the waters at Diablo Canyon, which sits on an 85-foot cliff overlooking the Pacific Ocean. Some hapless Salp were getting sucked into the plant’s intake structure and pulled up against screens that protect the condensers and heat exchangers from marine debris.

Some of creatures passed right through the screens within the intake structure and passed right through the plant; but others got caught up against the metal mesh, clogging the screens. The plant’s Unit 1 has been shut down since April 22 for a refueling outage that is expected to last several weeks. On April 23, operators reduced power in the Unit 2 reactor to 15 percent as a protective measure. The Salp don’t pose a danger to any of the plant’s safety systems, but operating at lower power minimizes the impact of a shutdown, if one becomes necessary.

On April 25, it did. The buildup of Salp in the intake prompted operators to manually shutdown the reactor. All systems functioned as designed and no unexpected equipment issues were encountered. Unit 2 restarted last weekend.

Victor Dricks
Public Affairs Officer, Region IV

How the NRC uses Enforcement to Protect People and the Environment

A big part of the NRC’s mission to protect people and the environment depends on the companies and individuals we regulate meeting our requirements. The NRC’s Office of Enforcement has a number of tools that serve as deterrents and emphasize the importance of compliance with NRC requirements. These tools encourage the prompt identification and timely correction of violations by the licensee, certificate holder, or applicant. They include, in part, Notices of Violations, civil penalties, and Orders that modify, suspend or revoke a License.

The NRC’s Enforcement Policy spells out the NRC’s policies and procedures in initiating enforcement actions and the responsibilities of the Commission in reviewing these actions. But it is important to remember that a policy statement is not a regulation and the Commission may decide to deviate from the policy statement to respond appropriately to the circumstances of a particular case.

To identify violations of its regulations, the NRC conducts inspections and investigations. Violations have varying levels of significance. In assessing the significance of a violation, the NRC considers four specific factors:

(1) actual safety or security consequences;

(2) potential safety or security consequences;

(3) impact on the ability of the NRC to perform its regulatory oversight function; and

(4) willfulness.

Willful violations are of particular concern to the NRC because the agency’s regulatory program is based on licensees and their contractors, employees, and agents acting with integrity. For most violations identified at power reactors, the significance of a violation is assessed using the significance determination process of the Reactor Oversight Process.

The Enforcement Policy was last updated on July 12, 2011, after interaction with affected stakeholders. We’re happy to take any questions or comments you have about the policy in the comments below.

John Wray
Sr. Enforcement Specialist

What’s So Hard(ened) About Vents?

The idea of “containment venting” has been front and center in discussions about the Fukushima Dai-ichi nuclear accident and what the NRC wants plants to do to improve their vents. But to most people outside the nuclear industry vents are the things in our houses that hot or cold air flows through. So here’s a little background.

The accident in Japan involved what’s called a Mark I boiling-water reactor. Mark I designs have a relatively small structure, or “containment,” to hold in steam and radioactive material if an accident occurs. If pressure inside the containment gets too high during an accident, the reactor’s safety systems will have trouble pumping water into the core to keep it cool – which will make the accident much worse and possibly lead to high levels of radiation escaping into the environment. Part of this accident scenario also involves hydrogen gas building up inside containment. As we saw at Fukushima, if hydrogen is not allowed to escape, it can explode and damage the reactor building, which also could lead to radiation leaking into the environment.

This is where vents come in. They can be used to reduce pressure in containment so that water can still be pumped through to cool the fuel rods. The vents can also safely release built-up hydrogen to prevent explosions.

Decades ago, U.S. Mark I plants installed vents, valves and piping, but the circumstances in the Fukushima accident suggest the vent designs should be improved. The NRC is also considering whether the vents should have filters to capture any radioactive material in the vented gas

On March 12, the NRC issued an Order to all U.S. Mark I plants, as well as similar Mark II reactors. The Order requires Mark I plants to ensure their vents are hardened and reliable, and it requires Mark II plants to install hardened, reliable vents.

“Hardened” means these vents must withstand the pressure and temperature of the steam generated early in an accident. The vents must also withstand possible fires and small explosions if they are used to release hydrogen later in an accident. The vents must be reliable enough to be operated even if the reactor loses all electrical power or if other hazardous conditions exist. The NRC staff will issue, later this summer, specific guidance on the requirements for containment vents.

In order to ensure these vent improvements are properly designed and installed, the NRC has set a deadline of Dec. 31, 2016, for the Mark I and II plants to comply with the Order.

Scott Burnell
Public Affairs Officer

Problems in the Aggregate – Literally

Economists and others like to talk about “problems in the aggregate,” or a big-picture view of the issues. But that phrase is taking on new meaning in the case of the Seabrook nuclear power plant, where there are concerns involving the aggregate used in the concrete.

More specifically, the problem at the New Hampshire facility is the intrusion of moisture into the foundation walls of certain structures, resulting in the degradation of some of the concrete.

The exact term for what is occurring at Seabrook is alkali silica reaction, or ASR, which involves the hydroxide ions in the pore solution in cement paste and the reactive silica in aggregate. (Aggregates are inert granular materials, such as sand, gravel or crushed stone that, along with water and cement paste, are an essential ingredient in concrete.) The main byproduct of ASR is a gel, which can expand and may cause micro-cracks in the concrete.

While the extent of the problem is still being evaluated, structures identified as being affected by ASR are considered “operable but degraded.”

What exactly does that mean? In layman’s terms, it means the NRC – while far from done with reviews of the issue – has determined the structures can continue to safely perform their function based on the following information:

1. Conservative safety load factors, or the extra safety margin that was included when the structures were designed and built;

2. Visual observations by qualified NRC inspectors;

3. The fact that the ASR is limited to localized areas; and

4. Because progression of the concrete degradation is occurring slowly.

That determination, contained in an NRC inspection report issued on March 26, was the result of reviews carried out by six of our inspectors over many months, dating back to last September. Among other things, we made use of concrete/structural integrity expertise at our headquarters office. We also had an inspector in our Region III office, in suburban Chicago, observe lab tests performed in Northfield, Ill., on concrete core samples taken from Seabrook.

An important next step for the NRC’s review of the Seabrook concrete degradation will be a public meeting scheduled for Monday, April 23, at our headquarters office in Rockville, Md. During that meeting, the NRC staff will discuss with NextEra, the plant’s owner and operator, its analysis of the issue, planned corrective actions and dates to fully correct the problem, as well as other details.

Based on the outcome of that session, the NRC will determine its next steps regarding the issue. One thing we have already made clear is that no decision will be made by the agency on a license renewal application for the plant until the extent of the concrete degradation is fully understood.

Members of the public who would like to listen in on the meeting but cannot travel to NRC headquarters will be able to do so by phone bridge. What’s more, the slides to be used during the session will be available via an online webinar.

More details regarding the April 23rd meeting are available at: http://www.nrc.gov/public-involve/public-meetings/index.cfm .

Neil Sheehan
Region I Public Affairs Officer

The Terrible Twos

In celebrating the second birthday of our Open Government Plan, we did what any proud parent would do, we made a movie! You can see our story on YouTube.

During the past two years we have successfully begun to use social media services, redesigned the agency’s website, www.nrc.gov, made finding documents easier, and published a significant amount of raw data in formats that enable stakeholders to more easily analyze our information.

We have also provided more opportunities for stakeholder and public engagement and have worked to improve the experience of those who participate. We have provided subscription-based services to keep stakeholders informed, expanded the use of virtual meeting and Web conferencing technologies, increased the agency’s capacity for webcasting from 50 to 100 meetings per year, and introduced new channels for engagement through this blog,  our Twitter feed, and our YouTube site.

In addition, we’ve made special efforts to reach out to the public on topics of high interest, such as concerns raised by the events at the Fukushima nuclear plants in Japan and the effects of the Missouri River flooding on the Fort Calhoun nuclear plant in Nebraska. And, to improve the experience of participants, we have expanded our internal meeting best practices website, and our meeting facilitator and advisor program.

But we are not done! On April 9th we published an addendum to our plan to provide the roadmap for the next two years. Over the next two years we will build on our accomplishments by increasing our focus on the use of plain language, continuing to strengthen our use of social media, improving the rulemaking comment process, and furthering collaboration with our state regulatory partners. In addition, we will implement Mobile NRC, a new effort to provide mobile access to key agency content.

Finally, stakeholder feedback helped us formulate our forward plans, and as always, we welcome your thoughts!

Fran Goldberg and Stu Reiter
CoChairs, NRC Open Government Advisory Group
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